Walter J. Rejeski

Using Network Science to Evaluate Exercise-Associated Brain Changes in Older Adults

Literature has shown that exercise is beneficial for cognitive function in older adults and that aerobic fitness is associated with increased hippocampal tissue and blood volumes. The current study used novel network science methods to shed light on the neurophysiological implications of exercise-induced changes in the hippocampus of older adults. Participants represented a volunteer subgroup of older adults that were part of either the exercise training (ET) or healthy aging educational control (HAC) treatment arms from the Seniors Health and Activity Research Program Pilot (SHARP-P) trial. Following the 4-month interventions, MRI measures of resting brain blood flow and connectivity were performed. The ET groups hippocampal cerebral blood flow (CBF) exhibited statistically significant increases compared to the HAC group. Novel whole-brain network connectivity analyses showed greater connectivity in the hippocampi of the ET participants compared to HAC. Furthermore, the hippocampus was consistently shown to be within the same network neighborhood (module) as the anterior cingulate cortex only within the ET group. Thus, within the ET group, the hippocampus and anterior cingulate were highly interconnected and localized to the same network neighborhood. This project shows the power of network science to investigate potential mechanisms for exercise-induced benefits to the brain in older adults. We show a link between neurological network features and CBF, and it is possible that this alteration of functional brain networks may lead to the known improvement in cognitive function among older adults following exercise.

Validation of the PASE in older adults with knee pain and physical disability.

PURPOSE To examine the validity of the Physical Activity Scale for the Elderly (PASE) among individuals with disability. METHODS A sample of 471 participants (mean age = 71.36) in an epidemiological study of chronic knee pain completed the PASE and self-report measures of knee pain, perceived physical function, satisfaction with physical function, and importance of physical function. A 6-min walk test and an isokinetic assessment of knee strength were also administered. RESULTS PASE scores were significantly correlated in expected directions with performance on the 6-min walk, knee strength, frequency of knee pain during transfer, and perceived difficulty with physical functioning. Gender and age were identified as significant moderators of PASE scores and the scales construct validity was supported by testing a conceptually driven hypothesis regarding patterns of physical activity. CONCLUSIONS These results support the PASEs validity for the assessment of physical activity among older adults with pain and disability.

Effects of mental stress on brachial artery flow-mediated vasodilation in healthy normal individuals

BACKGROUND Mental stress is associated with increased risk for cardiovascular events, possibly because of acute increases in endogenous catecholamines. Recently, brachial artery flow-mediated vasodilation has been used for noninvasive assessment of macrovascular endothelial function. The effect of mental stress and its associated changes in sympathetic activation on brachial artery endothelium-dependent vasomotor tone in vivo remains unknown. METHODS AND RESULTS Two-dimensional ultrasound was used to measure brachial artery flow-mediated vasodilation before and after mental stress (provoked by a standard arithmetic challenge) in 21 healthy individuals (10 men, 11 women; average age 23.5 years). The flow stimulus resulted from a 3-minute cuff occlusion of distal forearm blood flow, causing distal hyperemia and a transient 2- to 3-fold increase in brachial artery blood flow on cuff release. During mental stress, heart rate increased on average by 29.6% and blood pressure increased on average by 17.9%. The sympathetic stimulus resulted in a 64% average increase in flow-mediated vasodilator response (P <.001). The enhanced vasodilator response during mental stress was similar for men and women. CONCLUSIONS Mental stress can have marked effects on endothelium-dependent, flow-mediated vasodilation in healthy, normal individuals. Similar studies in individuals with impaired endothelial function may further our understanding of the role of mental stress in the development of cardiovascular events.

Effects of exercise on mobility in obese and nonobese older adults.

Coupled with an aging society, the rising obesity prevalence is likely to increase the future burden of physical disability. We set out to determine whether obesity modified the effects of a physical activity (PA) intervention designed to prevent mobility disability in older adults. Older adults at risk for disability (N = 424, age range: 70–88 years) were randomized to a 12 month PA intervention involving moderate intensity aerobic, strength, balance, and flexibility exercise (150 min per week) or a successful aging (SA) intervention involving weekly educational workshops. Individuals were stratified by obesity using a BMI ≥30 (n = 179). Mobility function was assessed as usual walking speed over 400 m and scores on a short physical performance battery (SPPB), which includes short distance walking, balance tests, and chair rises. Over 12 months of supervised training, the attendance and total amount of walking time was similar between obese and nonobese subjects and no weight change was observed. Nonobese participants in the PA group had significant increases in 400‐m walking speed (+1.5%), whereas their counterparts in the SA group declined (−4.3%). In contrast, obese individuals declined regardless of their assigned intervention group (PA: −3.1%; SA: −4.9%). SPPB scores, however, increased following PA in both obese (PA: +13.5%; SA: +2.5%) and nonobese older adults (PA: +18.6%; SA: +6.1%). A moderate intensity PA intervention improves physical function in older adults, but the positive benefits are attenuated with obesity.

Nonverbal Expression of Effort as Causally Relevant Information

The effects of nonverbal effort cues on causal attributions were assessed. Subjects watched a videotape of an athlete running on an exercise treadmill. The athlete either succeeded or failed and was either expressive or nonexpressive. As hypothesized, expressive athletes were seen to exhibit more effort than nonexpressive athletes. More important, significant interactions showed that for failure conditions nonexpressive athletes were seen to have less ability and as more responsible for their failure than expressive athletes. Implications for attribution research, attribution theory, and self-presentation were discussed.

Drive for consumption, craving, and connectivity in the visual cortex during the imagery of desired food

There is considerable interest in understanding food cravings given the obesogenic environment of Western Society. In this paper we examine how the imagery of palatable foods affects cravings and functional connectivity in the visual cortex for people who differ on the power of food scale (PFS). Fourteen older, overweight/obese adults came to our laboratory on two different occasions. Both times they ate a controlled breakfast meal and then were restricted from eating for 2.5 h prior to scanning. On 1 day they consumed a BOOST® liquid meal after the period of food restriction, whereas on the other day they only consumed water (NO BOOST® condition). After these manipulations, they had an fMRI scan in which they were asked to image both neutral objects and their favorite snack foods; they also completed visual analog scales for craving, hunger, and the vividness of the imagery experiences. Irrespective of the BOOST® manipulation, we observed marked increases in food cravings when older, overweight/obese adults created images of favorite foods in their minds as opposed to creating an image of neutral objects; however, the increase in food craving following the imagery of desired food was more pronounced among those scoring high than low on the PFS. Furthermore, local efficiency within the visual cortex when imaging desired food was higher for those scoring high as compared to low on the PFS. The active imagery of desired foods seemed to have overpowered the BOOST® manipulation when evaluating connectivity in the visual cortex.

Design and implementation of the mobility assessment tool: software description

BackgroundIn previous work, we described the development of an 81-item video-animated tool for assessing mobility. In response to criticism levied during a pilot study of this tool, we sought to develop a new version built upon a flexible framework for designing and administering the instrument.ResultsRather than constructing a self-contained software application with a hard-coded instrument, we designed an XML schema capable of describing a variety of psychometric instruments. The new version of our video-animated assessment tool was then defined fully within the context of a compliant XML document. Two software applications—one built in Java, the other in Objective-C for the Apple iPad—were then built that could present the instrument described in the XML document and collect participants’ responses. Separating the instrument’s definition from the software application implementing it allowed for rapid iteration and easy, reliable definition of variations.ConclusionsDefining instruments in a software-independent XML document simplifies the process of defining instruments and variations and allows a single instrument to be deployed on as many platforms as there are software applications capable of interpreting the instrument, thereby broadening the potential target audience for the instrument. Continued work will be done to further specify and refine this type of instrument specification with a focus on spurring adoption by researchers in gerontology and geriatric medicine.