Motion representation in hMT+/V5 : influence of cross-modal inputs and visual deprivation
(2021)
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- Authors
- Supervisors
- Collignon, Olivier
- Abstract
- The research presented in this thesis investigates the cross-modal representation of motion information in hMT+/V5 and the impact of visual deprivation using functional magnetic resonance imaging (fMRI). hMT+/V5 is a region in the dorsal visual pathway that is known to be dedicated to processing visual motion. To unravel how hMT+/V5 represents motion information across the senses and how it develops in the absence of visual experience, we performed the following studies: In the first study, we relied on fMRI recordings to characterize the representation of visual and auditory motion directions in individually and functionally defined hMT+/V5. We showed that auditory and visual motion directions can be reliably decoded in hMT+/V5. Additionally, motion directions in one modality can be predicted from the activity patterns elicited by the other modality. Despite shared motion-direction information across the senses, vision and audition produced opposite voxel-wise responses in hMT+/V5. Our results revealed a multi-faced representation of multisensory motion information in hMT+/V5. In the second study, we investigated how the absence of early visual experience in cataract-reversal patients shapes the development of the visual motion network using fMRI. Our results suggest that an early and brief period of visual deprivation leads to a reduced recruitment of the early visual areas while processing motion information when compared to matched controls with typical visual development. The reduced recruitment in the early visual cortex in cataract-reversal patients correlated with the duration of visual deprivation. Univariate and multivariate analyses showed no impairments in visual motion processing in the higher order visual motion area hMT+/V5 in the cataract-reversal patients. The results suggested that a brief and transient period of visual deprivation early in life has a region-specific impact on the visual motion network with V1 being permanently affected while hMT+/V5 shows some resilience to deprivation. In the third study, we investigated the resting-state connectivity architecture of hMT+/V5 with other regions within the visual motion network in early blind (EB) and late blind (LB) people. Our results demonstrated that the connectivity profile of hMT+/V5 with the different areas within the visual motion network was highly similar in all groups, and was not dependent on visual experience. Additionally, we investigated the connectivity profile of hMT+/V5 with the non-visual sensory networks, and found reduced connectivity with the somatosensory cortex during rest in the EB. Moreover, the connectivity profile of hMT+/V5 with the different sensory networks was not similar in the EB and the sighted. In contrast, there was no difference in the connectivity profile of hMT+/V5 between the LB and the sighted. These results demonstrate that blindness onset impacts the connectivity architecture of hMT+/V5 with non-visual networks. While hMT+/V5 reorganizes its resting connectivity profile as a consequence of early visual deprivation, the hMT+/V5 connectivity architecture was not significantly affected in the LB. Overall, our findings suggest: [1] hMT+/V5 represents motion information in a multisensory fashion with shared information between the senses. [2] Early and brief visual deprivation has a region-specific impact on the motion network, mostly affecting early visual areas but leaving hMT+/V5 somehow functionally preserved. [3] The age of onset of visual deprivation affects the multisensory connectivity profile of hMT+/V5.
- Affiliations
Citations
Rezk, M. (2021). Motion representation in hMT+/V5 : influence of cross-modal inputs and visual deprivation. https://hdl.handle.net/2078.5/113946