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Striate cortex increases contrast gain of macaque LGN neurons

Published online by Cambridge University Press:  01 July 2000

ANDRZEJ W. PRZYBYSZEWSKI
Affiliation:
Department of Neurology, University of Massachusetts Medical Center, Worcester
JAMES P. GASKA
Affiliation:
Department of Neurology, University of Massachusetts Medical Center, Worcester
WARREN FOOTE
Affiliation:
Department of Neurology, University of Massachusetts Medical Center, Worcester
DANIEL A. POLLEN
Affiliation:
Department of Neurology, University of Massachusetts Medical Center, Worcester

Abstract

Recurrent projections comprise a universal feature of cerebral organization. Here, we show that the corticofugal projections from the striate cortex (V1) to the lateral geniculate nucleus (LGN) robustly and multiplicatively enhance the responses of parvocellular neurons, stimulated by gratings restricted to the classical receptive field and modulated in luminance, by over two-fold in a contrast-independent manner at all but the lowest contrasts. In the equiluminant plane, wherein stimuli are modulated in chromaticity with luminance held constant, such enhancement is strongly contrast dependent. These projections also robustly enhance the responses of magnocellular neurons but contrast independently only at high contrasts. Thus, these results have broad functional significance at both network and neuronal levels by providing the experimental basis and quantitative constraints for a wide range of models on recurrent projections and the control of contrast gain.

Type
Research Article
Copyright
© 2000 Cambridge University Press

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