Knowing when to stop


Inhibitory control is the ability to withhold or modify prepotent or planned actions that are no longer appropriate in a behavioral context. We are studying the computational and neurophysiological basis of inhibitory control in healthy individuals and those affected by conditions such as ADHD and stimulant abuse.

Inhibitory control is often studied using the stop-signal paradigm, which reveals deficits in individuals with ADHD, substance abuse, and obsessive-compulsive disorder. Using computational models that assume subjects optimally integrate sensory inputs and select actions, we have shown that a wide range of observed behavior in the task naturally arises--encompassing not only the basic stop-signal task, but also variants that manipulates various contextual factors such as motivation and stimulus statistics (Shenoy, Rao, & Yu, 2010; Shenoy & Yu, 2011).

More recently, we have begun investigating the neural basis of stopping behavior.  Preliminary analysis of an fMRI experiment (Ide, Shenoy, Yu, & Li, in preparation) suggests that distinct regions of the medial frontal cortex participate in the prediction and evaluation of surprising events, which are critical for pro-active control in the stop signal task.  Separately, we have also pinpointed the noradrenergic modulatory system as being important for alerting the brain to unexpected events, such as a stop trial in the stop-signal task.  We propose that it is the failure of this alerting system in ADHD patients that result in an impairment in inhibitory control, which is then ameliorated by the norepinephrine reuptake-inhibitor drug atomoxetine (Shenoy & Yu, in preparation).

Further details, and our other research projects, are available at our lab homepage: http://www.cogsci.ucsd.edu/~ajyu/