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NEURO·science·letter, February 2010
The NEURO science letter is a quarterly electronic newsletter highlighting activities at the Montreal Neurological Institute and Hospital. If you have any comments, please send them to Communications. To subscribe and receive e-mail notification when a new issue becomes available, click here.
Neuroscience 101 How Do Our Thoughts Cause Our Actions?
Consider this: you think to reach out to pick up a coffee cup, and then you
do it. What just happened? Well that’s obvious. Your conscious thought
caused your action. You perceive conscious will as a force, freely
directing your decisions and actions. This feeling is undeniable. But wait
a minute, how can something as weightless and intangible as a thought
activate the nerve cells in the part of your brain that controls arm
movement? The fact of the matter is, from the point of view of modern
neuroscience, it really makes more sense to think of the whole process the
other way around; the sensation of conscious will is a
consequence or side-effect of the decision-making activity of the brain.
Conscious will is a feeling, not a force.
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What can a mollusk tell us about memory?
The Sossin lab works on the molecular changes that occur when a memory is
formed, what we term the molecular memory trace. How memories are formed is
one of the great, unsolved mysteries in science and we take a reductionist
approach, studying memory formation in a very simple animal, the mollusk
Aplysia. The major advantage of Aplysia is that the synaptic connections
that are changed during memory formation have been identified and these
changes can be recapitulated in cultured neurons under controlled
conditions. Using this preparation we can not only identify specific
molecules involved in learning, but by using modern imaging techniques, we
can also watch the changes as memories are formed.
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Deciphering cerebral blood flow to change the course of disease
Brain imaging techniques allow us to see the brain in action and,
particularly, to visualize the changes in the activity of specific
populations of neurons in an individual performing tasks such as looking at
a picture, listening to music, smelling odors, reading, counting or
sleeping. Literally, brain imaging sees the “brain at work” and identifies
the exact regions involved in the execution of any given task. Brain
imaging techniques are also widely used to look at the sick brain in
pathologies such as Parkinson’s disease, Alzheimer’s disease, epilepsy, or
stroke in order to get insight into the areas that are malfunctioning.
There is convincing evidence showing that in action, but also at rest, a
sick brain does not behave like a healthy brain.
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Of Mice and Men, Worms and Flies, Axon Guidance and Multiple Sclerosis
A human brain contains something like 1,000,000,000,000 nerve cells
(neurons). A relatively easy way to remember this number, a one followed by
twelve zeros, is that it correspond to one million million neurons. An
easier way is to simply acknowledge that it is a lot of neurons. It is so
many neurons that it is essentially unimaginable, at least using the power
of one human brain. The circuitry of the nervous system is defined by the
specialized connections that these cells make with each other, the synapses
where one cell bumps up against another. To an important extent, the
pattern of synaptic connections and neuronal circuits determines how the
nervous system works, and in a potent way defines who each of us are. In my
laboratory, we are interested in how these neural circuits are built during
development and how they are maintained in the mature adult brain.
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