Aerobic fitness, hippocampal viscoelasticity, and relational memory performance

Abstract

The positive relationship between hippocampal structure, aerobic fitness, and memory performance is often observed among children and older adults; but evidence of this relationship among young adults, for whom the hippocampus is neither developing nor atrophying, is less consistent. Studies have typically relied on hippocampal volumetry (a gross proxy of tissue composition) to assess individual differences in hippocampal structure. While volume is not specific to microstructural tissue characteristics, microstructural differences in hippocampal integrity may exist even among healthy young adults when volumetric differences are not diagnostic of tissue health or cognitive function. Magnetic resonance elastography (MRE) is an emerging noninvasive imaging technique for measuring viscoelastic tissue properties and provides quantitative measures of tissue integrity. We have previously demonstrated that individual differences in hippocampal viscoelasticity are related to performance on a relational memory task; however, little is known about health correlates to this novel measure. In the current study, we investigated the relationship between hippocampal viscoelasticity and cardiovascular health, and their mutual effect on relational memory in a group of healthy young adults (N=51). We replicated our previous finding that hippocampal viscoelasticity correlates with relational memory performance. We extend this work by demonstrating that better aerobic fitness, as measured by VO2max, was associated with hippocampal viscoelasticity that mediated the benefits of fitness on memory function. Hippocampal volume, however, did not account for individual differences in memory. Therefore, these data suggest that hippocampal viscoelasticity may provide a more sensitive measure to microstructural tissue organization and its consequences to cognition among healthy young adults.

Hippocampal Network Modularity Is Associated With Relational Memory Dysfunction in Schizophrenia

“…These findings suggest that some patients may rely on a relatively spared anterior temporal lobe memory network to compensate for a dysfunctional posterior network (40). Future studies examining changes in anterior and posterior hippocampal network connectivity in schizophrenia patients before and after interventions that increase relational memory performance, such as exercise (71), will aid in clarification of these findings.…”

Reconstructing relational information

“…SR tasks have proven enormously informative in that they provide sensitive measures of relational memory abilities that have been tied not only to hippocampal damage, but to more subtle hippocampally related measures such as subjective memory complaints (Lucas et al, ), spatial pattern separation (Clark et al, ), and medial temporal lobe viscoelasticity (Schwarb et al, , ). Precision and specificity of the metrics and the ability to distinguish between several different types of spatial relational errors will undoubtedly serve these lines of investigation well as it will allow a far more resolute picture of the specific impairments that may be tied to particular behavioral, functional, and structural phenotypes.…”

Optimization of a Multifrequency Magnetic Resonance Elastography Protocol for the Human Brain

“…There is growing interest for the accurate mechanical characterization of soft tissues, specifically brain tissue, since such characterization could be helpful in various clinical applications. Some examples include the preoperative assessment of meningioma consistency, the monitoring of neurodegeneration, or even more engineering‐oriented and basic science applications (eg, modeling of brain tissue under impact and blast loading to understand traumatic brain injury, improvements in helmet design, assessment of the relationship between cognitive performance and brain viscoelasticity) . Until recently, however, there has been a scarcity of data on the in vivo characterization of the brain tissue.…”