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

Abstract

It has been hypothesized that individuals who have higher demands for spatially based behaviours should show increases in hippocampal attributes. Some avian species have been shown to use a spatially based representation of their environment during migration. Further, differences in hippocampal attributes have been shown between migratory and non-migratory subspecies as well as between individuals with and without migratory experience (juveniles versus adults). We tested whether migratory behaviour might also be associated with increased hippocampal neurogenesis, and whether potential differences track previously reported differences in hippocampal attributes between a migratory (Zonotrichia leucophrys gambelii ) and non-migratory subspecies (Z. l. nuttalli ) of white-crowned sparrows. We found that non-migratory adults had relatively fewer numbers of immature hippocampal neurons than adult migratory birds, while adult non-migrants had a lower density of new hippocampal neurons than adult and juvenile migratory birds and juvenile non-migratory birds. Our results suggest that neurogenesis decreases with age, as juveniles, regardless of migratory status, exhibit similar and higher levels of neurogenesis than non-migratory adults. However, our results also suggest that adult migrants may either seasonally increase or maintain neurogenesis levels comparable to those found in juveniles. Our results thus suggest that migratory behaviour in adults is associated with maintained or increased neurogenesis and the differential production of new neurons may be the mechanism underpinning changes in the hippocampal architecture between adult migratory and non-migratory birds.

Seasonal Variation in Cell Proliferation and Cell Migration in the Brain of Adult Red-Sided Garter Snakes <b><i>(Thamnophis sirtalis parietalis)</i></b>

“…Thus, the higher rate of cell proliferation within the cortex during the fall may be related to differences in recent migratory history [e.g. Ladage et al, 2011]. Future studies comparing rates of cell proliferation and cell migration in both preand postmigratory snakes within each season would aid in understanding whether neuroplasticity within the cortex is involved in spatial memory formation.…”

Neurogenesis in the Adult Avian Song-Control System

“…Migration may take several weeks and ongoing neuronal addition may enable pattern separation of the different spatial memories that must be stored during the successive stages of these journeys. LaDage et al (2011) reported that there are more DCX þ adult-born neurons in the HC of a migratory subspecies of white-crowned sparrow than a nonmigratory subspecies. A potential confound of this study, however, is that migratory birds experience intense and prolonged physical exercise, which could influence one or more components of neuronal addition to the HC (Kempermann et al 2010).…”

Region-specific neuron recruitment in the hippocampus of brown-headed cowbirdsMolothrus ater(Passeriformes: Icteridae)

“…Adult neurogenesis is regulated by internal and external factors such as species, sex, singing activity, social environment, environmental conditions, hormones, seasonality, photoperiod, stress, aging and activity levels (Patel et al 1997;Adar et al 2008;Day et al 2008;LaDage et al 2009LaDage et al , 2010LaDage et al , 2011Delgado-Gonzalez et al 2011;Yamamura et al 2011;Maruska et al 2012;Onksen et al 2012;Alward et al 2014). In food caching bird species neuron recruitment is also regulated by experiences with food caching and retrieval (Clayton & Krebs 1994;Clayton 1995aClayton , 1996Patel et al 1997).…”

“…Birds are an excellent system in which to understand the relationship of Hp and spatial memory as birds require spatial memory for food caching, homing, migration and nest searching (Rothstein et al 1987;Krebs et al 1989;Clayton 1995a,b;Healy et al 1996;White et al 2009;LaDage et al 2010LaDage et al , 2011Guigueno et al 2014). For example, Hp lesions cause deficits in spatial orientation of homing pigeons (Bingman & Mench 1990) as well as in the acquisition of new spatial memories in black-capped chickadees (Parus atricapillus) and dark-eyed juncos (Junco hyemalis; Hampton & Shettleworth 1996).…”