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Published on: July 13, 2019
Pulsed transcranial electric brain stimulation enhances speech comprehension
Philipp Ruhnau1, Katharina S Rufener1, Hans-Jochen Heinze1
1Department of Neurology, Otto-von-Guericke-University, Magdeburg, Germany; Center for Behavioral Brain Sciences, Otto-von-Guericke-University Magdeburg, Germany.
Pulsed transcranial electrical stimulation (tES) improved speech comprehension in noise by delivering brief pulses aligned to speech transients. This method aids cortical entrainment without requiring continuous oscillation, offering a new approach for auditory processing enhancement.
Area of Science:
- Neuroscience
- Auditory Neuroscience
- Cognitive Neuroscience
Background:
- Cortical brain rhythm alignment to acoustic input (entrainment) is crucial for speech processing.
- Transcranial electrical stimulation (tES) at speech-relevant frequencies enhances speech perception.
- The necessity of oscillatory tES versus transient stimulation for speech processing remains unclear.
Purpose of the Study:
- To investigate if transiently pulsed tES, rather than oscillating tES, can improve speech processing.
- To evaluate the efficacy of a novel pulsed-tES protocol for enhancing auditory comprehension.
Main Methods:
- Subjects listened to sentences in noise while receiving brief direct current pulses.
- Pulses were applied to auditory cortex regions, timed with speech transients (syllable onsets).
- Temporal delays between tES pulses and speech transients were manipulated to test for entrainment.
Main Results:
- Speech comprehension improved significantly when tES pulses were applied with a 100 ms delay relative to speech transients.
- No periodic modulation of behavior was observed, contrary to some previous findings.
- Potential spurious periodic modulations were noted due to coarse behavioral data sampling.
Conclusions:
- Pulsed-tES enhances speech comprehension, particularly in noisy environments, by aiding cortical entrainment to speech.
- Transient pulsed-tES is sufficient to benefit speech processing, negating the need for continuous oscillation.
- Pulsed-tES appears to facilitate cortical entrainment to speech input but does not directly entrain brain oscillations itself.
