ABSTRACT
Thalamic nuclei are thought to funnel sensory information to the brain's primary cortical areas, which in turn transmit signals afresh to higher cortical areas. Here we describe a direct projection in the macaque monkey from the lateral geniculate nucleus (LGN) to the motion-selective middle temporal area (MTor V5), a cortical area not previously considered 'primary'. The constituent neurons are mostly koniocellular, send virtually no collateral axons to primary visual cortex (V1) and equal about 10% of the V1 population innervating MT. This pathway could explain the persistence of motion sensitivity in subjects following injury to V1, suggesting more generally that residual perception after damage in a primary area may arise from sparse thalamic input to 'secondary' cortical areas.
