Psychology
|
Dr. Nestor Matthews
|
Research
As a perceptual psychologist, my research interests are in psychophysics (the science establishing quantitative relations between physical stimulation and perceptual events). My psychophysical studies are often motivated by the complimentary disciplines of neural modeling and visual physiology. For instance, various neural models inspired me to quantify the relationship between light intensity and the salience with which illusory contours are seen. Similarly, my psychophysical investigation of a motion illusion, known as direction repulsion, was motivated by the physiological finding that the firing-rates of certain visual cortical neurons are reduced when opposite directions of motion are spatially proximal.
A particular line of research that interests me addresses the issue of plasticity in the adult human brain. Plasticity can be inferred psychophysically from perceptual learning experiments, which measure practice-based improvements in subtle perceptual discriminations. In a recent perceptual learning study, my collaborators and I had observers practice identifying subtle angular differences between two moving stimuli or two stationary lines. Contrary to many previous studies suggesting that perceptual learning was specific to the trained stimulus, we found that practice-based improvements on the motion stimuli transferred significantly to the stationary lines. We believe that this transfer reflects an overlap in the neural mechanisms mediating direction and orientation discrimination, and that transfer was not found earlier because the previously examined tasks depended on non-overlapping neuronal populations. Thus, perceptual learning experiments not only provide direct evidence for plasticity in the adult human brain, but also serve as a tool for probing the neuronal responses that mediate various visual tasks.
My present research program includes a series of perceptual learning experiments that can be readily shared with students who seek to gain research experience. One experiment involves investigating the relationship between the angular resolution and the temporal resolution of orientation-tuned neural mechanisms. In particular, we will establish psychophysically whether practice-based improvements in angular resolution subsequently affect temporal resolution, and vice versa. Other perceptual learning experiments that I plan to conduct pertain to motion discrimination. An issue to be addressed here is whether practice-based improvements in direction discrimination can occur simultaneously for opposite directions. Each of these perceptual learning experiments will provide new information about the neural mechanisms responsible for subtle spatial discriminations.
Peer Reviewed Publications With Denison Student Co-Authors
Dr. Matthews joined the faculty at Denisonin 2001 following completion of a four-year post-doctoral fellowship in the Center for Neurobiology & Behavior at Columbia University. Dr. Matthews teaches Sensation & Perception, Research Methods, and Introductory Psychology. Some seminars he has offered include "Perceptual Learning and Brain Plasticity", and "The Cognitive Neuroscience of Music". His research interests are in human vision and audition.