Delta-theta-gamma interplay for contextualized speech parsing
Olesia Dogonasheva (ENS Paris and Moscow University)
Hybrid: onsite seminar + zoom.
Meeting ID: 918 7755 9782
Rhythms stretching across multiple interacting frequencies and spatial scales are ubiquitous in brain activity during complex cognitive tasks. Yet their functional significance is hotly debated between a structural epiphenomenon of brain activity and mechanisms implementing computations. Speech processing, with its temporal cadence and multi-scale of syntactic invariants (syllables, words), is a paradigmatic example where rhythms have been proposed to play a key role, with a speech-modulated hierarchical structure of intercoupled cortical oscillations correlating with successful comprehension. Experiments show that speech recognition remains largely intact when compressed up to a certain temporal factor, and the re-spacing of chunks of incomprehensible compressed speech with silences recovers comprehension. Previous models proposed that theta-gamma interactions enable syllable parsing. However, this did not resolve questions about word/phrase recognition and, notably, the observed role of delta rhythm in top-down information flow. To address the above questions, we propose an inference model (BRyBI) that incorporates a wide range of brain-rhythm data mechanistically and accounts for time-invariant word recognition. Our model predicts that delta-implemented word context allows for syllable parsing without precise locking of the theta-rhythmic activity.