Figure 2.

Illustration of the developmental trajectory of the retino-pulvinar-MT pathway and the effects of early-life damage to V1, identified by neural tracing and imaging in the New World marmoset monkey. (A) In the neonate, a prominent direct pathway (blue arrow) carries retinal information through the optic tract (OT) to the medial division of the inferior pulvinar (PIm), in addition to the lateral geniculate nucleus (LGN). A thalamocortical pathway from PIm (red arrow) is thought to pass this image information to cortical area MT, thus completing the early visual pathway to the extrastriate cortex. (B) During normal development, as the LGN pathway matures and begins to dominate visual input to the cortex through the optic radiations (OR), the early visual pathway through PIm regresses. (C) When animals develop in the context of an early life V1 lesion, this regression fails to occur. The LGN undergoes significant degeneration and both the afferent and efferent components of the PIm visual pathway remain intact. It may be for this reason that early life V1 lesions lead to a significant retention of vision. However, following a lesion of V1 in adulthood (not shown), the degeneration of the LGN is not accompanied by a strenghtening of the PIm-MT pathway, which has already regressed. [Reproduced with permission from Trends in Cognitive Sciences (Bridge et al., 2016)].