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要旨:
We measured responses of macaque ganglion cells as a
function of contrast in a simple hyperacuity task, detection
of displacement of an achromatic edge. Responses of ganglion
cells of the magnocellular (MC) pathway were much
more vigorous than those of cells of the parvocellular (PC)
pathway. From the variability in the number of impulses in
the response as compared with the distribution of impulses
in maintained activity, it was possible to generate receiver
operating characteristics for cells of the two pathways, and
to predict individual cells capability to detect a displacement
with 75 probability. On comparing cell sensitivities
to human psychophysical thresholds (75 probability of
correct identification of displacement direction) at an equivalent
retinal eccentricity (-SO), we found that one or two
additional impulses in two MC pathway cells would suffice
to support an ideal detector underlying psychophysical performance,
at all contrast levels. Many more PC pathway cells
would be required, especially at low contrasts. The much
higher signal-to-noise ratio in the MC pathway relative to the
PC pathway indicates that the MC pathway is likely to support
this and other hyperacuity tasks.
