Running Subjects

A Darren Parker Presentation

Life as a Subject

Good Experiences as a subject?

Bad Experiences as a subject?

Subject’s Perspective

Subjects are often in first year. They don’t really know what they are in for when

they show up. They may be afraid of doing poorly on tasks

(hopefully).

To Help Alleviate Fears

Experimenter should be personable but professional. Subjects need to feel like you know what you are doing.

Experimenter should encourage subject to ask questions and should explain everything as clearly but thoroughly as possible.

Problem Subjects

Monitor performance to see if the task is being done correctly.

Monitor EEG waves and watch for sporadic behaviour.

Let the subject know you can tell how they are doing and what they are doing

Some subjects are just looking for their credit and don’t care otherwise.

In the Beginning…

Answer the phone and get the subject.

Set up all the necessary forms, letter of information and consent form for them, ERP Summary sheet for you.

Explain each, and offer to answer questions.

Subject Setup

Experimenter may want to prepare gel applicators beforehand.

Measure head and check back tag of caps for the right fit.

Digitize heads (new).

Subject Setup: Digitization

Turn digitizer on Click “Locator” Digitize -> Receivers -> 3 File -> Open -> loc128active2.seq Digitize -> Electrodes Follow on screen instructions Save in subject’s folder Turn digitizer off

Subject Setup: Digitization

3 Important points: NZ - Nasion LPA – Left Periaural Axis RPA – Right Periaural Axis

Edited from BESA version 5.1

Subject Setup: Gel application

If there is too little gel, electrodes won’t make connection with scalp.

If there is too much gel, electrodes may bridge.

To apply: place tip of applicator right at scalp, move around to remove any hair in the way. Then as gel is added, move applicator away from scalp, leaving a column of gel.

Subject Setup: Electrodes

Electrodes should snap into their corresponding holes.

The electrode sets are expensive! Its generally best to hang them around your neck so they do not get dropped.

Make sure when plugging into AD box that pins are oriented correctly.

Biosemi Corp. www.biosemi.com

Subject Setup: Eye Electrodes

The port each electrode is placed in is critical. Refer to picture on right (green # = port #).

Place eye electrode adhesives around grey spot on eye electrodes. Apply gel to grey spot.

Subject Setup: Bad Channels

Open ActiView on Red. Click on Start in top left corner. Check Electrode Offset (click tab at top) and

make sure that red bars are not fluctuating, and that they are not off the charts.

Go back to Monopolar Display (if noisy set reference to avg of disp) and make sure that channels are stable, and not crossing over other channels, or completely flat.

1. Start and Stop

5. Save Status

3. Channel List

2. Electrode Offset

4. Trigger Format

Running the Experiment

On Blue, open up Presentation and select the proper experiment and form, if applicable.

Explain the experiment as thoroughly as possible. Ask the subject to repeat back the main points so you are sure they understand.

Ask the subject to remain still except during breaks. Blinking should be avoided as much as possible, but tell the subject when the optimum time is for blinking (in between epochs).

Running: Monitoring Subject

Watch the monopolar display. Make sure that no channels lose connectivity.

Also watch to make sure that subjects are not moving around, grinding or chattering their teeth, or blinking excessively during the epochs.

Watch the triggers, to make sure that subject understands the task and is trying to do the task properly.

Documentation! Make notes on ERP summary sheet always.

Running: Checking in on Subject

Experiments in this lab are generally repetitious and monotonous (boring).

Human interaction helps! Check in on subjects during some breaks, offer water, ask how the task is going, tell them they are doing well/crappy.

Finishing Session

Before the subject is done, take a screen capture of their brainwaves and print it off for them.

Get the sink ready, with the nozzle hooked up, and towel ready, shampoos displayed. Make sure to clean up gel and applicators.

Finishing Session: Experiment Done

Stop ActiView recording. Remove cap and electrodes from subject

carefully, place on rack below the AD box. Turn the AD box off!

Let subject wash off. Don’t be a creepster and hang around, close the door to the preparation room most of the way.

Finishing Session: Subject’s Swag

1. Coloured credit slip all filled out.2. The Information Sheet is for them to keep.3. A Picture of their EEG recording.4. The Debriefing form letting them know

what the point of the last two hours of their life have been for.

5. Your gratitude (whether they were a stellar subject or not).

Items to have ready for the subject:

What’s Left?

Clean cap and electrodes (sooner the better).

Close ActiView and Presentation (files should have saved automatically).

Organize and transfer files to Tomcat.

Handling Electrodes

Never pull electrodes by the wires. Only pull by electrode heads, or by connector.

Wash and dry electrodes right after the subject leaves. The gel dissolves the AgAgCl pellets at the tips of the electrodes, and over time the signal becomes noisier.

Use warm water, don’t use harsh soaps. Keep connectors clear from water.

Next Episode…

Look at ERPs What they are Why they are useful Steps to get them from our raw data