CNP SCAP
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Contents
Basic Task Description
The goal of this task is to probe behavior across different levels (loads) of a spatial working memory capacity task. There is evidence that spatial working memory is impaired in schizophrenia, and the deficit may be a core feature of the disease. From our previous schizophrenia twin studies we have evidence that the spatial working memory deficit (as assessed by a version of this task) may be heritable (Glahn et al, 2003). There is further evidence that performance on this task may differentiate between bipolar patients with and without a history of psychosis (Glahn, 2006).
The Cannon lab has a great deal of experience with this task, and it has been administered in a very wide variety of populations at a number of sites. We have administered it to adolescents with schizophrenia, prodromal subjects, aging Finnish twins with and without schizophrenia, chronic schizophrenia patients, bipolar patients, patients with neurofibromatosis-1, and healthy controls. The version that we have administered most frequently is the one used in the LA2K, a block design task with 4 memory loads (1,3,5 and 7 locations).
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 CNP_VCAP.
First, subjects undergo a training period
Sample 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
Task Structure Detail
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
Task Schematic
Task Parameters Table
Stimuli
Dependent Variables
Cleaning Rules
Code/Algorithms
Data Distributions
References
Cannon et al, 2005, Archives of General Psychiatry
Glahn et al, 2003, Biological Psychiatry
Glahn et al, 2002, Neuroimage
Glahn et al, 2006, Bipolar Disorders