Continuous speech with pauses inserted between words increases cortical tracking of speech envelope

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Speech Processing

Background:

• The decoding multivariate Temporal Response Function (decoder) assesses cortical tracking of speech envelopes by analyzing correlations between speech stimuli and neural responses.
• Auditory late responses are known to improve with longer stimulus gaps, but its effect on speech envelope reconstruction accuracy remains unclear.

Purpose of the Study:

• To investigate if adding pauses to continuous speech enhances speech envelope reconstruction accuracy using the decoder.
• To determine if pauses affect delta and theta frequency bands and if responses are dominated by speech onset regions.

Main Methods:

• Participants listened to continuous natural speech, speech with short (250 ms) pauses, and speech with long (500 ms) pauses.
• Electroencephalography (EEG) and speech envelopes were recorded and filtered into delta (1-4 Hz) and theta (4-8 Hz) bands.
• Analysis focused on whole speech envelope and segmented onset/non-onset regions.

Main Results:

• Continuous speech with inserted pauses significantly increased speech envelope reconstruction correlations compared to natural speech in both delta and theta bands.
• The increase in reconstruction accuracy was predominantly observed in the onset regions of the speech envelope.
• Longer pauses led to greater increases in reconstruction accuracy.

Conclusions:

• Inserting pauses into continuous speech stimuli enhances speech envelope reconstruction accuracy, particularly in delta and theta bands, and is driven by speech onsets.
• This technique may improve auditory evoked response detectability in clinical settings, though it impacts speech naturalness.
• The influence of pauses and onsets on decoders needs consideration when comparing different speech corpora.