Jeffrey D. Schall, Ph.D.
Office: 004 Wilson Hall
Phone: (615) 322-0868
Schall's laboratory seeks to elucidate the neural decision mechanisms that guide, control and monitor eye movements. The activity of individual or sets of neurons as well as local field potentials and surface event-related potentials are 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 to present stimuli that can be interpreted as either a target for an eye movement or as a distracter. The processes of target selection and attention allocation are measured as the modulation of neural spikes, local field potentials and event-related potentials. 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 and how the brain monitors the consequences of performance. We use a stop signal (countermanding) task to probe the timecourse of saccade preparation. 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 have also found that neurons in the supplementary eye field and anterior cingulate cortex register errors and success in the context of conflict.
A third research program funded by the National Eye Institute is a collaboration with Gordon Logan and Tom Palmeri in which stochastic models of decision mechanisms are employed to bridge the explanatory gap between neural events, performance and cognition.