Simple cells can show nonlinear binocular combination

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Simple cells can show non-linear binocular
combination

• Jenny Read1
• Bruce Cumming1
• Andrew Parker2

1 National Eye Institute, National Institutes of
Health 2 Laboratory of Physiology, University of
Oxford
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how many eyes in monocular?

• a well-known fact

• in primary visual cortex, some neurons are
  monocular and others are binocular

• are these words really well-defined?

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(No Transcript)
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right monocular stimulus
left right
30
25
20
firing rate (spikes / s)
15
10
5
0
5
left monocular stimulus
left right
30
25
20
firing rate (spikes / s)
15
10
5
0
6
this cell is monocular
left right
30
25
20
firing rate (spikes / s)
15
10
5
0
7
left image right image
30
25
20
firing rate (spikes / s)
15
10
5
0
8
disparity tuning curve
left image right image
left right
30
25
20
left right
firing rate (spikes / s)
15
10
left right
5
0
-1.5
-0.5
0
0.5
1
disparity (degrees)
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left eye has purely inhibitory effect
30
25

20
-
firing rate (spikes / s)
15
10
5
0
-1.5
-0.5
0
0.5
1
disparity (degrees)
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population data

• how common is this pattern?

• how common is this pattern?

dominant monocular

• 93 disparity-selective neurons in V1 of awake
  behaving monkeys

one monocular response gt uncorrelated response
uncorrelated

• 38 showed this behaviour

AND
minimum binocular
other monocular response lt minimum binocular
response
?for 41, one eye has purely inhibitory effect
nondominant monocular
disparity
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circuitry of the energy model
binocular simple cell
eyes
disparity-selective complex cell
BS
Cx
inputs from the two eyes are combined linearly
excitatory inhibitory
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• the energy model says that each eye sends both
  excitatory and inhibitory input

receptive fields
left eye right eye
BS
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• the energy model says that each eye sends both
  excitatory and inhibitory input

receptive fields
BS
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a modified version
eyes
monocular simple cells
binocular simple cell
disparity-tuned complex cell
BS
Cx
one eye provides purely inhibitory input
or both eyes provide purely excitatory input
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Original energy model
BS
Cx
left / right inputs cancel
Our modified version
MS
BS
Cx
MS
left / right inputs cannot cancel
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disparate drifting grating
right eye
left eye
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phase difference 0o
right eye
MS

BS

MS
left eye
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phase difference 180o
right eye
MS

BS

MS
left eye
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phase difference 180o
half a cycle later
right eye
MS

BS

MS
left eye
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energy model modified version
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energy model modified version
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disparity-dependent frequency-doubling

• detect with second Fourier harmonic (F2)
• data-set containing 38 simple cells
• 13 (one-third ) had F2gtF1 at disparity where F1
  is minimal

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-180o
-90o
interocular phase difference
spikes / s
0o
90o
180o
time (1 stimulus period)
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summary

• energy model of disparity-tuned neurons
• cannot explain all aspects of data
• maybe because of its linear binocular combination
• we posit non-linearities prior to binocular
  combination
• this explains disparity selectivity in
  monocular neurons
• it predicts novel disparity-dependent frequency
  doubling in simple cells
• some evidence that this occurs