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Drosophilalarvae are an established model system for studying the mechanisms of innate and simple forms of learned behavior. They have about 10 times fewer neurons than adult flies, and it was the low total number of their neurons that allowed for an electron microscopic reconstruction of their brain at synaptic resolution. Regarding the mushroom body, a central brain structure for many forms of associative learning in insects, it turned out that more than half of the classes of synaptic connection had previously escaped attention. Understanding the function of these circuit motifs, subsequently confirmed in adult flies, is an important current research topic. In this context, we test larvalDrosophilafor their cognitive abilities in three tasks that are characteristically more complex than those previously studied. Our data provide evidence for (i) conditioned inhibition, as has previously been reported for adult flies and honeybees. Unlike what is described for adult flies and honeybees, however, our data do not provide evidence for (ii) sensory preconditioning or (iii) second-order conditioning inDrosophilalarvae. We discuss the methodological features of our experiments as well as four specific aspects of the organization of the larval brain that may explain why these two forms of learning are observed in adult flies and honeybees, but not in larvalDrosophila.
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DARPP‐32 distinguishes a subset of adult‐born neurons in zebra finch HVC
Abstract Adult male zebra finches (Taeniopygia guttata) continually incorporate adult‐born neurons into HVC, a telencephalic brain region necessary for the production of learned song. These neurons express activity‐dependent immediate early genes (e.g.,zenkandc‐fos) following song production, suggesting that these neurons are active during song production. Half of these adult‐born HVC neurons (HVC NNs) can be backfilled from the robust nucleus of the arcopallium (RA) and are a part of the vocal motor pathway underlying learned song production, but the other half do not backfill from RA, and they remain to be characterized. Here, we used cell birth‐dating, retrograde tract tracing, and immunofluorescence to demonstrate that half of all HVC NNs express the phosphoprotein DARPP‐32, a protein associated with dopamine receptor expression. We also demonstrate that DARPP‐32+ HVC NNs are contacted by tyrosine hydroxylase immunoreactive fibers, suggesting that they receive catecholaminergic input, have transiently larger nuclei than DARPP‐32‐neg HVC NNs, and do not backfill from RA. Taken together, these findings help characterize a group of HVC NNs that have no apparent projections to RA and so far have eluded positive identification other than HVC NN status.
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- Award ID(s):
- 1828327
- PAR ID:
- 10362353
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Journal of Comparative Neurology
- Volume:
- 530
- Issue:
- 5
- ISSN:
- 0021-9967
- Page Range / eLocation ID:
- p. 792-803
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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