Effects of Musical Training on Brain Development
Laurel Trainor - ljt@mcmaster.ca
McMaster University
Popular version of paper 4aMU2
Presented Thursday Morning on October 29, 2009
158th ASA Meeting, San Antonio, TX
A number of claims have been made concerning the benefits of musical training on brain development. In a series of studies, we are evaluating these claims.
Development in general involves neuroplasticity, or structural and functional changes in the brain that enable the emergence of new processing capabilities and behaviors. Mechanical energy in the form of sound waves produced by objects in the environment is transduced into electrical neural signals in the inner ear. A series of subcortical and cortical neural circuits process and evaluate this sound input. Development is genetically guided by general waves of synaptic proliferation (increases in the number of connections between neurons) and synaptic pruning (elimination of connections that are less useful). However, experience in the form of sound input through the ears affects the details of the wiring (i.e. which connections are formed and which eliminated), such that the brain becomes specialized at processing the information that is prominent in the sound input. Through experience, representations of complex sounds in the world, including speech and music, are formed in auditory cortex.
One way that we examine the effects of musical experience on brain development is to compare how the brains of musicians and non-musicians respond to sound. When a group of neurons fire at the same time, they generate an electrical field that is large enough to measure at the surface of the head with electroencephalography (EEG). The presentation of a sound event generates an event-related potential (ERP)reflecting changes in electrical activity over timethat tracks the brain's processing of that sound from early sensory evaluation of frequency and duration, to later complex representations of speech and music to still later processes involving evaluation of the sound. One of our interesting findings is that ERPs change dramatically through childhood as the brain develops, and don't reach adult levels until the late teenage years.
In one series of studies we used EEG to compare adult musicians and non-musicians. These studies reveal that musicians have larger responses to isolated musical tones, to wrong notes in melodic sequences, and to simultaneous melodies (polyphonic music). These differences may be the result of the extensive musical practicing of the musicians during childhood, but it might also be the case that children with genetically superior brains for auditory processing are naturally attracted to music, and that the adult musician/non-musician differences are largely genetic in origin. To begin evaluating whether these differences are the result of musical experience, we compared children engaged in musical lessons with children engaged in other activities. In a first set of studies, we found that effects of musical experience can be seen in the brain responses of children as young as 4 to 5 years of age for components of the event-related potential related to sensory processing and to evaluative (making decisions about the sounds) and attentional processing. Furthermore, in another study we compared two groups of children, one just starting music lessons and the other engaged in other activities such as sports. We tested each child every 3 months for a year. Both groups changed over the course of the year as the children developed, but the music group changed more, particularly in ERP components related to attentional processing. This is significant because it suggests a mechanism whereby music lessons could affect other cognitive processes, such as language and mathematical skills. Superior attentional abilities would aid learning across a wide range of areas.
Further evidence that musical training affects general cognitive skills comes from another study in which we measured oscillatory EEG activity (induced gamma band), which reflects communication between brain regions. Induced gamma band activity has been associated with attention, memory, and the ability to inhibit behavior, skills collectively known as executive functioning. We found that this activity emerged after one year of music lessons in 5-year-old children, but was not seen in same-aged children not taking music lessons. Thus, the benefit of musical training for other cognitive domains is likely mediated by the development of superior executive functioning.