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Retinal adaptation

S A J Winder mapsajw at midge.bath.ac.uk
Wed Nov 10 07:27:08 EST 1993

  I have a question about the adaptation responses of retinal ganglion
neurons in the primate to diffuse chromatic and achromatic light.

  It appears from the literature that RGNs adapt completely to changes
in achromatic retinal illumination, in that when this illumination is
increased the neuron's firing rate will increase initially, but
eventually fall back to the level of its maintained activity (for an
on-centre neuron) over a period of say, 30 seconds. It also appears that
such neurons do not adapt in this way to standing contrast in their RFs.

  My question is: do RGNs adapt completely to diffuse coloured light?
It is hard to see how they could do, because for a neuron with a
centre driven by red cones and surround driven by green cones, diffuse
red light ought to produce a contrast-like effect between centre and
surround which is indistinguishable from the case where the centre is
driven by stronger *achromatic* illumination than the surround.
However for psychophysical experiments using image stabilisation (e.g.
Kelly 1983), chromatic gratings are known to disappear completely due
to adaptation regardless of spatial frequency, so I want to know the
site of this adaptation.

  If you can offer any insight into this and any references I'd be
very greatful.

 Simon A.J. Winder                Vision Research
 sajw at maths.bath.ac.uk    University of Bath Computing Group
 Tel: +44 (0)225 826183   /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\

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