Activity-dependent plasticity in visual forebrain areas of the zebra finch

Abstract

It has previously been shown that the activity of some areas of the forebrain of birds is dependent on the arousal level of the animal. Other areas do not show this dependency. This paper, on the basis of 2-DG experiments and spine density measurements on Golgi-impregnated tissue, shows that primary telencephalic target areas of the two visual pathways of zebra finch males are not dependent on arousal for activation. In contrast, secondary areas of both visual pathways show arousal-dependent activation. Only the secondary visual areas also show effects of rearing conditions on the spine density: isolation of the birds from day 40 reduces spine density in the hyperstriatum accessorium (HA) of the thalamofugal pathway, and enhances spine density in the lateral neo/hyperstriatum (LNH, tectofugal pathway) significantly from day 80, if compared to aviary-reared birds. A 1-week exposure to a female eliminates the isolation effects in both areas. A second isolation period again reduces the spine density in the HA, but does not enhance it again in the LNH. By comparison with previous studies, we conclude that the spine density in the HA reflects the complexity of the social environment. The irreversible reduction of spine density in the LNH as consequence of the 7-day exposure to a female is interpreted as physiological correlate of an imprinting process, which has previously been shown to occur at the same time. The effects in both areas, the HA and LNH, are dependent on arousal, which may be mediated by brainstem efferents innervating the secondary, but not the primary, visual areas in birds and in mammals.

c‐fos is induced in the hippocampus during consolidation of sexual imprinting in the zebra finch (Taeniopygia guttata)

“…Such discrepancies in identical behavioral testing paradigms have also been shown by others (Duncan et al, 1993;Tlemçani et al, 2000), and the two methods could supplement each other (Sharp and Sagar, 1992). Studies in our laboratory have shown that the primary visual areas, ectostriatum and intercalated nucleus of hyperstriatum accessorium (IHA) that depict enhanced 2-DG accumulation, do not express fos (Sadananda and Bischof, 2001) and do not show morphological changes in synaptic connectivity (Rollenhagen and Bischof, 1996) on consolidation of sexual imprinting, whereas secondary visual areas HAD and LNH do.…”

“…These areas, which depict enhanced accumulation of 2-DG (Bischof and Hermann, 1986), fos expression after chasing and first courtship (Sadananda and Bischof, 2002), and changes in spine densities with changing social contexts (Rollenhagen and Bischof, 1996), are probably affected by exposure to the imprinting stimulus. Both are innervated by the hippocampus (Casini et al, 1986;Székely and Krebs, 1996), and parts of both project to the LNH (Sadananda and Bischof, 1997).…”

ZENK protein regulation by song in the brain of songbirds

“…ZENK protein levels at any given time could represent an integration of the animal's activity resulting from its wakefulness or arousal state, as described in Cirelli et al (1996). Interestingly, activity in HA and HD, as revealed by 2-deoxyglucose uptake, is known to be modulated by arousal (Bischof and Herrmann, 1986;Rollenhagen and Bischof, 1996). 2) ZENK protein expression in nuclei of the anterior forebrain pathway (area X and lMAN) related to singing was quite variable, indicating the influence of an unidentified factor.…”

Filial imprinting in domestic chicks is associated with spine pruning in the associative area, dorsocaudal neostriatum

“…Further evidence that social experience and learning leads to dramatic rearrangements of neuronal connectivities has also been found in other avian species. In zebra finches arousal, different rearing conditions and social experience induced significant changes of neuronal morphology in the MNH and in the so called archi‐neostriatum caudale ( Rollenhagen & Bischof 1991; Rollenhagen & Bischof 1994), whereas no changes were found in the ectostriatum ( Rollenhagen & Bischof 1996). Song or speech learning, another juvenile learning process, induces a 41% decrease of spine density in the lateral part of the magnocellular nucleus of the anterior neostriatum of male zebra finches ( Wallhäusser‐Franke et al .…”