Functional Asymmetries in visual pathways carrying S-Cone signals in macaque

In the lateral geniculate nucleus of macaque, we recorded from neurons with substantial input from S-cones and found that, on several important dimensions, the properties of neurons that receive inhibitory input from S-cones (" S -") are quite unlike those of neurons that receive excitatory input from S- cones (" S +"). First, the organization of chromatic inputs differs substantially: in S+ cells, S- cone signals were usually opposed by those of L- and M- cones; in S - cells, signals from L- cones were usually opposed to those of S- and M- cones. Second, to pure S- cone modulation, S+ cells are twice as sensitive as S -cells, but S - cells were much more susceptible to contrast adaptation. Third, in S - cells but not S + cells, the spatial frequency resolution for achromatic modulation was often greater, the tuning curve and more bandpass, than that for S- cone modulation. Along the dimensions on which we measured, the properties of the S - cells were relatively tightly clustered, suggesting a homogenous class. Although the chromatic properties of S + cells are heterogeneous, the distribution of their tuning along other stimulus dimensions does not suggest multiple subtypes.