Neural computations that underlie decisions about sensory stimuli

Decision-making behavior has been studied extensively, but the neurophysiol ogical mechanisms responsible for this remarkable cognitive ability are jus t beginning to be understood. Here we propose neural computations that can account for the formation of categorical decisions about sensory stimuli by accumulating information over time into a single quantity: the logarithm o f the likelihood ratio favoring one alternative over another. We also revie w electrophysio-logical studies that have identified brain structures that may be involved in computing this sort of decision variable. The ideas pres ented constitute a framework for understanding how and where perceptual dec isions are formed in the brain.