Some transformations of color information from lateral geniculate nucleus to striate cortex

摘要

We have recorded the responses of single cells in the lateral geniculate nucleus (LGN) and striate cortex of the macaque mon- key. The response characteristics of neurons at these successive visual processing levels were examined with isoluminant gratings, cone-isolating gratings, and luminance-varying gratings. The main findings were: (Ⅰ) Whereas almost all parvo- and konio-cellular LGN cells are of just two opponent-cell types, either differencing the L and M cones (L_o and M_o cells), or the S vs. L+M cones (S_o cells), relatively few striate cortex simple cells show chromatic responses along these two cardinal LGN axes. Rather, most are shifted away from these LGN chromatic axes as a result of combining the outputs (or the transformed outputs) of S_o with those of L_o and/or M_o cells. (Ⅱ) LGN cells on average process color information linearly, exhib- iting sinusoidal changes in firing rate to isoluminant stimuli that vary sinusoidally in cone contrast as a function of color angle. Some striate cortex simple cells also give linear responses, but most show an expansive response nonlinearity. resulting in narrower chro- matic tuning on average at this level. (Ⅲ) There are many more +S_o than -S_o LGN cells. but at the striate cortex level -S_o input to simple cells is as common as +S_o input. (Ⅳ) Overall, the contribu- tion of the S-opponent path is doubled at the level of the striate cortex, relative to that at the LGN.