Childhood Markers of Health Behavior Relate to Hippocampal Health, Memory, and Academic Performance

There has been an increasing body of evidence that a variety of factors, including physical activity, nutrition, and body composition, have a relationship with brain structure and function in school-aged children. Within the brain, the hippocampus is particularly sensitive to modulation by these lifestyle factors. This brain structure is known to be critical in learning and memory, and, we suggest, for progress in the classroom. Accordingly, the aims of this article include (1) examining the role of hippocampus and hippocampal-dependent memory in supporting academic performance; (2) reviewing the literature related to the associations between hippocampal-dependent memory and a number of lifestyle factors, including physical activity, nutrition, and body composition; and (3) discussing the implications of these findings in an educational setting. The findings discussed suggest that, through interventions that target these lifestyle factors, it may be possible to improve hippocampal function and academic performance in school-aged children. Understanding lifestyle factors that contribute to cognitive health is of growing concern globally and considerable research is focused on both identifying factors that affect cognition and developing interventions to improve cognitive 1The University of Illinois at Urbana-Champaign 2Neuroscience Program 3Department of Kinesiology and Community Health 4Department of Psychology Address correspondence to Kelsey M. Hassevoort, Beckman Institute for Advanced Science and Technology, 405 N. Mathews Avenue, Urbana, IL 61801; e-mail: [email protected] function. Understanding contributing health factors during childhood, when the brain and body are developing rapidly, is of particular interest to families, physicians, educators, and lawmakers. Indeed, there is a growing body of literature touting the contributions of physical activity, nutrition, and obesity to cognition across the lifespan (for reviews see Gomez-Pinilla, 2011; Hillman, Erickson, & Kramer, 2008). In the case of school-aged children, cognitive performance is often quantified using measures of academic achievement, and an emerging body of literature suggests that these factors play a role in academic performance as well (Hillman, Khan, & Kao, 2015). Specifically, aerobic fitness and physical activity are positively associated with academic achievement in cross-sectional studies (Carlson et al., 2008; Castelli, Hillman, Buck, & Erwin, 2007; Desai, Kurpad, Chomitz, & Thomas, 2015; for a review see Howie & Pate, 2012), and a number of physical activity interventions have produced improvements in this area (Caterino & Polak, 1999; Gabbard & Barton, 1979; McNaughten & Gabbard, 1993; Tomporowski, Lambourne, & Okumura, 2011). Similarly, overall dietary quality may also play a role in academic achievement. Children and adolescents who adhere to recommended dietary guidelines or patterns have been shown to exhibit superior academic achievement, relative to counterparts who regularly consume poorer quality diets (Esteban-Cornejo et al., 2015; Florence, Asbridge, & Veugelers, 2008; Glewwe, Jacoby, & King, 2001). Conversely, overweight and obesity are negatively related to measures of academic performance, including grade point average and standardized reading and math scores (Datar, Sturm, & Magnabosco, 2004; Li, Dai, Jackson, & Zhang, 2008; Shore et al., 2008), though these associations are not universally © 2016 International Mind, Brain, and Education Society and Wiley Periodicals, Inc. 1 Childhood Markers of Health Behavior Relate to Hippocampal Health, Memory, and Academic Performance observed (Gunstad, Spitznagel et al., 2008; LeBlanc et al., 2012). Complemented by the animal literature, studies of the relationship between physical activity, nutrition, obesity, and cognitive function in humans have allowed researchers to identify promising targets within the brain for physical activity and nutritional interventions. One such target, and the neural focus of this review, is the hippocampus, a highly metabolically active brain structure located within the medial temporal lobe that has long been known to support declarative memory and more specifically relational memory—the ability to bind together and store relations among the constituent elements of an experience (Eichenbaum & Cohen, 2001; Konkel & Cohen, 2009). In this review, we examine the ways in which the hippocampus and hippocampal-dependent memory contribute to academic achievement. We review the research to date exploring the relationship between specific health factors—physical activity/fitness, nutritional intake, and obesity—and hippocampal structure and function and focus primarily on studies involving school-aged children. We conclude by discussing the implications of these findings in an educational setting. THE ROLE OF THE HIPPOCAMPUS IN LEARNING, MEMORY, AND ACADEMIC ACHIEVEMENT Scoville and Milner’s work involving the patient known as “H.M.” was the first to establish that the hippocampus is necessary for episodic memory (Scoville & Milner, 1957). Since then, research has sought to better characterize the ways in which the hippocampus supportsmemory function.There is substantial evidence that the hippocampus specifically plays a role in relational memory, which is defined as the ability to create and flexibly use bindings between arbitrary elements that make up an experience to guide behavior (Cohen & Eichenbaum, 1993; Eichenbaum & Cohen, 2001; Konkel, Warren, Duff, Tranel, & Cohen, 2008). Examples of the situations in which the relational memory system is engaged include learning new information in science class, remembering a friend’s name when you see their face, or integrating the places, people, and dates you learned about when it comes time to write that history paper.These examples highlight the fact that the relational memory system is critically important in an educational setting, in which individuals are expected to acquire vast amounts of knowledge in a variety of subject areas. The rich and flexible representations built by the hippocampus also play a role outside of what is traditionally considered “memory.” Beyond its role in supporting memory for all manner of relations, the hippocampus interacts with other structures to play a vital role in the learning strategies (Voss, Gonsalves, & Federmeier, 2010; Voss et al., 2011). According to proponents of “active learning,” the effectiveness of this educational practice stems from the control students have over their individual learning processes, and it is this control over the learning process in which the hippocampus, along with the prefrontal cortex, plays a part. Voss et al. (2011) demonstrated that the hippocampus serves as the hub of a network involving prefrontal and parietal regions that supports effective learning strategies, which are in turn associated with superior memory for learned information. In addition to its role in the implementation of learning strategies, the hippocampus also operates as part of a network of brain regions that support flexible cognition, which includes critical thinking and problem solving, creative thinking, and social behavior (Buckner, 2010; Duff, Kurczek, Rubin, Cohen, & Tranel, 2013; Rubin, Watson, Duff, & Cohen, 2014).The development of effective learning strategies and flexible cognition is particularly important amongst school-aged children as these processes lay the groundwork for future academic success. The hippocampus is particularly sensitive to the effects of a number of health factors. Specifically, a number of activityand nutrition-related maladies like type II diabetes (Korf, White, Scheltens, & Launer, 2006), hypertension (Korf, White, Scheltens, & Launer, 2004), and obesity (Dore, Elias, Robbins, Budge, & Elias, 2008; Jagust, Harvey, Mungas, & Haan, 2005), all appear to detrimentally influence hippocampal volume. The effects of health factors on hippocampal volume may be especially pronounced during childhood when the hippocampus is still developing and hippocampal volume is rapidly changing (Casey, Giedd, & Thomas, 2000; Gogtay & Thompson, 2010). Furthermore, given the relationship between hippocampal volume and memory ability (Chaddock et al., 2010; Erickson et al., 2011; Maguire et al., 2000), it is likely that those health factors that affect hippocampal volume may, in turn, impact memory performance. Thus, for children, whose academic success relies upon hippocampal-dependent memory, these kinds of health issues could have a substantial impact. At the cellular and molecular level, the maladies mentioned previously lead to decreased hippocampal neurogenesis and synaptic plasticity, and increased neuroinflammation (Stranahan et al., 2008; Tucsek et al., 2014), all of which decrease the functional capabilities of the hippocampus. However, while it is highly prone to stress induced by metabolic dysregulation, the hippocampus is also a highly plastic structure and the detrimental effects of metabolic dysregulation can be ameliorated through physical activity and nutritional interventions. Physical activity and nutritional interventions, either individually or in combination, result in increased rates of hippocampal neurogenesis and upregulation of key neurotrophic factors within the hippocampus (Casadesus et al., 2013; Gómez-Pinilla, Ying, Roy,