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| Illustration by Logan Parsons. Photo: UC Santa Cruz |
Led by researchers at the University of California, Santa Cruz, the study reveals details of how brain circuits are rewired during the formation of new motor memories. The researchers studied mice as they learned new behaviors, such as reaching through a slot to get a seed. They observed changes in the motor cortex, the brain layer that controls muscle movements, during the learning process. Specifically, they followed the growth of new "dendritic spines," structures that form the connections (synapses) between nerve cells.
Initial results of the spatial analysis showed that one third of the newly formed synapses were located next to another new synapse. These clustered synapses tended to form over the course of a few days during the learning period, when the mouse was repeatedly performing the new behavior. Compared to non-clustered counterparts, the clustered synapses were more likely to persist through the learning sessions and after training stopped.
In addition, the researchers found that after formation of the second spine in a cluster, the first spine grew larger. The size of the spine head correlates with the strength of the synapse. "We found that formation of a second connection is correlated with a strengthening of the first connection, which suggests that they are likely to be involved in the same circuitry," Zuo said. "The clustering of synapses may serve to magnify the strength of the connections."
In addition to Zuo and first author Min Fu, the coauthors of the paper include UCSC graduate student Xinzhu Yu and Stanford University biologist Ju Lu. This research was supported by grants from the Dana Foundation and the National Institute of Mental Health.
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Source: Eureka! Science News and University of California - Santa Cruz,
