Perceptual Coherence : Hearing and Seeing

Characteristics of Auditory and Visual Scenes 143
Figure 3.15. Sparse coding in V1. The white line in (A) represents the simulated
visual scan path. The small white circle portrays the classical receptive field (CRF)
size, while the larger white circle is four times the CRF diameter. The response of
one V1 neuron to a presentation of the movie confined to the CRF is pictured in (B).
The responses were summed in 13.8 ms bins. The selectivity index of these data is
only 13%, which implies a dense distribution of responses across the stimulus set.
(The selectivity will equal 0 if the cell responds to every stimulus and will equal 1 if
it responds to only one stimulus.) The response distribution to 20 presentations of
the movie using a stimulus size four times the CRF diameter is shown in (C). Stimulation
of the nonclassical receptive field increases the selectivity to 51%. Increases
in the firing rate are indicated in black. The underbar highlights increases in rates
(black) and decreases in rates (white). Increases occur at onset transients. From
“Natural Stimulation of the Nonclassical Receptive Field Increases Information
Transmission Efficiency in V1,” by W. E. Vinje and J. L. Gallant, 2002, Journal of
Neuroscience, 22, 2904–2915. Copyright 2002 by the Society for Neuroscience.
Reprinted with permission.