Grant Number: 5R01EY012106-07
Project Title: Predictive Representation of Motion in Visual Cortex
PI Information: ASSISTANT PROFESSOR JOHN A. ASSAD,  jassad@hms.harvard.edu 

Abstract: DESCRIPTION (provided by applicant):
A great deal of evidence suggests that visual perception is affected by our predictions about the visual world. Prediction allows us to exploit and adapt to the causal, non-random structure of our visual environment, and is essential for rapid and accurate control of visually guided behavior. We previously identified neuronal signals in the monkey lateral intraparietal area (LIP) that provide a predictive representation of the direction of visual motion. The overarching issues in this new proposal are the relationship of predictive signals to behavior and the mechanisms by which predictive signals develop. Predictive motion signals in LIP seem ideally suited for feedforward control of behavior, but little is known about the relationship between predictive neuronal signals and behavior. We will address this issue by looking for trial-by-trial correlation between predictive neuronal signals and reaction time. We will examine 1 both manual reactions and eye movements to test whether the activity of single neurons is specific for particular behaviors, or rather provides a general predictive signal that is useful for multiple behaviors. We will also examine whether predictive neuronal signals and behavioral advantages arise as a result of learning based on the recent trial history of visual stimulation. We specifically hypothesize that predictive neuronal signals are updated based on prediction errors, the difference between the predicted visual stimulus and the actual visual stimulus. Moreover, we hypothesize that predictive behaviors and predictive neuronal firing will be similarly affected by recent trial history. Finally, another "extraretinal" process, selective attention, has been shown to enhance sensorimotor behaviors and to modulate neuronal responses. A key question is whether the dynamics of the neuronal modulation can account for the behavioral advantage. We will simultaneously examine the time course of neuronal modulation and the time course of the performance advantage that is gained when an animal endogenously switches attention between two visual stimuli in response to a cognitive cue. The time course of attentional modulation of a neuronal response should reflect the role that a neuron plays in endogenous shifts of attention. Our experiments will provide a mechanistic perspective on how the brain uses prior information about the sensory world to facilitate perception and action. Gaining basic information on perceptual mechanisms is an essential step for understanding normal and abnormal brain processing.

Thesaurus Terms:
behavior prediction, motion perception, sensory signal detection, visual cortex, visual perception
attention, cue, eye movement, learning, neurophysiology, psychomotor reaction time, sensorimotor system, sensory discrimination
Macaca mulatta, behavior test, behavioral /social science research tag, electrophysiology, visual stimulus

Institution: HARVARD UNIVERSITY (MEDICAL SCHOOL)
MEDICAL SCHOOL CAMPUS
BOSTON, MA 02115
Fiscal Year: 2006
Department: NEUROBIOLOGY
Project Start: 01-JUL-1998
Project End: 31-AUG-2010
ICD: NATIONAL EYE INSTITUTE
IRG: CVP

The Journal of Neurophysiology Vol. 88 No. 4 October 2002, pp. 1777-1790

Copyright ©2002 by the American Physiological Society

Distinct Nature of Directional Signals Among Parietal Cortical Areas During Visual Guidance

Emad N. Eskandar^1,2 and John A. Assad^1
 
1Department of Neurobiology, Harvard Medical School, Boston 02115; and ²Department of Neurosurgery, Massachusetts General Hospital, Boston, Massachusetts 02114

The animals were trained to use a joystick to guide a spot of light to a target on a monitor. The vertically mounted joystick allowed full two-dimensional control of the displacement of the spot and was hidden from the animal's view by the neck plate of the primate chair. Before each trial, the animals had to return the spring-loaded joystick to the center position, so the hand movements were always made relative to the starting center position. During training, both animals developed an exclusive hand preference that was maintained throughout the experiments. Once the animals mastered the task, an aseptic surgery was performed, following National Institutes of Health and Harvard Medical School guidelines, to implant a titanium head-post, celux recording chamber (Crist Instruments), and scleral search coil (Judge et al. 1980 ). The recording chamber was dorsally positioned at stereotactic coordinates P3,L10 in the hemisphere contralateral to the hand used to move the joystick.

J Neurophysiol 95: 2391-2403, 2006

Activity of Tonically Active Neurons in the Monkey Putamen During Initiation and Withholding of Movement

Irwin H. Lee*, Aaron R. Seitz* and John A. Assad
 
Department of Neurobiology, Harvard Medical School, Boston, Massachusetts

Submitted 7 October 2005; accepted in final form 30 December 2005

Behavioral paradigm
Two male rhesus monkeys (13.6 and 7.2 kg) were trained to guide a spot of light to a target using a vertically mounted joystick, which allowed full two-dimensional control of the displacement of the spot. The spring-loaded joystick returned to the center before each trial, so that the movements were always made relative to the starting center joystick position. Animals were required to confine the spot's movement to a 5°-wide (visual angle) invisible "corridor", although after training, the movements were very accurate and rarely strayed from the corridor boundaries. For every neuron, we first determined the preferred direction of movement using a direction-tuning task (see following text). In the main task, the preferred direction of movement was used on every trial.

Electrophysiological recording
Once the animals were trained, they were surgically implanted with head post, scleral search coil, and recording chambers following National Institutes of Health and Harvard Medical School guidelines. The chambers were placed in the left hemisphere because both animals exclusively used their right hands to move the joystick.