Contracted spans of temporal integration in adults with attention deficit hyperactivity disorder
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ADHD is a highly prevalent disorder in both children and adults that involves significant impairment throughout the lifespan, and yet the core cognitive deficits of the disorder are not well understood. Accumulating evidence of dysfunctioning dopamine systems motivated the theory that delay-of-reinforcement gradients are altered in ADHD in such a way that reinforcers must arrive earlier in time following a response for an association between the two to be learned. The current work is motivated by the conjecture that dopamine dysfunction has consequences for the maximum timescales over which connections can be formed, not just in reinforcement learning, but also in the processes of temporal integration and scene formation that allow humans to understand and navigate their world. There is a maximum window of temporal separation over which discrete events can be integrated into a unified experience, and the current experiments indicate that this maximum window of integration is contracted in ADHD. The experiments included multiple tasks designed so that the participant response required implicit integration over temporal intervals, and the length of those intervals was varied as an independent variable. Adults with and without ADHD completed these tasks, and the strength of temporal integration was measured with respect to interval length and compared between the two groups. This methodology was applied in five types of tasks: rhythmic tapping, spatial cuing, irrelevant feature priming, and two apparent motion tasks. On the whole, this suite of studies was successful in demonstrating a contraction in the maximum interval over which temporal integration can occur in ADHD relative to controls. Two of the tasks, rhythmic tapping and spatial cuing, generated unexpected and interesting results, and several follow-up tasks were designed to further explore these findings. As a result, a somewhat improved tapping task was discovered. This tapping task, as well as the irrelevant feature priming task and one of the apparent motion tasks, demonstrated potential utility for the diagnosis of adults with ADHD.