[language] [Fwd: [evol-psych] Individual neurons reveal complexity of memory within thebrain]

H.M. Hubey hubeyh at mail.montclair.edu
Sat Jan 5 18:05:09 UTC 2002


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-------- Original Message --------
Subject: [evol-psych] Individual neurons reveal complexity of memory
within thebrain
Date: Sat, 05 Jan 2002 17:53:50 +0000
From: Ian Pitchford <ian.pitchford at scientist.com>
Reply-To: Ian Pitchford <ian.pitchford at scientist.com>
Organization: http://human-nature.com/
To: evolutionary-psychology at yahoogroups.com

Public release date: 3-Jan-2002
Contact: Walter Neary
wneary at u.washington.edu
206-685-3841
University of Washington
http://www.washington.edu/

Individual neurons reveal complexity of memory within the brain

An investigation of the activity of individual human nerve cells during
the act
of memory indicates that the brain’s nerve cells are even more
specialized than
many people think – no pun intended.

Although nerve cells that change activity during the use of memory are
widely
distributed in the brain, individual neurons generally respond to
specific
aspects of memory.

"For the first time, we’ve been able to show differences within regions
of the
temporal lobe in the way individual neurons respond to memory.
Everything we’ve
done to this point was to show that there are individual neurons that
change
activity --but we hadn’t been able to sort them out in any meaningful
way. Now
we can," says Dr. George Ojemann, professor of neurological surgery at
the
University of Washington.

The findings appear in the January 2002 issue of Nature Neuroscience.

Ojemann is an internationally renowned neurosurgeon who has developed
surgical
techniques for treating epilepsy, brain tumors and Parkinsonism, and
ways to
explore the detailed organization of the human brain for language,
memory,
thought and learning. He has co-authored two books for lay readers on
the
higher functions of the brain: Inside the Brain and Conversations with
Neil's
Brain.

This research involves patients with epilepsy who were awake during
surgery and
agreed to respond to requests to recall words, names of pictures and
sounds.
The recordings were from relatively healthy brain tissue that must be
removed
in order to reach problematic parts of the brain responsible for
epileptic
seizures. In a typical procedure, surgeons insert four microelectrodes
and
record the electrical activity as neurons communicate with other cells.
After
the microelectrodes are in place, patients are asked questions that
measure
stages of memory.

The microelectrodes, sharpened tungsten wire about the thickness of a
human
hair, identify electric impulses from neurons. There are only a few
programs
worldwide that have investigated neuronal activity changes with human
cognition. Given the size and complexity of neurons and their
interconnections,
it is difficult to measure the activity of any given neuron for a given
time.
The electrodes pick up discharges of a pool of neurons that are then
separated
into activity of individual neurons based on the shape of their
individual
discharges.

The latest study was able to identify the behavior of 105 neurons at 57
sites
in 26 patients; before, Ojemann says, his team’s largest sample was
about 25
neurons.

The findings reinforce the message that neurons are very specialized.
For
example, researchers identified 16 of the 105 neurons that significantly
changed activity with different stages of memory – encoding, storage and
retrieval – and found that in 13 of those, changes were observed in only
one
modality (auditory, six; text, four; objects, three).

"We just don’t find neurons that are generic memory neurons. What we
find are
neurons that show statistically significant relationships to memory for
a
particular thing," Ojemann says.

There are three regional differences in brain activity that have not
been noted
before:


There is a cluster of neurons that changes activity from encoding, to
storage,
to retrieval, in the basal temporal area, below the temporal lobe.

Neurons that may help people recall something quickly after they have
seen it
earlier in the day – what scientists call ‘implicit memory’ -- seem very
active
in the superior temporal gyrus of the temporal lobe.

There are neurons in the language-dominant hemisphere that respond to
more than
one modality – memory of both visual and auditory material.
At this point, the research is helping to illuminate the vast mysteries
of the
human brain. Someday, scientists may be able to use this knowledge to
assist
ailing brains. For example, it may be possible to externally activate
neurons
related to memory encoding in order to enhance memory.


###
TELEVISION PROGRAM: Dr. Ojemann’s work will be featured on the Discovery
Health
cable channel during a documentary on brain surgery.
The program airs 6 p.m. P.T., 9 p.m. E.T., on Sunday, Jan. 6.

These studies are supported by a grant from the National Institute of
Neurological Disorders and Stroke, and are a collaborative project with
Professor David Corina of the UW Department of Psychology.

http://www.eurekalert.org/pub_releases/2002-01/uow-inr010302.php



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