Balancing Strength and Number

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Science  21 Dec 2007:
Vol. 318, Issue 5858, pp. 1837
DOI: 10.1126/science.318.5858.1837a

Homeostasis, the ability to maintain a steady state in the face of stresses, is a fundamental part of life for cells and for organisms. Wilson et al. have analyzed homeostatic changes at the level of synaptic connections in hippocampal neurons seeded onto a microfabricated surface. Imprinting the surface with a template of squares of increasing sizes created a series of micrometer-scale islands hosting neurons at identical densities but with an increasing number of potential partners. As the number of neurons on a square increased, the number of synaptic connections increased, but, surprisingly, the functional activity of the neurons as a population (measured in voltage clamp and current clamp experiments) did not. This scaling was mediated by a change in the kinds of connections the neurons made. As network size increased, the proportion of connections between excitatory and inhibitory neurons increased; in other words, neurons made more weaker connections. Changes in neuronal connectivity occur as a consequence of development, aging, and disease (such as Alzheimer's disease and autism), and analyses of this kind may help us to understand the ability of the brain to respond to changes and the pathologies that occur when it cannot. — BJ

J. Neurosci. 27, 13581 (2007).

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