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In human and other primate brains, the dominant route of visual information flow
relies on the primary visual cortex (V1), which then projects to extrastriate visual
cortex. The common residual motion sensitivity after V1 damage implies that
directionally selective neurons characteristic of the extrastriate middle temporal
(MT) and medial superior temporal (MST) areas are preserved. Altered metabolic
demands may be placed on MT/MST due to its increased dependence on alternate
visual inputs, such as those involving the superior colliculus (SC) and pulvinar or
the lateral geniculate nucleus (LGN). Thus, it was hypothesized that reorganization
may occur in MT/MST to increase the efficiency of alternate inputs, specifically
supported through changes in vasculature. Vascularization was examined by
quantifying the density of blood vessels in various areas of MT/MST in stained brain
slices from five macaque monkeys who received a V1 lesion as adults or as infants.
The densities of small and large blood vessels and of the total amount of blood
vessels were compared between the lesioned and intact hemispheres of the
monkeys. Few statistically significant differences were found between the
vascularization in the lesioned and in the intact hemispheres, failing to support the
hypothesis, although we found some suggestive trends. The results could indicate
that V1 lesions do not affect MT/MST vascularization. However, technical
limitations, such as ambiguity in distinguishing blood vessels or a limited number of
samples, may have influenced the results. Future analyses using different
methodology or staining could further explore this topic.
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