Alladi Ramakrishnan Hall

How does the brain initiate learned motor sequences: lessons from a songbird

Raghav Rajan

Indian Institute of Science Education and Research (IISER), Pune

Movements are ubiquitous in our lives. From the simple reaching movements to the more complex learned movement sequences, like the serve of a tennis player or the straight drive of Tendulkar, we learn and execute a number of different movements and movement sequences every day. With extensive practice, execution of these movements becomes automatic and we hardly notice executing them, let alone initiating these movements. However, how the brain initiates learned movement sequences like the serve of a tennis player is poorly understood. My lab uses the zebra finch, a songbird as a model system to address this question.

The song of an adult male zebra finch consisting of a stereotyped sequence of sounds (syllables) separated by silent gaps is a well-studied example of a learned movement sequence. The song is learned by young birds in a process similar to human speech learning. Each song bout of an adult bird begins with a variable number of short, repetitive, sounds called introductory notes (INs). We have previously shown that the sequence of INs speeds up and converges on similar timing and acoustic properties, each time the bird produces his song (Rajan and Doupe, Current Biology 2013). Further, we recorded the activity of individual neurons in the motor area of a singing zebra finch and showed that the activity of individual neurons also reaches a consistent (and sometimes distinct) end-point just before song begins (Rajan and Doupe, Current Biology 2013). These data suggested that INs reflect a process by which the zebra finch brain gets ready to sing - similar to the way a tennis player bounces the ball before each serve! More generally, it suggests that repeating a simple movement many times might serve to get the brain ready to perform a more complex movement sequence.