The relationship between migratory behaviour, memory and the hippocampus: an intraspecific comparison

Abstract

It has been hypothesized that memory-demanding ecological conditions might result in enhanced memory and an enlarged hippocampus, an area of the brain involved in memory processing, either via extensive memory experience or through evolutionary changes. Avian migration appears to represent one of such memory-demanding ecological conditions. We compared two subspecies of the white-crowned sparrow: migratory Zonotrichia leucophrys gambelii and non-migratory Z. l. nuttalli. Compared to non-migratory Z. l. nuttalli, migratory Z. l. gambelii showed better memory performance on spatial one-trial associative learning tasks and had more hippocampal neurons. Migratory subspecies also had larger hippocampi relative to the remainder of the telencephalon but not relative to body mass. In adults, the differences between migratory and non-migratory sparrows were especially pronounced in the right hippocampus. Juvenile migratory Z. l. gambelii had relatively larger hippocampal volume compared to juvenile non-migratory Z. l. nuttalli. Adult migratory Z. l. gambelii had more neurons in their right hippocampus compared to juveniles but such differences were not found in non-migratory Z. l. nuttalli. Our results suggest that migratory behaviour might be related to enhanced spatial memory and an enlarged hippocampus with more neurons, and that differences in the hippocampus between migratory and non-migratory sparrows might be experience-dependent. Furthermore, for the first time our results suggest that the right hippocampus, which encodes global spatial information, might be involved in migratory behaviour.

Hippocampal neurogenesis is associated with migratory behaviour in adult but not juvenile sparrows ( Zonotrichia leucophrys ssp.)

“…They were also morphologically similar to doublecortin-labelled cells described by Boseret et al [34]-round multipolar cells and fusiform cells, which are typical morphotypes of differentiating neurons and migrating neurons, respectively. From a previous study with these individuals, we had used stereological measurements to estimate hippocampal volume using the Cavalieri method (StereoInvestigator software, Microbrightfield, Inc., Colchester, VT, USA; microscope, Leica M4000B, Bannockburn, IL, USA; values reported in and taken from Pravosudov et al [12]). …”

“…All subjects were collected as part of an earlier study [12]. Briefly, 14 migratory Z. l. gambelii were captured on 8 October 2004 during migration near Davis, CA, USA.…”

“…All birds were perfused and their brains were removed, processed and sectioned as previously described [12]. Briefly, birds were anaesthetized with a lethal overdose of Nembutal and transcardially perfused with 4 per cent paraformaldehyde in 0.1 M phosphate buffer.…”

Changes in brain gene expression during migration in the white-crowned sparrow

“…It is possible that, in addition to having evolved a number of behavioral, physiological and morphological adaptations to the demands of migration, (Dawson et al 1983;Andrews 1995;McWilliams and Karasov 2001;Kullberg et al 2003;Mettke-Hofmann and Gwinner 2003;Wikelski et al 2003;Mouritsen and Ritz 2005;Pravosudov et al 2006) migratory birds have also evolved adaptations to combat the negative consequences of sleep loss. To date, however, evidence of potential mechanisms for sleep loss compensation in migratory birds is absent.…”

Age and sex specific brain biometrical study in Vanaraja chickens

“…A larger relative brain size is more successful when introduced into novel environments. The comparison among the relative brain volume of three subspecies of whitecrowned sparrow showed that telencephalon volume relative to body mass differed significantly among the three subspecies (P < 0.001) (Pravosudov et al, 2006). The maximum brain length and height contributed to brain volume, the maximum brain width provided the largest contribution (Kawabe et al, 2013).…”