Flicker light stimulation induces thalamocortical hyperconnectivity with LGN and higher-order thalamic nuclei

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Psychiatry

Background:

• The thalamus, beyond sensory relay, is crucial for higher-order cortical functions.
• Thalamocortical hyperconnectivity is implicated in hallucinations across psychopathologies and altered states of consciousness.
• The precise role of thalamocortical hyperconnectivity in hallucination generation remains unclear.

Purpose of the Study:

• To investigate the functional contribution of thalamocortical hyperconnectivity in visual hallucination.
• To examine how flicker light stimulation (FLS) modulates thalamocortical connectivity in healthy individuals.
• To identify specific thalamic nuclei and visual cortical areas involved in FLS-induced hallucinations.

Main Methods:

• Utilized fMRI combined with flicker light stimulation (FLS) to induce transient visual hallucinations.
• Analyzed changes in thalamocortical connectivity between specific thalamic nuclei and visual processing areas.
• Correlated connectivity alterations with the frequency-dependent intensity of experienced visual phenomena.

Main Results:

• FLS induced significant thalamocortical hyperconnectivity between the lateral geniculate nucleus (LGN) and early visual areas (e.g., hV4, VO1).
• Exploratory analysis revealed involvement of higher-order thalamic nuclei (anterior, mediodorsal) in response to FLS.
• Observed a direct relationship between connectivity changes and the subjective intensity of visual phenomena.

Conclusions:

• FLS effectively modulates thalamocortical connectivity, providing a model for studying hallucinations.
• Specific thalamocortical circuits, including the LGN and higher-order nuclei, are critical for visual hallucination.
• Findings advance understanding of neural mechanisms underlying visual hallucinations and altered states of consciousness.