Development of the catecholaminergic innervation of the song system of the male zebra finch

Abstract

Catecholamines (CA) have been proposed to have neuromodulatory actions, particularly on attention and learning, in a number of neural systems. Because several of the interconnected brain nuclei that mediate song learning and production in the adult male zebra finch (Taeniopygia guttata) contain these neurotransmitters, we investigated the appearance of the catecholaminergic innervation of the song nuclei of male zebra finches during posthatch development, specifically during the period in which song learning occurs. We studied the development of immunoreactivity for tyrosine hydroxylase (TH) in the song nuclei HVc, RA, NIf, LMAN, and Area X in young males aged 20, 35, and 60 days as well as in adults (>90 days). We also visualized catecholamines directly in Area X using CA histofluorescence. Both TH immunoreactivity and CA histofluorescence were initially low in Area X relative to their levels in the surrounding parolfactory lobe (LPO), and then increased during development to become more intense than in LPO by days 60–90. Similarly, TH immunoreactivity in HVc was initially low relative to that in the surrounding neostriatum, then increased during development to become more intense than that in the surround by day 60. TH immunostaining also increased markedly in NIf, RA, and LMAN over the same period. These results show that the levels of catecholamines and their major synthetic enzyme increase in song nuclei during development and thus raise the possibility that these transmitters contribute to the development of the song system or to song learning. © 1996 John Wiley & Sons, Inc.

Long-Term Potentiation in an Avian Basal Ganglia Nucleus Essential for Vocal Learning

“…This trend parallels the developmental increase in the density of dopaminergic innervation in area X relative to the surrounding medial striatum (Soha et al, 1996;Harding et al, 1998), consistent with the D1-like DA receptor dependence of LTP induction. Thus, although LTP is present in both juvenile and adult birds, its properties may be modulated in part by developmental changes in the dopaminergic innervation.…”

Task-related “cortical” bursting depends critically on basal ganglia input and is linked to vocal plasticity

“…Effects of experimental manipulations on song were quantified using two measures that represent separately how well the spectral and The AFP of songbirds indirectly connects the motor nuclei HVC and RA, and consists of the basal ganglia (striato-pallidal) nucleus Area X (9, 10), the thalamic nucleus DLM, and the cortical nucleus LMAN. Although LMAN is not a layered structure with classic pyramidal cells, it shares many anatomic and physiologic similarities with the mammalian prefrontal cortex: LMAN lies anterior to motor and premotor areas, receives input from a dorsal thalamic nucleus that is not a primary sensory area, projects to the basal ganglia and to the primary song motor nucleus RA, and is more densely innervated by dopaminergic fibers than the region surrounding it (31,(60)(61)(62). Moreover, as with the prefrontal cortex, stimulation of LMAN does not evoke motor (song) output (24,46,63).…”

Intrinsic and Extrinsic Contributions to Auditory Selectivity in a Song Nucleus Critical for Vocal Plasticity

“…In LMAN, neuromodulators may also be important for gating song-related auditory information to RA. Candidate neuromodulators include catecholamines, whose regulatory enzymes are developmentally modulated in LMAN (Soha et al, 1996;Mello et al, 1998), which could ultimately affect LMANЈs ability to influence RA during sensorimotor learning. In the adult, a behavioral regulator of LMAN excitability that hints at neuromodulatory influences is social context; spontaneous and singing-related electrical activity and activity-dependent gene expression in LMAN strongly depend on whether or not the song is directed toward another bird (Jarvis et al, 1998;Hessler and Doupe, 1999).…”