Natural visual behavior consists of scanning a visual image, extracting relevant attributes of a target object, and generating an arbitrary response based on those attributes. The computational and neurophysiological bases of these processes are not understood. Current state-of-the-art models of perceptual decision making consist of a single decision process preceded by raw visual processing and followed by reflexive response preparation. Using a more natural and complex task, this project will decompose visual processing and gaze behavior into distinct computational and associated neurophysiological parts. This research training plan is comprised of two aims directed at achieving a better understanding of the role of frontal eye field (FEF) in visual search and eye movement planning.
Aim 1 will characterize performance on a visual search task that requires the subject to: (1) locate the target; (2) decode the response required based on target shape; and (3) execute the appropriate response. Analyses of diverse measures of response (e.g. timing, accuracy, and vigor) will provide new insights into the dynamics of attention allocation and response preparation during visual search.
Aim 2 will characterize neural activity in FEF, a prefrontal region uniquely situated at the interface of visual processing, memory retrieval and eye movement planning. Data from single neuron and ensemble neuron recordings will be quantified in relation to stimulus presentation, movement initiation and the associated intermediate representations and transformations such as stimulus localization, object encoding, stimulus-response mapping, gaze endpoint selection and response preparation. The two-fold training goals of this project are (1) to acquire expertise in training macaque monkeys to perform complex visual tasks and (2) to master the fundamentals of single-unit neural recordings in cortex in awake behaving primates. Successful completion of this project will contribute to the National Eye Institute mission to better understand sensory and motor processing in the visual system and will prepare the trainee for an independent research career in vision science.
This project will provide new insights into the cortical basis of visual search, including processes of visual target selection, stimulus-response rule retrieval and saccade preparation and execution. The findings will elucidate the contribution of frontal eye field (FEF) to the greater circuit that guides behavior during visual search. As such, this project will contribute to understanding central nervous system deficits in vision and gaze manifest in attention and ocular motility disorders.
