Cross-modal functional connectivity supports speech understanding in cochlear implant users.

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Cross-modal Plasticity

Background:

• Sensory deprivation can induce cross-modal cortical changes, where deprived brain regions adapt to new functions.
• In postlingually deaf cochlear implant (CI) users, auditory cortex shows enhanced visual responses, potentially involving language regions.
• The adaptive or maladaptive nature of this cross-modal activity for speech comprehension remains unclear.

Purpose of the Study:

• To investigate if increased activation in language regions correlates with better speech understanding in CI users.
• To determine the adaptive significance of cross-modal activity in the auditory cortex of CI users.
• To explore the relationship between neural activity, functional connectivity, and speech perception abilities.

Main Methods:

• Functional near-infrared spectroscopy (fNIRS) measured hemodynamic responses in CI users (n=14) and normal-hearing listeners (n=17).
• Task-related activation and functional connectivity were assessed using auditory and visual speech/non-speech stimuli.
• Visually presented linguistic and non-linguistic stimuli were used to probe neural processes.

Main Results:

• CI users demonstrated beneficial cross-modal effects in response to visual speech stimuli.
• Increased connectivity between left auditory and visual cortices positively correlated with speech understanding in noise.
• Cross-modal activity in the auditory cortex of CI users was observed.

Conclusions:

• Cross-modal activity in the auditory cortex of postlingually deaf CI users may represent adaptive neural recruitment.
• This adaptive activity appears to involve a distributed, multimodal speech network enhancing speech understanding.
• Findings suggest that cross-modal plasticity in CI users can be beneficial for auditory rehabilitation.