[ExI] Possible seat of consciousness found
avant at sollegro.com
Fri Feb 14 01:32:45 UTC 2020
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.
"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:
"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."
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