Natural time-varying images possess significant temporal correlations
   when  sampled  frame   by   frame   by   the  photoreceptors.   These
   correlations persist even after retinal  processing  and hence, under
   natural  activation  conditions,  the  signal  sent  to  the  lateral
   geniculate  nucleus  is  temporally  redundant  or  inefficient.   We
   explore the hypothesis that the LGN is concerned, among other things,
   with improving  efficiency  of  visual  representation through active
   temporal decorrelation of the retinal  signal  much  in  the same way
   that  the  retina  improves  efficiency  by  spatially  decorrelating
   incoming images.  Using some recently measured statistical properties
   of  time-varying  images,  we  predict  the spatio-temporal receptive
   fields that achieve this decorrelation.  It is shown that, because of
   neuronal nonlinearities, temporal decorrelation requires two response
   types,  the  lagged  and  nonlagged,  just  as spatial  decorrelation
   requires  on  and  off  response  types.   The  tuning  and  response
   properties of the  predicted  LGN  cells  compare quantitatively well
   with what is observed in recent physiological experiments.

   (Network: Computation in Neural Systems. Vol 6(2): page 159-178. 1995)

   (Papers' Index of Dawei Dong)