TY - JOUR T1 - The effect of environmental harshness on neurogenesis: a large-scale comparison JF - Developmental Neurobiology Y1 - 2011 A1 - Chancellor, L.V. A1 - Roth, T.C. A1 - LaDage, L.D. A1 - Pravosudov, V.V. KW - black-capped chickadee KW - food hoarding KW - hippocampus KW - latitudinal gradient KW - neuron KW - spatial memory AB -

Harsh environmental conditions may produce strong selection pressure on traits, such as memory, that may enhance fitness. Enhanced memory may be crucial for survival in animals that use memory to find food and, thus, particularly important in environments where food sources may be unpredictable. For example, animals that cache and later retrieve their food may exhibit enhanced spatial memory in harsh environments compared with those in mild environments. One way that selection may enhance memory is via the hippocampus, a brain region involved in spatial memory. In a previous study, we established a positive relationship between environmental severity and hippocampal morphology in food-caching black-capped chickadees (Poecile atricapillus). Here, we expanded upon this previous work to investigate the relationship between environmental harshness and neurogenesis, a process that may support hippocampal cytoarchitecture. We report a significant and positive relationship between the degree of environmental harshness across several populations over a large geographic area and (1) the total number of immature hippocampal neurons, (2) the number of immature neurons relative to the hippocampal volume, and (3) the number of immature neurons relative to the total number of hippocampal neurons. Our results suggest that hippocampal neurogenesis may play an important role in environments where increased reliance on memory for cache recovery is critical. © 2010 Wiley Periodicals, Inc. Develop Neurobiol 71: 246–252, 2011.

VL - 71 UR - https://onlinelibrary.wiley.com/doi/abs/10.1002/dneu.20847 ER - TY - JOUR T1 - Learning capabilities enhanced in harsh environments: a common garden approach JF - Proceedings of the Royal Society Biological Sciences Y1 - 2010 A1 - Roth, T.C. A1 - LaDage, L.D. A1 - Pravosudov, V.V. KW - behaviour KW - cognition KW - evolution AB - Previous studies have suggested that the ability to inhabit harsh environments may be linked to advanced learning traits. However, it is not clear if individuals express such traits as a consequence of experiencing challenging environments or if these traits are inherited. To assess the influence of differential selection pressures on variation in aspects of cognition, we used a common garden approach to examine the response to novelty and problem-solving abilities of two populations of black-capped chickadees (Poecile atricapillus). These populations originated from the latitudinal extremes of the species's range, where we had previously demonstrated significant differences in memory and brain morphology in a multi-population study. We found that birds from the harsh northern population, where selection for cognitive abilities is expected to be high, significantly outperformed conspecifics from the mild southern population. Our results imply differences in cognitive abilities that may be inherited, as individuals from both populations were raised in and had experienced identical environmental conditions from 10 days of age. Although our data suggest an effect independent of experience, we cannot rule out maternal effects or experiences within the nest prior to day 10 with our design. Nevertheless, our results support the idea that environmental severity may be an important factor in shaping certain aspects of cognition. VL - 277 ER - TY - JOUR T1 - Hippocampal volumes and neuron numbers increase along a gradient of environmental harshness: a large-scale comparison JF - Proceedings of the Royal Society B Y1 - 2009 A1 - Roth, T.C. A1 - Pravosudov, V.V. AB -

Environmental conditions may provide specific demands for memory, which in turn may affect specific brain regions responsible for memory function. For food-caching animals, in particular, spatial memory appears to be important because it may have a direct effect on fitness via the accuracy of cache retrieval. Animals living in more harsh environments should rely more on cached food, and thus theoretically should have better memory to support cache retrieval, which may be crucial for survival. Consequently, animals in harsh environments may benefit from more neurons within a larger hippocampus (Hp), a part of the brain involved in spatial memory. Here, we present the first large-scale test of the hypothesis that Hp structure is related to the severity of the environment within a single food-caching species (the black-capped chickadee, Poecile atricapillus) with a large range encompassing a great diversity of climatic conditions. Hp size in birds collected at five locations along a gradient of environmental harshness from Alaska to Kansas ranked perfectly with climatic severity. Birds from more harsh northern climates (defined by lower ambient temperature, shorter day length and more snow cover) had significantly larger Hp volumes and more Hp neurons (both relative to telencephalon volume) than those from more mild southern latitudes. Environmental pressures therefore seem capable of influencing specific brain regions independently, which may result in enhanced memory, and hence survival, in harsh climates.

VL - 276 UR - https://royalsocietypublishing.org/doi/10.1098/rspb.2008.1184 ER - TY - JOUR T1 - Tough times call for bigger brains JF - Communicative and Integrative Biology Y1 - 2009 A1 - Roth, T.C. A1 - Pravosudov, V.V. AB -

Memory is crucial for survival in many animals. Spatial memory in particular is important for food-caching species and may be influenced by selective pressures such as climate. The influence of climate on memory may be facilitated through the hippocampus (Hp), the part of the brain responsible in part for spatial memory. In a recent paper, we conducted the first large-scale test of the relationship between memory, the climate, and the brain in a single food-caching species, the black-capped chickadee (Poecile atricapillus). We found that birds from more harsh northern climates had significantly larger hippocampal volumes and more neurons than those from more mild southern latitudes. This work suggests that environmental pressures are capable of influencing specific brain regions, which may result in enhanced memory, and hence survival, in harsh climates. This work gives us a better understanding of how the brain responds to different environments and how animals can adapt to their environment in general.

VL - 2 UR - https://www.tandfonline.com/doi/abs/10.4161/cib.2.3.8099 ER -