An elegant technique using light to control the activity of brain cells is described in the 05 April 2007 issue of Nature (Vol. 446, No. 7136, pp. 633-639). By expressing a light-responsive membrane protein in neurons, researchers can inhibit neural activity on a millisecond timescale.
Karl Deisseroth and colleagues introduced NpHR - a light-driven chloride pump that occurs naturally in microorganisms known as archaea - into cultured mammalian neurons and brain tissue in the laboratory. Training light pulses of a particular wavelength onto these cells effectively inhibited neural activity. This builds on the authors' previous work using the protein ChR2 – a light-responsive channel found in algae - to optically excite nerve cells with light of a different wavelength. By simultaneously expressing both membrane proteins in the muscle cells or motor neurons of the nematode worm Caenorhabditis elegans, the authors were able to control its locomotive behaviour - the worms stopped and started muscle contractions when yellow and blue lights were shone on them.
These findings demonstrate that light-responsive proteins can be used simultaneously to permit fast, bidirectional and reversible control over living neural circuits. They can also be used in conjunction with calcium imaging techniques and, together, provide a powerful tool for studying and manipulating brain activity with high precision.
Karl Deisseroth (Stanford University, CA, USA)
Michael Hausser (University College London, UK) N&V author
(C) Nature press release.
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