How does cognitive performance change in relation to seasonal and experimental changes in blood glucose levels?

Abstract

In some species, cognition can change flexibly in response to environmental changes. These changes can be adaptive or can result from physiological constraints, such as when energy availability decreases seasonally. Here, we investigated: (1) how cognitive performance changes between seasons that differ significantly in food availability; (2) how these changes are related to environmentally induced physiological changes (blood glucose); and (3) whether experimental increase in blood glucose levels during the dry season impacts cognitive performance. We studied 93 free-ranging African striped mice, Rhabdomys pumilio, in the Succulent Karoo, South Africa during the hot summer dry season with low food availability, and the cold wet winter with high food availability. Striped mice had reduced blood glucose levels during the food-restricted dry season. We measured their attention using the standardized orientation response test and their spatial memory using the Barnes maze test. Neither attention nor spatial memory changed seasonally. However, high basal and experimentally increased blood glucose levels impaired cognition in most cases. We also found sex differences in cognitive performance. Even though food was restricted in the dry season and blood glucose levels were reduced, cognition was not affected by these changes, indicating cognitive resilience, which represents an evolved adaptation to cope with seasonally changing energy supply in striped mice.