Temporal dynamics of a neural solution to the aperture problem in visual area MT of macaque brain

Pack & BornNature (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 V1What if there is no problem in V1?

Need to measure time course in V1V1 should never converge