Sunday, November 23, 2008

Monkeys Hear Voices

Reference: Belin, Pascal. (2008). Monkey’s Hear Voices. Scientific American Mind: Brain, 19(4), 14-15.


This particular article discusses new research suggesting that a brain area devoted to processing voices is not as uniquely human as previously thought. Most species use vocalizations to communicate with each other. However, humans are the only species in which these vocalizations have reached the effective method of communication: speech. The researchers asked questions such as, “How did our ancestors become the only speaking animals, some tens of thousands of years ago? Did this change happen abruptly, involving the sudden appearance of a new cerebral region or pattern of cerebral connections?” These are interesting questions that the researchers began to explore in this article.

Researchers think they may have found the missing link between the brain of vocalizing nonhuman species and the human brain. This suggests that there is evidence of a cerebral region that is specialized for processing voice in humans that also exists in rhesus macaques. “Neuroscientist Christopher I. Petkov of the Max Planck Institute for Biological Cybernetics in Tubingen, Germany, and his colleagues used functional magnetic resonance imaging to explore the macaque brain.” The monkeys listened to different natural sounds, including macaque vocalizations. The researchers found a “discrete region of the anterior temporal lobe in which activity was greater for macaque vocalizations than for other sound categories.” Another phenomenon observed was that the macaques showed “neuronal adaptation,” recognizing different calls coming from the same individual.


This is quite fascinating research as we are beginning to realize that the voice area in the human brain is not unique to our species. As the article states, this could also mean that the voice area has a long evolutionary history in both humans and macaques. It is also neat that Petkov and his colleagues have actually located a cerebral location for these abilities. Another fascinating aspect of this research is that the “identity-specific neuronal adaptation was observed only in the right hemisphere of the macaque brain, exactly as in the human studies.” This points to the fact that the right hemisphere played the main role in how speech appeared in our ancestry. This is also quite exciting research as humans and macaques can be studied and compared to one another using similar methodologies. 

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