Transcranial Direct Current Stimulation for Cognitive Improvement in Parkinson's Patients

A visual search task will be given in which the participant looks for a T among L's. The contextual cuing task will consist of a practice block and forty test blocks. Eight of the trials in a block will consist of search configurations that repeat from block to block (repeat configurations); the other eight trials in a block will be randomly-generated configurations (new configurations). After the final trial, a recognition task will be presented to determine whether participants realized that repeat configurations were presented (not expected; cueing effects appear to result from implicit learning). Reaction time for each block will be recorded, with cognitive fatigue measured as deterioration of RT over the 40 blocks. This measure of change in RT will be compared across the 4 visits (pre-test, 6th visit, 7th visit, and 8th visit). Improved cognition fatigue based on tDCS treatment would predict reduced change in RT in the later visits compared to the pre-test.

A visual search task will be given in which the participant looks for a T among L's. The contextual cuing task will consist of a practice block and forty test blocks. Eight of the trials in a block will consist of search configurations that repeat from block to block (repeat configurations); the other eight trials in a block will be randomly-generated configurations (new configurations). After the final trial, a recognition task will be presented to determine whether participants realized that repeat configurations were presented (not expected; cueing effects appear to result from implicit learning). Error rate for each block will be recorded, with cognitive fatigue measured as increased errors over the 40 blocks. This measure of change in error rate will be compared across the 4 visits (pre-test, 6th visit, 7th visit, and 8th visit). Improved cognition fatigue based on tDCS treatment would predict reduced change in error rate in the later visits compared to the pre-test.

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The Stroop Test is a measure of processing speed, attention, and inhibition. In Stroop A, the participant is required to read color words (e.g., Red, Green, etc.) out loud quickly for 45 seconds. In Stroop B, the participant is required to name ink colors out loud as quickly as possible for 45 seconds. In Stroop C, the participants are required to name the color ink of opposing color words (e.g., the word "blue" written in red ink with the correct response being "red"). Digit Span forward is a measure of simple attention. Participants repeat progressively longer series of numbers until the participant can no longer complete the task. Digit Span Backward is a measure of working memory. The participant repeats back a series of numbers in reverse order. The series length increase until the participant can no longer complete the task.

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