Evolution of the primate visual system: Anterograde degeneration studies of the tecto‐pulvinar system

Abstract A partial answer to the question of the precocious development of the temporal lobe in fossil lemurs is offered by the presentation of evidence that in the tree shrew, in prosimians, and probably in all primates the temporal lobe contains primary visual cortex. The visual pathway to the temporal lobe is achieved by relays through the superficial layers of the superior colliculus and pulvinar nucleus. This pathway parallels the geniculo‐striate system. Still a third visual system can be identified with sensory‐motor connections in the deeper layers of the superior colliculus.