A STUDY OF VISUAL SYSTEM TRANSFORMATION AND TEMPORAL SUMMATION RULES AS A FUNCTION OF DARK AND LIGHT ADAPTATION

LOLIN T WANG, Purdue University

Abstract

Two major adaptation questions were addressed in this thesis: The first was an examination of the contribution of postreceptor adaptation and nonlinearities to visual function. The transfer function between the photoreceptor and the optic nerve was obtained from intracellular recordings made under controlled dark and light adaptation. The second examined the effect of dark and light adaptation on the generality of a temporal summation rule previously described by Kong and Wasserman (1978a). The study of postreceptor adaptation and receptor to optic nerve function showed that: (1) a central nonlinearity exists, possibly located at the spike generation zone, (2) the transfer function is discontinuous and involves three piecewise linear segments, (3) the major contribution to postreceptor adaptation is a large subtractive change in the transfer function, (4) postreceptor adaptation also involves a smaller multiplicative shift in the transfer function. The temporal summation study replicated Kong and Wasserman's (1978a) finding that the critical duration and latency are related in dark adaptation by a subtractive relation. But a fractional relation was found in light adaptation. This effect of adaptation resolves disparities among a number of previous studies. This temporal summation experiment extended out to much longer durations than previously. Supersummation was obtained by integrating the receptor signal over long duration. Supersummation continued up to 4 second duration in light adaptation and even longer in dark adaptation.

Degree

Ph.D.

Subject Area

Psychobiology

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