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Mavis Kusi, Lindsey Thurston, Catherine Crandell, Martin Paré; Atomoxetine has no effects on visual working memory but benefits motivation. Journal of Vision 2018;18(10):689. doi: https://doi.org/10.1167/18.10.689.
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Atomoxetine (ATX) is a selective catecholamine reuptake inhibitor and is increasingly prescribed to individuals with attention deficit hyperactivity disorder (ADHD). To date, there is equivocal evidence that ATX improves cognitive abilities in nonhuman primates and humans, including people with ADHD. We examined the effects of ATX on visual working memory in three adult female rhesus macaques. The animals were tested with a range of ATX doses (0.03-3 mg/kg) that span beyond the therapeutic range (0.5-1.4 mg/kg); they were orally administered the drug. A visual sequential comparison (VSC) task was used to assess visual working memory. Each trial of the VSC task begins with the presentation of a memory array of 2 to 5 coloured stimuli. Following a one second retention interval, a test array is presented and the animals are required to make a saccade to the item that has changed colour to receive a liquid reward. We found that ATX did not significantly enhance the monkeys' response accuracy and response latency in the VSC task. However, ATX had significant effects on improving the animals' motivation (task engagement) in the VSC task. To more directly assess motivation following the administration of ATX, we developed a task with a progressive ratio (PR) schedule of reinforcement. In this PR task, the animal must fixate a gradually increasing number of visual stimuli to obtain the reinforcer (liquid) and the number of fixations made to obtain the last reinforcer (the breakpoint) estimates motivation. We found that the animals' breakpoint in the PR task varied as a function of ATX dose, with an optimal dose falling within 0.3 and 3 mg/kg. Overall, our results suggest that ATX does not directly enhance visual working memory and may be best described as boosting motivation.
Meeting abstract presented at VSS 2018
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