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wednesday :: february 19, 2003
   
 
synapses: plasticity and stability

A Duke University Medical Center neurobiologist has identified key mechanisms by which the intricate 'protein machines' that govern the strength of connections among neurons build and remodel themselves to adjust those connections.

Such remodeling of the connections, called synapses, is central to the establishment of brain pathways during learning and memory, said the scientists. Also, malfunction of the synaptic machinery might well play a fundamental role in the pathology of neurodegenerative disorders including Parkinson's and Alzheimer's diseases.

Neurobiologist Michael Ehlers reported extensive experiments revealing the function of a structure known as the 'post-synaptic density' (PSD). The PSD is so named because it is a thickening of the membrane at the connection point between neurons, where one neuron receives biochemical signals called neurotransmitters from its neighbor. Such neurotransmitters are themeans by which one neuron triggers the receiving neuron to launch a nerve impulse. Ehlers explored the gain or loss of a multitude of known PSD proteins. "I found that neurons in these cultures replace the content of this signaling machine multiple times a day," said Ehlers. "And if this recapitulates what's going in the mammalian brain, this means that synapses are completely turning over all of their constituents multiple times a day a stunning finding."

Neuroscientists have long been intrigued in how the brain changes with learning and experience, a phenomenon called plasticity. Yet, as Ehlers points out, "perhaps we need to think more closely about how connections in the brain remain stable in the face of such incredible ongoing turnover." >from *New insights into how the nerve connection machinery remodels itself*, february 9, 2003

related context
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synaptic plasticity: how experiences rewire the brain. january 23, 2003

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