Seeing in motion

Aclass of neurons known as starburst amacrine cells compute the direction of a visual stimulus, according to new results from Thomas Euler, Peter Detwiler (University of Washington, Seattle, WA), and Winfried Denk (Max Planck Institute for Medical Research, Heidelberg, Germany). The experiments show that starburst dendrites signal independently of the electrical activity of the soma, an ability that dendrites of other neurons may share.

Starburst cells are radially symmetric interneurons with synaptic outputs and inputs coexisting on neuronal processes, called dendrites. Based on their position in the retina, starburst amacrine cells have been hypothesized to activate directionally selective ganglion cells. Genetic experiments have supported this theory, but how the cells calculate direction was unknown.

Now, the power of these cells to use Ca²⁺ to report direction is...