Since at least the 1960s brain scientists have thought that nerve cell dendrites may discriminate amongst sequences of signal inputs that vary across time and space but experimental methods were not able to control and measure signals at the very small time (submillisecond) and space (submicron) precision necessary to test the idea.

New experimental techniques using two-photon glutamate uncaging in identified dendritic spines now enable the idea to be directly investigated. The paper “Dendritic Discrimination of Temporal Input Sequences in Cortical Neurons” published September 24, 2010 issue of Science tests to see if dendrites discriminate between different temporal and spacial input sequences.

Indeed, the result is yes and some of the specific mechanisms underlying the discrimination are exposed. Impedance along the dendritic shaft was shown to be important and NMDA receptors were shown to be crucial. In fact, the research showed that a large dynamic range provided by NMDA receptor activation enabled high fidelity discrimination between different spatial-temporal sequences whether the input was all on the same dendritic branch or dispersed across the dendritic tree.

As neuroscientists demonstrate the computational complexity of axon terminals and dendritic trees I expect the focus for those interested in how signal processing is carried out in the brain to move from the neuron to the microstructure known as the neuropil.