Uncovered: The role of high-order thalamic nuclei in human conscious perception

Using direct, intracranial brain recordings in humans, a new study finds that the thalamus, a small region located deep within the brain, plays a pivotal role in conscious perception. According to the authors, specific high-order thalamic regions act as a gateway to awareness by sending signals to the prefrontal cortex. The findings shed new light on the mysteries of human consciousness. Understanding the neural foundations of human consciousness is among the most challenging tasks in neuroscience. Previous research has suggested that consciousness can be divided into two components: the conscious state (i.e., awake or asleep) and conscious content (i.e., specific experiences or perceptions). While subcortical structures are primarily involved in regulating conscious states, many theories emphasize the importance of subcortical-cortical loops in conscious perception. However, most studies on conscious perception have focused on the cerebral cortex, with relatively few studies examining the role of subcortical regions, particularly the thalamus. Its role in conscious perception has often been seen as merely facilitating sensory information.

To better understand the role of the thalamus in conscious perception, Zepeng Fang and colleagues performed a unique clinical experiment and simultaneously recorded stereoelectroencephalography (sEEG) activity in the intralaminar, medial, and ventral thalamic nuclei and prefrontal cortex (PFC), while five chronic, drug-resistant headache patients with implanted intracranial electrodes performed a novel visual consciousness task. Feng et al. discovered that the intralaminar and medial thalamic nuclei exhibited earlier and stronger consciousness-related neural activity compared to the ventral nuclei and PFC. Notably, the authors found that activity between the thalamus and PFC – especially the intraluminal thalamus – was synchronized during the onset of conscious perception, suggesting that this thalamic region plays a gating role in driving PFC activity during conscious perception.