Visual Neuroscience



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


NICK  BARRACLOUGH  a1 c1 , CHRIS  TINSLEY  a2 , BEN  WEBB  a3 , CHRIS  VINCENT  a4 and ANDREW  DERRINGTON  a4
a1 Department of Psychology, University of Hull, East Yorkshire, United Kingdom
a2 Department of Experimental Psychology, University of Bristol, Bristol, United Kingdom
a3 School of Psychology, University of Nottingham, Nottingham, United Kingdom
a4 The School of Psychology, University of Newcastle, Newcastle, United Kingdom

Article author query
barraclough n   [Google Scholar] 
tinsley c   [Google Scholar] 
webb b   [Google Scholar] 
vincent c   [Google Scholar] 
derrington a   [Google Scholar] 
 

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.

(Received October 7 2005)
(Accepted June 1 2006)


Key Words: Primate; Physiology; V1; Luminance; Contrast.

Correspondence:
c1 Address correspondence and reprint requests to: Nick Barraclough, University of Hull, Department of Psychology, East Yorkshire HU6 7RX, United Kingdom. E-mail: n.barraclough@hull.ac.uk