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A quadratic nonlinearity underlies direction selectivity in the nucleus of the optic tract

Published online by Cambridge University Press:  07 July 2001

MICHAEL R. IBBOTSON
Affiliation:
Developmental Neurobiology Group, Research School of Biological Sciences, Australian National University, Canberra, ACT 2601, Australia
COLIN W.G. CLIFFORD
Affiliation:
Department of Psychology, Macquarie University, Sydney, NSW 2109, Australia
RICHARD F. MARK
Affiliation:
Developmental Neurobiology Group, Research School of Biological Sciences, Australian National University, Canberra, ACT 2601, Australia

Abstract

A nonlinear interaction between signals from at least two spatially displaced receptors is a fundamental requirement for a direction-selective motion detector. This paper characterizes the nonlinear mechanism present in the motion detector pathway that provides the input to wide-field directional neurons in the nucleus of the optic tract of the wallaby, Macropus eugenii. An apparent motion stimulus is used to reveal the interactions that occur between adjacent regions of the receptive fields of the neurons. The interaction between neighboring areas of the field is a nonlinear facilitation that is accurately predicted by the outputs of an array of correlation-based motion detectors (Reichardt detectors). Based on the similarity between the output properties of the detector array and the real neurons, it is proposed that the interaction between neighboring regions of the receptive field is a second-order nonlinearity such as a multiplication. The results presented here for wallaby neurons are compared to data collected from directional systems in other species.

Type
Research Article
Copyright
1999 Cambridge University Press

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