Perceptual Coherence : Hearing and Seeing

44 Perceptual Coherence
Static Spatial-Temporal Receptive Fields: Simple Cells The receptive
fields of simple cells are elongated and orientation specific and respond at
their highest rates for white-and-black patterns at one frequency and at one
orientation. These cells are phase-specific, much like the ganglion cells described
previously.
The receptive fields of simple cortical cells were determined by Jones
and Palmer (1987b) using reverse correlation. Bright and dark spots were
presented randomly, and the spatial field was calculated by subtracting the
regions where the darker stimuli (i.e., off-responses) evoked spikes from
the regions where brighter stimuli (i.e., on-responses) evoked spikes. The
regions of the receptive field that respond to dark and bright are shown in
figure 2.7A as increases in firing rates, and then the dark regions are subtracted
in figure 2.7B. An example of the response to bright and dark stimuli
at different times before a spike is shown in figure 2.7C.
Figure 2.7. Derivation of
simple cortical cells. The first
step is to isolate the retinal
areas that affect the firing rate.
Both excitation and inhibition
areas are plotted as positives
in (A). The inhibitory areas
are subtracted in (B). An
example of the response to
bright and dark stimuli at
three times before the spike is
depicted in (C). The strongest
response occurs 50 ms before
the spike. From “The two dimensional
spatial structure of
simple receptive fields in cat
striate cortex,” by J. P. Jones
and L. A. Palmer, 1987b,
Journal of Neurophysiology,
58, 1187–1911. Copyright
1987 by the American Physiological
Society. Reprinted
with permission.
(A)
Excitation-Inhibition
y Spatial
Dimension
(B)
Excitation-Inhibition
y Spatial
Dimension
x Spatial Dimension
x Spatial Dimension