Top-down modulation of dichotic listening affects interhemispheric connectivity: an electroencephalography study

Area of Science:

• Neuroscience
• Auditory Perception
• Cognitive Psychology

Background:

• Dichotic listening (DL) investigates auditory processing and hemispheric lateralization.
• The callosal relay model explains the right ear advantage (REA) via direct left hemisphere access.
• Interhemispheric gamma-band coupling, assessed by lagged phase synchronization (LPS), is crucial for DL auditory perception.

Purpose of the Study:

• To explore the effects of top-down attention modulation on interhemispheric gamma-band LPS in DL.
• To extend previous findings on the neurophysiological mechanisms of DL.
• To investigate the interplay between attention and brain connectivity during auditory tasks.

Main Methods:

• 31 healthy right-handed participants underwent EEG recording during DL with varied attention conditions (no-attention, left-ear, right-ear).
• Source analysis utilized exact low-resolution brain electromagnetic tomography (eLORETA).
• Interhemispheric functional connectivity was measured using gamma-band LPS between auditory areas.

Main Results:

• 24 participants (77%) showed REA in the no-attention condition.
• Attention significantly altered REA, decreasing it with left-ear attention and increasing it with right-ear attention.
• Increased gamma-band LPS was observed between auditory Brodmann areas (BAs 41/42) during left-ear reports, while right-attention enhanced connectivity in BA 42, especially for right-ear reports.

Conclusions:

• Gamma-band synchronization supports interhemispheric connectivity in DL, aligning with the callosal relay model.
• Attentional modulation influences interhemispheric connectivity, supporting the attention-executive model.
• Reciprocal inhibition may play a role in hemispheric lateralization during dichotic listening.