John R. Kirn
The songbird telencephalon continually receives new neurons. Peak levels of neuron addition in singing-related areas have been associated with maximal vocal learning. The caudomedial nidopallium (NCM), analogous to mammalian auditory association cortex, is a crucial brain region for acquiring tutor song memory. NCM contains a high number of inhibitory interneurons, including parvalbumin-expressing (PV) interneurons, which are known to be important for proper development of many critical period processes across several organisms. We used a cell birth marker, to quantify NCM neurons and PV neurons formed during the critical period for song learning in zebra finches. We found a peak density of both neurons, as well as PV neurons, generated at 40 days-post-hatch (dph), that persisted into adulthood, in normally raised males which is consistent with the timeline for tutor song copying. Lateral NCM is known to have activity patterns that correlate with the degree of tutor song copying. We report a positive correlation between the rate of PV neuron addition in lateral NCM at 40 dph and tutor song copying. Another group of zebra finches was raised without tutors—a procedure known to delay the normal end of the critical period. We found elevated levels of neuron addition, including PV neuron addition, at 60 dph and in adulthood, compared to normally raised birds. Our findings suggest a relationship between peak levels of neuron addition and the critical period for vocal learning in zebra finches.
Asik, Kemal, "Post-Hatch Neuron Incorporation in The Zebra Finch Caudomedial Nidopallium (NCM) in Relation to Vocal Learning" (2016). Dissertations. 57.
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