FIGURE 10.

Coordinate transforms in the primate dorsal visual system. Three stages of coordinate transforms that take place at different levels of the primate dorsal visual system are shown. At each stage the coordinate transform is performed by gain modulation of the receptive field by an appropriate modulator, that is usefully combined with slow learning of the type implemented in VisNet which helps the same neurons at a particular stage to develop what are effectively representations that become independent of the modulating signal. In Layer 1 gain modulation by eye position combined with slow learning enables neurons to develop representations in head-centered coordinates that are invariant with respect to retinal and eye position. In Layer 2 gain modulation by head direction combined with slow learning enables neurons to develop representations in allocentric bearing to a stimulus such as a landmark coordinates that are invariant with respect to head direction. In Layer 3 gain modulation by the place where the individual is located combined with slow learning enables neurons to develop representations of a stimulus such as a landmark that are in allocentric spatial view coordinates with invariance with respect to where the individual is located. The diagram shows the architecture of the VisNetCT model in which gain modulation combined with short-term memory trace associative learning was shown to implement these transforms (Rolls, 2020). Each neuron in a Layer (or cortical area in the hierarchy) receives from neurons in a small region of the preceding Layer. It is proposed that idiothetic update through this dorsal visual cortical stream is used for idiothetic update of hippocampal spatial view cells useful for navigation when the environment may not be visible for short periods (Rolls, 2020, 2021b). PCC, posterior cingulate cortex; RSC, retrosplenial cortex.