The Early Maturation of Visual Cortical Area MT is Dependent on Input from the Retinorecipient Medial Portion of the Inferior Pulvinar

Abstract

The hierarchical development of the primate visual cortex and associated streams remains somewhat of a mystery. While anatomical, physiological, and psychological studies have demonstrated the early maturation of the dorsal "where"/"how" or motion cortical stream, little is known about the circuitry responsible. The influence of the retinogeniculostriate pathway has been investigated, but little attention has been paid to the role of two more recently described disynaptic retinothalamic projections to the middle temporal (MT) area, an early maturing dorsal stream cortical field, and which bypass the primary visual cortex (V1). These pathways are via the koniocellular layers of the lateral geniculate nucleus (LGN) and the medial portion of the inferior pulvinar (PIm). Both have been demonstrated in the adult nonhuman primate, but their influence during the maturation of the visual cortex is unknown. We used a combination of neural tracing and immunohistochemistry to follow the development of LGN and PIm inputs to area MT in the marmoset monkey. Our results revealed that the early maturation of area MT is likely due to the disynaptic retinopulvinar input and not the retinogeniculate input or the direct projection from V1. Furthermore, from soon after birth to adulthood, there was a dynamic shift in the ratio of input from these three structures to area MT, with an increasing dominance of the direct V1 afference.

Quantifying the pattern of optic tract degeneration in human hemianopia

“…Indeed, these pathways have been posited to underlie the ability of some of these patients to make unconscious ‘guesses’ about visual stimuli (blindsight) 24. Thus, where damage is specific to V1, any projections from the LGN or the pulvinar25 that may project to V2,26 V5/MT27 28 or other extrastriate regions may still be intact, and therefore OT fibres are preserved. As the lesion size is increased within the occipital lobe, the additional pathways are also affected, and therefore there is no longer a useful function for the OT.…”

Global Motion Perception in 2-Year-Old Children: A Method for Psychophysical Assessment and Relationships With Clinical Measures of Visual Function

“…79,80 In fact, it recently was found that the early maturation of area MT likely is to be reliant on retinopulvinar input. 81 An alternative explanation is that OKR is less susceptible to response errors. Whatever the reason for the absolute difference between behavioral and OKR responses in adults, the close correlation between the two measures suggests that they target a common neural mechanism, which is likely to be global motion processing within the extrastriate visual cortex.…”

The Davida Teller Award Lecture, 2016

“…The early connections through the pulvinar, shown in orange, have been suggested (e.g., Johnson, 2005; Warner, Kwan, & Bourne, 2012), although such links have not been demonstrated in human development. These links, colored in orange, are additions to earlier published versions of this figure (Atkinson, 2000; Atkinson & Braddick, 2012b).…”