Abstract
Human middle temporal complex (hMT+) responds also to the perception of non-visual motion in both sighted and early blind individuals, indicating a supramodal organization. Visual experience, however, leads to a segregation of hMT+ into a more anterior subregion, involved in the supramodal representation of motion, and a posterior subregion that processes visual motion only. In contrast, in congenitally blind subjects tactile motion activates the full extent of hMT+. Here, we used fMRI to investigate brain areas functionally connected with the two hMT+ subregions (seeds) during visual and tactile motion in sighted and blind individuals. A common functional connectivity network for motion processing, including bilateral ventral and dorsal extrastriate, inferior frontal, middle and inferior temporal areas, correlated with the two hMT+ seeds both in sighted and blind individuals during either visual or tactile motion, independently from the sensory modality through which the information was acquired. Moreover, ventral premotor, somatosensory, and posterior parietal areas correlated only with the anterior but not with the posterior portion of hMT+ in sighted subjects, and with both hMT+ seeds in blind subjects. Furthermore, a correlation between middle temporal and occipital areas with primary somatosensory seeds was demonstrated across conditions in both sighted and blind individuals, suggesting a cortico-cortical pathway that conveys non-visual information from somatosensory cortex, through posterior parietal regions, to ventral extrastriate cortex. These findings expand our knowledge about the development of the functional organization within hMT+ by showing that distinct patterns of brain functional correlations originate from the anterior and posterior hMT+ subregions as a result of visual experience.
Highlights
Visual perception of motion in humans activates specific areas of the temporo-occipital cortex that classically includes the human middle temporal complex, hMT+ (Watson et al, 1993; Zeki et al, 1993; Tootell et al, 1995)
The aim of the present study was to explore the functional correlations between hMT+ and the rest of the brain during visual and tactile motion processing tasks and the effects of visual experience and, of lack of visual experience, on the development of these correlations
A common network for motion processing functionally connected with both subregions of hMT+ Overall, we found that, both in sighted and congenitally blind subjects, a common set of bilateral brain areas, including ventral and dorsal extrastriate regions – such as the fusiform, parahippocampal and lingual cortex – middle and inferior temporal areas, and inferior frontal areas were positively correlated with both seed-ROIs in the anterior and posterior subregions of hMT+, during either the visual or tactile motion perception runs
Summary
Visual perception of motion in humans activates specific areas of the temporo-occipital cortex that classically includes the human middle temporal complex, hMT+ (Watson et al, 1993; Zeki et al, 1993; Tootell et al, 1995). HMT+ responds to the perception of auditory and tactile motion in sighted (Hagen et al, 2002; Ricciardi et al, 2007; Ptito et al, 2009; Summers et al, 2009), as well as in congenitally blind individuals (Poirier et al, 2006; Ricciardi et al, 2007) These latter findings indicate that hMT+ processes non-visual sensory inputs of motion, and that visual experience is not a prerequisite for the development of the functional organization of this motion-responsive area. In line with these findings, Beauchamp et al (2007) using fMRI to localize functional responses to visual and tactile stimuli within hMT+ demonstrated that the anterior and dorsal middle-superior temporal area (MST), but not the remaining portion, responded to simple vibrotactile stimuli
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