David L. Gilden, Ph.D - US grants

perception; psychophysics; performance; mathematical model; model design /development; cognition; clinical research; human subject;

[unreadable] DESCRIPTION (provided by applicant): The perception and representation of object motion is of primary importance in both the processing of environmental information and in the execution of competent performance. This observation has motivated a systematic inquiry into the abilities that people display in perceiving, remembering, attending to, and understanding different kinds of motion. Research over the past three decades has made it clear that though our cognitive and perceptual faculties are exquisitely attuned to the translational motion of objects, these systems suffer dramatic and general failures when confronted with virtually any form of object rotation. In this proposal we explore the extent to which these failures are the result of attentional and memorial limitations in the processing of motion information. Attentional limitations in the analysis of motion are examined in Phase I using a multiple target visual search methodology. The ensemble of proposed experiments in Phase I are based on measurements of response time (RT) and accuracy to signal the presence/absence of one or more specified motion targets hidden in a field of motion distractors (e.g. a clockwise rotation among counter-clockwise rotations). The RT and accuracy data are then accounted for simultaneously using a capacity-limited, random walk model of search with key parameters that correspond to stimulus discriminability, attentional limitation, and decisional bias. This hybrid approach has the power to distinguish serial from parallel processes, and to provide continuous measures of attentional limitation during visual search for motion features. Memorial limitations in the perception of motion are examined in two separate lines of proposed work that probe explicit (phase II) and implicit (phase III) memory systems. Explicit memory for motion information is assessed using a standard "old"/"new" recognition paradigm in which people are shown a series of moving objects and are tested at a later time on their abilities to recognize various aspects of object motion. Implicit memory is examined using a novel temporal priming methodology that assesses processing speed contingent on prior motion experience. Patterns of facilitation and inhibition are used to decide what aspects of motion information receive implicit registration. [unreadable] [unreadable]

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.