| Sensory experience has a profound influence in shaping the functional organization of the
cerebral cortex. Over 30 years ago, Hubel and Wiesel described a critical period of
postnatal development for the formation of binocular connections in cat visual cortex. They
demonstrated that thisconnectivity can be dramatically altered by simple forms of sensory
deprivation, such as the temporary closure of one eyelid (monoculardeprivation). Besides
the obvious relevance of this neural plasticity to the development of visual capabilities in
humans and animals, it seems likely hat similar processes form the basis for some forms of
learning and memory in the adult brain. Indeed, visual cortical plasticity, like learning
andmemory formation decreases with age and depend on the internal state of the animal.
The research in this lab is directed toward elucidating thebasic mechanisms by which visual
experience can modify cortical connections in the visual cortex, and how those mechanisms
are regulated. We investigate in visual cortical slices two forms of activity-dependent
synaptic plasticity: long-term potentiation (LTP) and long-term depression (LTD). These
two forms of synaptic plasticity are currently the most comprehensive models of the
elementary mechanisms underlying naturallyoccurring plasticity. Research done the past few
has established that LTP and LTD have the appropriate properties to account for important
features of naturally-occurring synaptic modification in visual cortex. Furthermore, changes
in LTP and LTD during development correlate withchanges in naturally-occurring synaptic
modification. We are currently focused on how synaptic inhibition and the action of
neuromodulators regulate the induction of LTP and LTD duringdevelopment. The results of
these investigation suggest two hypotheses. 1) The development of synaptic inhibition
restricts the induction of LTPand LTD, and henceforth, the modification by experience to a
short critical period. 2) The action of neuromodulators released during arousal is to enhance
the induction LTP and LTD by orders of magnitude, thus enabling experience to modify the
visual cortex. Our expectation is that by testing these specific hypothesis we are stand to
gain a better understanding of how naturally occurring plasticity is regulate |
