CNP SCAP

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Basic Task Description

This task was developed in the Cannon Lab, originally by David Glahn. This behavioral version is the most basic, traditional version of the task. It differs from the LA5C SCAP version, in a few ways described below. This task has been run on most of the local Cannon Lab UCLA samples including Aftercare (first episode), CAPPS (prodromal), chronic and NF1 subjects. It has also been run in Finnish and Swedish samples.

Task Procedure

This task manipulates working memory load. The loads were selected to be of parallel difficulty, in terms of performance, to the loads in the VCAP.

Loads: 1, 3, 5 or 7 dots

There are 12 trials per load, the trials are blocked in sets of 2, and analyzed in those blocks.

Trial layout:
1. Fixation for 1sec
2. Target array for 2 sec
3. Delay period for 3 sec
4. Probe array (single dot) for 3 seconds

Each trial lasts 9 seconds. TR=3s

Text
During the SDRT, subjects were shown a target array of 1, 3, or 5 yellow circles positioned pseudorandomly around a central fixation. After a fixed delay, subjects were shown a single green circle and were required to indicate whether that circle was in the same position as one of the target circles. A relatively long stimulus presentation was used to allow subjects to fully encode the target array, minimizing a potential encoding on the basis of set size interaction. Likewise, decision or selection requirements were kept constant across set sizes to reduce possible effects of set size on response processes. Trial events included a 2-sec target-array presentation, a 3-sec delay period, and a 3-sec fixed response interval. A central fixation was visible throughout each of the 36 trials (12 per memory set size).
Glahn, 2003