Running Subjects

1
Running Subjects

• A Darren Parker Presentation

2
Life as a Subject

• Good Experiences as a subject?
• Bad Experiences as a subject?

3
Subjects Perspective

• Subjects are often in first year.
• They dont really know what they are in for when
  they show up.
• They may be afraid of doing poorly on tasks
  (hopefully).

4
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.

5
Problem Subjects
Some subjects are just looking for their credit
and dont care otherwise.

• 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

6
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.

7
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).

8
Subject Setup Digitization

• Turn digitizer on
• Click Locator
• Digitize -gt Receivers -gt 3
• File -gt Open -gt loc128active2.seq
• Digitize -gt Electrodes
• Follow on screen instructions
• Save in subjects folder
• Turn digitizer off

9
Subject Setup Digitization

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

Edited from BESA version 5.1
10
Subject Setup Gel application

• If there is too little gel, electrodes wont 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.

11
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
12
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.

13
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.

14
2. Electrode Offset
1. Start and Stop
3. Channel List
4. Trigger Format
5. Save Status
15
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).

16
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.

17
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.

18
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.

19
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. Dont be a creepster and
  hang around, close the door to the preparation
  room most of the way.

20
Finishing Session Subjects Swag
Items to have ready for the subject

• Coloured credit slip all filled out.
• The Information Sheet is for them to keep.
• A Picture of their EEG recording.
• The Debriefing form letting them know what the
  point of the last two hours of their life have
  been for.
• Your gratitude (whether they were a stellar
  subject or not).

21
Whats Left?

• Clean cap and electrodes (sooner the better).
• Close ActiView and Presentation (files should
  have saved automatically).
• Organize and transfer files to Tomcat.

22
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, dont use harsh soaps.
• Keep connectors clear from water.

23
Next Episode

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