Please use this identifier to cite or link to this item: http://hdl.handle.net/10316/92461
Title: Pivotal role of hMT+ in long-range disambiguation of interhemispheric bistable surface motion
Authors: Duarte, João Valente 
Costa, Gabriel Nascimento Ferreira da 
Martins, Ricardo Filipe Alves 
Castelo-Branco, Miguel 
Keywords: connectivity; decision-making; fMRI; interhemispheric integration; visual motion
Issue Date: 28-Jun-2017
Serial title, monograph or event: Human Brain Mapping
Volume: 38
Issue: 10
Abstract: It remains an open question whether long-range disambiguation of ambiguous surface motion can be achieved in early visual cortex or instead in higher level regions, which concerns object/surface segmentation/integration mechanisms. We used a bistable moving stimulus that can be perceived as a pattern comprehending both visual hemi-fields moving coherently downward or as two widely segregated nonoverlapping component objects (in each visual hemi-field) moving separately inward. This paradigm requires long-range integration across the vertical meridian leading to interhemispheric binding. Our fMRI study (n = 30) revealed a close relation between activity in hMT+ and perceptual switches involving interhemispheric segregation/integration of motion signals, crucially under nonlocal conditions where components do not overlap and belong to distinct hemispheres. Higher signal changes were found in hMT+ in response to spatially segregated component (incoherent) percepts than to pattern (coherent) percepts. This did not occur in early visual cortex, unlike apparent motion, which does not entail surface segmentation. We also identified a role for top-down mechanisms in state transitions. Deconvolution analysis of switch-related changes revealed prefrontal, insula, and cingulate areas, with the right superior parietal lobule (SPL) being particularly involved. We observed that directed influences could emerge either from left or right hMT+ during bistable motion integration/segregation. SPL also exhibited significant directed functional connectivity with hMT+, during perceptual state maintenance (Granger causality analysis). Our results suggest that long-range interhemispheric binding of ambiguous motion representations mainly reflect bottom-up processes from hMT+ during perceptual state maintenance. In contrast, state transitions maybe influenced by high-level regions such as the SPL. Hum Brain Mapp 38:4882-4897, 2017. © 2017 Wiley Periodicals, Inc.
URI: http://hdl.handle.net/10316/92461
ISSN: 1065-9471
1097-0193
DOI: 10.1002/hbm.23701
Rights: openAccess
Appears in Collections:I&D ICNAS - Artigos em Revistas Internacionais

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