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(NAS Colloquium) Vision From Photon to Perception (1999) / Chapter Skim
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Computational models of cortical visual processing
Pages 67-71

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From page 67...
... , there is an established tradition of modeling simple cells as linear neurons (5-9~. The response of a linear visual neuron is a weighted sum, over local space and recently past time, of the distribution of light intensity values in the stimulus.
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From page 68...
... For both real neurons and model neurons there is a unimodal response, a single preferred direction, for drifting grating stimuli. The direction tuning curves for plaids, however, are very different, with two distinct lobes.
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From page 69...
... Pattern direction selectivity arises in the model because each MT neuron sums inputs from several V1 afferents. Each of the V1 afferents is selective for a different direction of component motion, but their component motions are all consistent with the same overall pattern motion.
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From page 70...
... The direction tuning curves for plaids are unimodal, indicating that these neurons responded to the combined motion of entire plaid pattern, not to the motions of the component gratings. Pattern selectivity arises in the model because each model MT neuron sums inputs from several V1 afferents; each V1 afferent is selective for a different component motion, but all of these component motions are consistent with the same pattern motion.
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From page 71...
... Available Implementation. A simulation program for Macintosh computers that implements these two models (as well as the linear model of simple cell receptive fields)
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Key Terms

  • simple cells
  • preferred direction
  • simple cell
  • direction tuning
  • data replotted

  • direction selectivity
  • tuning curves
  • preferred orientation
  • normalization model
  • stimulus contrast

  • cortical neurons
  • linear weighting
  • moving dots
  • coherently moving
  • firing rate

  • horizontal lines
  • directionally selective
  • receptive field
  • visual cortex
  • component motion

  • component gratings
  • dashed horizontal
  • selectivity arises
  • dot field
  • component motions

  • neuron sums
  • spontaneous firing
  • nearly linearly
  • pattern motion
  • motion signal


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