What is the function of Broca’s area? Typically, it’s considered a language production area, but does it have a more general function? This Wednesday, February 7th, at Sensorimotor Journal Club, Srikantan Nagarajan will present an article where the authors propose that Broca’s area has a more general function in making associations between motor actions (not just speech) and their acoustic consequences – associations that are active during passive listening to sounds:
Lahav, A., Saltzman, E., & Schlaug, G. (2007). Action representation of sound: Audiomotor recognition network while listening to newly acquired actions. Journal of Neuroscience, 27(2), 308-314. (link to pdf of article)
The discovery of audiovisual mirror neurons in monkeys gave rise to the hypothesis that premotor areas are inherently involved not only when observing actions but also when listening to action-related sound. However, the whole-brain functional formation underlying such "action-listening" is not fully understood. In addition, previous studies in humans have focused mostly on relatively simple and overexperienced everyday actions, such as hand clapping or door knocking. Here we used functional magnetic resonance imaging to ask whether the human action-recognition system responds to sounds found in a more complex sequence of newly acquired actions. To address this, we chose a piece of music as a model set of acoustically presentable actions and trained non-musicians to play it by ear. We then monitored brain activity in subjects while they listened to the newly acquired piece. Although subjects listened to the music without performing any movements, activation was found bilaterally in the frontoparietal motor-related network (including Broca's area, the premotor region, the intraparietal sulcus, and the inferior parietal region), consistent with neural circuits that have been associated with action observations, and may constitute the human mirror neuron system. Presentation of the practiced notes in a different order activated the network to a much lesser degree, whereas listening to an equally familiar but motorically unknown music did not activate this network. These findings support the hypothesis of a "hearing-doing" system that is highly dependent on the individual's motor repertoire, gets established rapidly, and consists of Broca's area as its hub.