TABLE OF ANSWERS ABOUT DIMENSIONS

A published version, with modified format but identical content, is in Graham, N. (1992) Breaking the visual stimulus into parts. Current Directions in Psychological Science, 1, 55-61.

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The rows of the table give the dimensions necessary to specify the spatiotemporal receptive field of a neuron or analyzer. Alternatively, these dimensions can be described as dimensions necessary to characterize a particular visual stimulus -- a sinusoidal patch). These dimensions also illustrated in figures on another page.

The columns of the table summarize the results of near-threshold studies in terms of 4 questions, each of which can be answered by near-threshold experiments.
-Are there multiple analyzers on a given dimension?
-Are the outputs of the multiple analyzers labeled?
-Are the multiple analyzers probabilistically independent?
-Is there mutual inhibition among the analyzers?

*Bandwidths are given as full width at half peak height. The bandwidths, while typical, generally depend on values on other dimensions, which could only be noted in table when dramatic. See Graham (1989), especially Ch. 12, for more information.

QUESTION

 

 

DIMENSION

Multiple analyzers?*

Labeled outputs?
 Proba-
bilistic indepen-
dence?		 Mutual inhibition?
Spatial
frequency

Yes

with bandwidth of
0.5-1.5 octaves.

Yes Yes Perhaps,weak
near threshold
Orientation

Yes

with bandwidth of 15-60 degs of rotation.

Yes Yes Perhaps,weak
near threshold
Spatial position
(x and y)

Yes

Along one dimension
the receptive field has
an excitatory center
and inhibitory flanks
and (maybe)
excitatory outer flanks.
Along other dimension it has
only excitatory center.
Full receptive field is
approximately circular.

Yes Yes Perhaps,weak
near threshold
Spatial extent
(width, length)		 Probably not near threshold. ____ ____ ____
Spatial phase
(symmetry)		 Unclear ____ ____ ____
Temporal
frequency		 No narrowly-tuned analyzers,
but 2 or 3 very broadly-
tuned.		 Yes Unknown Unknown
Temporal
position

Yes

with impulse response
that is purely excitatory at
high spatial frequencies,
and biphasic
at low spatial frequencies.

Yes Yes Unknown
Temporal extent
(duration)		 Unknown ____ ____ ____
Temporal phase
(symmetry)		 Unclear ____ ____ ____
Direction of
motion

Yes

at high velocities,
no at low velocities.

Yes Probably
yes		 Perhaps, little
evidence
Eye of origin

Yes

May differ in degree of
binocularity as well.

No Unclear Unclear

 

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