Sex-dependent structural asymmetry of the medial habenular nucleus of the chicken brain.
ABSTRACT An investigation of structural asymmetry in the avian brain was conducted on the epithalamic medial habenular nucleus of the chicken. Twelve male and ten female two-day-old chickens were used for a morphometric evaluation of asymmetry. The medial habenular nucleus was measured from paraffin-wax-embedded, 8 micron-thick sections by use of a semiautomatic image analyser. The volumes of the right and left medial habenula of each animal were statistically analysed ('within animal experimental design'). The right medial habenula in males showed significant group asymmetry. In contrast, females failed to demonstrate group bias in favour of either hemisphere. However, individual females were lateralised, with either a larger right or left medial habenula. Although individuals of both sexes were lateralised, there was no significant sex difference in volume in either the right or left medial habenula. We propose that sex-linked structural asymmetry may be influenced by steroid hormonal effects in the central nervous system, and that such asymmetry could be more prevalent in the non-mammalian vertebrate brain than previously considered.
- SourceAvailable from: Anton Reiner[show abstract] [hide abstract]
ABSTRACT: Histochemical and autoradiographic analyses of the axonal transport of horseradish peroxidase and tritiated amino acids were employed to study the central connectivity of the lizard parietal eye. Somata and processes of centrifugal fibers to the parietal eye were localized in tissue of the dorsal sac and in the leptomeningeal sheath of the pineal gland. Analyses of series of transverse sections of the brain showed the left medial habenular nucleus to be subdivided into pars dorsolateralis and pars ventromedialis, and the right medial habenular nucleus not to be so subdivided. Centripetal fibers of parietal eye ganglion cells project to only the pars dorsolateralis of the left medial habenular nucleus and terminate there in two distinct fields. The asymmetry of the lizard habenula may be a specialization associated with the unilateral projection from the parietal eye.The Journal of Comparative Neurology 06/1981; 198(1):155-65. · 3.66 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: A stereological analysis was made of synapses in the left and right hemispheres of chick medial hyperstriatum ventrale (MHV) 24h after passive avoidance training (PAL) and in water trained controls (W-control). The synaptic parameters examined were (D), the mean length of the postsynaptic thickening; (NV.syn), the number of synapses per unit volume of neuropil; (VV.syn), the volume density of the pre-synaptic bouton; (NV.ves), the number of synaptic vesicles per unit volume of neuropil and (ves.syn), the mean number of synaptic vesicles per pre-synaptic bouton. No significant differences exist in NV.syn between the left or right hemispheres of W-control and trained chicks, nor is NV.syn influenced by training. However, in W-control chicks D in the right MHV is significantly greater (12%) than in the left MHV and this difference disappears on training. There are no differences in VV.syn between left and right hemispheres of W-control chicks but following training VV.syn is 22.7% greater in the left MHV than in the right MHV. Training als influences the number of synaptic vesicles; in W-control chicks NV.ves in the right MHV is 12.25% greater than in the left MHV but following training these differences are reversed. When the data are expressed as numbers of vesicles per synapse (ves.syn), values for the left hemisphere of trained chicks exceed those in the right hemisphere by a staggering 61.38%. These results are discussed in the context of biochemical and electrophysiological studies which suggest that there is lateralization of the memory trace.Brain Research 03/1984; 314(2):261-9. · 2.88 Impact Factor
- [show abstract] [hide abstract]
ABSTRACT: Neonatal tail posture is a sexually dimorphic behavior with females more biased leftwards than males. Prenatal exposure of female pups to testosterone propionate (TP) but not dihydrotestosterone propionate (DHTP) shifts the population pattern of tail posture to the right. No effects were found with male pups. Since TP is aromatizable and DHTP is not, it is concluded that TP exerts its effects on tail posture via the CNS.Brain Research 08/1983; · 2.88 Impact Factor