Watching a Living Brain in the Act of Seeing -- With Single-Synapse Resolution

ScienceDaily (Apr. 30, 2010) — Pioneering a novel microscopy method, neuroscientist Arthur Konnerth and colleagues from the Technische Universitaet Muenchen (TUM) have shown that individual neurons carry out significant aspects of sensory processing: specifically, in this case, determining which direction an object in the field of view is moving. Their method makes it possible for the first time to observe individual synapses, nerve contact sites that are just one micrometer in size, on a single neuron in a living mammalian brain.
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Focusing on neurons known to play a role in processing visual signals related to movement, Konnerth's team discovered that an individual neuron integrates inputs it receives via many synapses at once into a single output signal -- a decision, in essence, made by a single nerve cell. The scientists report these results in the latest issue of the journal Nature. Looking ahead, they say their method opens a new avenue for exploration of how learning functions at the level of the individual neuron.
When light falls on the retina of the human eye, it hits 126 million sensory cells, which transform it into electrical signals. Even the smallest unit of light, a photon, can stimulate one of these sensory cells. As a result, enormous amounts of data have to be processed for us to be able to see. While the processing of visual data starts in the retina, the finished image only arises in the brain or, to be more precise, in the visual cortex at the back of the cerebrum.