The overall layout of the cerebral cortex -- such as the existence of various sensory and motor 'maps' and the presence of 'columns' of cells that share functional properties -- is well known. But details of its fine-scale functional architecture have not been as clear, largely because of sampling and resolution limitations of electrophysiological and optical imaging techniques. In the 20 Jan 2005 issue of Nature (Vol. 433, No. 7023), scientists report on a tool that can capture the activity of neuronal populations at single-cell resolution and up to four times deeper into the brain than before.
Clay Reid and his colleagues used a calcium-sensitive indicator and two-photon microscopy to map out the precise architecture of the visual cortex. Cortical neurons have distinct response properties, such as responding preferentially to particular orientations of visual stimuli. Reid and colleagues were able to measure these properties for virtually every neuron in a local area of both rat and cat visual cortex. Their findings suggest a much finer degree of spatial precision in cortical maps than had been assumed previously, thus challenging current theories of how cortical circuits are assembled and function. Their comparison represents only the beginning of a new, promising method for studying brain organization with single-cell calcium imaging in vivo.
Harvard Medical School, Boston, MA, USA.
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(C) Nature press release.
Message posted by: Trevor M. D'Souza