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Comparative Color Psychophysics
Proper design and interpretation of visual neurophysiology experiments requires understanding the similarities and differences between human vision and animal vision. One approach to this goal is to compare visual performance in humans and animals.
Below are data from one monkey and one human performing a contrast detection task. Upper panels show detection thresholds for a 15 Hz flickering light that was blue or green in interleaved trials. As expected, thresholds increase with retinal eccentricity. This is due to changes in cone density. Less expected is the difference between the monkey and the human blue thresholds. In the monkey, blue thresholds depend weakly on retinal eccentricity. In the human, the dependence is stronger.
To show this difference more clearly, the lower panels show the ratio of blue and green detection thresholds as a function of retinal eccentricity. Monkeys are relatively sensitive to short wavelength flicker. This result has implications for the optical filtering that occurs within the monkey and human eye.
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Vision is the result of computations occurring in the eye and brain. We want to understand what these computations are and how they are implemented by neurons.
Our current research focuses on color vision. Thanks to decades of physiological and psychophysical studies, we know a great deal about how color is processed in the eye and about human color perception. We know relatively little, however, about the links between the two, that is, how color is processed in the cerebral cortex. Our primary experimental techniques are electrophysiological (single neuron recording and electrical microstimulation), psychophysical (measurement of detection thresholds), and computational (analysis of spike-triggered stimulus distributions). We are particularly interested in interactions between visual pathways that may serve to enhance color perception at luminance edges.
We are also exploring gene delivery techniques to manipulate components of the visual system and thereby tease apart their contributions to perception. We are developing in vivo assays of gene products that enhance or suppress neuronal signaling, and we are investigating methods for targeting virally mediated gene expression to specific subclasses of neurons.
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