Steady State Auditory Evoked Potentials (SSAEP)¶
Overview¶
The SSAEP task is an auditory task that presents 1 second sine wave tones with their
amplitude modulating at frequencies 6Hz and 40Hz. There is a jittered period of silence
between the 1-second tone presentations (Inter-trial-Interval; ITI), either 700,
900, 1100 or 1300 ms. While the sine waves are presented, an abstract video
is played on the screen (See the Resting-State task for more details on the abstract video
stimuli).
Conditions¶
- 6Hz
The 1-second tone presentations modulate in amplitude at 6Hz
- 15Hz
The 1-second tone presentations modulate in amplitude at 15Hz
Blocks / Trials¶
The experiment conists of 4 blocks of 40 trials each (20 per condition), resulting in about 80 seconds per block. Breaks are given between blocks, and are controlled by the experimenter. A quasi-random trial sequence allows a maximum of 4 frequency repetitions in a row (i.e. 6hz, 6hz, 6hz, 6hz; for a total of 4 seconds).
Note
The SSAEP_A.dat and SSAEP_B.dat files contain the specification for the
trial sequence, including the jittered ITI. These files assure that the various
ITI’s are evenly distributed throughout the experiment, such that an ITI of
700ms will not only precede the 6Hz condition, etc. These dat files
are assigned prior to each session and are selected by the experimenter.
Animations¶
- Baseline videos
The baseline videos are the same as the Resting-State task, and are present throughout the experiment for the participant to view.
Interest Areas¶
There are no interest areas defined for this task.
Gaze Triggers¶
There are no gaze triggers defined for this task.
Classifiers¶
There are no tiral classifiers defined for this task.
Event Messaging¶
Experiment Builder will send experiment event codes to both the Eyelink and EGI acquisition systems, and the event code patterns differ slightly:
EGI acquisition¶
EGI Netstation does not support the same event messaging as the Eyelink Host PC, as event codes are generally restricted to 4 characters. The table below shows the corresponding event codes for the EGI Netstation acquisition, and the DIN event triggered by the photo-diode on the screen for each event.
Event Description |
EGI Event |
DIN |
|
|---|---|---|---|
Condition |
6Hz |
40Hz |
|
Jittered ISI |
|
|
|
Onset of 1-second tone |
|
|
|
Note
DIN events represent the auditory rise onset of each 1-second tone stimulus stream, and are generated by the Cedrus Stimtracker that is connected to the speakers (audio output jack), and are used for assurance of event timing accuracy.
In addition to the event codes above, the following codes are also sent to the EGI Netstation acquisition system, but generally are not needed for offline analysis:
Description |
EGI Event |
begin task |
|
Netstation misc event |
|
display start menu |
|
display break menu |
|
display end screen |
|