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1. Set Reference H Show Heference Alr 5 Set LFA Ctrl L Bottom View Alt LER EA EES Let Vertex Ctri T Set Ini Chal Cut Right Alt EM O Cut Bottom Ab Copy to Clipboard Ctrl C Lut Top Alt P Save as bmp Ctrl Seale 1 0 Ald Help F1 Scale AU Alte Frontalto Bottom Views Thevarious views will changethe viewing perspective for the rendered and the Maximum IP views Cut sections The Cut options let you selectively cut out parts of the rendered view Cut Left Right cuts out the left right side of the head Cut Bottom Top cuts the bottom top half ofthe head You can combine options like Cut Left and Cut Top to display only the lowerright quadrant shown below Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Scale 1 0 Scale 2 0 These options provide a quick means for changing the size ofthe SLICE display Scale 1 0 is the small size Scale 2 01s the large size units display pixels mm Set Reference Show Reference These two features are used to measure physical distances inthe image and have nothing to do with the Reference electrode Inthis example we are using a single fixed dipole and we want to measure the distance between its location and the skin surface Position the crosshairs on the dipole source ifthey are not already there Right click inside the SLICE display and select Set Reference This sets that point as the Reference point for measurement Then right click again a
2. 2001 Neurosoft Inc Document number 2231 RevisionA Operating SOURCE Torunthe SOURCE program offline go into EDIT and retrieve an AVG EEG or CNT file You will then notice that the SOURCE icon on the Toolbar will become active za Select one electrode and enlarge it to mid size or full size AVG and EEG files Click the icon and you will see the SOURCE Startup display Source Startup E pi5 pike lng Log file C Match Labels Ce Electrode Positions Load Positions Recommended Cancel The log file is created when you use SOURCE and it will contain the electrodes that were used and their 3D positions the landmark positions that were used and results from the analyses you perform in summary form Subsequentresults may be added to the same file The file can be viewed witha text editor Use the Log file button if you wish to save the analyses you will be performing to a different log file or type in a different name if you wantto create anew log file The Match Labels and Electrode Positions fields may or may not be grayed out Ifboth are grayed out that means that the program was unable to match any of the labels in your data file see Appendix A The OK button is also grayed out leaving you with Load Positions and Cancel as the only options Use Load Positions to selecta3DD file that matches the data file Ifthe Match Labels field 1s active but the Electrode Positions field is grayed out you have the optio
3. Atthis point in time there are no absolute answers to many of these kinds of questions Source reconstruction 1s ahypothesis driven analysis Therefore the approach adopted for source reconstruction must be driven by a priori assumptions and by known physiological constraints Even then it may not be possible to decide which reconstruction model to apply If you are not sure which dipole model to use try several different ones Look for converging results across models Look forresults that are reasonable Use common sense and rely on established neuroanatomy and neurophysiology as much as possible For example if you are looking at dipole source solutions for the major components of an SEP recording it may not make sense to look for multiple dipoles with mirrored results With auditory stimuli itis reasonable to expect bilateral homologous dipoles In other instances the expectations and predictions may be more ambiguous Let s go through a couple of examples and include some of the thought processes Example 1 Retrieve the EpiSpike avg demo file and load the electrodes positions using the EpiSpike 3dd file you should use the actual measured positions whenever possible This is asingle sweep of EEG showing an epileptic spike and slow wave complex from the left frontotemporal region The question we might ask is what is the anatomical source of the spike Even if prior studies have shown some consistencies for localization of epileptic spike
4. BEM 5000 nodes Scaled The BEM Boundary Element Model volume conductor options are inactivated and reserved for future developments Display Options Ifthe automatic coordinate system orientation detection fails it can be overwritten using the x y z yz x or zZ y x options referring to the order of the coordinate system axes in the electrode positions file where x means right left y means anterior posterior and z means bottom top Contour incr uV The Contour setting 1s used to determine the increment between the contour lines For example ifsetto0 5uVs the contour lines will be drawn for each 0 5 uV interval You may also use the up and down arrows from the keyboard to change the contour interval inthe SOURCE display Movie rotation delay ms The Movie rotation delay time ms 0 1000ms determines the replay speed for AVI movies and also in thesaved movies as well The smallerthe number the fasterthe replay time the number is the number of ms each frame is displayed Saved AVImovies can also be replayed with Microsoft s Media Player and edited by JASC s PaintShop Pro see www jasc com Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Hypothesis testing If you get a dipoleresultinthe vicinity ofthe true location that you expect from your paradigm you can easily move the dipole position to the expected location grab and drag it ina plane parallel to the screen plane and see how well the
5. The Keep Results option retains the latest dipole solution on the display while you compute new results new mode latency interval etc onthe same display The kept results are shown in pink and the new results are showninred Clicking Reset Results will remove the kept results SLICE 1 0 Warp MRI Jal OF x A s 0 823 40 1154 942 575 37 0 17 5 39 7 160 4mm d Source 33 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Maximum IP The MaximumIP Maximum Intensity Projection option affects the image in the rendered view lower right corner ofthe SLICE display The figures below show the image right side view with Maximum IP disabled and then enabled Reset Grayscale In Maximum IP mode you can vary the intensity of the white end and the black end of the grayscale by rotating the mouse wheel white and by holding the Shift key down while rotating the mouse wheel black Use the Reset Grayscale option to return to the default settings View The View option lets you select the viewing perspective of the rendered head the one in the lower right hand corner of the SLICE display The Cut options allow you to cut out parts of the rendered view and the Scale options let you quickly change the size of the SLICE display These options are discussed in more detail below Source 34 d vw Frontal View At Left View Alt L Aight View A SE Top View Alt T Set Masion Ctrl M Back View Abu
6. bottom gt top The origin is in the lower right frontal corner The next set of three numbers are the x y z coordinates in PAN coordinate system mm if all anatomical landmarks are set Source 13 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Thelastnumberisthe distance from the reference pointto the actual cursor position mm The Reference point can be set by pressing R or by right clicking in the SLICE window and selecting Set Reference This is discussed more fully in the Set Reference Show Reference section below SOURCE Help screen Click the right mouse button inside the SOURCE display screen and click the Help F1 line from the list ofoptions You will see the following screen Source 14 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA SOURCE Help Initial Model Settings Fitted Center mm H adii mm Shell Shell Shells m y z has arog nss bai os ize L onductrvities 5 m Shell Shelz Shell 3 0 33 0 0042 0 33 Rotation and positioning Press the left button of the mouse 1 to Rotate around vertical and horizontal ares te 2 Over a dipole to reposition for hypothesis testing 3 to Select a latency in the waveferms display Press the right button n 1 for Contest menu and source model properties to Enlarge or shrink the views Move the mouse wheel E NEURO SCAN LABS a to Enlarge Dr shrink the VIEWS AM oJ Naurasoft
7. C3 Cz C4 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA P4 O2 T6 O2 XXX XXX FPI FP2 FPZ MNI MN2 PAL PAR NZ l5 PZ T6 T3 CZ P8 O2 notused for reconstruction LPA RPA INI NAS Ini Nas 80 81 82 83 84 85 86 87 88 89 90 9 92 93 94 95 96 23 98 99 100 101 102 103 104 105 106 107 TS F7 F3 Fz F4 FS Oz P5 PI P2 P6 C5 CI C2 C6 F5 FI F2 F6 F9 T9 P9 MI M2 Al A2 TI T2 T4 FZ OZ The standard 10 20 system electrode positions are shown below Note that some labels in the figure should be replaced with newer labels Forexample T3 isnow T7 T4 1s now T8 T5 is now P7 T6 is now P and so forth Source 55 Copyright 2001 Neurosoft Inc Document number 2231 Revision A eh a C Pan ET 4 ui Ti LE I PA DG Oo NION 1 N 6069098 3 j BA 67 ez ee G06000046 L RA zh I e T T D oO T 0 To foo Aa OO DAOG QO o ird CH FJ An interesting paper about the 10 20 system and the electrode labels is G E Chatrian E Lettich P L Nelson Ten Percent Electrode System for Topographic Studies of Spontaneous and Evoked EEG Activities Am J EEG Technol 25 83 92 1985 SOURCE SCAN ACQUIRE and EDIT are trademarks of Neurosoft Inc Windows is a registered trademark of Microsoft Source 56 Copyright 2001 Neurosoft Inc Document numbe
8. active with Moving dipoles only This parameter may be used to suppress bad fit results e g at latencies with low SNRs Ifyou select a large time range and set the threshold to for example 80 then only the fitted dipoles with a residual Deviation of 20 or better are displayed The results of the other latencies are suppressed in the display Volume Conductor Model three spherical shells The volume conductor model three spherical shells parameters are specified in these fields First a sphere representing the outermost compartment boundary skin surface 1s fitted to the electrodes then relative radii as well as conductivity values may be entered The defaults are standard values from the literature but you have the option to modify them You should not scale the volume conductor radii percent values for children or for smaller heads since then the volume conductor wouldno longer match the electrode positions and the anatomical context of SOURCE and SLICE You should see the estimated source positions as rough guesses only and not overinterpret the numerical results Y ou could scale all numbers offline by the ratio of the measured head circumference to the used value 55cm see the log file fornumerical details Especially for small head sizes however exactly measured electrode positions are essential If landmarks are given the model head surfaces skin skull and brain envelope are matched to these landmarks BEM 3000 nodes
9. asource located outside the head 1s nota valid solution Similarly an occipital lobe solution for an early SEP componentis not valid Solutions based on Label Matching and the generic MR head shape will not be as precise as those with measured electrode positions and the subject s own MR images View options The viewing perspective may be changed either by selecting a viewing angle from the Options Menu or by grabbing and moving the display with the mouse Source 23 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Front View Alt Lett View Alt L Right View Alt F Top View Alt T Back View Al Four Views Alt 4 Movie M Save Movie As Lid Rotation 360 deg H Save Rotation as Cile T Copy to Clipboard Ctrl C Save As bmp tle Print Hrl P w Front lt gt Back F Tilt View T Fixed view positions From the Option Menu you may select to display Front Left Right Top or Back views Or youmay grab the display using the left mouse button and spin rotate it to any desired perspective There is also the option to display Four Views as shown below EE DON D Klek Za d xi a s j m Cr z CHE T Front lt gt Back The Front lt gt Back option reverses front and back for whatever perspectiveis displayed Tilt View The Tilt View option tilts the display upward by about 20 degrees Source 24 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Movi
10. at the 3 points resulting from the Rotating dipole analyses we see that those 3 solutions fall nearly on the same line as shown above The single dipole solution we began with falls more or less in the middle of the path of the moving dipole In general the above methods provide converging validation for the left anterior temporal lobe apparently a progression along the anterior tip of the lobe as the source of this spike For comparison s sake we decided to look at the Fixed coh method solving for 3 dipoles during the 0 50ms span Source 45 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA 4138 1915 1115 nAm 152 8 20 pis ea ms We see first ofall that one solution is outside of the head suggesting right away that this model may not be appropriate Also the weakest dipole solution purple 1s in an inconsistent location Rerunning the analysis witha single dipole gives the approximate left frontotemporal lobe location STE ee fe ara RTE A EE E ous os Ee mU Ser Lus c Ss gs HS uma dw gree eS nen w IT Den h I um LE NN Ze weeny mm Sex An ene amp E l UN Daa CT gea Nr Ven P Tots atm mnt Hem LM b pf o ua Ital do werd w rr T as Ra 9 V o8 Qo QaT oan os T PELME a ete ay 8 ee TUS t6 tt ma a CU UT 0T ge s Qua m E ee LN EM Ze n Ts DER HO EHE MEN H Le enn on Ten A d aa I tttanmT A Li d at Ns V lepus 7 SS ge rt at pn eg DLE LL iiw ETE I ater dite QUOC N
11. data could be explained with a source at the right spot You will see the Source Waveform and Deviation vary with the new position Often the error hyperfunction has a very shallow sink especially if you try to analyze data with a low SNR if you double the SNR the confidence radius ofthe found solution reduces to one half and there is only aslightly better fitting position found e g 9 8 residual deviation by the minimization algorithm as compared to the correct position e g 9 995 residual deviation The figure below shows the original location on the left and the repositioned location on the right 2 ms 152 D 32 4 27 9 51 1mm 0 85 0 09 0 52 3966m z 2Ums 152 904 32 4 15 8 75 1mm U 83 0 13 0 54 35708 z The Option Menu for SLICE Click the right mouse button within the SLICE display and you will see the following list of options Some of these are the same as those described above in the SOURCE options The new ones are described below Source 31 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Display The Display options let you select the elements you wish to include in the SLICE display The Crosshair Dipoles Electrodes and Landmarks may be toggled on or off BI pla y The figures below show how the SLICE display will appear with all ofthe options offand on Source 32 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Keep Results Reset Results
12. fit with less than 10 deviation one starts to fit the noise e g when taking too many dipoles resulting in meaningless dipole positions but with well explained data On the other hand when the fit quality deviation is on the order of 20 which would correspond to an SNR of 5 only the source model is not adequate or the SNR was not estimated very well Keeping in mind that an adequate source model should exhibit similar traces for MGFP and explained deviation at latencies with high MGFP and thus high SNR the explained deviation should be high and the residual deviation which equals 1 explained deviation should be low Note that there appear to be at least 2 dipoles in the analysis interval We may wanttorun the analyses using the suggested intervals First however forinterest s sake we decide to use the Rotating dipole model this time with 3 dipoles Source 43 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Again we see dipole solutions in the lefttemporal area Usethe M key to play the Movie ofthe results or use the arrow keys to step through the analysis interval one pointatatime The solutions show an interesting rotation during the interval We then decide to use the Moving dipole model and we will limit the interval to the 0 50ms span based on the first peak in the MGFP Deviations and signal strength displays Disable the Source Waveforms option to see the results We increased the thresh
13. move to a different sweep just close the full sized channel display and the arrow keys will have their normal functions returned Setting the Interval for CNT files To select the interval for analysis with CNT files click the right mouse inside the data display window and enable the Use Interval Mode for Source option You will see two colored dashed vertical lines they may initially be superimposed in the Single Window display with the latency seconds into the file showing Grab and drag these to the desired interval The analyses will then be computed using the interval 76 88 el 176 948 s Deen rs Note You may change the color of the cursor by selecting Options Single Windows Settings The Cursor option may be used to select the color Perhaps the best way to introduce the various features of SOURCE 1s with an example data file Retrieve the EpiSpike avg file that was installed into the Scan4 2 Demo folder Make one of the channels Full Size such as F7 and click the SOURCE icon 3 From the Source Startup screen Load the EpiSpike 3dd electrode position file Enable the Use Interval Mode for Source option if needed Position the cursors to define the approximate 0 50ms interval Source 11 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA 032 mz i5 ms 3n hi 2000 100 0 UM UU 1000 20010 500 a00 H00 A00 ID un 1000 AUD xo amu By default the results for the Moving
14. 001 Neurosoft Inc Document number 2231 RevisionA 1 T im Ca Ko 3 T r P a wm Ki D CHE EE e DS ee 3 ILI WOON pA E KZ TU IUe TW UMY ons CE d PL DD Em SCH a ve LH hh r JE SEN E Ax TP ea Creel a ae LES bb similarly the results from the interval containing the N1 component 70 135ms also indicate 2 nearly homologous sources from the same areas The variation from precise expected sources may be due to thelack of measured electrode positions Source locations should be considered as approximations in these cases AIC Sc L 1 MEM bis EG ea oat D da e MN LPS rs rj EIAS KM NEE r De Irene PEER TE Es run HA Nat Od al PTE eent er ee OT re I LII EISE Ttg D Ikewck n mnie OM ARRETE 1 Ste gd tS a LEE GAREN E DUNS Looking at the P2 component 135 230ms however the solutions become less lateralized The more prominent one in yellow 1s fairly central while the weaker dipole shows an unlikely occipitoparietal location Note also that there is considerable residual deviation and that the SNR is low These are not particularly valid looking solutions Source 48 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA 6 45 22 7 nm 33 3 707 AALS 183 K IS Forcomparison s sake we again selected the interval containing the N1 component and applied the Fixed MUSIC model with 2 dipoles Very different sources were cal
15. 40 SOME Tips TOF USING SOURCE EE 42 m flne CH 42 EXAMDIG 2 ar LM EE 47 EX AI DIC SE e r add eRe 50 SE nali HESS 51 Suggested REFERENCES for more miormmaton 52 AppendixAsLbabelMatchllig sse t sias a man 53 Source 4 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Introduction to SOURCE The SOURCE program runs as part of the ACQUIRE and EDIT programs in SCAN 4 2 and newer versions It provides several models that may be used to calculate one or more dipole solutions for your SCAN averaged epoched or continuous data files Some of the main features include 9 Computation of single equivalent current dipoles moving dipoles rotating dipoles fixed coh dipoles and fixed MUSIC dipoles SOURCE solutions may be calculated online in ACQUIRE or offline in EDIT 9 In the SLICE part of the program the results are displayed on skin skull and or brain point clouds or ona generic MRI head display or you may import your own MRI CT data 9 Anequivalent electrode label matching algorithm recognizes and includes variations on the 10 20 system labels or you may import your own electrode position information 9 Dipoles are calculated using a three concentric sphere model 9 Single point or user defined latency interval analyses 9 Displays of measured and fitted contours 9 Easy methods for viewing the results from various perspectives and options for displaying skin skull
16. AS 25 Miscellaneous otptons 25 Copy to Clipboard Rs 25 err cIMMono m 26 mile eT PK 26 Source 5 Copyright 2001 Neurosoft Inc Document number 2231 Revision A mj Me E 26 Source Paramelels snintentav taie Vea ob dU tmd Dd a RUE 27 Dipole VIGO Sl MEE 27 Juego en in in 27 ROUNO rss sn 28 FIXE COM ns hr cena 28 Be KC e sens pen nee 29 N mber OF DIPOLES EE 29 MF GS TANGO d un RR 29 Seeddistance MM eieiei reegen 29 Mirrored yz plane 29 PES NOIR a lt TE 30 Volume Conductor Model 30 DISDIAY ODIIODS aeeie Ananas 30 Fy DOUMESIS liget 31 TIhneOptonmenultor SLICE EE 31 BI ania 32 Keep Results Reset Results 33 MaXIMUM MES E 34 PRESET Grayscale m MM 34 MGW e RR 34 Frontal to Bottom Views 34 KEE EE 34 ocdle 1 076ale 2 camini tenent iie bind Sn olo 35 Set Reference Show Reference 35 Set Nasion through Inion ss 36 Miscellaneous e d Se ne dt een 38 Select D aldea tetto bi Ep o DU Ou Act dads ui 38 RIES Te nn 38 Image Data Parameters 39 Slice Orientation rer 39 Anatomical Landmarks mm 40 Thresnold 6Gfayscale itn tct tt ttti 40 Sly EE
17. Dipole solution are displayed in the SOURCE screen To change the size of the images in the SOURCE display simply rotate the mouse wheel or hold down the right mouse button while moving the cursor The results are also displayed ona generic MRI head in the SLICE screen shown below You may change the levels ofthe slices in any of the perspectives by clicking the left mouse button to the desired pointin one of the cross section displays or you may grab and drag the cross hair to a desired location Moving the cross hair in one display will shift the level of the slice in the other two cross section displays SOURCE Status Bar On the Status bar at the bottom of the Source display you will see a series of numbers grms 3 29 13 9 55 8 86 0mm 40 75 0 98 0 09 64 43n amp m 2 11 F4 98 64 Source 12 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA The first number is the time pointin the interval that has the least value in the Deviations function the best fit latency After an analysis has been run the program will return to this point automatically The second number is the Mean Global Field Power MGFP value taken from the same time point in the interval a measure of signal strength The next three numbers are the fitted dipole coordinates 1n mm s The next set of three numbers are the dipole orientation values unit vector The ninth number is the dipole strength innAm s atthe indicated time poin
18. Lewis PS Leahy RM Multiple Dipole Modeling and Localization from Spatio Temporal MEG Data IEEE Trans Biomed Eng 1992 39 541 557 MosherJC Leahy RM Recursive MUSIC A Framework for EEG and MEG Source Localization IEEE Trans Biomed Eng 1998 45 1342 1354 H Buchner M Fuchs H A Wischmann O D ssel I Ludwig A Knepper P Berg Source analysisof mediannerve and finger stimulated somatosensory evoked potentials Multichannel simultaneous recording of electric and magnetic fields combined with 3D MR tomography Brain Topography Vol 6 No 4 1994 pp 299 310 M Fuchs M Wagner H A Wischmann Th Kohler A TheiDen R Drenckhahn H Buchner Improving Source Reconstructions by Combining Bioelectric and Biomagnetic Data Electroenceph Clin Neurophysiol Vol 107 pp 93 111 1998 M Fuchs R Drenckhahn H A Wischmann M Wagner An Improved Boundary Element Model for Realistic Volume Conductor Modeling IEEE Biomed Eng Vol 45 No 8 pp 980 997 1998 M Fuchs M Wagner Th Kohler H A Wischmann Linear and Nonlinear Current Density Reconstructions J Clin Neurophysiol Vol 16 No 3 pp 267 295 1999 Source 52 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Appendix A Label Matching SOURCE uses alabel matching algorithm to retrieve the electrode positions positions ofthe 10 20 system by their labels if no actual 3D positions are given or available All electrodes with a matchi
19. P ef Se D E e Mans ster d SE S lUa A oV Zeen SE en E z PP KT DEA 3 E tomar xia s Ni p Dem a te ce ee aa e m s sw S on soon a o nm nm GE A i ics 9 75 E ae 2 qu pu or MAE E puce D d Ge d m ER t A il B 152 9 Lv zu mz 2zlms 162 Du 173 0 74 7 B 5mm 0 40 0 60 0 69 2581n amp m 3 7 99 12 SE Interpreting the functions The Source Waveforms Deviations and MGFP functions are useful in helping you determine ifthe dipole solution is a valid one Loosely stated the Source Waveforms show the strength and time course of the dipole s The Deviations function displays the residual standard deviation MGFP is a composite measure that indicates the strength of the signal against the noise background Fora valid dipole you would expect to see during the approximate same time course a strong dipole peak in the Source Waveforms low residual or unexplained standard deviation displayed as a peak in the Deviations function and a good signal to noise ratio peak in the MGFP function In other words you would expect to see approximately concurrent peaks among the three measures There are no hard and fast rules as to how strong the dipole must be how low the residual standard deviation must be less than 10 1s good or how high the SNR from MGFP must be This becomes a subjective determination influenced also by the physical location of the dipole solution s and by your a priori expectations Obviously
20. User Manual Source Neuroscan Labs 45150 Business Court Suite 100 Sterling VA 20166 USA Voice 703 904 9600 Fax 703 904 7870 e mail sales neuro com techsup neuro com web site www neuro com Source 1 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Mgr For Technical Support If you have any questions or problems please contact Technical Support through any ofthe following routes If you live outside the USA or Canada and purchased your system through one of our international distributors please contact the distributor first especially if your system is under warranty In all other cases please use techsup neuro com or see the other Support options on our website http www neuro com neuroscan support htm Or if you live in the USA or Canada please call 1 800 474 7875 International callers should use 915 587 0875 For Sales related questions please contact your local distributor or contact us at sales neuro com Copyright 2001 Neurosoft Inc All rights reserved Printed in the United States of America No part of this document may be used or reproduced in any form or by any means or stored in a database or retrieval system without prior written permission of the company Making copies of any part of this document for any purpose other than your own personal use is a violation of United States copyright laws For information contact Neuroscan Labs Neuroscan Labs A d
21. a further requirements can be imposed These are called constraints and their purpose is to make the dipole fit more stable and its result more reasonable in certain situations SOURCE supports several types of dipole constraints The dipole location does not change over time rotating dipole The dipole location and orientation do not change over time fixed dipole The locations of two dipoles are mirrored with respectto the midsagittal plane mirrored dipoles Multiple Signal Classification MUSIC Multiple Signal Classification MUSIC is amethod which does not compute the misfit ofa given dipole model per location but a specific MUSIC metric 2 I A Il WE EE Amino UmUmU with A XIthe minimum eigenvalue ofthe matrix Xand the SV Ds ofthe one dipole lead field matrix L and the spatiotemporal measured data matrix m respectively i _ re L ia mm o d F i L ULV andm U2 The signal subspace is associated with the leading singular values of U_ standing forthe subspace orthogonal to the signal subspace and associated with the trailing singular values ofm The number of singular values that make up the signal subspace is a parameter of the method This metric peaks atthe locations of multiple non coherent i e temporally independent sources fora given time range in justa single scan It gives the bestresults fortemporally independent sources with fixed orientations e g SEPs Source 7 Copyright
22. alone you cannot judge for or against one model you have to know about the physiological aspects to find the adequate model Also different volume conductor models lead to different dipole localizations but both models may be able to explain the measured data Source 46 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Example2 In this example we will look at the group averaged auditory evoked responses in a group of adolescent females n 5 ages 14 15 A word list consisting of animate and inanimate objects was presented binaurally The task was to count the number of words that represented mammals 64 channels of EEG were recorded Knowing that there is bilateral temporal lobe processing of auditory stimuli and that the primary projection areas are relatively focal in comparison to the secondary and tertiary processing areas we anticipate that a 2 dipole model would be appropriate and that earlier components P1 and N1 may have more stable solutions than later components N2 and P2 We llbegin with a2 dipole Fixed coh model looking atthe interval encompassing the P1 component 28 82ms Measured electrode position information was notavailable so Label Matching was used gun Zul 24 17 mz zu m ta OS UM du 100 0 du 10 0 2000 Ad ann S000 The results show 2 nearly homologous dipole solutions which are close to our temporal lobe expectations Source 47 Copyright 2
23. an uto e ee Fora tas op Stet uu Puls ee ee a hE Poe ee Oe ae See E ee ke aot DW a DI D Nt n dU ebe agep a E T T Ta uns etat nsa mV em iar t tT x WEN LV eet A E ye a ur mer d tam wem cr pps rure a a X imr ue E aat t a B T n tan o La Le LIE fev aA ae CE a e eae ML ee at 1 n e YS RE Dal RW Wa Ware M e ee RUN A T 1 ne ta us nen d D ole Ip S M oua Uu 2772 4 oa EU DTE DLP M e IM y dein E A Tear geg DN d WEEN EEGENEN Fa pe a pete a ae Ge x wa Gus Wi S ee ERN ma T aga o SCH OI V se IS Sir IO Te l2 ae ee ri ar ees ut on MT PL A Kai LE EIE Keep in mind that source reconstruction is somewhat of an art and there are frequently no straightforward procedures to follow You typically have to try several source models until you meet your expectations of the underlying brain activity based on your a priori assumptions and until the chosen model can explain your data The inverse problem has no unique solution Only with additional assumptions like the number and characteristics moving rotating fixed coherent of the sources cana unique solution in a mathematical sense be achieved For example three fixed dipoles can explain well enough the spike of the spike wave complex we analyzed above and three rotating sources can explain the data even better since they have more degrees of freedom However the true source model would be a moving dipole in this case from the residual deviation
24. and brain point clouds 9 Default oruser determined radii and conductivities 9 Manual repositioning of the dipole source for hypothesis testing The programs are easily installed and quickly mastered If you have any questions or difficulties please contact Technical Support see Page 2 above Source 5 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Installing SOURCE SOURCE and its related files are installed automatically from the SCAN 4 2 CD ornewer version The actual programs used are SourceOC XS oc SliceOCX ocx acompatible version of acquire exe and someancillary files These will be copied to your Scan4 2 folder along with some demonstration files Ifyou bought SOURCE as an add on it will come with its own CD Install the SOURCE software as you would with any other CD installation Itis largely an automatic process Dipole Model Introduction The following information will provide a brief introduction to dipole source localization and describe the different models that may be applied with SOURCE A source model is a configuration of generators which makes sense for the given data Itis the responsibility of the user to choose an adequate source model Source models are defined by the number of dipoles the temporal characteristics of the dipoles the dipole locations the dipole orientations and the dipole strengths Dipole models are made up of a small number of dipoles whi
25. ch hardly ever exceeds ten Each dipole is characterized by six parameters per time point namely its location and its components Single Dipole Models The simplest dipole modelis the single equivalent current dipole Its three location parameters are fitted and its three components are determined for a given time point so as to minimize the deviation between measured and forward calculated data Anextension ofthe single equivalent current dipole is the moving dipole Its three location parameters per time point are fitted and its three components are determined for each in a series of time points Ifthe location ofa moving dipole is held fixed over time we get the rotating dipole Its location is jointly fitted for all time points while its three components are determined for each time pointindependently Ifthe location and orientation are kept fixed we have a fixed dipole Location and orientation are jointly fitted for all time points while for each time point the dipole strength is determined only Source 6 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Fora fixed coh dipole a common position and orientation for all time points is fitted and the dipole strengths for every time point are calculated If more than one dipole is fitted they will all have coherent loadings same temporal behavior Dipole Constraints In addition to the requirement thatthe dipoles to be fitted shall explain the measured dat
26. culated Again the residual deviation is high and the SNR is low suggesting that these solutions may not be valid 1 r et Bee DE He en e OR LRO RAD kai kauri ia Solera Source 49 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Thisis in contrast to the results from Example 1 in which the Fixed MUSIC solution fit well with the other models whilethe Fixed coh model did not How canthis be interpreted With early somatosensory EP data forexample one tries to achieve a functional mapping of well localized brain activity Inthis case one expects two or perhaps three centers of dipolar activity depending on the chosen latency range which can be well represented by two or three fixed MUSIC dipole and not coherent fixed dipoles because you do not expect coherent activity AEPs are more difficultto analyze as one may well anticipate simultaneous coherent mirrored activity in both hemispheres which is not quite as well localized as in the SEP case Later latencies as with the P2 component above are almostalways more difficultto analyze since activity has then already more diffuse Example3 Fora final brief example we will look at an SEP recording right median nerve stimulation The time interval is 12 25ms and we used the Fixed MUSIC model with three dipoles 12 00 mz 202 mz A UU UM 05 10 0 Du mu za Au DI The power of the Fixed MUSIC source model is demonstrated very
27. d that you need to adjust the segmentation Copyright 2001 Neurosoft Inc Document number 2231 RevisionA threshold The figures below show an example left wherethe threshold was settoo high and the skin surface has been eroded away The example on the right shows the same data with the correct threshold Ifthe threshold 1s set too low the surface electrodes will disappear The wheel is also used to vary the graylevel scaling in Maximum IP mode To do this click the Maximum IP option from the right mouse accessed Option list Then rotate the wheel by itself to vary the intensity of the white end of the gray scale Hold the Shift key down and rotate the wheel to vary the black end of the gray scale Click the Reset Grayscale option to return to the default levels Looking again at the SOURCE display itis possible to change the perspective of the image in several ways described below The SPLICE display above was from the right side The contour display below is a top view Inthis example a Moving Dipole model was used and you can see the dipole source solutions as they vary as a function oftime The display on the left shows the Measured data contour equipotential lines electrodes and the dipole locations The image on the right displays the Modeled potential contour lines electrodes and dipole location In this figure the skin point cloud is displayed you can also show the skull and or brain point clouds and other infor
28. data only Source 38 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA The Image Parameters window displays the set parameters and allows you to edit them if you read in real MR or CT data If you try to read an image data set for the first time where no parameters have been set you will see the Image Parameters window and you will need to fill in the information that is necessary to read the data correctly After pressing Apply the parameters file will be written 1mp image parameters and the image data will be read dat 1mg 1so and displayed Inorderto coregister with the EEG sensors and reconstruction results the five landmarks have to be set the actual cursor position will be taken and the coordinates will be transferred to the parameters window see Set Nasion through Set Inion above When all five landmarks are setand Apply is pressed the 1mp file will be overwritten the image data will be reloaded and are now ready to display electrodes and reconstruction results from SOURCE Image Data Parameters This section of the display contains descriptive information about the raw data 2D slices Bits per Pixels Image data can be stored with one byte 8 bits one and a halfbytes 12 bits ortwo bytes 16 bits per pixel Each pixel contains the gray level information of one 2D image point pixel Significant Bits Within the 8 12 or 16 bits per pixel not all bits may be used sometimes on
29. display options wuz contour ier Jul C C i S LU movie rotation delay m Dipole Model The dipole model section shows the source models that may be selected Youhave the option of selecting a single time point ora latency range for analyses If youselecta single time point all of the models will produce the same results Ifyou select a latency range by positioning the vertical cursors in the data display window then the models will be applied Note You may select or vary any of the options in the Source Parameters display and see the effects by clicking Apply without closing the Source Parameters window The Options menu right mouse button will remain accessible while the Source Parameters display is seen Moving The moving dipoles may be displayed as atrace as seen below using the EpiSpike avg file oras a Movie as described above ource 27 Copyright 2001 Neurosoft Inc Document number 2231 Revision A The dipole positions the nonlinear parameters orientations and strengths the linear parameters for every time point are calculated independently Rotating Forarotating dipole acommon position for all time points is fitted andtheorientation and strength for every time pointare calculated so arotating orientation may result Theresults below are forthe same file during the same latency range Fixed coh For fixed coherent dipole a common position and orientation for a
30. e Ki 1 Im gt es P e e are VI T dk Er d 1 EE em Ces D a Tg ofa To is ee nn Biss P o A pb IE SATAA Au ater re roo 2 pre ss C W P WO UN UNS us as Rai a d hes QU ZS Ren 2 ks E AE RENE eer E Su xe aN ac ee E E ea ee ao dear t Ti se ai woe a v Sa Eu o LL WEE o ns t Ius IET eot ice sc sn ag ee Turi f o a W Be ama oT Le i oh E wy sn ss Sg ex D Iia LA ge DRM T NE GMT D I MC D S ws yt e en Di Volume Conductor Enabling this option will display the three concentric spheres used in the dipole models Source 20 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Skin Skull and Brain Thesetoggle on and offthe display ofthe generic Skin Skull and Brain pointclouds UNE ba 7 n Te o m dn iens umm pue Source Waveforms TheSource Waveforms window displays the dipole strength Stren results for the selected time range Enable this option to see the waveform displays ofthe Deviations RDev and Mean Global Field Power MGFP Note that these options become active when you enable the Source Waveforms option and you may select either or both of them The Source Waveforms are the ones in the top region left side of the following figure SOURCE 1 0 ba il et with 3dd loq 3llms 14b5 Bp 203 4 78 1 110 1mm 0 38 0 85 0 36 438 9n amp m 7 53 33 45 In this example three dipoles were computed and the Min Max Scaling
31. e Rotation options Nextontherightmouse option list are Movie and Rotation options Movie M Save Movie As Ctrl 0 Rotation 360 deg H Save Rotation As Ui Movie Dipolesource solutions are calculated for each data point in the defined interval When you selectthe Movie option the dipoles will be displayed at each point through the interval orpress the M key This willletyouseethe movement ofthe dipole and orthe changes inthe contour lines depending on which dipole model you have selected The rate at which the Movie is played is controlled by the 100 r maovie ratation delay ms field on the Source Parameters display If you wantto control the movements manually selectthe Source Waveforms option below A green vertical cursor will appearin the waveform display Grab this with the left mouse button and move it manually through the interval to see the dipole movement at a desired speed or use the keyboard arrows to step through the interval After a movie thetime cursorreturns to the best fit latency Movies may be savedusing the Save Movie As option described below Save Movie As Thisoption allows you to save the Movie described above as an AVI file Clicking it displays the standard Save As utility Note the movies are sequences of individual screen shots and the movie files can get very large Rotation 360 deg The Rotation option will rotate the display one time through 360 degrees or press the R key The rate o
32. f the rotation is controlled by the 100 movierrotation delay ms field in the Source Parameters display The rotation movie may besavedusing the Save Rotation As option described below Save Rotation As This option allows you to save the Rotation described above asan AVI file Clicking it displays the standard Save As utility Note the rotation movies are sequences of individual screen shots and the movie files can get very large Miscellaneous options The following right mouse options pertain to copying the display with the focus to the Windows clipboard saving graphic screens and printing Copy to Clipboard Ctrl C Save As bmp Chrl 4 Print Ctrl F Copy to Clipboard Selecting this option will copy the highlighted display to the Windows clipboard where it may be pasted in other Windows applications such as Paint Source 25 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Save As bmp Selecting this option opens a standard Save As utility in which you may save the contents ofthe highlighted display as a bitmap file bmp Print The Print option displays the standard printing screen in Windows The contents ofthe SOURCE display will be printed Prnt 3 HP DeskJet 870C hi Properties Status Default printer Ready Type HP DeskJet 8700 Where LPT Comment Copies Number of copies f Pages fom tof f Selection
33. ivision of Neurosoft Inc 45150 Business Court Suite 100 Sterling VA 20166 6707 Telephone 703 904 7875 Fax 703 904 7870 E mail techsup neuro com Web www neuro com Source 2 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Iuble of Contents INMFOCUGTIONIO SOU RG GE 5 stalling SOURCE E 6 Dipole Model Introduction ss 6 Single Dipole Models 6 Dipole CONS Ta T Multiple Signal Classification MUSIC 7 Operating SOURCE E 8 Modes ofOperation a i aiea 9 Use Tracking Mode for Gource 10 Use Interval Mode for Gource 10 SOURCE E Ee TE 12 SLICE Stat s Dal ntis otc soot dept utaris tips raso acr M un RU m QUUM eee 13 SIE ee EE 14 SLICE Help screen 15 Image Data arameierg 16 Position and Gcalmg 16 The Option menu for GOUIRCE nnne 18 RI Ie Ve ele d RUSO DE T 18 Lontourl mes 18 miele HI 19 Landmarks nee pi nanas EI MI EX PR A tata 20 Volume onduchor 20 Skin SKUI ana Bali EE 21 Source VWa vetormme 21 Deviations T l 22 MESURES X A 22 Boetium L 22 Min Max Gcalmg eene 22 Interpretnghefunchons 23 lu ee len EERRMMMERTA 23 Fixed view Doeitons nen 24 melee ce TE T T UN 24 DEL APTE RE a 24 Movie Rotation options 25 OW Gia C 25 Save Movie As 25 miele ET TEL a Ga ae 25 Save Rotation
34. kground window for example the SOURCE or SLICE display will stick to it This option provides a little more control over the presence absence ofthe displays Notice the presence of the Stickyness button at the tops of the SOURCE and All of the operations may be accessed with the mouse Many have alternate key board controls and these can be very convenient such as simply pressing the M key to play the Movie or the R key to performthe Rotation Keyboard commands are displayed onthe rightside ofthe menu lists such as Contour Lines L Electrodes E Landmarks L Volume Conductor W Skin Sat Skull ARE Brain GAP Modes of Operation SOURCE has two modes of operation Tracking and Interval Click the right mouse button in the data display the original waveforms to see these options Source 9 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Use Tracking Mode for Source Use Interval Mode for Source Use Tracking Mode for Source When enabled if you move the mouse within the data display you will see the corresponding single dipole solution in the SOURCE and SLICE windows The dipoles are recomputed as the mouse is moved When Tracking Mode is disabled youneed to use the left mouse button to drag the cursor to the point ofinterest in the data file The corresponding dipole will be displayed in the SOURCE and SLICE windows Since these are all single time points you will not see Moving or Rotating dipoles You ma
35. l from noise or background activity periods Estimating the SNR from the MGFP together with the Deviations percentage can tell you ifthe chosen source modelis at least able to explain the signal part of your data The MGFP is computed as follows Let Si be the measured data i 1 n n electrodes fora given timepoint The common average C is C n Sum S1 the re referenced measured data Ri S1 C MGFP Sart 1 n Sum Ri R1 LOG MGFP Toggle this on to display the log of the MGFP values Min Max Scaling Min Max Scaling Alt M allows you to switch between autoscaled Minimum Maximum scales for all traces andacommon scale for all dipole loadings strengths and 0 Maximum scaling for the other traces Deviations and MGFP Inthe example below 3 Fixed coh dipoles were calculated and Min Max Scaling was enabled The strengths of the 3 dipoles are displayed separately and are color coded with the dipoles in the fitted display Grab the vertical green cursor with the left mouse button to drag it to any desired location note that the Source display will show the results for the corresponding time point You may also use the left and right arrows from the keyboard to move the cursor If you disable Min Max Scaling the Source waveforms will be superimposed with a common scaling Source 22 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA SOURCE V1 U epispike with 3dd lag nAm oS wis w
36. ll time points is fitted and the dipole strengths for every time pointare calculated If more than one dipole is fitted they will all have coherent loadings sametemporal behavior Source 28 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Fixed MUSIC Forfixed MUSIC dipoles the dipoles are fitted recursively using the MUSIC metric thus coherent sources cannot be separated The results inthis example are virtually identical to the Fixed coh model Number of Dipoles The number of fitted dipoles can be adjusted for moving dipoles without mirror constraint only one dipole is possible Min distance mm For more than one dipole a minimum distance between the dipole positions can be chosen to avoid strong opposing cancelling source configurations Seed distance mm The seed distance is the maximum distance from the start point seed ofthe dipole fit Currently no start position algorithm is used therefore you should not modify the default value Mirrored yz plane The Mirrored field forces two mirrored source positions at the yz plane midsagittal Ifno landmarks are specified then the mirror plane normalis parallel to the left right axis ofthe original coordinate system notthe PAN system This constraint cannot be applied when using the Fixed MUSIC model Source 29 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Source 30 Threshold The Threshold field is
37. ly 8 or 12 of 16 bits are actually used This can be accounted for by this setting Swap Bytes Image data can be stored in MOTOROLA or INTEL byte order depending on the raw data processing machine Byte order can be toggled by this setting Offset Header Size Bytes Each slice of the image data often contains a header of a defined size e g ACR NEMA data The set number of bytes will be skipped The size of the header can in most cases be calculated from the file size S where the size of one slices S No of Slices Bytes Header size per slice H s No of Horizontal Pixels No of Vertical Pixels Bits per Pixel Theremaining fields are fairly self explanatory and display the number of pixels inthe horizontal and vertical axes the horizontal and vertical pixel size 1n mm s thetotal numberof slices and the distance thickness Slice Orientation Order These fields describethe sequence and orientation ofthe 2D raw data slices in their 3D context and are for the most part self explanatory Iso isthe8 Bits per Pixels isotropic data format Curry can generate and dump to disk Special care should be taken with the Invert X Right Left checkbox since without an image marker this can cause problems the effect of the other checkboxes shows up immediately Source 39 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Anatomical Landmarks mm Anatomical Landmarks are needed for coregistration of
38. mac h tp WAL neura Com neurazcan saurce htm The upper part of the display shows the XYZ coordinates for the Fitted Center in mm s the Radii in mm s forthe three concentric shells and the Conductivities for the three concentric shells The outermost shell the skin 1s fitted to all used electrodes and the inner shells are at 93 outer skull compartment and 85 inner skull or brain compartment of the outermostradius These values as well as the Conductivities can be overwritten manually described below The coordinate system for the Fitted Center is the same system used with the electrode position coordinates The lower part of the display describes the function of the mouse buttons and the mouse wheel Uses of the mouse buttons and wheel will be discussed more below SLICE Help screen A different Help screen will be shown if you select Help from the SLICE window right mouse options Source 15 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA SLICE Help Positioning and Scaling Image Data Parameters Field of view mm Ma of Slices m p E V z hee 201 6 hee 32 E E EENEURO SCAN LABS Oe OV PNebraso Ic http LP zw neura cam zneurascanzsaurce htm Press the left button of the mouse E 1 ta Set the cursor position in any of the three shice windows 2 to Retrieve the surface position in the rendered view Press the right button L 1 for Contest menu and
39. mation as described below Measured Modeled Source 17 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA The Option Menu for SOURCE Allofthe display and analysis options may be selected from the Option Menu seen by clicking the right mouse button within the SOURCE display Thereare some differentoptions thatare available if you click the right mouse button within the SLICE display Display k View k Movie ha Save Movie As Chl 0 Rotation 360 deg 1 P Save Rotation s Ctrl T Copy to Clipboard Ctrl C Save As bmp tre Print Ctrl F FAM Coordinates Alt P Help F1 Source Parameters P Display options The first twelve options let you select what information is to be displayed You may select any all ornone of the options selecting none of them displays the dipole solution only Display wv Contour Lines L View t w Electrodes E nume r pM Save Movie As ON E Rotation 360 deg bh w Skin Alt S Save Aotation s Chal Skull ARE Brai Alt B Copy To Clipboard Ctrl C i Save As bmp Ctri vw Source Waveforms WW Print Ctri P w Deviations 4 Alt D SS EEE Alte FAM Coordinates A r P LOG MEER Alben Help F1 Min Max Scaling Ath Source Parameters P Contour Lines The Contour lines are equipotential lines where the blue lines are negative voltages and the red lines are positive voltages The black line is the zero potential line So
40. n of using the SOURCE label matching algorithm or importing your own electrode position data If you use the default Match Labels option SOURCE will attempt to use your existing labels conventional extended 10 20 system nomenclature see Appendix A for placing and fitting your electrodes If you use conventional labels and do not have their 3D position coordinates select Match Labels and click OK Whenever possible you should use the actual measured electrode positions otherwise you may well introduce unnecessary systematic errors If you have the actual electrode position information forthe data file s you will be using click the Load Positions The next time you retrieve the same data file the Electrode Positions field will be active automatically You will see the following display Selectthe 3DD file created from 3 DSpaceDx that corresponds to your data file and then click the OK button Source 8 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Load 3dd file Ei Ea Look in E Demo Al ce Files of type 200 Files 3dd Cancel vee You will then see two new windows appear SOURCE and SLICE The Status bar at the bottom of the SOURCE display will show how many electrodes were matched label matching recognized 28 sensors if label matching was used Bi x SLICE displays When you push in the thumbtack the display will stick to whatever window is under it Ifyou minimize the bac
41. nd select Show Reference Now as you move the crosshairs around you will see the measurement line going from the current position to the reference point Measured distances are displayed atthe bottom of the display on the Status bar 0 9297 404 48 4 41 1 115 0 35 1 67 0 83 37 832mm The lastnumber is the distance in mm between the Reference pointand the cursor position Source 55 Copyright 2001 Neurosoft Inc Document number 2231 Revision A SLICE warm mg a ls R 0 9297 407 46 4 41 1 115 0 7 35 1 67 0 88 8 89 2mm Ue Set Nasion through Set Inion These options must be used when you are importing your own MR or CT data to indicate the locations of the landmarks To set the Nasion position the mouse cursor at the nasion on the rendered surface and click the left mouse button Source 36 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Masion In this example the nasion has already been registered Then click the right mouse button and select the Set Nasion option or use the Ctrl n combination keystrokes Change the view of the rendered surface to Left View and select the left preauricular point using the same procedure LPA Repeat the process to register all 5 landmarks Source 37 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Miscellaneous options These include Copy to Clipboard and Save As BMP and are Copy to Clipboard Ctrl C Save A
42. ng label seelistbelow will be used inthe source reconstruction non matching ones will be excluded Each line contains up to four equivalent electrode labels for aknown electrode position Where there is asingle label on a line no equivalent labels are recognized Numbers 41 46 are not used in source reconstruction l TP10 2 TP9 3 TP11 4 TP12 5 FT11 6 FT10 7 FT12 8 FT9 9 AF7 10 AF3 11 AFz 12 AF4 13 AF8 14 FT7 15 FC5 16 FC 17 FC 18 FCz 19 FC2 20 FC4 21 FC6 22 EIS 23 TP7 24 CP 25 CP3 26 CPI 27 CPz 28 CP2 29 CP4 30 CP6 31 TP8 32 PO7 33 PO3 34 POz T10 P10 T9 P9 T11 P11 T12 P12 FII TII F10 TIO F12 TI2 F9 T9 FPI F7 FP1 F3 AFZ FP2 F4 FP2 F8 F7 T3 F5 C5 F3 C3 FI CI FCZ F2 C2 F4 C4 F6 C6 F8 T4 T3 T5 C5 P5 C3 P3 CI P1 CPZ C2 P2 C4 P4 C6 P6 T4 T6 T5 OI P3 OI POZ Fpl F7 Fp1 F3 FPZ FZ Fp2 F4 Fp2 F8 F7 T7 FZ CZ F8 T8 T7 P7 CZ PZ T8 P8 P7 OI PZ OZ Fpz Fz Fz Cz Cz Pz Pz Oz Source 53 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA 35 36 37 38 39 40 XXX 41 XXX 42 XXX 43 XXX 44 XXX 45 XXX 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 71 78 79 Source 54 PO4 POS P05 P09 P010 P06 IOI IO2 SOI SO2 LOI LO2 O9 O10 CBI CB2 SPI SP2 Fpl Fp2 Fpz F11 F10 F12 T10 T11 T12 P10 P11 PI Pal Par OI O2 P7 P3 Pz P4 P8 T7
43. nicely The data exhibit very stable accurate and well localized focal sources atangential dipole at about 19 ms a radial dipole at about 21 ms and the early brainstem activity at about 14 ms Source 50 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA SOURCE LogFile SEP65 with 300 0 713 Lv 19 4 mz 13 4ms 0 ZT39 131 2 153 3 215 5mm 0 61 0 14 0 78 11 54n amp m 7 83 99 4 SE GE d Fa dr J a ue L sp Ta A m oU a a rr mg T 77 8 E Ee Ve r iei IMS D de dh e PORC RE KM My i Geen sar T VERO uL f r 4 Ki Ve D Vu E EN EC H Summary Theaboveexamples demonstrate some ofthe procedures and interpretational considerations that are used with SOURCE Depending on the model used there may be widely varying results Legitimate applications require careful consideration ofthe results validation of findings using different methods knowledge ofthe computational differences among the various methods and a supporting foundation of neuroanatomy andelectrophysiology For more information see the suggested references Source 51 Copyright 2001 Neurosoft Inc Document number 2231 Revision A Suggested REFERENCES for more information Scherg M von Cramon D Two bilateral sources ofthe late AEP as identified by aspatiotemporal dipole model Electroenceph clin Neurophysiol 1985 65 32 44 Scherg M Ebersole JS Models of brain sources Brain Topogr 1993 5 419 423 MosherJC
44. old to 75 to display only the most robust solutions DE EE s Pre ao m E oum aoe SOS we wf 5 ea e 7 D E d no 1 2c vw a cn e ERA S Quee cQt Eg Du t ae D D wx sl Toi z A ean ws em ps EE e E P Sr E ae lu s zl Ee D VE Fu LET es ee e Es a y ae 1 Ee VIN Se we ZP e m ME REN ERN P SO CIN Ae m us ate M Se wm ao E Ae sh oe ee E e d T Ae EAR a m E E z5 e al CRW Se Q t P r uu D EC aon T DE EN PL e o ew e a La aa RAN I ES e D BE Fart LIN NS Mg o x llc EL ek St arn SA dek V ECKE of ul elUIA EMI a DNE ML DI d H D L 2 D D D I D P ag D waa pta 7 1 a PF SEC RE z Sr ae tel D D n S Gu m Ca D G ee HN fe D DEA JEE En Ut nw AL m hie Ll Te ee m os s n QUI Fun Dale age i Ze Pata c e WE EE AE d VU Se gt an e Wi Poner AP NI TELS TAM zen em a Now we see a very interesting progression through the analysis interval Play the movie now and see the progression from inferior to relatively superior sites following the contour of the anteriortip ofthe left temporal lobe The SLICE display also points to the general anterior temporal lobe area Note that left and right are reversed on the SLICE display Source 44 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Ifwe compare these results to those ofthe prior analysis methods we see acorrelation among the dipole sources For example looking
45. r 2231 RevisionA
46. s bmpl Ctrl Help F1 thesameas described above underthe SOURCE right mouse options description The Help option displays the SLICE Help screen also described above Select Data The Select Data option allows you to import other MR files The standard Open File utility window will let you select IMG DAT orISO data files The Data Parameters display will appear see immediately below Data Parameters Clicking this option displays the Image Parameters window SLICE Image Parameters Image Data Parameters Bits per Pixel Ge iB C 12 C 16 Significant Bits g Swap Bites fo Offset Header Size Bytes 0 Ma of Fisel Horizontal 7 Vertical 108 Ma af Slices E Piselgize mm Horizontal 1 8 Vertical 1 8 Distance mm 1 2 Slice Onentation Order Sagittal Ge Axa Coronal Iso T Invert Right Left v Invert Front Back P Invert Z Bottom Up Anatomical Landmarks mm Mason e 4 3 28 8 Vertes e 4 93 6 fi 57 5 LFA 160 2 104 4 153 Irion 81 3 EA 42 3 RPA 3 6 104 4 153 Threshold Grayscale Threshold 40 Grayvalues Lower E Upper 255 If you are using the internal warped MRI data set that is compiled into the SLICE program these fields cannot be modified You will see an error message on the bottom ofthe SLICE window after pressing the Apply button saying cannot overwrite internal data parameters parameters can be edited stored for external image
47. s it may be that there 1s insufficient information to make an a priori decision as to which reconstruction method we should use In fact our prior experience indicates that a moving dipole is the best model to use in these instances but for the sake of demonstration letus assume we have no prior knowledge Select the interval between about 15 and 330ms to encompass the entire spike and slow wave interval For demonstration s sake we will apply the Fixed MUSIC model single dipole which should give goodresults fortemporally independent sources with fixed orientations Source 42 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA 584 m nam e HA e HK EET mug vdd K nn HEEL 61 6 E 31 25 uv ms NE ie al er he Over the entire interval we see a localization in the left frontotemporal lobe area Now look at the MGFP and Deviations results The MGFP is an averaged measure for the signal strength and thus the Signal to Noise Ratio or SNR One can easily distinguish latency ranges with meaningful signal from noise or background activity periods Estimating the SNR from the MGFP together with the Deviations percentage can tell you ifthe chosen source model is at least able to explain the signal part of your data For example assume an SNR of 10 10uV signal 1 uV noise then an adequate source model should be able to explain the signal part resulting in a residual deviation of about 10 Ifone has a better
48. suchas online averages or sorted averages There is currently no online application of SOURCE for continuous acquisition and Tracking mode is not available online Once acquisition has begun click the amp 1con from the Toolbar Make sure the desired window has the focus Then set the analysis interval and the functions are the same online as they are offline For an illustration we collected online binaural AEPs and computed the moving dipole solutions The waveforms after 100 sweeps appeared as follows Source 40 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA The SOURCE solution for the approximate 1 10 260ms span appeared as Measured Modeled RE pee o F a andthe SLICE display appeared as follows The dipole solutions were apparent early in the recording after about 14 sweeps coincident with the appearance ofthe components in the online average Source 41 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Some tips for using SOURCE Note If you apply transforms in EDIT to the same data file that is being used in SOURCE the transforms will NOT be transferred to the file in SOURCE Users new to source reconstruction techniques typically ask questions like Which dipole model do I use with my data How do I know what options to use and what settings to select How do I interpret the results from the Source Waveform Deviations and MGFP
49. t in the interval The tenth number is the fit quality in Vo residual standard deviation Square that number 9 9 100 2 approx 1 and subtract it from 100 to get the explained variance The final number is the explained variance SLICE Status Bar The Status bar at the bottom ofthe SLICE display has the following series ofnumbers 0 9997 40 99 4 103 3 20 97 16 9 1 9 5 3 4144 4mm The first number is the Scaling factor or the number of screen pixels per mm This can be changed by resizing the size of the whole window or by clicking the right mouse inside the SLICE display and selecting Scale 2 0 to go to the larger size window There isa slight rounding that may occur a Scale of 1 may really be 999 as in the example above The second number is the threshold value for surface rendering in rendering mode This can be changed by rotating the mouse wheel or by holding down the right mouse button while moving the cursor If you are in Maximum IP mode this number 1s the grayscale value also may be changed by rotating the mouse wheel or by holding down the right mouse button while moving the cursor Both ofthese numbers may be set from the Image Parameters screen right click in the SLICE window and select Data Parameters Threshold Grayscale Threshold ES Grayvalues Lower jo Upper 241 The next three numbers are the x y z coordinates in the image coordinate system mm X right gt left y front gt back z
50. tee Lancel PAN Coordinates The PAN Coordinates toggle PreAuricular points Nasion allows you to switch between the PAN system assuming that at least the left and right preauricular points and nasion have been recorded and the original coordinate system the electrodes and the landmarks Inthe PAN system the x axis goes from the left to the right preauricular point The y axis goes from the inion to the nasion and is perpendicular to the x axis pointing to the front of the head and intersecting PAL PAR at the halfway point The z axis points upwards and is perpendicular to the x and y axes Enable the option and see the changes in the dipole position and orientation in the status bar at the bottom of the SOURCE display FAM Coordinates Alt P Help Clicking the Help option displays the Help screen described above Source 26 Copyright 2001 Neurosoft Inc Help F1 Document number 2231 RevisionA Source Parameters The Source Parameters Source Parameters P display isthe screen where you select the dipole model that you wish to use as well as other parameters Source Parameters C fixed coh fixed MUSIC number af dipoles min distance mm seed distance mm 1 5 200 mirored vz plane atl threshold 72 volume conductor model relative radi 5 three spherical shells UU E E PEM Sunnie conductivittes 5 m C BEM tides 0 33 0 0042 0 33 C Sealed
51. the anatomical image data with the functional data EEG The five landmarks have to be set by using the Set Nasion through Set Inion items described above on the SLICE options menu click the right mouse inside the SLICE window oruse the keyboard combination strokes The actual cursor position will be taken and the coordinates will be transferred to the parameters window When all five landmarks are setand Apply is pressed the 1mp file will be overwritten and the image data will be reloaded You are now ready to display electrodes and reconstruction results in SOURCE Threshold Grayscale The Threshold Grayscale parameters are the initial settings for the surface rendering and graylevel scaling of the MR CT images These can also be modified interactively by the mouse wheel with and without the Shift key The Apply button saves the settings to the 1mp file image parameters and reloads the image data using these parameters Note You may select or vary any of the options in the SLICE Image Parameters display and see the effects by clicking Apply without closing the Parameters window The Options menu right mouse button will remain accessible while the SLICE Parameters display is seen Online SOURCE The information above has described the functions of SOURCE in offline processing Itis also possible to use most of the same features during online acquisition SOURCE can be used with any online Multiple Window Display
52. urce 18 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA The Contour Interval can be varied by clickingthe right mouse button to see the Option Menu then selecting Source Parameters then changing the interval using the up and down arrows in the Contour Interval region 20 contour incr uv Click Apply to see the new contours you do not have to close the Parameters window An easier way is to just use the up and down arrows on the keyboard to change the contour interval Electrodes Enablingthis option will display the positions ofthe electrodes green dots ENER EC AACHEN EE Be Ee E E e e ir ae r Mor en mt e La UR A x E Dee WTA d e e zw BA Se ui m zer ech e r3 SC te s s a de CH d T MET us Mu D s n M a na og a oaa D w ETUR e E o n To o I o8 uu ota n D BC eg 2 E DH eo Qt ai z E Se e ee m DM dote wo Fier a mt PP EUM Inthe picture above the Skin was enabled also to provide a source ofreference Source 19 Copyright 2001 Neurosoft Inc Document number 2231 Revision A Landmarks Enabling this option will display the PAN and other Landmarks if any vertex andinion The figure below shows the left and right preauricular points and the nasion blue dots PRE lf rx cen da y p Ab a v PET WA SNO DC ECH ZH o Dtm P pri a ZS DM id P E S Ni kW W EA D HI Ua eU e ram Qus c oW Dil ET moat eee te RK uw a Ka n ot ee ped
53. view selection 2 to Set the segmentation threshold in rendering mode 3 ta Modify the gray level scaling in M asimuml P made Move the mouse wheel 1 ta Set the segmentation threshold in rendering mode b 2 to Modify the gray level scaling in MaximumlP mode press Shift for lower level modification Image Data Parameters This group of fields displays the maximum value for the Field of View mm for the three axes and it displays the number of slices along each axis Positioning and Scaling The information summarizes the functions of the left and right mouse buttons andthe mouse wheel Source 16 Left mouse button The left mouse is used primarily to position the crosshairs in any of the three slice windows Click it in the rendered view the lower right image to set the crosshair on a desired point on the surface Right mouse button The right mouse button is used to display the Option menu for the SLICE window described in more detail below Itis also used in place ofthe mouse wheel For example click and hold the right button down in the SLICE rendered view and then move the mouse to adjust the segmentation threshold see the next figure In Maximum IP mode the same operation will modify the gray level scaling Mouse wheel Rotate the mouse wheel to vary the segmentation threshold in the renderedimage The default settings are correct for the generic head shape however if you import your own MRI data you may fin
54. was disabled so all three source waveforms will be superimposed Source 21 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Deviations o The Deviations D or standard deviation is a measure for the fit quality how well the source model explains the measured data Itis the middle region on the leftin the figure above Notice that the Y axis is inverted that is the numbers get smaller as you go higher on the graph Dis the root mean square of the difference between measured R1 and calculated signals F1 D sart 1 n sum CRI Fiy Ri Fig MGFP Sgt Sum HRI Fi Ri Fi sum CRI Ri normalized for the measured field MGFP which corresponds better to the Signal to Noise ratio SNR than variances The residual or rest variance V 1s simply the square of the standard deviation V D D Sum Ri Fi Ri Fi Sum Ri Ri The explained variance is minus the residual variance EV 7 1 V MGFP uV MGFP mean global field power is a commonly used measure to enable a quick overview ofthe measured EEG time courses since it collapses the information ofall electrodes into a single trace Itis displayed in the lower region on the leftinthe figure above As the name suggests the MGFP is an average ofthe common average re referenced data The MGFP is anaveraged measure forthe signal strength and thus the Signal to Noise Ratio or SNR One can easily distinguish latency ranges with meaningful signa
55. y selectto compute multiple dipoles with the Rotating and Fixed coh models see the Source Parameters discussion below for more details about selecting dipole methods Use Interval Mode for Source When enabled you may select the interval for analysis With Interval Mode all of the dipole analysis methods are possible see the Source Parameters section below There are slight differences in how the interval is selected among the types of data files Setting the Interval for AVG or EEG files With AVG or EEG files you will see that there are two additional vertical cursors in the data display window initially they may be superimposed Use the left mouse to grab and drag them If both cursors move together one will be dropped when youreverse direction Note one of the electrode channels must be enlarged to mid size or full size to see the cursors 1 54 mz 52 70 ms 200 0 200 0 100 0 UV UU 100 0 200 0 300 0 400 0 500 0 400 0 300 0 200 0 100 0 UU 1000 200 0 300 0 400 0 me Source 10 Copyright 2001 Neurosoft Inc Document number 2231 RevisionA Thecursor positions may be controlled by the mouse or by the arrow keys on the keyboard The arrow keys by themselves move the left cursor Using the Shift arrow keys moves theright cursor The Ctrl arrow keys will move both cursors together keeping the same interval between them When you have retrieved an EEG file and you wish to

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