MoBI: EEG

This page is under construction

Under the Purview of Rita Beransky

Overview

Hardware

1. Amplifiers

a. Use the 128 channel amplifier for the 128 channel caps

b. Use the 256 channel amplifier for the 256 channel caps (either the two-piece model with head and neck or the 128 cap with the 128 channel EMG sleeve)

c. Use the eBay amplifier for data piloting sessions

2. Batteries

a. There are 4 batteries total

b. A and B are labeled “good” batteries, meaning that they last longer than the others

c. C is labeled “bad” because it does not last as long, otherwise it works fine

d. The last one is labeled as “short lifetime” because it also does not last long as A and B

e. The battery charger is located in room B171E; DO NOT OVERCHARGE THE BATTERIES!

3. Receiver

a. There are 2 receivers total

b. Only one is necessary per experiment

4. Cable Banks

a. Each cable bank has 32 electrodes

i. Use 4 cable banks for 128 ch setup

ii. Use 8 cable banks for 256 ch setup

b. Electrodes that are not working and that will cause CM to be out of range (and prevent data collection) are wrapped in tape.

5. CMS/DRL cable

a. One per cap/amplifier

b. Connects to connector marked CMS/DRL on the amplifier on the far left

6. External electrodes

a. Up to 8 can be connected per amplifier

b. Connects to row marked EX1 throughEX8

7. Cables

a. USB

b. Optical fiber

8. Caps

a. 128 channel caps (2 small, 2 medium, 2 large)

b. 256 channel caps

i. 6 MoBI caps (2-piece: neck and head; 2 small, 2 medium, 2 large)

Disposable materials

1. Electrode gel (green bottle)

2. Double-sided stickers for external electrodes

3. Syringes with needle tips (blunt needle with purple base)

4. Alcohol abrasive wipes

5. Medical tape

6. Rubbing alcohol

7. Q-tips

C. Checkout Procedure

1. Notify the SRAs what equipment you need and on what day/time

2. Make sure that the equipment is reserved out on the Google SCCN EEGLab calendar if the SRAs are not scheduling the session for you.

3. If the SRAs are not there during the session to prepare the EEG equipment, it is ESSENTIAL that you check out and check back in the equipment using the Wufoo equipment log

Collecting Data

Hardware setup

1. Select a fully-charged battery (plug into the charger; green light means that it is fully charged) and connect the DC output on the battery to the DC input on the amplifier you’ve chosen (128 or 256). Make sure the battery is powered off for now so that it doesn’t drain.

2. Optical fiber cable

a. Connect one end of the optical fiber cable to the optical out connector on the amplifier

b. Connect the other end of the cable to the optic link connector on the receiver

3. USB cable

a. Connect one end of the USB cable to the USB link connector on the receiver

b. Connect the other end of the USB cable to the computer you want to view the data on (see below for further instructions on which computer to use)

Digitizing

1. The Zebris unit creates a file with the 3-D coordinates of the electrodes on the cap, on the subject’s head which will later be used during EEG data analysis

2. Reference electrode

a. If choosing the mastoids, use the alcohol wipes to wipe behind the ear.

b. Affix a two external electrodes with double-sided stickers, one behind each ear, to the bony part behind the area, making sure to avoid any blood vessels

3. Put the cap on the subject’s head (and neckband on the neck if using the 256 ch cap) with the midline of the cap aligned to the midline of the subject’s head

4. Boot the digitizing laptop. The digitizing software for the Zebris is installed there.

a. Login: MoBI

b. Password: SCCN

5. Open the digitizing software (El Guide icon on desktop)

a. Go to Set Up--> Hardware Set Up--> Temperature Calibrate (click on the tab and then hold the stylus 1 meter from the transmitter until the error level drops under 1)

b. Click on the Measure tab--> enter the appropriate information and choose your template from the drop down menu

c. Press and hold button on stylus to take a measurement; single click to go back one point; double click to review points

d. When finished hit Next and then Finish (file will not save if you do not hit Finish!)

Prepping the subject

1. Using a syringe filled with gel, squeeze a small amount of gel into each electrode well while abrading the skin with the needle; press firmly but not so firmly that the subject experiences pain; DO NOT PUT TOO MUCH GEL IN, otherwise the gel will spread between electrode wells across the scalp and multiple distinct EEG signals will turn into one.

2. Once all the wells have been filled, take the cable banks and match the number on the cable electrode to the electrode well label; pop them in one by one using one cable per colored section

Note: The letters on the cable bank do not have to match the letters on the electrode well labels (e.g. cable bank A does not need to go to section A necessarily if there are no A cable banks available for use; a G can be used instead); any other cable bank letter can be substituted as long as the numbers match up.

Checking impedances

1. Connect the black connectors at the end of the cables to the top of the amplifier in the order that they are attached on the cap (section A on the cap, then section B on the cap, then section C and so forth). Do not follow the alphabetical order of the cable bank designation because they might not correspond to the letter of the section they’re attached to on the cap.

2. Connect the other end of the USB cable that’s plugged into the receiver to the Digitizing Laptop

3. Open ActiView, a BioSemi data viewing and recording software. Use the ActiView shortcut on the desktop.

4. Press Start at the top left to view the live streaming EEG data

5. Click on the Electrode Offset tab to view electrode offsets

a. Use the dropdown menu under Channels on the left toolbar (under the high and low pass filter options) to select which channel groups you’d like to view.

b. If any electrode has an offset higher than 25, remove that electrode from the electrode well, use the needle to scrape and move the hair around a little while adding a little more gel, and put the electrode back into the well; do so until the offset is below 25

c. If any electrode is broken and is plugged into the cap, it will cause the ALL channels to be at the max offset and blink; remove the offending electrodes from the cap and take note of them.

d. Once satisfied with the offsets, switch to the Monopolar view which will have the live streaming EEG; fix any that look noisy in the method describe in step e.ii.

6. Troubleshooting: ActiView gives an error message (see image below) when you press Start

a. Check the speed mode

i. For a 1-person experiment, check that the speed mode to the left of the DC input on the amplifier is set to 4 (arrow points to 4, need a screwdriver to move it)

ii. For a 2-person experiment where the amplifiers are daisy-chained together the slave 128 channel amplifier speed mode should be set to 1 and the master amplifier (256 channel) speed mode should be set to 0

b. Check that the battery is turned on and the optical fiber cable is connected to both the amplifier and the receiver

c. Check that the USB is plugged in far enough into the computer

d. Close and reopen ActiView and if there is still an error message, the CMS/DRL cable may be shorted; get a different one and replace the one in the cap and repeat.

e. If doing all of the above does not help, it’s possible that ActiView is malfunctioning (if someone copied over it or updated the previous version). Check impedances on the Control computer and later do the following to fix the problem:

i. Go to C:\Program Files\ActiView605 (Biosemi)\Windows 32bit\Windows 32bit\Developers kit\C-code

ii. Copy the file Laview_DLL.dll

iii. Paste it in C:\Program Files\ActiView605 (Biosemi)

iv. If ActiView still doesn’t recognize the amplifier, go to the Biosemi forum online (http://www.biosemi.nl/forum/) under the topic 'Biosemi Software (ActiView executable) and try the various fixes described in thread #488 “error 500 on laptops”

7. Troubleshooting: In the Electrode offsets tab, all the electrodes are at the highest impedance and are flashing in unison; the blue light (CM in range) is blinking

a. This means that an electrode that is plugged into the cap is broken.

b. Remove the offending electrodes from the cap and take note of them.

c. If it’s unclear which is broken, you will have to take each out one by one until the light stops blinking; however, all known broken electrodes will be wrapped in tape so do not put them into the electrode wells

Wireless EEG Physical Setup

1. Disconnect the USB cable from the impedance laptop

2. Connect the USB cable to the Netbook laptop (make sure that it is fully charged beforehand and powered on)

3. Check that the Netbook is connected to MoBI Wireless through Network Settings

4. Setting up the wireless EEG backpack

a. With the subject sitting down, place the closed Netbook first on the side that would be against the subject’s back

b. Carefully place the amplifier (with all the cables and external electrodes plugged in) into the backpack with the side with cables plugged in facing away from the Netbook

c. Put the receiver on the side of the amplifier

d. Pull on the drawstring around the top as tight as possible so that nothing can fall out

e. Hook the shoulder straps over the shoulders of the subject and make sure that the straps are securely connected to the base (double and triple check this because if the shoulder straps disconnect then the amplifier will break!)

5. For more information on setting up the Wireless EEG system in DataSuite see Wireless EEG

Clean Up

A. EEG Caps

1. Wash the caps in warm water using ivory liquid soap (do not make the water too hot or else it might ruin the cap)

2. The warm water and soap should dislodge the gel from the electrodes; however you may need to go through with a q-tip and remove the gel from each electrode individually

3. Once all the gel and soap have been washed off, spray the cap with rubbing alcohol from the spray bottle (apply liberally) to disinfect

4. Put the cap on a rounded surface to air dry

B. Electrodes

1. Collect all the cable banks, CMS/DRLs, and external electrodes used during the experiment

2. Lightly clean the electrodes on both types of cables either using a toothbrush or your fingers; run under lukewarm water

3. IMPORTANT:

a. Make sure that the electrodes don’t get hit or bumped by anything, ESPECIALLY metal which can damage the electrodes

b. Make sure the connectors at the end opposite from the electrodes do not get wet (but it’s ok if they touch metal)

4. Gently dry the electrodes using a dry towel (either paper or cloth) to remove most of the excess water

5. Hang the cables on the drying rack in the control room and spray liberally with rubbing alcohol to disinfect

6. Make any notes on the condition of the cable banks or any troublesome electrodes in the EEG Equipment Log Wufoo form

C. Amplifiers & Batteries

1. Disconnect the batteries from the amplifiers and turn the batteries off.

2. Connect the batteries to the charger in the control room, but DO NOT leave to charge longer than necessary; leaving the batteries to charge for too long (especially overnight) will greatly decrease battery life

3. Put everything back in an organized manner

Created: --Rita Beransky 16:29, 19 October 2010 (UTC)

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