The role of theta oscillations for prelexical abstraction

• Applicant: Antje Strauß, Ph.D.
• Subject Area: General and Comparative Linguistics, Experimental Linguistics, Typology, Non-European Languages ; Human Cognitive and Systems Neuroscience
• Term: from 2017 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 391911866

Speech comprehension is a complex task, although we seem to manage it effortlessly in everyday life. Recent advances in cognitive neuroscience propose that the auditory cortex tracks speech streams at various time scales corresponding to prelexical speech units (phonemes and syllables mainly) in order to achieve comprehension. Despite the lacking evidence, it has been claimed that it is the syllabic rhythm to which slow neural oscillations in the theta frequency range (3 to 7 Hz) in the auditory cortex entrain. Mechanistically, it is suggested that by entrainment time windows of high cortical excitability are aligned with the most informative parts of the speech signal. The current project aims at determining the underlying mechanism of cortical entrainment to the speech signal. In particular, we want to investigate whether cortical entrainment is a purely acoustic process or a signature of higher-level linguistic processes. If it is a speech specific mechanism as suggested by some sparse studies, we aim at clarifying at which prelexical level (phonemic or syllabic?) it is effective. Therefore, three work packages were designed targeting different aspects of prelexical processes in the framework of slow neural oscillations. By using electro¬encephalo¬graphy (EEG), we aim, first, at showing the role of slow oscillations for phonemic categorization versus syllable tracking. Second, we aim at investigating whether speech comprehension under adverse hearing conditions measured by cortical entrainment can be improved by using individually preferred speaking rates. Third, by driving cortical oscillations externally with tACS (transcranial alternating current stimulation) we aim at showing a more causal relationship between slow oscillations and speech comprehension, which might be useful in the future for clinical populations with linguistics deficits.

• DFG Programme: Research Grants
• International Connection: Switzerland
• Co-Investigator: Professor Dr. Carsten Eulitz
• Cooperation Partners: Professorin Dr. Anne-Lise Giraud; Professor David Poeppel, Ph.D.