Early Experience May Shape our Sensory Perceptions,
New Research Shows
Editor: New research by the folks at Wake Forest indicates that an
infant's brain must learn to combine different kinds of sensory
information (e.g. sight and hearing)
WINSTON-SALEM, N.C. - Our brain's ability to combine sensory information
from a single event - such as seeing an ambulance and hearing its siren
- has been shown to speed our reactions, help us identify objects and
heighten our awareness. New research in animals suggests that it's
unlikely that we're born with this ability. Instead, its development may
depend on our sensory experiences during the early months of life.
"The way in which this ability develops has profound
implications for those who are born blind or deaf, or who suffer from
disorders such as autism and dyslexia in which early sensory processes
are altered," said Mark Wallace, Ph.D., a neuroscientist at Wake
Forest University School of Medicine. "Knowing how these brain
circuits mature may one day be used to tailor treatment strategies for
those who have problems in basic sensory processes."
Wallace and colleagues presented the results from two related studies
this week at the 35th annual meeting of the Society for Neuroscience in
The goal of the studies was to learn more about multisensory
integration, which refers to the brain's ability to combine information
from our different senses. Although much is now known about how
multisensory integration is carried out in "lower" brain
regions such as the brainstem, little is known about multisensory
integration in "higher" brain regions such as the neocortex -
a region responsible for our perceptions.
The researchers studied individual neurons in the neocortex of cats
to see how they respond to sight, sound and touch. Surprisingly, they
found that many of the neurons could respond to stimuli in several of
"The neurons responses to combinations of sensory stimuli were
often much greater than we predicted," said Wallace. "This
suggests that these neurons have the capacity to greatly amplify their
signals when confronted with stimuli from multiple senses."
He said this finding may explain how multisensory stimuli can lead to
improvements in our perceptions - such as how seeing a friend speaking
across a crowded and noisy room can help us better "hear" what
he or she is saying.
In addition to studying these neurons in adult cats, the researchers
also examined how multisensory neurons mature in the developing brain.
They found that immediately after birth, multisensory neurons were not
present in the neocortex. Only after several months of development did
these neurons first appear, and they were strikingly immature, lacking
the ability to amplify their signals. Several weeks later, these neurons
began to acquire this multisensory capability.
Next, the researchers examined development in animals raised in an
abnormal sensory environment in which lights and sounds were always
presented at the same time, but from different locations. Wallace said
this arrangement is at odds with the normal world, where sensory cues
from a single event typically occur at the same time and place.
"Intriguingly, the neurons in animals raised in this strange
sensory world tailored their integration to fit their environment,"
he said. "The neurons were able to amplify their signals only when
visual and auditory stimuli were presented at different locations -
locations that were very similar to those experienced during early
Wallace said the results show that multisensory processes in brain
circuits mature slowly, a finding that dovetails with studies showing
that perceptual processes are similarly immature early in human life. He
said findings also suggest that the multisensory circuitry is highly
malleable and reflects the sensory world of the newborn.
"This implies that changes in our early sensory experiences
resulting from disease or environmental factors will likely have a
substantial impact on brain development," he said.
The research was funded by grants from the National Institute of
Mental Health and the National Institute of Neurological Disorders and
Stroke. Wallace's co-researchers were Brian Carriere, B.S., Thomas
Perrault, Ph.D., Jenna Schuster, B.S., Barry Stein, Ph.D., and William
Vaughan, Ph.D., all from Wake Forest.