The neurobiology of perceptual decision-making elucidates fundamental neural mechanisms of higher cognitive function, the understanding of which will inspire new strategies to treat neurological and psychiatric diseases affecting thought, perception and awareness. The inquiry focuses on processes that intervene between the acquisition of sensory evidence and commitment to a proposition, behavioral choice, or plan. Progress was facilitated by the discovery of persistent neural activity in prefrontal and parietal association cortex of the monkey. By requiring a monkey to communicate its decision with an eye movement, the decision process is observable as an evolving neural commitment to one action or another. Much is now understood about the neural mechanisms that underlie the accumulation of evidence, the tradeoff between speed and accuracy, the assessment of confidence in a decision, and the incorporation of bias. However, it is unknown how these mechanisms can apply to more complex decisions that are not construed as a dedicated chain from a single source of evidence to action selection. A critical limitation to progress is a gap in knowledge about the flow of information between circuits when the path from evidence to action is indirect and flexibly controlled. The current proposal addresses this problem by developing new behavioral tasks in which the path from sensation to decision to action is diverted or elaborated, and it exploits emerging tools to measure and manipulate neural activity in order to characterize interactions between populations of neurons in the service parallel, serial and multiplexed computations.
Aim 1 elucidates context-dependent interactions between two parietal areas that mediate decisions communicated by an eye or arm movement. Simultaneous multichannel neural recording from the medial and lateral intraparietal areas will expose patterns of serial inheritance or parallel processing of evidence, the decision and termination.
Aim 2 elucidates the dynamical changes in the representation of a decision when the decision to action mapping changes during the decision itself. Neural recordings are obtained from the parietal cortex of monkeys during a perceptual decision that is suspended by an intervening eye movement task. If successful, Aim 2 will forge a connection between the stability of vision across changes of gaze and the integrity of a decision across changes of intention.
Aim 3 investigates a processing bottleneck that arises when two streams of evidence support two distinct decisions about a single object, that is, a double decision. Behavioral evidence from humans and monkeys indicates that sensory evidence can be acquired in parallel, but is incorporated sequentially into the double-decision.
Aim 3 thus promises to elucidate the neural mechanisms of this serial incorporation and thus begin to explain why mental operations take the time they do. Together the proposed research will open new areas of computational and mechanistic interrogation of circuit interactions in the service of decision-making and cognitive control.
A wide range of cognitive functions depend on brain mechanisms that support decision-making. Restoring these mechanisms will likely play an essential role in future treatments of brain disorders affecting cognition. The present proposal leverages knowledge of visual processing by the brain to reveal how the brain makes increasingly complex decisions.
