How does the brain create sequences?

When you learn how to play the piano, first you have to learn notes, scales and chords and only then will you be able to play a piece of music. The same principle applies to speech and to reading, where instead of scales you have to learn the alphabet and the rules of grammar.

But how do separate small elements come together to become a unique and meaningful sequence?

It has been shown that a specific area of the brain, the basal ganglia, is implicated in a mechanism called chunking, which allows the brain to efficiently organise memories and actions. Until now little was known about how this mechanism is implemented in the brain.

In an article published today (Jan 26th) in Nature Neuroscience, neuroscientist Rui Costa, and his postdoctoral fellow, Fatuel Tecuapetla, both working at the Champalimaud Neuroscience Programme (CNP) in Lisbon, Portugal, and Xin Jin, an investigator at the Salk Institute, in San Diego, USA, reveal that neurons in the basal ganglia can signal the concatenation of individual elements into a behavioural sequence.

"We trained mice to perform gradually faster sequences of lever presses, similar to a person who is learning to play a piano piece at an increasingly fast pace." explains Rui Costa. "By recording the neural activity in the basal ganglia during this task we found neurons that seem to treat a whole sequence of actions as a single behaviour."

The basal ganglia encompass two major pathways, the direct and the indirect pathways. The authors found that although activity in these pathways was similar during the initiation of movement, it was rather different during the execution of a behavioural sequence.

"The basal ganglia and these pathways are absolutely crucial for the execution of actions. These circuits are affected in neural disorders, such as Parkinson or Huntington's disease, in which learning of action sequences is impaired", adds Xin Jin.

The work published in this article "is just the beginning of the story", says Rui Costa. The Neurobiology of Action laboratory at the CNP, a group of around 20 researchers headed by Rui Costa, will continue to study the functional organisation of the basal ganglia during learning and execution of action sequences. Earlier this year, Rui Costa was awarded a 2 million euro Consolidation Grant by the European Research Council to study the mechanism of Chunking.
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About Rui Costa

Dr. Costa received his D.V.M. from the Technical University of Lisbon in 1996. He entered the GABBA graduate program from University of Porto in 1997, and performed his Ph.D. studies with Dr. Alcino Silva at UCLA from 1998 to 2002 in the field of learning and memory, investigating the molecular and cellular mechanisms underlying the learning disabilities associated with NF1. For this work, Dr. Costa received the Young Investigator Award from the National Neurofibromatosis Foundation in 2001, and was a finalist of the Lindsley Prize from the Society for Neuroscience in 2003. He then joined Dr. Miguel Nicolelis at Duke University for his postdoctoral training, where he established multi-site neuronal recordings in behaving mice to investigate mechanisms of action generation and skill learning. Dr. Costa became a Section Chief at the National Institutes of Health in 2006. In 2009 he became an Investigator of the Champalimaud Neuroscience Programme, and received a Marie Curie International Reintegration Grant and a European Research Council Starting Grant. In 2010 he received the Seeds of Science Prize for Life Sciences, and in 2012 the Young Investigator Award from SFN.