Michael A. Paradiso
Ph.D., Brown University, 1984
Associate Professor
Department of Neuroscience
320 Metcalf Research Laboratories
Tel. (401) 863-1159
Research Summary
Despite its seeming simplicity, visual perception involves neural computations in numerous cortical areas throughout the brain. To understand the neural mechanisms responsible for vision, we use extracellular recording, human psychophysics, and computer modeling to study the relationship between visual attention, visual perception and neural activity elicited by visual stimuli. For the past few years we have sought to clarify the manner in which the brain computes and represents the surface properties of objects such as their brightness and color. From a neurobiological perspective this is a challenge because, in the absence of contrast, brightness and color are not effective stimuli for activating most neurons. Our past physiological and psychophysical experiments suggest that these surface properties are computed through neural interactions over a range greatly exceeding the size of receptive fields in the retina and striate cortex. Our ongoing research is aimed at clarifying the nature of these neural interactions and their locations in the brain, with the ultimate goal of understanding the neural basis of perception.
Publications
Rossi AF, Rittenhouse CD, Paradiso MA (1996) The representation of brightness in primary visual cortex. Science 273: 1104-1107.
Paradiso MA, Hahn S (1996) Filling-in percepts produced by luminance modulation. Vision Research 36: 2657-2663.
Rossi AF, Paradiso MA (1996) Temporal limits of brightness induction and mechanisms of brightness perception. Vision Research 36: 1391-1398.
Rossi AF, Paradiso MA (1995) Feature-specific effects of selective visual attention. Vision Research 35: 621-634.
Paradiso, M.A. and Nakayama, K. (1991) Brightness perception and filling-in. Vision Research 31:1221-1236.
A neuron in striate cortex is unresponsive when the light level outside its receptive field is modulated (second row). When light hitting the receptive field is modulated at 0.5 Hz, the response follows at that frequency (third row). If there is steady illumination of the receptive field, modulation of light outside the receptive field causes the central gray area to perceptually appear to vary between light and dark. In this situation, the neuron responds in a manner correlated with the perceptual brightness modulation (fourth row).