Transcript Temporal dynamics of a neural solution to the aperature

Temporal dynamics of a neural
solution to the aperture problem in
visual area MT of macaque brain

Pack & Born
Nature (2001)
Harvard Medical School
Q:
Who solves the aperture problem?
OR…
What is the function of MT?
Alternatives:
MT solves aperture problem
MT does not solve aperture problem
L:
 V1
creates aperture problem because it
has a small RF (is looking for edge) and
MT solves because it’s neurons/RF are
bigger
 MT response should be tuned for actual
direction of motion and not for
orientation of the contour (not in actual
direction of the motion)
Methods:

Train macaques to fixate on small red square
for liquid reward
 Using microelectrodes record monkey’s
tuning curve in MT once fixated
 Field of moving bars (8 directions, 3 relative
orientations) as stimulus presented 10 times
 Spikes recorded from 60-80 ms after onset of
stimulus motion and recorded during the last
1,500 ms
Results:

In the beginning, is MT fooled and tuned like V1
 Response then converges regardless of
orientation
Interpretation:
MT
solves the aperture problem
Problems:
 Assumes
that early MT responses
reflects output from V1
 What if there is no problem in V1?
Need to measure time course in V1
V1 should never converge