Thalamic contributions to predictive coding and disconnected consciousness in human volunteers

Area of Science:

• Neuroscience
• Cognitive Science
• Consciousness Studies

Background:

• Consciousness can exist without external awareness, such as in dreams.
• The higher-order thalamus synchronizes cortical activity for conscious experience.
• Sensory information is ignored when consciousness is disconnected.

Purpose of the Study:

• To investigate the role of cortical synchronisation in response to surprise during wakefulness versus disconnected states.
• To test the hypothesis that cortical synchronisation to surprise is reduced in disconnected states.

Main Methods:

• Auditory oddball paradigm with EEG recording in 18 volunteers.
• Dexmedetomidine sedation used to induce disconnected consciousness, confirmed by serial awakening.
• Computational model of surprise (prediction error) and voxel coactivation analysis.

Main Results:

• Surprise was more strongly associated with awake EEG data than in disconnected states.
• Cortical synchronisation (coactivation) was stronger when awake and correlated with surprise.
• This synchronisation was significantly reduced in the disconnected state, irrespective of surprise.

Conclusions:

• Disconnection results from a loss of cortical synchronisation proportional to stimulus salience.
• Impaired higher-order thalamic synchronisation may cause sensory disconnection.