Experience-dependent modification of synaptic plasticity in visual cortex
Abstract
IN many regions of the cerebral cortex, Ca2+ influx through NMDA (N-methyl-D-aspartate) sensitive glutamate receptors (NMDA receptors) can trigger two forms of synaptic plasticity: long-term depression (LTD) and long-term potentiation (LTP)1. LTD is induced by low levels of postsynaptic NMDA-receptor activation, for instance in response to low-frequency stimulation, whereas LTP is induced by the stronger activation that occurs following high-frequency stimulation2-4. Theoretical studies have shown that the properties of synaptic LTD and LTP can account for many aspects of experience-dependent plasticity in the developing visual cortex, provided that the LTD-LTP crossover point (the modification threshold, Θm) varies as a function of the history of cortical activity5-7. Here we provide direct experimental evidence that the value of Θm depends on sensory experience. We find in visual cortex of light-deprived rats that LTP is enhanced and LTD diminished over a range of stimulation frequencies, and that these effects can be reversed by as little as two days of light exposure. Our findings support the idea that a variable synaptic-modification threshold allows synaptic weights in neural networks to achieve a stable equilibrium.
- Publication:
-
Nature
- Pub Date:
- June 1996
- DOI:
- 10.1038/381526a0
- Bibcode:
- 1996Natur.381..526K