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Processing of first-order motion in marmoset visual cortex is influenced by second-order motion

Published online by Cambridge University Press:  04 October 2006

NICK BARRACLOUGH
Affiliation:
Department of Psychology, University of Hull, East Yorkshire, United Kingdom
CHRIS TINSLEY
Affiliation:
Department of Experimental Psychology, University of Bristol, Bristol, United Kingdom
BEN WEBB
Affiliation:
School of Psychology, University of Nottingham, Nottingham, United Kingdom
CHRIS VINCENT
Affiliation:
The School of Psychology, University of Newcastle, Newcastle, United Kingdom
ANDREW DERRINGTON
Affiliation:
The School of Psychology, University of Newcastle, Newcastle, United Kingdom

Abstract

We measured the responses of single neurons in marmoset visual cortex (V1, V2, and the third visual complex) to moving first-order stimuli and to combined first- and second-order stimuli in order to determine whether first-order motion processing was influenced by second-order motion. Beat stimuli were made by summing two gratings of similar spatial frequency, one of which was static and the other was moving. The beat is the product of a moving sinusoidal carrier (first-order motion) and a moving low-frequency contrast envelope (second-order motion). We compared responses to moving first-order gratings alone with responses to beat patterns with first-order and second-order motion in the same direction as each other, or in opposite directions to each other in order to distinguish first-order and second-order direction-selective responses. In the majority (72%, 67/93) of cells (V1 73%, 45/62; V2 70%, 16/23; third visual complex 75%, 6/8), responses to first-order motion were significantly influenced by the addition of a second-order signal. The second-order envelope was more influential when moving in the opposite direction to the first-order stimulus, reducing first-order direction sensitivity in V1, V2, and the third visual complex. We interpret these results as showing that first-order motion processing through early visual cortex is not separate from second-order motion processing; suggesting that both motion signals are processed by the same system.

Information

Type
Research Article
Copyright
2006 Cambridge University Press

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