Sister smell act
doi:10.1038/nindia.2010.146 Published online 26 October 2010
Mice use over 1,000 kinds of molecular detectors to identify smells. These detectors generate signals that converge with great precision in groups of neurons called mitral cells.
Because all mitral cells within the same group (sister cells) get inputs from the same type of molecular detectors, it is believed that their response to such inputs is similar. Unfortunately, however, it is difficult to figure out which mitral cells are sister cells. New research now attempts to answer this question.
The researchers used a transgenic mouse line that expresses a light-sensitive algal protein in the odour-detecting cells. Using a standard projector and some simple optics, the researchers were able to play back selected patterns of light onto the brain, just where the odour detectors converge on the mitral cells. This let them use light, rather than smells, to precisely activate groups of mitral cells.
The researchers simultaneously recorded the electrical activity of a few mitral cells and used the coincident responses to the light as a signature for the sister cells. Having classified the cells as either sister or non-sister, they then presented the animal with a panel of 42 odorants to ask the original question: do all sister cells respond in the same way?
Interestingly, it turned out that although the average activity did look the same, the precise timing of the responses differed between sister mitral cells. "This tells us that these cells are not just a relay station. They compute additional features of the odorant stimulus, and use both timing and average activity to carry this extra information on to other parts of the brain," explains Upinder Bhalla, one of the researchers.
The authors of this work are from: Cold Spring Harbor Laboratory, New York, USA; National Centre for Biological Sciences, Bangalore, India; Department of Molecular and Cellular Biology, and Center for Brain Science, Harvard University, Cambridge, Massachusetts, USA.
- Dhawale, A. K. et al. Non-redundant odor coding by sister mitral cells revealed by light addressable glomeruli in the mouse. Nature Neuroscience. doi: 10.1038/nn.2673 (2010)