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Neurons cast votes to guide decision-making
http://www.physorg.com/news205764416.html
October 8, 2010
We know that casting a ballot in the voting booth involves politics,
values and personalities. But before you ever push the button for your
candidate, your brain has already carried out an election of its own
to make that action possible. New research from Vanderbilt University
reveals that our brain accumulates evidence when faced with a choice
and triggers an action once that evidence reaches a tipping point.
The research was published in the October issue of Psychological Review.
"Psychological models of decision-making explain that humans gradually
accumulate evidence for a particular choice over time, and execute
that choice when evidence reaches a critical level. However, until
recently there was little understanding of how this might actually be
implemented in the brain," Braden Purcell, a doctoral student in the
Department of Psychology and lead author of the new study, said. "We
found that certain neurons seem to represent the accumulation of
evidence to a threshold and others represent the evidence itself, and
that these two types of neurons interact to drive decision-making."
The researchers presented monkeys with a simple visual task of finding
a target on a screen that also included distracting items. The
researchers found that neurons processing visual information from the
screen fed that information to the neurons responsible for movement.
These movement neurons served as gatekeepers, suppressing action until
the information they received from the visual neurons was sufficiently
clear. When that occurred, the movement neurons then proceeded to
trigger the chosen movement.
The researchers also found that the movement neurons mediated a
competition between what was being seen—in this case, the target and
distracting items—and ensured that the decision was made to look to
the proper item.
"What the brain seems to do is for every vote it receives for one
candidate, it suppresses a vote for the other candidate, exaggerating
the differences between the two," Jeffrey Schall, E. Bronson Ingram
Chair in Neuroscience and co-author of the study said. "The system
that makes the response doesn't listen to the vote tally until it's
clear that the election is going towards one particular candidate. At
that point, the circuitry that makes the movement is triggered and the
movement takes place."
The findings offer potential insights into some psychological disorders.
"Impairments in decision-making are at the core of a variety of
psychological and neurological impairments. For example, previous work
suggests that ADHD patients may suffer deficits in controlling
evidence accumulation," Purcell said. "This work may help us to
understand why these deficits occur at a neurobiological level."
An important piece of this research is the novel model the researchers
used in the study. The new model combined a mathematical prediction of
what they thought would transpire with actual data about what the
neurons were doing.
"In a model, usually all the elements are defined by mathematical
equations or computational expressions," Thomas Palmeri, associate
professor of psychology and a co-author of the study, said. "In our
work, rather than coming up with a mathematical expression for the
inputs to the neural decision process, we defined those inputs with
actual recordings from neurons. This hybrid model predicts both where
and when the eyes move, and variability in the timing of those
movements."
"This approach provides insight between psychological processes and
what neurons are doing," Schall said. "If we want to understand the
mind-brain problem, this is what solutions look like."
Provided by Vanderbilt University
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"Ethics" is simply a last-gasp attempt by deist conservatives and
orthodox dogmatics to keep humanity in ignorance and obscurantism,
through the well tried fermentation of fear, the fear of science and
new technologies.
There is nothing glorious about what our ancestors call history,
it is simply a succession of mistakes, intolerances and violations.
On the contrary, let us embrace Science and the new technologies
unfettered, for it is these which will liberate mankind from the
myth of god, and free us from our age old fears, from disease,
death and the sweat of labour.
Rael
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