The neurodynamic organization of modality-dependent hallucinations

Area of Science:

• Neuroscience
• Psychiatry
• Medical Imaging

Background:

• The underlying mechanisms of hallucinations are not fully understood.
• Spontaneous brain activity, particularly resting-state networks, may play a crucial role.

Purpose of the Study:

• To investigate the relationship between hallucinations and spontaneous resting-state brain activity.
• To explore the neural correlates of hallucinations in adolescents with brief psychotic disorder.

Main Methods:

• Multimodal magnetic resonance imaging (MRI) was employed in 20 drug-free adolescents experiencing hallucinations.
• Participants were compared to 20 matched controls during rest and exteroceptive stimuli.
• Anatomical and functional imaging techniques were used to map brain activity.

Main Results:

• Reduced cortical thickness and increased blood oxygen level-dependent (BOLD) signals were observed in association sensory cortices during various hallucinations.
• Primary sensory cortex recruitment varied and correlated with hallucination vividness.
• A withdrawal from the default mode network (DMN) was observed during hallucinations, similar to healthy individuals' response to external stimuli.
• DMN spatial and temporal instabilities correlated with hallucination severity and persisted even during symptom-free periods.

Conclusions:

• Hallucinatory experiences may arise from a spontaneous withdrawal of the default mode network (DMN).
• This finding provides a potential model for understanding hallucinations across different sensory modalities.
• DMN abnormalities may represent a persistent vulnerability factor in individuals experiencing hallucinations.