Mechanisms of experience-induced plasticity in the speech system in the adult human brain

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The healthy adult brain retains a remarkable capacity to modify its structure and organization across the entire lifespan, following the acquisition of new skills, such as learning to speak a new language. This phenomenon is known as experience-dependent brain plasticity. Prior studies have suggested that repeated vocal activities, such as acting and television and radio broadcasting, can modify the neural organization of the brain systems that supports speech production. This results in enhanced vocal performance such as a better control of one's voice and more precise articulation. However, the neural mechanisms involved in the development of vocal expertise are still poorly understood. The objective of this program is to better understand the neurobiological correlates of non-musical vocal expertise (e.g. in television and radio broadcasters, actors and interpreters) in healthy young and older adults. This objective will be addressed via a series of studies using various methods including brain stimulation, magnetic resonance imaging (MRI) and measurements of biological compounds that have been associated with plasticity, such as glutamate and BDNF. In the first experiment, we will study the brain of healthy young and older adults with different levels of vocal expertise and compare it to the brain of healthy young and older adults with no vocal expertise, using molecular and MRI techniques. In subsequent studies, we will stimulate different parts of the brains of young and older non-experts to examine the effect that stimulation has on vocal control and brain chemistry. Because brain stimulation technologies are not yet optimized for the study of vocal expertise, we will test different protocols for inducing plasticity in the speech system and identify the one that produces the most significant changes in younger and older adults, which is important because the capacity for plasticity is known to decline with age. Using the knowledge generated in these studies, we will conduct a vocal training study combining molecular, MRI and brain stimulation methods to study plasticity induced by vocal experience. We will recruit three groups of healthy adults with no vocal expertise and train them for 4 weeks, twice a week, using a combination of vocal control, speech rate and articulation exercises. One of the groups will receive only the training. The other group will receive only brain stimulation. The third group will receive both. It is expected that the group receiving both will show the most evidence of vocal learning, behaviourally (better vocal performance) and in the brain, measured with molecular and MRI techniques. This research program will advance current knowledge of experience-induced plasticity mechanisms in the healthy aging human brain. This knowledge will contribute to the development of brain-enhancing technologies, cognitive training and cognitive stimulation applications, which are being developed and patented across the world.