Bent on intent in the brain.

A swatch of tissue centrally located in the brain's outer layer, or cortex, serves as a way station between perception and action by signaling the intention to carry out a behavior, according to an investigation in the March 13 Nature.

Neural pathways responsible for spatial perception wend their way into this region, known as the posterior parietal cortex, which itself maintains connections to brain areas that help to execute eye and hand movements.

"Our thoughts are more directly tied to our actions than we had imagined, and the posterior parietal cortex appears to be organized more around our intentions than our sensations," remarks neuroscientist Richard A. Andersen of the California Institute of Technology in Pasadena, who directed the study.

Three monkeys were trained to press a light when it turned green or to look toward another light when it turned red, in either case after waiting for about 1 second. Different parts of the posterior parietal cortex showed elevated electric activity during the brief delay. Where that cortical activity occurred depended largely on whether hand or eye movements were in the offing, not on the location of the lights in the animals' visual field.