Biomedical subjects

Carsten Lieshoff

Publications and source records attributed to Carsten Lieshoff.

4 recordsLinked to original sources

PubMed2006

ZENK expression in a restricted forebrain area correlates negatively with preference for an imprinted stimulus.

Sexual imprinting is an early learning process by which young birds acquire the characteristics of a potential sexual partner. The physiological basis of this learning process is an irreversible reduction of dendritic spines in two forebrain areas, the LNM (lateral nido-mesopallium) and the MNM (medial nido-mesopallium). The aim of the present study was to investigate whether these two brain areas are activated if the imprinted stimulus is presented to the adult bird after the end of the sensitive period. One group of zebra finch males was reared by their own parents. These birds, as adults, showed an exclusive preference for their own species in choice tests between a zebra finch and a Bengalese finch female. If exposed as adults to a zebra finch female, LNM and MNM showed lower activation, as measured by ZENK expression, compared to males exposed to a Bengalese finch female. A second group was reared by Bengalese finches and was exposed at day 100 to a zebra finch female for 1 week. As shown earlier, this regime leads to mixed choices, the birds are courting Bengalese and zebra finch females with a fixed ratio (preference score). If these birds were exposed to a zebra finch female as adults, the ZENK expression within LNM was much higher compared to group 1, and it showed a strong tendency to correlate negatively with the preference score: Birds with higher zebra finch preference showed lower activation compared to those with a low zebra finch and a high Bengalese finch preference. We propose that higher ZENK activation in group 2 is due to the rearing by a foster species which may result in a more complex neuronal network. The negative relation between activation and preference score may be explained by special properties of the LNM and MNM networks.

Animals↗

PubMed2006

Spatial memory and hippocampal function in a non-foodstoring songbird, the zebra finch (Taeniopygia guttata).

Spatial memory and hippocampal function have as yet been investigated mainly in pigeons and food storing songbirds. We show here that the zebra finch, a songbird not specialized in food storing and caching, is also able to learn a spatial memory task and uses a spatial map for finding food in a 'dry water maze'. Hippocampal lesions prevent learning and retention of this spatial task. The immediate early gene (IEG) products Zenk and Fos are expressed within the hippocampus when the bird is learning the task. Spatial learning cannot be assigned to any hippocampal subregion; IEG expression within the hippocampus is patchy and seems almost arbitrarily located. The IEG activation pattern in spatial memory experiments is compared with those in other learning experiments with zebra finches.

Animals↗

PubMed2004

Sexual imprinting leads to lateralized and non-lateralized expression of the immediate early gene zenk in the zebra finch brain.

Sexual imprinting is an early learning process by which young birds acquire the features of a potential sexual partner. The physiological basis of this learning process is an irreversible reduction of spine densities in two forebrain areas, the lateral neo- and hyperstriatum (LNH) and the medial neo- and hyperstriatum (MNH). The aim of the present study was to investigate whether the immediate early gene zenk, which has been shown frequently to play a role in plastic processes in the song system of zebra finches, may also be involved in the structural changes observed in these areas. The first exposure to a female after an isolation period enhances zenk expression in a variety of brain areas including LNH, MNH, and optic tectum. In contrast to earlier results, it was only the neostriatal part of LNH which showed an enhancement on first courtship, while exposure to a nestbox enhanced the label within the entire LNH area. Unexpectedly, the IEG expression was clearly lateralized in some layers of the optic tectum. Because lateralization occurred independent of the experimental condition, our study adds to recent results which also support the idea of a lateralized organization of the avian visual system.

Animals↗

PubMed2003

The dynamics of spine density changes.

Numerous papers have been published describing the effects of learning and environmental changes on the wiring of brain areas in mammals and birds. The density of dendritic spines, which can be taken as a measure of the complexity of a given neuronal network, has been shown to increase or to decrease depending on the experiment and on the brain area involved. Almost no information is available concerning the speed with which a given network reacts to learning events or environmental changes. We therefore examined the time course of spine density changes in two areas of the zebra finch forebrain, which have been shown previously to be either involved in sexual imprinting (LNH, lateral part of the neo-hyperstriatum) or to react to environmental changes (ANC, archi-neostriatum caudale). The decrease of spine density in LNH of zebra finch males after sexual imprinting is very fast, the new level of spine density is reached after 2 days. In contrast, decrease of spine density within ANC as a consequence of transferring birds from a social condition into isolation is very slow, lasting about 3 weeks. The increase of spine density within ANC after transfer of the males from isolation to a social condition occurs within 3 days. The differences in adaptation times cannot be due to limitations in the growth speed of single spines, because this has been shown to be much faster (hours instead of days). Instead, the speed of adaptation may be dependent on the availability of information about the final wiring diagram and on functional aspects like the energy demands for maintenance or alteration of a given neuronal network, or the necessity of quick adaptation to enhance the fitness of the animal.

Animals↗