Processing of first-order motion in marmoset visual cortex is influenced by second-order motion.
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.
Barraclough
Nick
N
Department of Psychology, University of Hull, East Yorkshire, United Kingdom. n.barraclough@hull.ac.uk
Tinsley
Chris
C
Webb
Ben
B
Vincent
Chris
C
Derrington
Andrew
A
D000200:Action Potentials / Q000502:physiology; D000704:Analysis of Variance; D000818:Animals; D001931:Brain Mapping; D002144:Callithrix / Q000033:anatomy & histology / Q000502:physiology; D009038:Motion; D009039:Motion Perception / Q000502:physiology*; D009474:Neurons / Q000502:physiology*; D009949:Orientation; D010775:Photic Stimulation / Q000379:methods; D011601:Psychophysics; D014793:Visual Cortex / Q000166:cytology / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology*