Illusion - Is Seeing Really Believing?/Illusion - Is Seeing Really Believing (1998)(Marshall Media)[Mac-PC].iso/pc/illusion/hub_fie.cxt/00110_Field_frep64a.txt

Text File | 1996-12-30 | 2KB | 50 lines

    In the monkey cortex, the
cells that receive the input
from the geniculates, those
whose fields have circular
symmetry, are also like
geniculate cells in being
monocular. We find about an
equal number of left-eye and
right-eye cells, at least in parts
of the cortex subserving vision
up to about 20 degrees from the
direction of gaze. Beyond this
center-surround stage,
however, we find binocular
cells, simple and complex. In
the macaque monkey over half
of these higher-order cells can
be influenced independently
from the two eyes.

    Once we have found a
binocular cell we can compare
in detail the receptive fields in
the two eyes. We first cover the
right eye and map the cell's
receptive field in the left eye,
noting its exact position on the
screen or retina and its
complexity, orientation, and
arrangement of excitatory and
inhibitory regions; we ask if
the cell is simple or complex,
and we look for end stopping
and directional selectivity. Now
we block off the left eye and
uncover the right, repeating all
the questions. In most
binocular cells, we find that all
the properties found in the left
eye hold also for the right-eye
stimulation--the same position
in the visual field, the same
directional selectivity, and so
on. So we can say that the
connections or circuits
between the left eye and the
cell we are studying are present
as a duplicate copy between the
right eye and that cell.