Sensory deprivation, such as a lack of visual stimulation soon after birth, can lead to developmental abnormalities in the brain, but the exact mechanisms that underlie this system remain unclear. In October 3 Nature, Florian Engert and colleagues at the University of California, Berkeley, USA, show that moving visual stimuli can rapidly induce directional sensitivity in developing neural circuits and thus influence brain development (Nature, 419: 470-475, October 3, 2002.).

Engert et al. examined the Xenopus retinotectal system and observed that the receptive field of tectal neurons can be 'trained' to become direction-sensitive minutes after repetitive exposure of the retina to moving bars in a particular direction. The induction of direction-sensitivity depended on the speed of the moving bar and could not be induced by random visual stimuli. In addition, they showed that training-induced changes required spiking of the tectal neuron and activation of a N-methyl-D-aspartate glutamate receptor subtype, and was attributable to an activity-induced enhancement of glutamate-mediated inputs.

"Although the precise loci of circuit changes remain to be determined, the rapidity and persistence of receptive field modification shown here illustrate the susceptibility of developing neural circuits to the instructive influence by sensory inputs of specific spatiotemporal patterns," conclude the authors.