Schall Lab

Jeffrey D. Schall, Ph.D.

Office: 004 Wilson Hall

Phone: (615) 322-0868

Schall's laboratory seeks to elucidate the neural mechanisms that guide and control eye movements. The activity of individual or sets of neurons is recorded in behaving monkeys performing a variety of tasks that are motivated by theories of perception and cognition.

One research program funded by the National Eye Institute aims to understand how the brain selects the target for an eye movement. We use visual search or visual masking tasks to present stimuli that can be interpreted as either a target for an eye movement or as a distracter. We have found that neurons in the frontal eye field participate in the discrimination of the target from distracters. We are investigating the visual and cognitive influences on this selection process and how it relates to the preparation of the eye movement.

Another research program funded by the National Institute of Mental Health aims to understand how the brain regulates when to initiate a voluntary movement. The challenge is to explain the duration and variability of behavioral response time. We have found that gaze shifts are initiated when movement activity in frontal eye field reaches a fixed threshold; variability in reaction time arises from differences in the time the neural activity grows toward the threshold. We use the countermanding paradigm to distinguish whether single neurons generate signals that are logically sufficient to control movements. We have found that neurons in frontal eye field that carry only visual signals do not participate in the control of action but that neurons in frontal eye field that carry motor or fixation signals do generate signals sufficient to control gaze. We have also found that neurons in the supplementary eye field and anterior cingulate cortex register errors and success in the context of conflict.