Tectopulvinar pathway

The tectopulvinar pathway and the geniculostriate pathway are the two visual pathways that travel from the retina to the early visual cortical areas. From the optic tract, the tectopulvinar pathway sends neuronal radiations to the superior colliculus in the tectum, then to the lateral posterior-pulvinar thalamic complex.^[1] Approximately 10% of retinal ganglion cells (mostly magnocellular) project onto the tectopulvinar pathway.^[2]

The tectopulvinar pathway is a phylogenetically older pathway than the geniculostriate pathway,^[3] and is the only visual pathway present in fish, amphibians, and reptiles.^[1] The tectopulvinar pathway terminates at the prestriate cortex (also known as the extrastriate cortex or visual area V2),^[4] which receives large feedforward input from the striate cortex; the geniculostriate pathway also converges to the same location. . At the thalamic pulvinar nucleus, visual information is routed either to the medial pulvinar, which sends connections to cingulate, posterior parietal, premotor and prefrontal cortical areas; or to the lateral pulvinar, which sends connections to the temporal lobe dorsal stream cortical areas (and in particular, to region MT – a critical region for motion perception).^[5]

Damage to the tectopulvinar pathway is most commonly characterized by visual ataxia,^[1] a deficit characterized by an inability to perform visually guided hand movements in reaching and grasping objects,^[6] as well as by spatial attentional deficits.