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10/17/2007
Mushrooms, Memory and Consciousness
Last week I was reading an article by Christof Koch and Susan
Greenfield in the October issue of Scientific American titled
“How Does Consciousness Happen?” The article mentioned that
the compound psilocybin is a hallucinogen that is present in
mushrooms. I was reminded of an incident I wrote about in an
earlier column (8/8/2007). The incident involved a squirrel
eating a mushroom stalk as I watched from our breakfast room
window. After eating the mushroom stalk, the squirrel seemed to
go berserk, jumping and flipping in the air and rolling around on
the ground in a frenzy. Could it have been due to psilocybin?
Well, wouldn’t you know that the day after I read the Scientific
American article my wife and I were having lunch in the
breakfast room and watched as a squirrel approached. Was this
the same squirrel? It came up to a spot either very close to or
identical to the spot where the mushroom had been a couple of
months ago. Suddenly, the squirrel began digging furiously in
that spot; then it rolled over on its back, wriggling around for
perhaps 10 seconds much as the squirrel that ate the mushroom.
It then righted itself and ran off in a normal squirrelly fashion.
Could this squirrel have gotten a slight high from psilocybin
hallucinogen left over from the mushroom? A few minutes later,
we noted a chipmunk appear and briefly dig in the same spot as
the squirrel. However, the chipmunk quickly departed without
exhibiting any unusual behavior.
I don’t expect that I’ll ever know the explanation for our
strangely behaving squirrel(s). I also doubt that I’ll be around to
hear or read of the definitive answer to the question posed in the
title of the Scientific American article – how does consciousness
happen? Koch, at the California Institute of Technology, and
Greenfield, at the University of Oxford in England, are eminent
neuroscientists with opposing views on the consciousness
question. In 2006 at Oxford they engaged in a spirited debate,
which continues in a friendly but adversarial manner. In the
article, each expresses his or her view based on a wealth of
neuroscientific, clinical and psychological data.
In a nutshell, Koch proposes that each conscious experience
causes a unique collection or coalition of neurons to fire in a
specific manner. For example, Koch would say, if I understand
him correctly, that when I meet a new individual a specific group
or coalition of neurons will fire in a distinct pattern that will be
retained in my memory. When I see that person again, that same
coalition of neurons will fire in the same pattern. Should another
friend appear on the scene, another coalition of neurons will
replace the first set of neurons and my consciousness of the first
friend will dissolve.
Greenfield, on the other hand, considers that for any conscious
experience, neurons across the brain fire in synchronization,
forming coordinated assemblies of neurons that disband.
According to Greenfield, there is no magical quality in a given
set of neurons but it’s the process in the brain that counts when it
comes to consciousness. She maintains that Koch is studying the
content of consciousness, not consciousness itself. She also
insists that it’s necessary to determine the difference between
consciousness and unconsciousness to know what consciousness
really involves. To tell the truth, I found it difficult to follow and
understand Greenfield’ arguments.
One argument that Koch uses to bolster his thesis is based on
results on mice given hallucinogens, including psilocybin.
Workers have found that the hallucinogen acts on a certain
molecule known as a serotonin receptor in a certain set of
neurons in a specific part of the brain. Koch says that this shows
the hallucinogens don’t act by “messing up” the brain’s circuitry
but do their dirty work by acting on specific neurons.
Thinking it might be easier for me to understand memory than to
understand consciousness, I turned to an article by Sophie
Rovner in Chemical and Engineering News (C&EN) titled “Hold
That Thought”. This article deals with progress in the field of
the chemistry involved in the storage of memory in the brain. A
companion article by Rovner entitled “Molecules for Memory”
deals with progress and ethical issues involved in the quest for
drugs to enhance memory. Here, the Holy Grail would be to find
a drug that would reverse or prevent Alzheimer’s.
Silly me. Understanding the chemistry of memory is no easier
than understanding consciousness. The hundred billion neurons
in the brain are each connected to thousands of other neurons via
trillions of connections, or synapses. It is the “strength” of these
synapses that determines whether a memory is retained for a
lifetime or only a few minutes. But what determines the strength
of a synapse? The world of a synapse is replete with interactions
of various proteins, ion channels that allow passage of calcium,
magnesium, sodium and other ions, glutamate molecules released
at synapses and loads of other chemicals and interactions. It
boggles my feeble brain. Thousands of labs are working on
trying to pin down the key fundamental biochemical change that
really determines the strength of a synapse.
In spite of the complexity and unsolved problems that remain,
significant progress has been made. One example is that in lab
animals, workers can actually map the sites in the animal’s
cortex where specific memories are stored. Another example is
the finding that the level of a certain so-called transcription
factor known as CREB is a factor in determining the suitability
for a given neuron to store a memory. In the field of improving
memory, many companies have promising drugs in the pipeline.
Unfortunately, drugs to treat Alzheimer’s are only moderately
effective to date.
Aside from the scientific aspects of memory and memory
enhancing drugs, Rovner points out another impediment to the
development and marketing of such drugs. This concerns the
question as to what medical conditions are appropriate for these
drugs? Specifically, we hear more and more in the media these
days about “mild cognitive impairment”, a condition that is not
as serious as Alzheimer’s but which sometimes is a precursor to
Alzheimer’s. If a drug is found to prevent or reverse
Alzheimer’s, should it be used to treat mild cognitive
impairment? If yes, what about “age-associated memory
impairment”? This is a condition increasingly shared by large
numbers of people over 50-55 as they age. As I approach my
80th birthday, I suspect most of my vintage are in this category.
I certainly am. If a drug emerges, should we seniors all be taking
it? Should Medicare pay for it?
Now we’re into really complex and politically charged issues. I
think I’ll go back to writing about squirrels and mushrooms.
Allen F. Bortrum
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