Neuroscientists are feeling their way around sensory perception with help from rhesus macaques (Macaca mulatta).

Responding to sensory information may take more than a simple flip of a switch in one area of the brain, according to recent research performed in monkeys.

HHMI international research scholar Ranulfo Romo and his colleague Victor de Lafuente have found that a gradual buildup of information across numerous sections of the brain is needed. The duo's research findings appeared in the August 21, 2006, online version of the Proceedings of the National Academy of Sciences.

By attaching electrodes to single neurons in different areas of the brain, specifically the cortical areas in the frontal and parietal lobes, Romo and Lafuente, at the Institute of Cellular Physiology, National Autonomous University of Mexico, arrived at this answer by training a pair of monkeys to report the presence or absence of a vibratory stimulus applied to one of their fingertips. Animals pressed on one of two buttons to indicate whether the stimulus was present or not, and were rewarded with a drop of liquid for correct responses. The researchers found that the train of thought needed to pass through numerous stations as neuronal activity spread from the lower somatosensory cortices of the parietal lobe, which sensed or felt the vibration, to the higher premotor areas of the frontal lobe, which sent the signal to push the button.

“The action of these cortical areas gradually predicts whether the monkey is going to detect or not going to detect the stimulus,” says Romo, who plans to further confirm his findings by doing simultaneous recordings of multiple neurons in these brain regions.

Figuring out how sensory experiences arise from activity in the brain is a huge challenge in neurophysiology, says Romo, adding that the paper “helps fill in the gaps.”

Photo: Richard T. Nowitz / Photo Researchers, Inc.