Biomedical subjects

Kathy W Nordeen

Publications and source records attributed to Kathy W Nordeen.

3 recordsLinked to original sources

PubMed2005

Song tutoring triggers CaMKII phosphorylation within a specialized portion of the avian basal ganglia.

In several songbird species, a specialized anterior forebrain pathway (AFP) that includes part of the avian basal ganglia has been implicated specifically in song learning. To further elucidate cellular mechanisms and circuitry involved in vocal learning, we used quantitative immunoblot analysis to determine if early song tutoring promotes within the AFP phosphorylation of calcium/calmodulin-dependent kinase II (CaMKII), a multifunctional kinase whose phosphorylation at threonine 286 is critical for many forms of neural plasticity and behavioral learning. We report that in young male zebra finches likely to have begun the process of song acquisition, brief tutoring by a familiar conspecific adult promotes a dramatic increase in levels of phosphorylated CaMKII (pCaMKII) in Area X, the striatal/pallidal component of the AFP. In contrast, pCaMKII levels in this region were not elevated if 1) the tutor did not sing, 2) the tutor sang but was visually isolated from the pupil, or 3) the tutor was an unfamiliar adult. In young males that had not previously heard any conspecific song, first exposure to a song tutor produced a more modest, but significant rise in pCaMKII levels. Young females (who do not develop song behavior) did not exhibit any effect of tutoring on pCaMKII levels in that portion of the basal ganglia that corresponds to Area X in males. These data are consistent with the hypothesis that Area X participates in encoding and/or attaching reward value to a representation of tutor song that is accessed later to guide motor learning.

Acoustic Stimulation↗

PubMed2004

Developmental patterns of NMDAR expression within the song system do not recur during adult vocal plasticity in zebra finches.

All songbirds learn to sing during postnatal development but then display species differences in the capacity to learn song in adulthood. While the mechanisms that regulate avian vocal plasticity are not well characterized, one contributing factor may be the composition of N-methyl-D-aspartate receptors (NMDAR). Previous studies of an anterior forebrain pathway implicated in vocal plasticity revealed significant regulation of NMDAR subunit expression during the developmental sensitive period for song learning. Much less is known about the developmental regulation of NMDAR subunit expression in regions that participate more directly in motor aspects of song behavior. We show here that an increase in NR2A subunit mRNA and a decrease in NR2B subunit mRNA within the vocal motor pathway accompany song learning in zebra finches; however, manipulations that can alter the timing of song learning did not alter the course of these developmental changes. We also tested whether adult deafening, a treatment that provokes vocal change in songbirds that normally sing a stable song throughout adulthood, would render NMDAR subunit expression more similar to that observed developmentally. We report that NR2A and NR2B mRNA levels did not change within the anterior forebrain or vocal motor pathways after adult deafening, even after substantial changes in song structure. These results indicate that vocal plasticity does not require "juvenile patterns" of NMDAR gene expression in the avian song system.

Age Factors↗

PubMed2004

Synaptic and molecular mechanisms regulating plasticity during early learning.

Many behaviors are learned most easily during a discrete developmental period, and it is generally agreed that these "sensitive periods" for learning reflect the developmental regulation of molecular or synaptic properties that underlie experience-dependent changes in neural organization and function. Avian song learning provides one example of such temporally restricted learning, and several features of this behavior and its underlying neural circuitry make it a powerful model for studying how early experience sculpts neural and behavioral organization. Here we describe evidence that within the basal ganglia-thalamocortical loop implicated in vocal learning, song acquisition engages N-methyl-d-aspartate receptors (NMDARs), as well as signal transduction cascades strongly implicated in other instances of learning. Furthermore, NMDAR phenotype changes in parallel with developmental and seasonal periods for vocal plasticity. We also review recent studies in the avian song system that challenge the popular notion that sensitive periods for learning reflect developmental changes in the NMDAR that alter thresholds for synaptic plasticity.

Animals↗