[ExI] Possible seat of consciousness found

[Stuart LaForge]

According to a study published in Neuron, the thalamus modulates  
consciousness. The thalamus is a small portion of the brain that is  
located just above the brain stem and is associated with relaying  
sensory information to the cerebral cortex. Experimenters found this  
out by anaesthetizing monkeys and electrically stimulating various  
portions of the brain. When the researchers stimulated their thalamus,  
the anaesthetized monkeys opened their eyes, reached for things, and  
acted like they were awake, but when the stimulation ceased, they went  
back to being unconscious.

https://www.cell.com/neuron/fulltext/S0896-6273(20)30005-2#secsectitle0025

Abstract:
"Functional MRI and electrophysiology studies suggest that  
consciousness depends on large-scale thalamocortical and  
corticocortical interactions. However, it is unclear how neurons in  
different cortical layers and circuits contribute. We simultaneously  
recorded from central lateral thalamus (CL) and across layers of the  
frontoparietal cortex in awake, sleeping, and anesthetized macaques.  
We found that neurons in thalamus and deep cortical layers are most  
sensitive to changes in consciousness level, consistent across  
different anesthetic agents and sleep. Deep-layer activity is  
sustained by interactions with CL. Consciousness also depends on  
deep-layer neurons providing feedback to superficial layers (not to  
deep layers), suggesting that long-range feedback and intracolumnar  
signaling are important. To show causality, we stimulated CL in  
anesthetized macaques and effectively restored arousal and wake-like  
neural processing. This effect was location and frequency specific.  
Our findings suggest layer-specific thalamocortical correlates of  
consciousness and inform how targeted deep brain stimulation can  
alleviate disorders of consciousness."

Popular science article:

https://www.inverse.com/mind-body/tiny-area-of-the-brain-could-enable-consciousness

Excerpt:
"In a wild new experiment conducted on monkeys, scientists discovered  
that a tiny, but powerful area of the brain may enable consciousness:  
the central lateral thalamus. Activation of the central lateral  
thalamus and deep layers of the cerebral cortex drives pathways in the  
brain that carry information between the parietal and frontal lobe in  
the brain, the study suggests.

This brain circuit works as a sort-of “engine for consciousness,” the  
researchers say, enabling conscious thought and feeling in primates.

To zero in on this brain circuit, a scientific team put macaque  
monkeys under anesthesia, then stimulated different parts of their  
brain with electrodes at a frequency of 50 Hertz. Essentially, they  
zapped different areas of the brain and observed how the monkeys  
responded. When the central lateral thalamus was stimulated, the  
monkeys woke up and their brain function resumed — even though they  
were STILL UNDER ANESTHESIA. Seconds after the scientists switched off  
the stimulation, the monkeys went right back to sleep."

Stuart LaForge