Jeffrey D. Schall, Ph.D.
Office: 004 Wilson Hall
Phone: (615) 322-0868
E-mail: jeffrey.d.schall@vanderbilt.edu
Schall's laboratory investigates the neural and computational decision mechanisms that guide, control and monitor behavior. The activity of ensembles of neurons and local field potentials are recorded in 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 pioneered the use of visual search to elucidate how the brain distinguishes a target from distractors. The processes of target selection and attention allocation are measured in the modulation of neural spikes and local field potentials. We are investigating the visual and cognitive influences on this attentional selection process and how it relates to the preparation of eye movements.
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 were the first to use the stop signal (countermanding) task with monkeys. We were the first to show that gaze shifts are initiated when movement activity in frontal eye field reaches a fixed threshold and that variability in response time arises from random variation in the rate of accumulation of the neural activity toward the threshold. This work led to the identification of neural activity with accumulator models of decision-making. Using the saccade countermanding task, we were also the first to describe the neural mechanism of response inhibition through motor circuits. We were also the first to demonstrate that neurons in the supplementary eye field as well as anterior cingulate cortex register errors and success in the context of conflict. This work led to the identification of medial frontal cortex in monkeys with models of performance monitoring.
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.
A fourth research program, funded by the National Eye Institute, is a collaboration with Geoff Woodman in which EEG is recorded from the cranial surface of monkeys performing visual search, memory and countermanding tasks. This program is the first systematic investigation of the cortical sources of cognitive event-related potentials such as the N2-pc, contralateral delay activity, and error-related negativity.
