Cardiorespiratory fitness is associated with fMRI signal in right cerebellum lobule VIIa Crus I and II during spatial navigation in older adult women

Abstract

Spatial navigation is a cognitive skill critical for accomplishing daily goal-directed behavior in a complex environment; however, older adults exhibit marked decline in navigation performance with age. Neuroprotective interventions that enhance the functional integrity of navigation-linked brain regions, such as those in the medial temporal lobe memory system, may preserve spatial navigation performance in older adults. Importantly, a well-established body of literature suggests that cardiorespiratory fitness has measurable effects on neurobiological integrity in the medial temporal lobes, as well as in other brain areas implicated in spatial navigation, such as the precuneus and cerebellum. However, whether cardiorespiratory fitness modulates brain activity in these regions during navigation in older adults remains unknown. Thus, the primary objective of the current study was to examine cardiorespiratory fitness as a modulator of fMRI activity in navigation-linked brain regions in cognitively healthy older adults. To accomplish this objective, cognitively intact participants (N = 22, aged 60–80 years) underwent cardiorespiratory fitness testing to estimate maximal oxygen uptake (V·O2max) and underwent whole-brain high-resolution fMRI while performing a virtual reality navigation task. Our older adult sample demonstrated significant fMRI signal in the right and left retrosplenial cortex, right precuneus, right and left inferior parietal cortex, right and left cerebellum lobule VIIa Crus I and II, right fusiform gyrus, right parahippocampal cortex, right lingual gyrus, and right hippocampus during encoding of a virtual environment. Most importantly, in women but not men (N = 16), cardiorespiratory fitness was positively associated with fMRI activity in the right cerebellum lobule VIIa Crus I and II, but not other navigation-linked brain areas. These findings suggest that the influence of cardiorespiratory fitness on brain function extends beyond the hippocampus, as observed in other work, to the cerebellum lobule VIIa Crus I and II, a component of the cerebellum that has recently been linked to cognition and more specifically, spatial processing.

Cardiorespiratory fitness is associated with cortical thickness of medial temporal brain areas associated with spatial cognition in young but not older adults

“…Oxygen uptake (V̇O 2 ) was estimated from treadmill speed and grade using standard equations which take advantage of the known linear relationship between heart rate and oxygen uptake (Wasserman, 2012) and the oxygen cost associated with walking at increasing grade, based on ACSM guidelines (Equation (1)): where .1 and 1.8 ml/kg/min are the oxygen costs of walking horizontally and walking on an incline, respectively; 3.5 ml/kg/min is the resting V̇O2. The equation has previously been described in detail (Kern et al, 2020, 2022; Kronman et al, 2020). Finally, we used linear regression to predict V̇O 2max based on the known relationship between heart rate and V̇O 2 determined from work rate and the participant's age‐predicted maximum heart rate.…”

“…Data for this study comes from two larger randomized controlled clinical trials (study 1: Neuroimaging Study of Exercise and Memory Function, ClinicalTrials.gov Identifier: NCT02057354) (Kern et al, 2020;Kronman et al, 2020;Nauer, Dunne, et al, 2020); (study 2: The Entorhinal Cortex and Aerobic Exercise in Aging, ClinicalTrials.gov Identifier: NCT02775760) (Kern et al, 2020(Kern et al, , 2022, which are both focused on investigating the effects of aerobic exercise on MTL structure and function. Baseline data from 56 young adults (18-35 years), 20 older adults (55-85 years) from study 1 and 24 older adults (60-80 years) from study 2 were included for the purposes of the current study.…”

“…We operationally defined CRF as aerobic capacity determined by maximal oxygen uptake (V ̇O2max ). Following previous work (Kern et al, 2020(Kern et al, , 2022Kronman et al, 2020;Nauer, Dunne, et al, 2020) we used a submaximal graded treadmill exercise test using a modified Balke protocol (Dalleck & Tischendorf, 2014) at the Boston University Fitness and Recreation Center in Boston, MA. This test protocol includes a 3-min warm up followed by 8-12 min of data collection, followed by a 3-min cool down.…”

“…where .1 and 1.8 ml/kg/min are the oxygen costs of walking horizontally and walking on an incline, respectively; 3.5 ml/kg/min is the resting V ̇O2. The equation has previously been described in detail (Kern et al, 2020(Kern et al, , 2022Kronman et al, 2020). Finally, we used linear regression to predict V ̇O2max based on the known relationship between heart rate and V ̇O2 determined from work rate and the participant's age-predicted maximum heart rate.…”

“…In humans, aerobic exercise increases cardiorespiratory fitness (CRF) (Hagberg et al, 1989; Kohrt et al, 1991), which is a measure of one's capacity to support ongoing physical activity through the combined efforts of the respiratory, cardiovascular and musculoskeletal systems (Dalleck & Tischendorf, 2014). Previous research using a modified‐Balke protocol, shown to predictably measure CRF among young and older adults, has shown the efficacy of relating and predicting structural and functional neuroimaging outcomes (Kern et al, 2020, 2022; Kronman et al, 2020; Nauer, Schon, & Stern, 2020; Nauer, Schon, & Stern, 2020). In middle‐aged and older adults in particular, previous volumetric neuroimaging studies have shown positive associations between aerobic exercise, CRF, and neurocognitive integrity of cortical and subcortical regions (Erickson et al, 2014; Erickson & Kramer, 2009; Voelcker‐Rehage & Niemann, 2013; Voss et al, 2013).…”