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Directionally selective calcium signals in dendrites of starburst
amacrine cells
Winfried Denk
Max-Planck Institute for Medical Research
The detection of image motion is fundamental to vision. In many
species, unique classes of retinal ganglion cells selectively respond
to visual stimuli that move in specific directions. It is not known
which retinal cell first performs the neural computations that give
rise to directional selectivity in the ganglion cell. A prominent
candidate has been an interneuron called the "starburst amacrine
cell". Using two-photon optical recordings of intracellular calcium
concentration, here we find that individual dendritic branches of
starburst cells act as independent computation modules. Dendritic
calcium signals, but not somatic membrane voltage, are directionally
selective for stimuli that move centrifugally from the cell soma. This
demonstrates that direction selectivity is computed locally in
dendritic branches at a stage before ganglion cells.