Predicting attentional focus: Heartbeat-evoked responses and brain dynamics during interoceptive and exteroceptive...

Area of Science:

• Neuroscience
• Cognitive Science
• Psychophysiology

Background:

• Attention modulates sensory processing and conscious awareness.
• Interoceptive and exteroceptive attention may have distinct neural signatures.
• Detecting covert command-following in unresponsive patients is a clinical challenge.

Purpose of the Study:

• To investigate if interoceptive and exteroceptive attention elicit different brain dynamics and heartbeat-evoked potentials (HEP).
• To assess the utility of these neural markers in classifying attentional states and detecting command-following in brain-injured patients.

Main Methods:

• Healthy participants performed tasks engaging attention towards heartbeats (interoceptive) or auditory stimuli (exteroceptive).
• Brain dynamics (e.g., power spectral density, complexity, connectivity, oscillations) and HEP were analyzed.
• Machine learning classifiers were used to differentiate attentional states and command-following in patients with disorders of consciousness.

Main Results:

• Exteroceptive attention flattened power spectral density; interoceptive attention decreased complexity, increased frontal connectivity, theta oscillations, and modulated HEP.
• Classifiers based on HEP features accurately identified attentional states in most healthy participants.
• Power spectral density features achieved perfect classification accuracy.
• One patient with unresponsive wakefulness syndrome/vegetative state and one with locked-in syndrome showed willful HEP modulation, suggesting command-following.

Conclusions:

• Attentional mechanisms significantly shape interoceptive and exteroceptive sensory processing.
• Heart-brain interactions, particularly HEP modulation, offer a promising avenue for diagnosing covert command-following in disorders of consciousness.
• These findings expand diagnostic frameworks for assessing awareness in non-responsive patients.