Grantee: Columbia University, USA
Researcher: Vincent Ferrera
Grant Title: Neural Mechanisms of Fine Motion Discrimination
Program Area: McDonnell-Pew Program in Cognitive Neuroscience
Grant Type: Research Award
Amount: $150,000
Year Awarded: 1999
Duration: 3 years
The goal of this proposal is to test a general theory of perceptual discrimination first proposed by Helmholtz (1896). According to this theory, discrimination is based on differential neural responses. The theory posits that fine discrimination is mediated not by neurons that have the strongest response, but by neurons that have the greatest change in response. This theory makes several counterintuitive predictions about the relationship between neural activity and behavioral performance. These predictions will be tested using as a model system the cortical motion pathway in monkeys and humans. Although there is a large psychophysical literature on fine discrimination of motion direction and speed, relatively few studies have been devoted to the physiological mechanisms. Physiological studies, on the other hand, have mainly been concerned with distinguishing large stimulus differences, such as opposite directions of motion, in the presence of noise. The proposed study will have two parts: experimental and computational. We will first quantify the fine direction and speed discrimination of human and monkey subjects as a function of axis of motion. This will reveal whether the well known oblique effect for directional discrimination is also present for speed discrimination. We will then perform computer simulations to investigate what underlying neural mechanisms could potentially account for the psychophysical observations. Finally, we will perform single unit recording and microstimulation experiments on behaving monkeys to test specific predictions from the modeling work. Together, these studies should provide a better understanding of the neural basis of optimal perceptual performance.