Rhythmic electrical activity in the brain (neural oscillations) has been shown to align to the rhythm of speech, particularly when listeners successfully understand sentences. However, it remains unknown whether these oscillations truly cause successful speech processing, or are only a commonly-associated epiphenomenon.
In a recent publication in Current Biology, Benedikt Zoefel, Alan Archer-Boyd, and Matt Davis from the MRC Cognition and Brain Sciences Unit (MRC CBU), University of Cambridge, use transcranial alternating current stimulation (tACS) to modulate this rhythmic electrical activity and demonstrate that blood oxygenation responses measured with fMRI: (1) depend on alignment between oscillations and speech rhythm, (2) in brain regions critical for processing speech (the superior temporal gyrus), (3) predict individual differences in rhythmic processing of speech and (4) only if the presented speech is intelligible.
These findings suggest that alignment of brain oscillations to speech rhythm is a crucial mechanism that supports comprehension. This finding suggests new ways in which we can use brain stimulation to enhance speech processing in hearing-impaired listeners or others that struggle to understand speech.
The full article can be read here: Phase Entrainment of Brain Oscillations Causally Modulates Neural Responses to Intelligible Speech: Benedikt Z, Archer-Boyd A, Davis M.