Combined Senses Give Us A Better View Of The
World
November 13, 2008
From a young age we are taught about the five senses and how they help us to
explore our world. Although each sense seems to be its own entity, recent
studies have indicated that there is actually a lot of overlap and blending of
the senses occurring in the brain to help us better perceive our environment.
Researchers J.E. Lugo, R. Doti and Jocelyn Flaubert from the University of
Montreal, along with Walter Wittich from McGill University, wanted to know if a
feeling from an electrical stimulation of a body part (such as the leg) which
normally would not be perceived, would be felt if it was simultaneously
accompanied by a visual or auditory signal. The researchers studied this by
applying slight electrical stimulation to the right calf of volunteers - the
stimulation was so slight that it was not detected by the participants. The
researchers then paired that electrical stimulation simultaneously with a visual
signal, a distinct noise or a progressively louder white noise signal. The
volunteers reported when they felt anything in their leg and the electrical
response of the calf muscle activation was measured.
The results, reported in Psychological Science, a journal of the
Association for Psychological Science, reveal that if an electrical stimulation
of the leg is not initially detected, this sensation may be perceived by the
addition of a visual or auditory signal with a corresponding electrical
activation increase. The results described in this study indicate that the brain
not only constantly processes information received from the senses, but also
acts on that information to change what is happening in the peripheral system,
and thus changing what we actually detect.
The results of the last experiment are characteristic of stochastic resonance.
This is an interesting phenomenon where as noise is added to a system, the
system's performance improves until, at a certain point, the performance begins
to deteriorate. This is exactly what the researchers found in this study - as
they increased the signal, participants reported more feeling in their leg, but
this eventually decreased, even as the signal continued to get louder. They
found this resonance signature even if the stimulus they used in this experiment
was not noise but a pulse. These results show that a tactile stimulus combined
with a specific level of auditory stimulation results in optimal detection of
that sensation. However, too much signal energy will limit the response. It also
shows that these dynamics represent a fundamental principle of multisensory
integration.
This study gives us more insight into multisensory integration, which the
authors argue, will result in increased knowledge of how the brain normally
interacts with the peripheral system. In addition, learning more about
multisensory integration will lead to a better understanding of disorders such
as autism, in which altered sensory processing often occurs.
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Article adapted by Medical News Today from original press release.
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Psychological Science is ranked among the top 10 general psychology
journals for impact by the Institute for Scientific Information.
Article:"Multisensory Integration: Central Processing Modifies Peripheral
Systems"
Source: Barbara Isanski
Association
for Psychological Science
Medical News Today: http://www.medicalnewstoday.com
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