Not all NYU is a vermin pit.

Sensory Deprivation Affects Brain's Nerve Connections

New York, July 13- Scientists at New York University School of
Medicine reveal the important role of early experience in shaping
neuronal development and brain plasticity in a new study published in
the July 14 issue of the journal Nature.

In mice, the researchers found that sensory deprivation prevented the
substantial loss of synapses that typically occurs in growing animals.
The effects were most pronounced in the period from young adolescence
to adulthood. Synapses are the gaps between neurons through which
information travels.

Wen-Biao Gan, Ph.D., Assistant Professor of Physiology and
Neuroscience, and his colleagues captured images of brain
plasticity--its ability to adapt quickly to ever-changing
circumstances--and have started to unravel how this dynamic unfolds.
The scientists were able to deliver visible evidence of the effect of
sensory deprivation.

It is well known that a growing child learns many skills. "What is
less known," says Dr. Gan, "is that during childhood until puberty
in the human brain, as well as in the monkey and mouse, you see a
substantial loss of neuronal connections." In learning, it appears
the brain needs to lose as it gains. He believes this loss may well be
the fundamental process underlying the development and plasticity of
the brain.

After birth, the number of synapses increases and then decreases
sharply. From early childhood to adolescence the synaptic loss could be
as much as 50 percent.

Dr. Gan believes that in order for learning to occur, the brain's
neurons have to be pruned. "First there is a raw material, and then
it is sculpted," he says. In other words, learning isn't only about
making new connections between neurons, he says, it also involves
carving neuronal connections.

The authors of the new study are Yi Zuo, Guang Yang, Elaine Kwon, and
Dr. Gan of the Molecular Neurobiology Program at the Skirball Institute
of Biomolecular Medicine at NYU School of Medicine.

To get a glimpse of living neurons in mice, the researchers employed a
laborious technique for shaving the skulls of the animals. This creates
an ultrathin window on the brain through which one can peer using a
sophisticated optical technique called two-photon fluorescence
microscopy. Dr. Gan looked at dendritic spines, which are thorny nubs
found all along the branches of neurons. Spines, which are continuously
formed and eliminated, are where synapses are made.

Since mice use their whiskers to explore their world, Dr. Gan altered
their experience by trimming the whiskers for two weeks on one side of
the mice's snouts. The spines of these mice were then compared to
spines in mice of the same age with untrimmed whiskers. Young mice who
kept their whiskers showed more spine loss than their whisker-trimmed
litter-mates.

In the adult age group, whisker trimming for two weeks appeared to have
no significant effect on spine loss. When the sensory deprivation
continued for two months, however, spine loss was slightly reduced in
adult animals as well. The scientists therefore found that the period
of young adolescence to adulthood was particularly susceptible to
sensory deprivation.

Interestingly, in adolescent mice the effects of sensory deprivation on
spine loss could be largely reversed if whiskers were allowed to
re-grow during a subsequent recovery period, says Dr. Gan. However, the
effects of sensory deprivation in young adolescence couldn't be
reversed if sensory recovery occurred after the mice reached adulthood.
These findings suggest "that childhood experience has a long lasting
and perhaps permanent impact on later life," he says.