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NEURO·science·letter, October 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 The Evolution of Big Brains
If aliens landed on earth 100,000 years ago, to inventory the life on our
planet, they might have noticed, among the multitude of diverse plants and
animals, an apparently unremarkable, medium-sized species of primate,
wandering the savannahs of Africa. Aside from walking on two legs and
making modest use of simple tools, there would have been little to
distinguish these beings from other mammals. How times have changed. When
we look around at the ways in which the six billion members of Homo sapiens
currently dominate every corner of the world and transform the global
environment, it is difficult to grasp that recorded civilization accounts
for only a few percent of the 200,000 years that anatomically modern humans
have roamed the earth. Our modern scientific and technological worldview
has only been around for a few hundred years, something like one quarter of
one percent of human existence. For most of our time on earth, the human
relationship to nature was not greatly different from that of other
terrestrial species.
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The Mind's Eye: Deciphering Visual Processing in the Brain
Approximately half of the human brain's 100 billion neurons are involved in
vision. What is it about vision that requires so much processing power? It
certainly doesn’t seem difficult to recognize a face or to navigate through
a crowded shopping mall, but of course this is precisely the point. Our
visual systems are able to interpret the world around us in such way that
we are free to think about other things. Exactly how this happens is the
focus of the research carried out in the Pack Lab.
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Somatostatin Receptors Come Out of Hiding
Nerve cells, or neurons, talk to each other at specialized junctions called
synapses. There are perhaps 100 trillion synapses in the human brain, 1,000
or so for each of the brain's 100 billion neurons. When a "presynaptic"
neuron wants to talk to its "postsynaptic" partner, it releases chemicals
called neurotransmitters which bind to and activate proteins called
neurotransmitter receptors on the surface of postsynaptic cell (see the
figure below). Once the receptors are activated, they initiate electrical
and chemical events in the postsynaptic cell. In this way, information is
passed from one cell to another.
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