Visual cortex entrains to sign language [Psychological and Cognitive Sciences]
Despite immense variability across languages, people can learn to understand any human language, spoken or signed. What neural
mechanisms allow people to comprehend language across sensory modalities? When people listen to speech, electrophysiological
oscillations in auditory cortex entrain to slow (
<8 Hz) fluctuations in the acoustic envelope. Entrainment to the speech envelope may reflect mechanisms specialized for auditory
perception. Alternatively, flexible entrainment may be a general-purpose cortical mechanism that optimizes sensitivity to
rhythmic information regardless of modality. Here, we test these proposals by examining cortical coherence to visual information
in sign language. First, we develop a metric to quantify visual change over time. We find quasiperiodic fluctuations in sign
language, characterized by lower frequencies than fluctuations in speech. Next, we test for entrainment of neural oscillations
to visual change in sign language, using electroencephalography (EEG) in fluent speakers of American Sign Language (ASL) as
they watch videos in ASL. We find significant cortical entrainment to visual oscillations in sign language <5 Hz, peaking
at
∼1 Hz. Coherence to sign is strongest over occipital and parietal cortex, in contrast to speech, where coherence is strongest
over the auditory cortex. Nonsigners also show coherence to sign language, but entrainment at frontal sites is reduced relative
to fluent signers. These results demonstrate that flexible cortical entrainment to language does not depend on neural processes
that are specific to auditory speech perception. Low-frequency oscillatory entrainment may reflect a general cortical mechanism
that maximizes sensitivity to informational peaks in time-varying signals.
Publisher URL: http://feedproxy.google.com/~r/Pnas-RssFeedOfEarlyEditionArticles/~3/iD_dA-kt4Oc/1620350114.short
DOI: 10.1073/pnas.1620350114
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