Neural pathways conveying novisual information to the visual cortex

Abstract

The visual cortex has been traditionally considered as a stimulus-driven, unimodal system with a hierarchical organization. However, recent animal and human studies have shown that the visual cortex responds to non-visual stimuli, especially in individuals with visual deprivation congenitally, indicating the supramodal nature of the functional representation in the visual cortex. To understand the neural substrates of the cross-modal processing of the non-visual signals in the visual cortex, we firstly showed the supramodal nature of the visual cortex. We then reviewed how the nonvisual signals reach the visual cortex. Moreover, we discussed if these non-visual pathways are reshaped by early visual deprivation. Finally, the open question about the nature (stimulus-driven or top-down) of non-visual signals is also discussed.

Figure 1

Schematic of neural pathways that convey auditory signals into visual areas. The solid line represents the existing connections in the normal sighted animals or human; dash line represents the rewired connections after early visual deprivation; arrows with red, blue, and black color represent the bottom-up, top-down, and bidirectional auditory signals, respectively. All these connections are confirmed by previous animal or human studies (for details see Section 3). A1: primary auditory cortex; IC: inferior colliculus; MGN: medial geniculate nucleus; LGN: lateral geniculate nucleus; PPC: post parietal cortex; STS: superior temporal cortex; VLPFC: ventral lateral prefrontal cortex; V1: primary visual cortex.

Figure 2

Schematic of neural pathways that convey somatosensory signals into visual areas. The solid line represents the existing connections in the normal sighted animals or human; dash line represents the rewired connections after early visual deprivation; arrows with red, blue, and black color represent the bottom-up, top-down, and bidirectional somatosensory signals, respectively. LGN: lateral geniculate nucleus; PPC: post parietal cortex; S1: primary somatosensory cortex; STS: superior temporal cortex; VLPFC: ventral lateral prefrontal cortex; V1: primary visual cortex; VP: ventral posterior nuclei.