Using ADHD to Probe the Temporal Dynamics of Cognition

University Of Texas At Austin, Austin TX

Investigators

Abstract

Variability has always been an issue for experimental psychology, but it is only recently that it has been appreciated as information that is interesting in its own right. In cognitive and psychophysical assessments variability is not just sampling error, it is something produced by a nervous system that is organized and which embodies many different forms of memory. When viewed from a dynamical perspective, the residuals from typical cognitive methodologies are often found to be correlated as a particular type of fractal, 1/f noise. 1/f noises have been observed in a number of seemingly unrelated contexts (quasar light, river and tide height, traffic flow, to name a few) and its appearance is believed to be meaningful, especially as a signature of dynamical complexity. Notably, people who have attention-deficit hyperactivity disorder (ADHD) produce noises in speeded response tasks that are distinctly not of the 1/f variety . The work proposed here is designed to ascertain why this is so, and to use the disorder as a wedge to gain experimental leverage into an understanding of 1/f noise in normal human behavior. The two specific theories evaluated are 1) the possibility that disruptions of the ATP cycle in neuronal energy regulation create attentional dysfunction, and 2) that dopamine dysfunction and its attendant disruption of the reward system in learning affect the timescales over which temporal associations are constructed. The pairing of behavioral and cognitive assessments will allow a better understanding of the causal mechanisms of noise production in ADHD task performance. The significance of this research is twofold. First, 1/f noise combines aspects of order and disorder in a way that its presence is thought to signify aspects of dynamic complexity. Discovering what produces it in human cognition would be tantamount to describing what kind of thing thought is at the systems level. This is one of the unique places in psychology where meaningful contact can be made with fields as diverse as statistical physics and physiology. Second, identification of the cognitive deficits in ADHD has lagged behind advances in establishing its neurobiology. Exploiting the normal 1/f nature of behavior in or to identify core cognitive deficits in ADHD will clarify the nature of the disorder and may suggest directions for treatment.