Exercise and the Brain: Lessons From Invertebrate Studies

Abstract

Benefits of physical exercise for brain functions are well documented in mammals, including humans. In this review, we will summarize recent research on the effects of species-specific intense locomotion on behavior and brain functions of different invertebrates. Special emphasis is made on understanding the biological significance of these effects as well as underlying cellular and molecular mechanisms. The results obtained in three distantly related clades of protostomes, Nematodes, Molluscs and Artropods, suggest that influence of intense locomotion on the brain could have deep roots in evolution and wide adaptive significance. In C. elegans, improved learning, nerve regeneration, resistance to neurodegenerative processes were detected after physical activity; in L. stagnalis-facilitation of decision making in the novel environment, in Drosophila-increased endurance, improved sleep and feeding behavior, in G. bimaculatus-improved orientation in conspecific phonotaxis, enhanced aggressiveness, higher mating success, resistance to some disturbing stimuli. Many of these effects have previously been described in mammals as beneficial results of running, suggesting certain similarity between distantly-related species. Our hypothesis posits that the above modulation of cognitive functions results from changes in the organism's predictive model. Intense movement is interpreted by the organism as predictive of change, in anticipation of which adjustments need to be made. Identifying the physiological and molecular mechanisms behind these adjustments is easier in experiments in invertebrates and may lead to the discovery of novel neurobiological mechanisms for regulation and correction of cognitive and emotional status.

Keywords: cognitive functions; desicion making; intense locomotion; invertebrate model organisms; learning and memory; motor performance; nerve regeneration; orientation.

Figure 1

Effects of exercise (species-specific intense locomotion) on representatives of three big clades of Protostomes. Phylogenetic tree displaying the different species analyzed to study the effects of exercise on behavior and nervous system. The species are listed not in the order of appearance in the manuscript. Silhouettes are only illustrative. Species-specific forms of intense locomotion that were used as exercise are listed under the silhouettes. Exercise-induced changes in the brain and behavior are shown in color. Red color and down head arrow indicate downregulation, blue color and upward arrow indicate upregulation. In Drosophila, flying and or/vertical climbing increased endurance and life span, improved sleep and feeding behavior (for review, Watanabe and Riddle, 2019). In G. bimaculatus, flight improved orientation via conspecific phonotaxis (Sergejeva and Popov, ; Mezheritskiy et al., 2020), enhanced aggressiveness (Hofmann and Stevenson, ; Stevenson et al., 2005), promoted mating (Dyakonova and Krushinsky, 2008). In C. elegans, swimming protected against neurodegeneration, improved associative learning (Laranjeiro et al., 2019), accelerated nerve regeneration (Kumar et al., 2021). In L. stagnalis, previous terrestrial crawling increased activity and facilitated the decision making in novel environment (Korshunova et al., 2016).