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The Journal of Neuroscience, November 15, 2006, 26(46):11987-11991; doi:10.1523/JNEUROSCI.4024-06.2006
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Brief Communications
A Single Mechanism Can Explain the Speed Tuning Properties of MT and V1 Complex Neurons
John A. Perrone Department of Psychology, The University of Waikato, Hamilton 3240, New Zealand
Correspondence should be addressed to John A. Perrone, Department of Psychology, The University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand. Email: jpnz{at}waikato.ac.nz
A recent study by Priebe et al., (2006) has shown that a small proportion (27%) of primate directionally selective, complex V1 neurons are tuned for the speed of image motion. In this study, I show that the weighted intersection mechanism (WIM) model, which was previously proposed to explain speed tuning in middle temporal neurons, can also explain the tuning found in complex V1 neurons. With the addition of a contrast gain mechanism, this model is able to replicate the effects of contrast on V1 speed tuning, a phenomenon that was recently discovered by Priebe et al., (2006). The WIM model simulations also indicate that V1 neuron spatiotemporal frequency response maps may be asymmetrical in shape and hence poorly characterized by the symmetrical two-dimensional Gaussian fitting function used by Priebe et al., (2006) to classify their cells. Therefore, the actual proportion of speed tuning among directional complex V1 cells may be higher than the 27% estimate suggested by these authors.
Key words: speed tuning; visual motion processing; V1; MT; spatiotemporal frequency; contrast sensitivity
Received July 26, 2006; revised Sept. 28, 2006; accepted Oct. 4, 2006.
Correspondence should be addressed to John A. Perrone, Department of Psychology, The University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand. Email: jpnz{at}waikato.ac.nz
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