Howard Hughes Medical Institute (HHMI) international research scholar Ranulfo Romo of the Institute of Cellular Physiology at the National Autonomous University of Mexico and his colleagues--Rogelio Luna and Adrián Hernández, also of the National Autonomous University of Mexico, and Carlos D. Brody of Cold Spring Harbor Laboratory in New York--report their results in the September 2005 issue of the journal Nature Neuroscience, published online July 31, 2005.
Neuroscientists already knew that touching the skin with a vibrating object causes specialized sensory neurons in the brain to fire, and that firing of these neurons, which are found in a region of the brain known as the primary somatosensory cortex, is directly related to monkeys' ability to tell how fast something is vibrating, Romo said. But the neurons' firing patterns are complex, and it's been tricky to tease out "which component of the neuronal activity was more likely associated with behavioral performance," he explained.
Theoretically, there are many ways in which neurons could relay information about stimulus frequency, Romo said. Frequency information might be encoded in the time between consecutive neuronal firings, the overall rate of firing, or the number of times a neuron fires.
To distinguish among these possibilities, Romo and his colleagues designed an experiment in which they touched the monkeys' fingertips with a vibrating but painless probe for varying lengths of time. The monkeys were first taught to respond to varying vibration
Source:Howard Hughes Medical Institute