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EEG_Biopac Lesson L04

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    ...;~;:~~1;;': \ " ! : - : . , ; < G . r . 1 1 : ~ ~ ~ t~ \ t. : ~ : .~ . : : : . '\ ' , ~ ,, ~ ' \ \ ~ '~ ~ ~. \ ' . '~ : - ~ . ~ . : \: : : . >~ , . .

    ;~:. jO~~'Sttin~E "If-: ' .. ..:~~\~:I

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    Page 14v. DATA ANALYSIS.. F~ST TRAC~ Data Anf l iY!> is ....

    I. .E n t e i . t h e ~~~ewSavei"b.~~ ()d~~-..~.~~

    Note Channel Number(CH), -.desigrtatioris: ......

    .Channel Displays ... .CHI RawEEGCH40 alphaen 41 alpha RMS

    2. Setup your display windowforoptimalviewing of the entire recording:

    3. Set up the measurement boxes asfoUows:Channel Measurementcn I stddevCH40 stddevCH41 meanCH40 Freq

    I nata Anal~'sis continues ...

    Biopac S tuden t Lab

    Detailed Explanation of StepsEnter the Review Saved Data mode from the Lessons menu.

    The data window should come up the same as Fig. 4.10.0 i& ... WllllamM-L04 .

    , .~. ~a ~. [!].....).!J4~ olphoRnS open ~ = - L4ii'"0 v -0 0000 ~,2 0 0000 ~0

    ".,..J'~ t\ ~"""'V./\l ~0 00000000' 'J "7 ?5 -4/)5 j8 ?4. 0110.'K"'":)1 ~ .1'2Fig 4.10

    The following tools help you adjust the data window: WAutoscale horizontal Zoom PreviousAutoscale waveforms Horizontal(Time) Scroll BarZoom Tool Vertical (Amplitude) Scroll BarTurn Grids ON and OFF by choosing Preferences from theFile menu.

    The measurement boxes are above the marker region in the datawindow. Each measurement has three sections: channel number,measurement type. and result. The first two sections are pull-down menus that are activated when you click on them.Brief definition of measurements: iW

    stddev: standard deviation will be higher if there is a lot ofactivity and lower if there is less. The advantage of the stddevmeasurement is that extreme values or artifacts do not undulyinfluence the measurement.mean: displays the average value in the selected area.Freq: converts the time segment of the selected area tofrequency in cycles per second

    Note: The Freq measurement applies to all channels sinceit is calculated from the horizontal time scale.

    The "selected area" is the area selected by the I-beam tool(including the endpoints).

    I

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    Page 2 Lesson 3: EEG I Biopac Student

    I. INTRODUCTIONThe brain is encased by the cranium, bones of the skull which immediately cover and protectbrain surfaces. A thin cover of skin, called the scalp, covers most of the cranium. The largest partof the brain immediately beneath the bones of the cranium is the cerebral cortex. The cerebralcortex is composed of nerve cells (neurons), many of which are functionally connected to eachother. and connected to other parts of the brain. Electrical activity in the form of nerve impulsesbeing sent and received to and from cortical neurons is always present even during sleep. In abiological sense (as well as a medical or legal sense), absence of electrical activity in the humancerebral cortex signifies death.Functions of the cerebral cortex include abstract thought reasoning, voluntary and involuntarycontrol of skeletal muscle, and the recognition and differentiation of somatic, visceral. andspecial sensory stimuli. Specific regions of the cerebral cortex process or generate various kindsof information. For example, the occipital lobe processes visual information while the parietallobe processes somatosensory information such as cutaneous pain or temperature (Fig 3.1).

    C entral sulcusFrontal lobe Parietal lobe

    O ccipital lobe

    CerebellumTem poral lobe

    Fig 3.1 Regions of the brainThe sensory information is relayed from the periphery through lower centers in the brain, andthen the information is sent to various regions of the cerebral cortex. Since the cerebral cortex isjust under the cranium, electrodes placed on the scalp above the various regions of the brain candetect the electrical activity associated with functioning neurons. The recording of the brain'sactivity obtained by using electrodes is called electroencephalogram or EEG (electro =electrical. cnce pheh: = brain. gram = record).An ITer electrode will mainly detect the activity in the brain region just under it. Nevertheless,the electrodes receive the activity trom thousands of neurons. In fact. one square millimeter ofcortex has more than 100,000 neurons. Since each region of the cerebral cortex of an alert personis busy receiving, integrating. and sending many impulses. this activity is detected in the IT(I.(For more information about waveforms. see the Orientation chapter.)

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    Page 4 Lesson 3: EEG I Biopac Student L

    BetaBeta rhythms occur in individuals who are alert and attentive to external stimuli or exert specificmental effort, or paradoxically, beta rhythms also occur during deep sleep, REM (Rapid EyeMovement) sleep when the eyes switch back and forth. Notice that the amplitude of beta rhythmstends to be lower than for alpha rhythms. This does not mean that there is less electrical activity,rather that the "positive" and "negative" activities are starting to counterbalance so that the sumof the electrical activity is less. Thus, instead of getting the wave-like synchronized pattern ofalpha waves, desynchronization or alpha block occurs. So, the beta wave represents arousal ofthe cortex to a higher state of alertness or tension. It may also be associated with "remembering"or retrieving memories.Delta and ThetaDelta and theta rhythms are low-frequency EEG patterns that increase during sleep in the normaladult. As people move from lighter to deeper stages of sleep (prior to REM sleep), the occurrenceof alpha waves diminishes and is gradually replaced by the lower frequency theta and then deltarhythms.Although delta and theta rhythms are generally most prominent during sleep, there are caseswhen delta and theta rhythms are recorded from individuals who are awake. For example. thetawaves will occur for brief intervals during emotional responses to frustrating events or situations.Delta waves may increase during difficult mental activities requiring concentration. In general.the occurrence and amplitudes of delta and theta rhythms are highly variable within and betweenindividuals.Electrode positionsElectrode positions have been named according to the brain region below that area of the scalp:frontal. central (sulcus). parietal. temporal. and occipital. In the bipolar method. the EEG ismeasured from a pair of scalp electrodes. The pair of electrodes measures the difference inelectrical potential (voltage) between their two positions above the brain. A third electrode is puton the earlobe as a point of reference. 'ground". of the body's baseline voltage due to otherelectrical activities within the body. In todays lesson. you will record an ErG using the bipolarmethod.

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    Page 2 B iopac Student LabI. INTRODUCTIONThe brain constantly receives sensory input and integrates the information. The sensory infonnation isrelayed from the periphery through lower centers in the brain, and then the information is sent to specificregions of the cerebral cortex where it is processed. For example, the occipital lobe processes visualinformation while the parietal lobe processes non-visual. sensory information such as cutaneous pain(Fig 4.1). If you choose to, you can direct your attention to particular bits of sensory information: you canaccess memories associated with the sensory information: or you can selectively ignore this sensoryinput.

    Central sulcusFrontal lobe Parietal lobe

    Occipital lobeTemporal lobe

    Fig.4.1The blood/brain barrier separates cerebral spinal fluid from the blood. Oxygen. glucose. and carbondioxide can cross the blood/brain barrier, but the hydrogen ion can not. The brain requires oxygen andglucose for energy. Without a relatively constant source of oxygen and glucose. the brain ceases tofunction. Levels of carbon dioxide in the spinal fluid can change the pH of the spinal fluid, which can inturn change the body's respiration rate.Because brain activity is related to ions and charge movement. this activity can be detected byelectrodes. The record of the brain's activity is called an electroencephalogram (EEG) from the rootwords of electro (electrical), encephala (brain). and ~"(/II/ (record).The EEG records the electrical activity on the surface of the cerebral cortex. The EEG is complex andvariable between adults, although under certain conditions, the EEG exhibits simpler. rhythmic activity.Simpler patterns in the EEG occur when many cells synchronize their input to the surface of the cerebralcortex. The more synchronized the charge movement. the more rhythmic the EEG.~ Your EEG changes as you grow. The development of EEG is rapid with newborns. As

    \ neural development proceeds, the EEG recorded from the posterior regions of the brain- of an infant of 3-4 months begins to resemble EEGs recorded from the posterior region ofadults. The difference is that the 3-4 month old infants have EEGs in the frequency rangeof 3-4 Hz, whereas adults tend to have average frequencies of 10Hz. By the time theinfant is one year old, the posterior region EEG is approximately 6 Hz, by three years, 8Hz, and by 13-14 years (puberty), the average frequency is 10 Hz (similar to adults).One of the simpler patterns is the alpha rhythm. The alpha rhythm is characterized by a frequency of 8-IJ Hz and amplitudes of 20-200 pV. Each region of the brain has a characterist ic frequency of alpharhythm. Alpha waves of the greatest amplitude tend III he recorded from the occipital and parietal regionsof the cerebra I cortex.

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    Lesson 4: EEG II Page 3Just as the EEG is variable depending on the mental state of an individual, the frequency and amplitudeof alpha rhythms within an individual change. In general, the alpha rhythm is the prominent EEG wavepattern of an adult in a relaxed, inattentive state with eyes closed.More specific conditions of alpha rhythms are listed below:

    > - Hyperventilation (breathing abnormally quickly and deeply) causes the gascomposition of the blood to change. During hyperventilation, the carbon dioxidelevels of the blood fall, pH levels increase, and blood pressure decreases. Theseeffects of hyperventilation are associated with changes in brainwave activity. Withhyperventilation, the overall electrical activity of the brain increases, with theamplitude of the alpha rhythms often increasing as well.

    > - Females tend to have higher mean frequencies of alpha waves than males, althoughthe differences are small.

    ); > Frequency may affect the speed of "remembering" during memory tests and may beapproximately I Hz higher for high-scoring subjects than subjects who scored lower.

    , Amplitudes tend to be higher in subjects who are more "outgoing" and extroverted.~ Amplitudes vary with the difficulty of mental tasks performed with the eyes closed., Amplitudes of alpha waves dim inish when subjects open their eyes and are attentive

    to external stimuli. Thus, instead of getting the wave-like synchronized pattern ofalpha waves, desynchronization occurs .

    ., Amplitudes increase when subjects are less alert and tend to be higher from 1:30-4:30 p.m.

    In this lesson, you will record the EEG and alpha rhythm under several conditions. At the same time. theroot-mean-squared of the alpha rhythm (aJpha-RMS) and an "alpha thermometer" will be displayed.Alpha-RMS and the "alpha thermometer" are indices of the activity levels of the alpha rhythm.

    II. EXPERIMENTAL OBJECTIVESI) To record an EEG from an awake. resting subject under the following conditions:

    a) Relaxed with eyes closed:b) Performing mental arithmetic with eyes closed:c) Hyperventilating (breathing quickly and deeply) with eyes closed:d) Relaxed with eyes open.

    2) To examine differences in the level of alpha rhythm activity during mental arithmetic andhyperventilation. compared to the control condition of eyes closed and relaxed.

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    Page 4 Biopac Student Lab

    III. MATERIALS~ BIOPAC electrode lead set (SS2L),. BIOPAC disposable vinyl electrodes (EL503), 3 electrodes per subject,. BIOPAC electrode gel (GEL I) and abrasive pad (ELPAD)

    or

    Skin cleanser or alcohol prep,. Lycra" swim cap (such as Speedo" brand) or supportive wrap (such as 3M Coban"

    Self-adhering Support Wrap) to press electrodes against head for improved contact.;- Cot or lab table and pillow,. Computer system., Biopac Student Lab software v3.6.7 PC or v3.0.7 Mac or greater., BIOPAC acquisition unit (MP30),. BIOPAC wall transformer (ACIOOA)., BIOPAC serial cable (CBLSERA) or USB cable (USB IW) if using a USB port.

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    Lesson 4: EEG II Page 5IV. EXPERIMENTAL METHODS

    Overview) 0 > As you complete the Experimental Methods (Set Up, Calibration, and Recording) and the Analysis,

    you may need to use the following tools and/or display options. The window display shown below isonly a reference sample - it does not represent any lesson specific data. The sample screen shows 3channels of data and four channel measurement boxes, but your screen display may vary betweenlessons and at different points within the same lesson.

    channel measurement boxes(channcl e measurementrype resuh) marker marker tools

    channel boxes(Data analysis Illude only)

    JohnB.102

    marker labelJ Jl J.3 P"

    -, 00

    o vertical scales1 _ . . . 1859t~

    I !J!i r:orc.~.

    ~~~------------------~ooo._~,. I,

    -, 00 '< 'I~~.~ . . c:orods ra eeo

    vertical (amplitude)scroll bar

    ~~-------------------~-ooooo4IJOOOO~

    channel labels ~.~------------------~ooo

    " , j = :' ; : ...-: ..- :~~,. >UO

    ... ",:,,: :.: .::.,.1':

    horizontal (time) scroll har selection tool zoom toolhorizontal scale I-Beam cursor

    , The symbols explained below are used throughout Experimental Methods and Analysis.Key to Symbols

    m If you encounter a problem or need further explanation of a concept. refer to theOrientation Chapter for more details.! I i l I The data collected in the associated step needs to be recorded in the Data Report (in thesection indicated by the alpha character). You can record the data individually by hand orchoose Edit> Journal> Paste measurements to paste the data to your journal for futurereference.

    V Most markers and labels are automatic. Markers appear at the top of the window asinverted triangles. This symbol is used to indicate that you need to insert a marker and keyin a marker label similar to the text in quotes. You can insert and label the marker duringor after acquisition. On a Mac. press "ESC" and on a Pt,',press "F9:'

    , Each section is presented in a two-column format. as described below.FAST TRACK STEPS

    This side of the lesson (left, shadedcolumn) is the "fAST TRACK"through the lesson, which contains abasic explanation of each step.

    DETAILED EXPLANATION OF STEPSThis side of the lesson contains more detailedinformation to clarify the steps and/or concepts in theFAST TRACK. and may include reference diagrams.illustrations. and screen shots.

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    A. SET UPPage 6 Biopac Student Lab

    .'. 't-~~. - .Y - .. < : ; t ~ ~ ; > . : ~ ( : -. .: ; . , : . , . . r . .. _-T~ritjlieM~J,OData:'Atquisition Unit ..O N . : ' . ' - . - / y - -

    5. H a v e thesubject assume a relaxing .position.

    6, Position electrodes on the scalp. Fig4.3 shows a sample configuration.

    ~==IMPORT AN~T~~I~IElectrode adhesion to the scalp iscrucial for obtaining a meaningfulEEG recording.

    liiiiiiiiiiiiiiSiil'iitiil;;;;illii;)iciioiiniitiiinii"iil'iisii'ii'iiiiiiiiiiiiil

    Detailed Explanation of Set Up StepsThe desktop should appear on the monitor. If it does notappear. ask the laboratory instructor for assistance. W

    Plugs into Channel I

    SS2L Electrode Lead SetFig. 4.2

    A supine position with the head resting comfortably buttilted to one side is recommended. The best recordings occurwhen the subject is relaxed throughout the session.

    RED Lead

    Fig. 4.3Hints for obtaining optim al data:

    I. As much as possible. move the hair

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    Lesson 4: EEG II

    11. Choose Lesson 4 (L04-E .EG. ; .2 ) .:. . ", : : " ' . ": .

    12. Type in your filen~e.! ,"

    13. Click OK.I _ __ N _ D _ O _ F _ S _ E _ T_ _ U _ P ~ _ I

    Page 75. Wrap the subject's head to secure electrode placement.

    Guidelines for electrode placement: Wa) The placement of the scalp electrodes can vary (within

    limits) depending on your instructor's or the subject'spreference.

    b) Keep the electrodes on one side (right or left) of thehead.

    c) For this lesson, you will focus on the occipital lobe, andshould use a placement similar to Fig. 4.3.

    d) The third electrode is the ground electrode and isconnected to the earlobe (position "c"), Although theadhesive collar is larger than the earlobe, it can befolded under the ear for proper adhesion. Alternately,the ground electrode can be placed on the facial skinbehind the earlobe.

    The pinch connectors work like a small clothespin, but onlylatch onto the nipple of the electrode from one side of theconnector.Drape the electrode cables over the head so that they are notpulling on the electrodes.Place a Lycra" swim cap or supportive wrap on the Subject'shead to press the electrodes against the scalp with a constantpressure. Subject should not hold electrodes against scalp.Ideally, the room should be reasonably quiet to help thesubject mentally relax. This 5-minute period is alsoimportant to give the electrodes time to establish contactwith the surface of the skin.wwUse a unique idcntificr.lWThis ends the Set Up procedure.

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    B. CALIBRATIONPage 8 Biopac Student Lab

    The Calibration procedure establishes the hardwares internal parameters (such as gain, offset, andscaling) and is critical for optimum performance. Pay close attention to the Calibration procedure.

    :'.'. -' ~/"-. . " t-..

    .....::: : J ~ ' \ :...'.< ~~ i

    .. :J.... j:..

    i.: .. i f t ~ '.

    ~ If similar. proceed to th e.DataRecording section.

    ~ If different, Redo Calibration.

    I END OF CALIBRATION I

    Detailed Explanation of Steps

    The Calibrate button is in the upper left comer of the Setupwindow.A window will pop up, requesting that you check the electrodeattachments one last time.This will begin the calibration procedure. The BIOPAC StudentLab will begin recording data and use it to calculate optimalsettings for the subject. The calibration procedure will stopautomatically after 8 seconds.At the end of the 8-sec calibration recording, your screen shouldresemble Fig. 4.4.n 104-((6-1

    R.,ord] I RedoCalibration 11000

    500 0

    ~ ~ - - - - - - - - - - - - - - - - - - - - - - - -- - - - - - - - - - ~ o o o o-500 0

    -100000 00 .00 l'I 110.

    I(

    Fig. 4.4There should be a relatively flat line (as in Fig. 4.4).

    If the data shows any large spikes, then you must redocalibration by clicking on the Redo Calibration button andrepeating the entire calibration sequence.

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    Lesson 4: EEG II Page 9C. RECORDING LESSON DATA

    -"00

    liiiiiiiiiiiiRiiiiieiiciioiirdiiiiiin;;igi;;;;;;ciioiiniitiiiniiuiieiisii 'i i"iiiiiiiiii;;;;i~

    Detailed Explanation of StepsYou will record the Subject in four conditions: the Subject willperform tasks in the intervals between recordings.

    Segment I - Relaxed with eyes closedSegment 2 - Performing mental math with eyes closedSegment 3 - Recovering from hyperventilation with eyes

    closedSegment 4 - Relaxed with eyes open.

    In order to work efficiently, read this entire section so you willknow what to do for each recording segment.The Subject should remain in a supine position and continue torelax while you review' the lesson.Check the last line of the journal and note the total amount oftime available for the recording. Stop each recording segment assoon as possible so you don't use an excessive amount of time(time is memory). rnHintsfor obtaining optimal data:

    a) It is important that you pay attention to the specificinstructions for each recording segment.

    b) Good electrode contact is essential to minimize noiseand increase signal amplitude.

    c) The Subject should lie still and should not blink duringthe "eyes open" segment. Best results are obtained if theeyes remain still at all times.

    d) The Subject should not talk during any of the recordingsegments. and should not verbalize answers to themental arithmetic.

    e) The alpha signal will be increased during the relaxationsegment if the Subject concentrates on breathing slowlyand/or relaxing muscles.

    t) For the mental math segment: the Director shouldprepare by coming up with a math problem beforerecording begins. The math problem should bechallenging but not too difficult. e.g. take the numbertwo and double it. double again. double again. divide bythree. multiply by f i f teen. divide by seven. multiply bytwelve. The point is to make the Subject really work toget the answer. not to stump the Subject or make themgive up. The math problem should require a minimum oftwenty seconds.

    g) Before the recovery from hyperventilation segment: theSubject should breath quickly and deeply for twominutes. as if they had just finished exercising andneeded air. The Subject should not be hyperventilatingduring the recording.

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    Page 10

    . " .:;/.: ~/ ; ~ ; { 'y ! , i\,f ..........~,~,,~.~:~::.~.. . ".:. i.";

    3. .R eco rd fo r 1 0 se co nd s.l. -.'4. : C lic k on Suspend.5:.' R eview the data on the screen.

    ~; .If cotrect, go to Step 6.".a,.

    ~ If in co rre ct, c lic k o n Redo.

    I Recording continues.,; ~~~~

    Biopac Student LabSubject relaxed with eyes closed (Control)The recording will begin.

    Note: The graph window will resize and the Input valueswindow will appear on the right side of the graph window.The Input values window displays the alpha-RMS value inthermometer-like bar display. and can be used as a visual aidto determine fluctuations in alpha-RMS activity. It is onlydisplayed when data is recorded, and does not show in theReview Saved Data mode.

    llOi! Input lJolues ~0~

    Fig. 4.5Subject should be relaxed with eyes closed (seconds 0-10).The recording should halt. giving you time to review the dataand prepare for the next recording segment.If all went well. your data should look similar to Fig. 4.6 andyou can proceed to Step 6.;0 l04 [(6 2 0IResumel ~ ~

    sc n ncoe 1 = [ S C l n o n . ) = J I n o n . I =141~I'"'t' -0 00 ~r i ; !i

    0s: -0.0000 ~0

    20.00~ J- - - - - - - - - ,0 --------- 0.0001000 soo '00 '50 L"III~econdsI IQI ell;}]

    Fig. 4.6 Relaxed. Eyes ClosedThe data would be incorrect if:

    a) the suspend button was pressed prematurelyb) an electrode peeled up causing a large baseline drift.

    spike. or loss of signal.c) the subject did not follow the proper procedure.d) The subject had too much EMG artifact.

    In this case. you should redo the recording. by clicking. on"Redo" and repeating Steps 2-5. Note that once you press Redthe data you have just recorded will be erased.

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    Segment J12. Director.~~v!~ .,~~~~t~ :.~ ~ ,~.:.. _

    hyperven~~a~~ -(

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    Lesson 4: EEG II

    2l. Remove th e e le ct ro de s.

    I END OF RECORDING I

    Page 13Eyes OpenDirector should advise Subject to open his/her eyes.Subject should remain relaxed but open his/her eyes.The recording will continue from the point where it last stopped,and a marker will automatically come up when Resume ispressed, but the Recorder needs to key in the marker "EyesOpen" label.Subject should be in a relaxed state with eyes open and try tonot blink.The recording should halt.Ifall went well, your data should look similar to the Fig. 4.9 andyou can proceed to Step 22.lD L04-EEG-2 0-IResumel~~

    sc Io , . . 1 = [ S C ) n o n . J = [ S C ) n o n . J =ey~ open - 1 4 I~O Yo f ~ , . . . . . . . 000 :>~- 'V ~0s:

    -0.0000 3pti 20.00 3~I~~ ~ 0.000 0 0 -

    35.0 40.0 450 ;)UU nII~econds I elQ:Fig. 4.9 Relaxed, Eyes Open

    The data would be incorrect for the reasons in Step 5.If incorrect, you should redo the recording by clicking on"Redo" and repeating Steps 18-21. Note that once you pressRedo, the data you have just recorded will be erased.A pop-up window with four options will appear. Make yourchoice, and continue as directed.If choosing the "Record from another subject" option:

    a) Attach electrodes per Set Up Step 5 and continue theentire lesson from Set Up Step 8.

    b) Each person will need to use a unique file name.Remove the electrode cable pinch connectors, and peel off theelectrodes. Throw out the electrodes (BIOPAC electrodes arenot reusable). Wash the electrode gel residue from the skin,using soap and water. The electrodes may leave a slight ring onthe skin for a few hours. This is normal, and does not indicatethat anything is wrong.

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    Lesson 4: EEG II Page 15Fig. 4.11 shows an example of the selected area. The first datasegment is the area from Time 0 to the first marker..0 lllilllamM-L04

    '..> e a c h of~e d a ~ Segm~nts.. ..1;'_~... . : ; ~ : J j [ ; . ' ; i : ' - ' , ; f ' .6 '. z o G n i m onsma l f'secnoiioftheS~gm~qt l ( i~ t4;,::, , .7:' U~th~'I:'Beamcursor toselect an areafromone ~ak to the n e x t in t h e alphaband [ell 40]. .IllB

    8. Save or print the data file.

    9. Exit the program.

    I END OF DATA ANALYSIS I

    Fig.4.11

    Be sure to zoom in far enough so that you can easily measure thefrequency of the alpha wave.Fig. 4.12 shows a sample setup for measuring the frequency inthe alpha band [CH 40]..0 WllliamM104 - __

    -.-.~~- - ~''oooo=-----T:OO=--~i7-'i-seco-cs

    Fig.4.12YOll may save the data to a floppy drive. save notes that are inthe journal. or print the data file. W i

    ENIl OF LESSON 4Complete the Lesson 4 Data Report that follows.


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