Cardiovascular Fitness and Cognitive Spatial Learning in Rodents and in Humans

Abstract

The association between cardiovascular fitness and cognitive functions in both animals and humans is intensely studied. Research in rodents shows that a higher cardiovascular fitness has beneficial effects on hippocampus-dependent spatial abilities, and the underlying mechanisms were largely teased out. Research into the impact of cardiovascular fitness on spatial learning in humans, however, is more limited, and involves mostly behavioral and imaging studies. Herein, we point out the state of the art in the field of spatial learning and cardiovascular fitness. The differences between the methodologies utilized to study spatial learning in humans and rodents are emphasized along with the neuronal basis of these tasks. Critical gaps in the study of spatial learning in the context of cardiovascular fitness between the two species are discussed.

Keywords: Cardiovascular fitness; Exercise; Hippocampus; Navigation; Spatial learning.

Figure 1.

The mouse hippocampus neuroanatomy. (A) An illustration of the mouse brain and the entorhinal cortex–hippocampal subregions of the mouse brain. (B) Detailed diagram of the entorhinal cortex–hippocampal circuitry from A. The main input of the hippocampus comes from the entorhinal cortex through the perforant path to the dentate gyrus and the CA3 directly. From the dentate gyrus information is transferred through the mossy fibers to area CA3, from there it will be transferred to CA1 area through the schaffer collateral, and back to the entorhinal cortex. CA1 also receives direct input from the entorhinal cortex through the temporoammonic pathway. DG = dentate gyrus, EC = entorhinal cortex, GrDG = granular layer of dentate gyrus, Hi = hippocampus, MF = mossy fibers, PP = perforant path, SC = Schaffer collateral, TA = temporoammonic pathway.

Figure 2.

Schematic anatomical representation of the hippocampal-medial entorhinal cortex (MEC) circuitry that plays crucial role in spatial navigation in mouse. Spatial information about the environment is transported from the grid, border, and head-direction cells located in the MEC to place cells in the hippocampus by the perforant path (PP) and temporoammonic path (TP). In the dentate gyrus (DG), information from place cells in the granular cells of the dentate gyrus (GrDG) is transported to place cells in the CA3 by the mossy fiber (MF), and from there by the schaffer collateral (SC) to place cells located between the pyramidal (PY) cells of the CA1. Each of these hippocampal place cells fire in high frequency when the mouse is located in the place field of the relevant place cell. Blue = cells in the medial entorhinal cortex, yellow = place cell, red = place field, green = axonal projections.