The Journal of Neuroscience, September 15, 2002, 22(18):8334-8345
Signals in Macaque Striate Cortical Neurons that Support
the Perception of Glass Patterns
Matthew A.
Smith1,
Wyeth
Bair1, 2, and
J.
Anthony
Movshon1, 2
1 Center for Neural Science and 2 Howard
Hughes Medical Institute, New York University, New York, New York 10003
Glass patterns are texture stimuli made by pairing randomly placed
dots with partners at specific offsets. The strong percept of global
form that arises from the sparse local orientation cues has made these
patterns the subject of psychophysical investigations, yet neuronal
responses to Glass patterns have not been studied. We measured the
responses of neurons in macaque striate cortex (V1) to dynamic,
translational Glass patterns as a function of dot separation and
dot-pair orientation. Responses were selective, but were on average
more than an order of magnitude weaker than responses to sinusoidal
gratings. Response and selectivity were greatest when the dot-pair
orientation matched that of the preferred grating and when dot
separation was between one-quarter and one-half of the spatial period
of the optimal grating; changing the dot-pair separation or inverting
the contrast of one of the dots radically changed the orientation
selectivity. We computed the expected responses for a receptive field
model to translational Glass patterns and found that the complexity of
our V1 tuning curves could be understood in terms of the responses of
linear filters to pairs of dots. This modeling connects our
understanding of V1 receptive fields as rectified, quasi-linear filters
with results from psychophysical studies of Glass patterns. Our results
provide a basis for studying how subsequent visual areas integrate
weak, local signals into global form percepts.
Key words:
Glass patterns; macaque monkey; primary visual cortex; V1; random dots; orientation selectivity; linear filter; spatial
frequency
Copyright © 2002 Society for Neuroscience 0270-6474/02/22188334-12$05.00/0
