Comparison of Decision-Related Signals in Sensory and Motor Preparatory Responses of Neurons in Area LIP.

Neurons in the lateral intraparietal (LIP) area of Macaques exhibit both sensory and oculomotor preparatory responses. During perceptual decision making, the preparatory responses have been shown to track the state of the evolving evidence leading to the decision. The sensory responses are known to reflect categorical properties of visual stimuli, but it is not known whether these responses also track evolving evidence.

Truncation of the flash-lag effect by a fixed spatial landmark.

The flash-lag effect is a visual illusion where a moving image is perceived to be advanced in its spatial location relative to a flashed image. Multiple studies have shown that the flash-lag effect can be enhanced by increasing the uncertainty of the moving and/or flashed images. However, little is known about the effect of task-irrelevant visual objects on the flash-lag effect.

Robust quantification of orientation selectivity and direction selectivity.

Neurons in the visual cortex of all examined mammals exhibit orientation or direction tuning. New imaging techniques are allowing the circuit mechanisms underlying orientation and direction selectivity to be studied with clarity that was not possible a decade ago. However, these new techniques bring new challenges: robust quantitative measurements are needed to evaluate the findings from these studies, which can involve thousands of cells of varying response strength.

Elapsed decision time affects the weighting of prior probability in a perceptual decision task.

Decisions are often based on a combination of new evidence with prior knowledge of the probable best choice. Optimal combination requires knowledge about the reliability of evidence, but in many realistic situations, this is unknown. Here we propose and test a novel theory: the brain exploits elapsed time during decision formation to combine sensory evidence with prior probability.

Experience with moving visual stimuli drives the early development of cortical direction selectivity.

The onset of vision occurs when neural circuits in the visual cortex are immature, lacking both the full complement of connections and the response selectivity that defines functional maturity. Direction-selective responses are particularly vulnerable to the effects of early visual deprivation, but it remains unclear how stimulus-driven neural activity guides the emergence of cortical direction selectivity. Here we report observations from a motion training protocol that allowed us to monitor the impact of experience on the development of direction-selective responses in visually naive ferrets.

A role for neural integrators in perceptual decision making.

Decisions based on uncertain information may benefit from an accumulation of information over time. We asked whether such an accumulation process may underlie decisions about the direction of motion in a random dot kinetogram. To address this question we developed a computational model of the decision process using ensembles of neurons whose spiking activity mimics neurons recorded in the extrastriate visual cortex (area MT or V5) and a sensorimotor association area of the parietal lobe (area LIP).

Microstimulation of visual cortex affects the speed of perceptual decisions.

Direction-selective neurons in the middle temporal visual area (MT) are crucially involved in motion perception, although it is not known exactly how the activity of these neurons is interpreted by the rest of the brain. Here we report that in a two-alternative task, the activity of MT neurons is interpreted as evidence for one direction and against the other. We measured the speed and accuracy of decisions as rhesus monkeys performed a direction-discrimination task.