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 organize memories and actions. Until now little was known about how this mechanism is implemented in the brain. In an article published online on January 26, 2014 in Nature Neuroscience, neuroscientist Dr. Rui Costa, and his postdoctoral fellow, Dr. Fatuel Tecuapetla, both working at the Champalimaud Neuroscience Programme (CNP) in Lisbon, Portugal, and Dr. Xin Jin, an investigator at the Salk Institute, in San Diego, California, reveal that neurons in the basal ganglia can signal the concatenation of individual elements into a behavioral 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 Dr. 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 behavior." 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 behavioral sequence. "The basal ganglia and these pathways are absolutely crucial for the execution of actions.
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