Myelination of the right parahippocampal cingulum is associated with physical activity in young healthy adults

Abstract

Recent evidence suggests that individual differences in physical activity (PA) may be associated with individual differences in white matter microstructure and with grey matter volume of the hippocampus. Therefore, this study investigated the association between PA and white matter microstructure of pathways connecting to the hippocampus. A total of 33 young, healthy adults underwent magnetic resonance imaging (MRI). High angular resolution diffusion-weighted imaging and multi-component relaxometry MRI scans (multi-component driven equilibrium pulse observation of T1 and T2) were acquired for each participant. Activity levels (AL) of participants were calculated from 72-h actigraphy recordings. Tractography using the damped Richardson Lucy algorithm was used to reconstruct the fornix and bilateral parahippocampal cinguli (PHC). The mean fractional anisotropy (FA) and the myelin water fraction (MWF), a putative marker of myelination, were determined for each pathway. A positive correlation between both AL and FA and between AL and MWF were hypothesized for the three pathways. There was a selective positive correlation between AL and MWF in the right PHC (r = 0.482, p = 0.007). Thus, our results provide initial in vivo evidence for an association between myelination of the right PHC and PA in young healthy adults. Our results suggest that MWF may not only be more specific, but also more sensitive than FA to detect white matter microstructural alterations. If PA was to induce structural plasticity of the right PHC this may contribute to reverse structural alterations of the right PHC in neuropsychiatric disorder with hippocampal pathologies.

White matter microstructure variations contribute to neurological soft signs in healthy adults

“…Walther and colleagues [Walther et al, ] investigated young HP (age: 31.2 ± 6.5 years) and found that motor activity levels were negatively associated with FA variations within the left corticobulbar tract, the right posterior corpus callosum, and the left superior longitudinal fasciculus. In a more recent study by Bracht and colleagues [Bracht et al, ] on a sample of young HP (age: 24.5 ± 4.2 years), physical activity was significantly associated with myelin water fraction in the right parahippocampal cingulum. A persimonious explanation for these findings and the results of the present study is that not only one but a number of very different WM sub‐compartments variations within the motor relevant fiber tracts may contribute to quantitative and qualitative motor performance in young HP.…”

“…In elderly individuals, WM changes might be the result of different neuroplastic processes [Tseng et al, 2013], whereas young individuals exhibit predominantly myelination changes which have only subtle effects on FA [Bracht et al, 2016;Song et al, 2002]. Therefore, it is not possible to robustly answer the question whether sub-threshold depressive symptoms that might be present in this study group consisted of young healthy individuals had an influence on WM.…”

“…Although previous MRI studies found a significant association between subthreshold depressive symptoms and significant reductions in FA, increases in AD or RD [Allan et al, ], and volume reductions in specific frontal and temporal brain regions [Dotson et al, ], these studies investigated healthy adults aged 56 years and older. In elderly individuals, WM changes might be the result of different neuroplastic processes [Tseng et al, ], whereas young individuals exhibit predominantly myelination changes which have only subtle effects on FA [Bracht et al, ; Song et al, ]. Therefore, it is not possible to robustly answer the question whether sub‐threshold depressive symptoms that might be present in this study group consisted of young healthy individuals had an influence on WM.…”

Advances in noninvasive myelin imaging

“…Very few studies have yet used more myelin-specific MR measures to assess relationships between physical activity and white matter microstructure. A recent, cross-sectional study in young adults found a positive correlation between MWF in the right parahippocampal cingulum and amount of physical activity monitored over three days (Bracht et al, 2016). There is need for more interventional studies in humans to assess whether such relationships reflect a causal influence of physical activity on myelination.…”

An Examination of Psychomotor Disturbance in Current and Remitted MDD: An RDoC Study

“…Furthermore, while controls exhibited an association between actigraphy levels and perfusion within core motor areas, such as the cingulate motor area and external globus pallidus, this association was not found in MDD subjects [25]. MPI Walther has also shown that activity levels in MDD patients and controls are linked with white matter microstructure of motor pathways and limbic pathways [26,27,61,62]. However, the associations between white matter properties and activity differed between patients and controls within cortico-cortical motor pathways, suggesting that structural connectivity alterations between prefrontal and premotor/motor cortices hamper spontaneous motor behavior in patients [26].…”