Poster C6, Wednesday, August 21, 2019, 10:45 am – 12:30 pm, Restaurant Hall
Naturalistic auditory narratives drive shared neural responses in visual cortices across congenitally blind individuals
Marina Bedny1, Elizabeth Musz1, Rita Loiotile1, Rhodri Cusack2, Janice Chen1;1Johns Hopkins University, 2Trinity College Dublin, the University of Dublin
Studies of blindness provide insights into the contributions of nature and nurture to cortical function. Blindness enhances responses in ‘visual’ cortices to auditory and tactile stimuli (Sadato et al., 1996, Nature; Weeks et al., 2000 JoN, Roder et al., 2002 Euro J Neurosci). Whether visual cortices are reorganized systematically across different blind individuals, and if so, for what cognitive functions, remains debated. We used naturalistic stimuli to test the hypothesis that in blindness ‘visual’ cortices participate in higher-cognitive process, including plot-level semantic interpretation. Congenitally blind (CB; n = 18) and blindfolded sighted (S; n = 17) participants listened to three auditory narrative soundtracks excerpted from movies (6 minutes each) and one comedic routine (‘Pie-man’) while undergoing fMRI. Participants also heard versions of the ‘Pie-man’ story with parametrically degraded narrative and linguistic content: Pie-man with sentences presented in a scrambled order (intelligible language but no coherent storyline) and played backwards (i.e. uninterpretable). First, we correlated voxel-wise timecourses across participants and stimulus types to test for timecourse synchrony across different cortical networks. Second, we examined spatial organization of information across the cortex by measuring the distinctive spatial patterns of activity elicited by each 10-second segment of auditory stimuli (movies, narratives, sentence shuffle and backwards) (Chen et al., 2017, Nat Neuro). Replicating prior work in sighted participants, across blind and sighted individuals, movie soundtracks and the naturalistic narrative (‘Pie-man’) synchronized neural timecourses and elicited distinctive spatial patterns of activity for different time segments, in both higher-cognitive fronto-parietal and temporal areas and in low-level auditory networks (Lerner et al., 2011 JoN; Chen et al., 2017 Nat Neuro). By contrast, meaningless time-varying stimuli (e.g. backwards speech) elicit synchrony and event-specific spatial patterns only in low-level auditory cortices. An intermediate degree of synchrony was observed for shuffled sentences in higher-cognitive networks. Crucially, only among blind individuals, movie soundtracks and narratives elicited temporal synchrony and time-segment-specific patterns of activity in ‘visual’ cortices. These effects were observed only for the meaningful and cognitively complex stimuli (i.e. movie soundtracks and narrative) but not for backwards speech. These findings suggest that in blindness 1) ‘visual’ cortices respond to semantic/higher-cognitive information contained in naturalistic auditory narratives and movies; 2) ‘visual’ cortex representations are spatially organized in a similar fashion across blind individuals; 3) spatial patterns of activity within ‘visual’ cortices are sensitive to cognitive content. These results support the hypothesis that human cortices are highly cognitively flexible at birth.
Themes: Development, Signed Language and Gesture
Method: Functional Imaging