Single Neurons Can Detect Sequences
ScienceDaily (Aug. 13, 2010) — Single neurons in the brain are surprisingly good at distinguishing different sequences of incoming information according to new research by UCL neuroscientists.
A neuron in the visual cortex of the mouse was filled with a fluorescent dye so that the dendrites could be visualised. A laser was targeted to small spots on single dendrites to activate groups of inputs in different orders. The electrical response of the neuron was recorded and was found to be be different for each of the input sequences. (Credit: Tiago Branco/Hausser Lab: UCL)
The study, published August 12 inScience and carried out by researchers based at the Wolfson Institute for Biomedical Research at UCL, shows that single neurons, and indeed even single dendrites, the tiny receiving elements of neurons, can very effectively distinguish between different temporal sequences of incoming information.
This challenges the widely held view that this kind of processing in the brain requires large numbers of neurons working together, as well as demonstrating how the basic components of the brain are exceptionally powerful computing devices in their own right.
First author Tiago Branco said: "In everyday life, we constantly need to use information about sequences of events in order to understand the world around us. For example, language, a collection of different sequences of similar letters or sounds assembled into sentences, is only given meaning by the order in which these sounds or letters are assembled.
"The brain is remarkably good at processing sequences of information from the outside world. For example, modern computers will still struggle to decode a rapidly spoken sequence of words that a 5 year-old child will have no trouble understanding. How the brain does so well at distinguishing one sequence of events from another is not well understood but, until now, the general belief has been that this job is done by large numbers of neurons working in concert with each other."
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Read more here/Leia mais aqui: Science Daily
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Published Online August 12, 2010
Science DOI: 10.1126/science.1189664
Dendritic Discrimination of Temporal Input Sequences in Cortical NeuronsTiago Branco, Beverley A. Clark, Michael Häusser*
The detection and discrimination of temporal sequences is fundamental to brain function and underlies perception, cognition, and motor output. Applying patterned two-photon glutamate uncaging, we found that single dendrites of cortical pyramidal neurons exhibit sensitivity to the sequence of synaptic activation. This sensitivity is encoded both by local dendritic calcium signals and by somatic depolarization, leading to sequence-selective spike output. The mechanism involves dendritic impedance gradients and nonlinear synaptic NMDA receptor activation and is generalizable to dendrites in different neuronal types. This enables discrimination of patterns delivered to a single dendrite, as well as patterns distributed randomly across the dendritic tree. Pyramidal cell dendrites can thus act as processing compartments for detection of synaptic sequences, implementing a fundamental cortical computation.
Wolfson Institute for Biomedical Research and Department of Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, UK.
* To whom correspondence should be addressed. Email: m.hausser@ucl.ac.uk
Received for publication 16 March 2010. Accepted for publication 28 July 2010.
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