A new study finds that, as zebra finches learn new songs, it's the firing of inhibitory neurons - not the age of the bird - that locks in learning. Numerous species, including humans, learn behaviors through their parents and peers, but little is known about the neural mechanisms underlying this process. In juvenile zebra finches, exposure to songs by "tutors" influences neural plasticity within the region of their brain responsible for song, the HVC, driving patterned neuronal activity in a way thought to be critical to song imitation. Investigation by Daniela Vallentin and colleagues found that premotor neurons in the HVC not only respond to new songs in juvenile finches, but in adults as well. Their results counter some previous studies, prompting Vallentin et al. to dig deeper. They recorded the activity of local interneurons in both adults and juveniles as they learned songs. Curiously, while there was little difference between the two age groups, interneuron firing did correspond with how recently a finch was introduced to a new song. The researchers then used a synthetic tutor that taught finches one syllable (A). Once the finches had perfected that syllable, they were introduced to a new syllable (B). By altering these sequences (ABAB), the researchers were able to distinguish inhibition patterns of firing neurons between learned and new syllables, finding that inhibitory neurons spike in a coherent pattern during learned syllables, but not for those not yet learned and recognized. This was not just true for young finches; finches at the later learning stage, which could sing a good copy of both "A" and "B," showed equivalent interneuron firing and synaptic inhibition across both syllables. Further analysis revealed that interneuron firing precision correlated with the accuracy of the song. These findings provide new insights into the role of inhibitory neurons during learning.
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Journal
Science