A study pinpoints the subcortical correlates of consciousness

It took seven years to Michael Pereira, now a researcher at GIN, Nathan Faivre, Fosco Bernasconi and their colleagues to gather the data needed for this study. Seven years and the collaboration of eight research institutes in France, Switzerland, and the United States. 

“Research on consciousness has focused heavily on the cortex. But it has long been thought that subcortical structures, such as the thalamus and subthalamic nucleus, also play a decisive role. Until recently, there was no proof of this due to the difficulties of recording single neurons in these deep areas of the brain.” explains Michael Pereira.

The researcher therefore collaborated with neurosurgeons, and ultimately, 36 patients undergoing deep brain stimulation surgery agreed to participate in his experimental protocol. "During surgery, in the operating room, we subjected them to a tactile detection task, a vibration on the hand. The detection threshold was very close to their perceptual threshold: some stimuli were perceptible, others were not,“ explains the researcher. ”We recorded the activity of individual neurons located in their subthalamic nucleus and thalamus. We wanted to observe how the activity of these neurons varies when the patient is aware of the applied stimulus or not. "

In the end, 23% of the neurons recorded in these regions showed altered activity depending on whether the stimulus was consciously perceived or not. In the subthalamic nucleus more specifically, many of these neurons showed higher activity during unperceived stimuli, suggesting that they may play a critical role in gating the awareness of a stimulus.

This study therefore provides the first evidence from single-unit recordings in humans that the subthalamic nucleus and thalamus are directly involved in the conscious detection of sensory stimuli. As a result, our understanding of consciousness should not be limited to the cortex, but should also include subcortical contributions. “The subthalamic nucleus and thalamus do not necessarily encode conscious content itself, but may act as regulators of access to consciousness, influencing perceptual decisions,” concludes Michael Pereira.
 

Reference
Subcortical correlates of consciousness with human single neuron recordings
Michael Pereira*, Nathan Faivre*, Fosco Bernasconi*, Nicholas Brandmeir , Jacob E Suffridge, Kaylee Tran, Shuo Wang , Victor Finomore, Peter Konrad , Ali Rezai‡, Olaf Blanke‡ 
Elife. 2025 May 22:13:RP95272. 
doi: 10.7554/eLife.95272.