The occipital cortex of early blind individuals (EB) activates during speech processing, challenging the notion of a hard-wired neurobiology of language. But, at what stage of speech processing do occipital regions participate in EB? Here we demonstrate that parieto-occipital regions in EB enhance their synchronization to acoustic fluctuations in human speech in the theta-range (corresponding to syllabic rate), irrespective of speech intelligibility. Crucially, enhanced synchronization to the intelligibility of speech was selectively observed in primary visual cortex in EB, suggesting that this region is at the interface between speech perception and comprehension. Moreover, EB showed overall enhanced functional connectivity between temporal and occipital cortices sensitive to speech intelligibility and altered directionality when compared to the sighted group. These findings suggest that the occipital cortex of the blind adopts an architecture allowing the tracking of speech material, and therefore does not fully abstract from the reorganized sensory inputs it receives.
- Markus Johannes Van Ackeren
- Stefania Mattioni
- Roberto Bottini
- Olivier Collignon
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Human subjects: The project was approved by the local ethical committee at the University of Trento (protocol 2014-007). In agreement with the Declaration of Helsinki, all participants provided written informed consent to participate in the study.
- Andrew J King, University of Oxford, United Kingdom
© 2018, Van Ackeren et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.