New research puts a fresh spin on current thinking of speech evolution in humans
A study published today in the prestigious journal Nature by Dr. Michael Petrides and colleagues at the Montreal Neurological Institute (MNI) at McGill University, challenges current thinking that speech developed as a result of new structures that evolved in the human brain. Dr. Petrides and colleagues have identified a distinct brain region that controls jaw movements in macaque monkeys that is comparable to Broca’s area – the region in the human brain critical for speech production. This discovery is important as it suggests that this area of the brain evolved originally to perform high-order control over the mouth and the jaw, and that as humans evolved this area came to control the movements necessary for speech.
“Our study shows that nonlinguistic monkeys possess an area comparable to Broca’s area – it is located in the same region and has the same anatomical characteristics as Broca’s area in the human brain“, explained Dr. Michael Petrides, Coordinator of the Cognitive Neuroscience Unit at the MNI and Professor in the Department of Neurology and Neurosurgery, McGill University.
“The researchers performed quantitative microscopic analysis of the cytoarchitecture of the region of interest and electrophysiological stimulation and recording within this region.
When this area in the monkey was electrically stimulated, oral and facial motor responses were evoked – such as jaw movement sequences, as well as respiratory responses. In addition, Broca’s area is connected with a region of the brain immediately in front of it that is involved in the retrieval of information from memory.
“These connections suggest to us that Broca’s area is in a unique position to use information shared from past experience and which is stored in memory for the service of communicative acts,” explains Dr. Petrides. “That is, Broca’s area may have evolved originally as an area exercising high-level control over oral and facial actions, including those related to communicative acts, and that, in the human brain, this area eventually came to control also certain aspects of the speech act.“
The researchers hope that future studies of the anatomy and physiology of this region will yield major new insights as to why Broca’s area became involved with speech in the human brain.
This research was supported by grants from the Canadian Institutes of Health Research and the James S. McDonnell Foundation.
The Canadian Institutes of Health Research (CIHR) is the Government of Canadas agency for health research. CIHR’s mission is to create new scientific knowledge and to catalyze its translation into improved health, more effective health services and products, and a strengthened Canadian health care system. Composed of 13 Institutes, CIHR provides leadership and support to close to 10,000 health researchers and trainees across Canada.
The Montreal Neurological Institute (www.mni.mcgill.ca) is a McGill University research and teaching institute, dedicated to the study of the nervous system and neurological diseases. Founded in 1934 by the renowned Dr. Wilder Penfield, the MNI is one of the world’s largest institutes of its kind. MNI researchers are world leaders in cellular and molecular neuroscience, brain imaging, cognitive neuroscience and the study and treatment of epilepsy, multiple sclerosis and neuromuscular disorders. The MNI, with its clinical partner, the Montreal Neurological Hospital (MNH), part of the McGill University Health Centre, continues to integrate research, patient care and training, and is recognized as one of the premier neuroscience centres in the world. Already well known for its McConnell Brain Imaging Centre, the MNI will expand its brain imaging research in the next several years through a $28 million award from the Canada Foundation for Innovation, made in partnership with the government of Quebec. There will also be further development of MNI initiatives in multiple sclerosis, optical imaging and nano-neuroscience.
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