Last year, scientists from George Washington University published an amazing study arguing
that they had found the “on-off switch” to the human brain, a veritable
key to consciousness. The researchers found that when they stimulated a
particular portion of the brain of a woman with epilepsy, she reliably
slipped into a storing, near-catatonic state. When they removed the
stimulation, she “awoke” and had no memory of the lapse in time. Called
the “claustrum,” this area of the brain is poorly understood — but since
the consciousness study, it has unsurprisingly attracted attention from
brain researchers.
One study published
this month in the journal Consciousness and Cognition may
have constrained the realm of possibility for claustrum function, by
conducting a study using combat veterans with deep traumatic brain
injuries affecting the claustrum. What they found suggests that the
prior results showing that stimulation of the claustrum can forcibly
sever the brain from the conscious mind may have been due to the
peculiarities of that patient, an epileptic who had undergone brain
surgery in the past. In their combat veterans, who have a variety of
other brain-related injuries in addition to their claustrum damage, the
results were quite different.
The claustrum, below the neocortex, in a human brain
They found that patients with claustrum lesions have an increased duration, but not frequency, of
losing consciousness — showing that the claustrum may be related to
regaining, but not ending, the state of active consciousness. That’s
important, since the claustrum has been implicated in the maintenance of
certain forms of coma and certain forms of dissociation.
The claustrum (technically the claustra,
since there’s one per hemisphere) sits near the center of the brain and
seems to have a large-scale coordinating function. It receives signals
from virtually every portion of the neocortex, looking architecturally
not all that unlike the corpus collosum, of A Scanner Darkly fame.
In both cases, destruction can lead to truly odd and unsettling
psychological effects — could stimulating one little patch of your brain
really forcibly disengage the brain’s engine from its drive shaft,
leaving a person coasting in an involuntary neutral gear?
The claustrum receives information from all over the cerebral cortex.
As mentioned, the newest research seems to say that, thankfully, the
claustrum might not offer that kind of off switch. Patients with
permanently damaged brains can sometimes adapt to get lost function out
of some other brain structure, however, so it’s possible that people
will claustrum lesions (as opposed to reversible electrical stimulation)
show different effects.
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However, things are more complicated than that. There’s some evidence
that the hallucinogenic drug known as salvia may work partially by
affecting the claustrum — specifically, inhibition of the
kappa-opioid receptors that are so common on its surface. Due to the
impossibility of feeding college kids salvia in an ethics-approved
study, the academic literature on this is based largely on the
self-submitted trip-out reports on sites like Erowid.
If the claustrum does play some large-scale coordinating role in the
brain, that could explain why salvia can cause the brain to interpret
visual information in such bizarre ways — the parts of the brain that
are good at visual tasks aren’t being properly engaged to actually do
them. And it might also explain why it’s possible for someone with a
damaged or inhibited claustum to receive visual information through the
optic nerve, but not consciously see that visual information with the higher brain and snap back to reality.
There may be a whole textbook about it, but the claustrum is still poorly understood.
Francis Crick (of Watson and Crick fame) spent much of his career
pushing for continued study of the claustrum, which he believed was the
seat of consciousness. We now know that’s not true — people can be quite
conscious with their claustrum partially or entirely destroyed. But it
may be to be one of the crucial elements in taking the many powerful but
limited portions of the brain, and letting them complement each other’s
abilities. It’s been called the conductor of the brain’s orchestra.
As scientists begin to understand these systems-level structures in the
brain, our understanding of concepts like attention, memory, and
perception could change dramatically. And with them, concepts like
intention, self-awareness, and self.
