Voice cells for voice recognition

The human voice is as characteristic as a face - a friend can often be identified by a message on an answering machine, even if he or she forgot to mention their name. The main region for face recognition lies within the inferior temporal lobe in primates. There, groups of clustered nerve cells can be found that respond significantly stronger to faces than to other images.

Researchers at the Max Planck Institute for Biological Cybernetics in Tübingen, Germany, have begun to search for similar structures that process voice information in the brain. In the temporal lobe of rhesus monkeys they discovered ''voice cells'' that respond selectively to calls and sounds from conspecifics.

The eyes are the primary sensory organs used by humans and monkeys. In social interactions, faces of relatives and friends are instantly recognised and their mood is interpreted. People who cannot recognise faces - a condition called face blindness - cannot distinguish people from one another, yet are able to recognise individual faces of dogs or sheep.

''The voices of fellow human beings are similarly unique and of great importance in social relationships. It was to be expected that they are processed differently than other auditory information by individual nerve cells,'' says Catherine Perrodin of the Max Planck Institute for Biological Cybernetics.

Together with Christoph Kayser and Nikos K. Logothetis from the same Institute and Christopher I. Petkov from the Institute of Neuroscience of the Newcastle University Medical School in the UK, the researcher conducted new experiments on the processing of voices. The team extended previous studies in which the brain region that is active during voice processing was made visible through functional magnetic resonance imaging (fMRI). They have now recorded the activity of individual nerve cells in this brain region.

The researchers proved for the first time the existence of ''voice cells'' in the temporal lobe of the brain.  ''Voice cells'' - analogous to ''face cells'' - are neurons that react two-times stronger to conspecific voices than to voices of other animals or sounds from different sources. The voice cells were concentrated in specific clusters, but significantly less concentrated than face cells in the main region of face recognition.