I don't know if that's the right expression "coming out of left
field"), but wanted to set this apart from the other tedious thread.
Thanks, John, but whatever I wrote was lost way back in the slipstream
of this fast-paced torrent of contention, so what follows is fully your
own contribtion.
I am chagrined to realize that I had missed this, in my own back
yard--I know Joe LeDoux and a few others at NYU Ctr for Neural Science
(OCCASIONALLY make it to one of their symposia, a bit difficult for me
inasmuch as they are usually at noon and I work 40 miles away), but
these studies are news to me! Do recall seeing a study a year or so
ago (not necessarily from NYU) re different cortical activities related
not just to amount but to type of reward--but this is going in a
different (and interesting) direction.
Hmmm... Wonder if I can find a place in the NYNG/NYAS calendar for
them next year (i.e. as speakers at one of out evening meetings).
F. Frank LeFever, Ph.D.
New York Neuropsychology Group
In <932301399.223519 at server.australia.net.au> "John"
<johnhkm at netsprintXXXX.net.au> writes:
>>>F. Frank LeFever wrote in message
<7mq3vk$l6q at dfw-ixnews10.ix.netcom.com>...
>>>>>Since everyone is interested in this of late ...
>>EMBARGOED FOR RELEASE: 14 JULY 1999 AT 14:00:00 ET US
>Contact: John Beckman, Dir. of Public Affairs
>john.beckman at nyu.edu>212-998-6848
>New York University
>>NYU researchers uncover the neurobiology of decision-making
>>Findings By Glimcher and Platt Challenge Paradigm First Proposed 300
Years
>Ago by Descartes
>>How do the brains of humans and animals make decisions - what
direction to
>move, what food to eat, where to sleep? Decision theory, a branch of
the
>social sciences developed by economists and psychologists to explain
>behavior, has long proposed that humans and animals decide what to do
in a
>given situation by first assessing the relative value of each possible
>option and then selecting the option which is of greatest value. In
>contrast, biological studies of the mind have relied upon Descartes'
>conception of the 'reflex', which, like the knee-jerk response to a
>physician's hammer, simply connects a single sensation and a single
action.
>While this discrepancy between complex social scientific theories of
>behavior and simple biological reflexes has troubled neurobiologists
for
>much of this century, until now no researchers have been able to
identify
>specific neurobiological mechanisms for decision-making.
>>In the July 15th issue of Nature, NYU neuroscientists Michael L. Platt
and
>Paul W. Glimcher have provided evidence of a true decision-making
mechanism,
>of the type advocated by social scientists, within the brains of
macaque
>monkeys. These findings raise the possibility that biological
mechanisms
>which can account for the complex and often upredictable behavior of
living
>animals have been identified. Platt and Glimcher have found neurons in
the
>parietal cortex of monkeys that, although previously thought to
transform
>visual signals into eye movements in a reflexive way, actually carry
>information about the amount of reward a monkey expects to receive for
>making the movement. They found that the activity of these neurons
was, like
>the behavior of the monkey, not predictable simply from the appearance
of
>the visual world, but reflected the value the monkey placed on the
movement.
>>Glimcher said, "For over three hundred years, the Cartesian reflex,
which
>proposed a direct connection between sensation and movement, has
served as
>the fundamental paradigm for understanding the nervous system.
Contemporary
>neurobiologists, for example, still parcel the brain into 'sensory'
and
>'motor' areas but overlook the possibility that much of the brain must
be
>devoted to subjective evaluation and decision-making. Over the last 5
years
>our laboratory has identified signals that seem to participate in this
>decision-making, and in a way not predicted by the reflexological
paradigm."
>>"Our research has now demonstrated that the theories of
decision-making
>developed by social scientists present a viable biological alternative
to
>the Cartesian reflex. It has revealed that neurons in parietal cortex
carry
>signals correlated with both the probability that a particular eye
movement
>response will yield a fruit juice reward and the amount of reward that
can
>be expected. More importantly, when we permit animals to choose freely
>amongst two alternative responses, both the choices they make, at a
>behavioral level, and the brain activity we record at the neuronal
level,
>are correlated with the probability and size of an upcoming fruit
juice
>reward. Thus, the activation of parietal cortex really does appear to
>reflect the decision processes that behavioral scientists suggest
humans and
>animals use to guide their behavior.
>>"It is also important to point out that our research has implications
for
>the treatment of neurological disorders like stroke and brain cancer.
Our
>data suggests that the inability of a patient suffering from a
parietal
>stroke to make a particular movement may be more closely related to an
>inability to decide to make a movement than to an inability to
contract the
>muscles that produce a movement. If that turns out to be true, then we
will
>have made an important advance in understanding just what goes wrong
in
>these patients."
>>Glimcher and Platt's Nature article is based on two experiments, both
of
>which measured the activity of dozens of parietal neurons. In the
first
>experiment, during a series of tests macaque monkeys were shown two
lights
>illuminated against a dark backround. The animals were free to look at
>either light, but on each trial the experimenters indicated to the
animals
>that if they looked at one of the lights they would receive a fruit
juice
>reward and if they looked at the other light they would receive
nothing.
>Over groups of these tests, Platt and Glimcher varied the amount of
juice
>reward the animals would receive for making the correct movement. The
>researchers found that parietal neurons kept careful track of the
amount of
>juice each movement was worth, encoding each change in juice reward
imposed
>by the researchers.
>>In the second experiment, the monkeys were given the opportunity to
freely
>choose to look at either light for their fruit-juice reward. Although
the
>monkeys were rewarded for looking at either light, the juice reward
obtained
>for choosing one of the points was always greater than the other.
Under
>these conditions the researchers found that the monkeys behaved more
>unpredictably, most often choosing the movement that yielded more
reward,
>but not always. Most importantly, the researchers found that there was
a
>high correlation between the frequency with which monkeys looked at a
>particular target and the neuronal activity associated with that
movement,
>exactly the correlation that would be expected if the monkey's
unpredictable
>choice behavior was being produced by these neurons.
>>Paul Glimcher is an assistant professor of neural science and
psychology at
>NYU's Center for Neural Science. He is the principal investigator for
the
>Laboratory for Sensory-Oculomotor Research, which is funded by the
National
>Eye Institute. Glimcher received his Ph.D. from the University of
>Pennsylvania and his B.A. from Princeton University.
>>Michael Platt is a post-doctoral fellow in the Laboratory for
>Sensory-Oculomotor Research. He also received his Ph.D. from the
University
>of Pennsylvania and received his B.A. from Yale University.
>>>###
>The Center for Neural Science (CNS) is the focus for inquiry in the
brain
>sciences at the Washington Square Campus of New York University.
Formed in
>1987, CNS is regarded as an international center for research and
teaching.
>The research interests of the faculty span a broad range of topics in
neural
>science, and utilize techniques ranging from molecular and cellular
analyses
>to fully integrated systems, computational, and cognitive studies.
>>>>
