Faculty Bibliography

Recent research in rodents suggests that extended and chronic hormone therapy can exacerbate memory impairments and irreversibly damage cells. However, aerobic fitness regimens have been shown to spare brain tissue and cognitive function. In addition, interactions between estrogen treatment and exercise have been reported in rodents. However, whether aerobic fitness and hormone treatments show interactive effects on human brain tissue and cognition has yet to be determined. Here we report two unique and important results: (a) HRT treatment up to 10 years in duration spares gray matter in prefrontal cortex and is associated with better performance on measures of executive function, whereas HRT treatment beyond 10 years in duration increases the degree of prefrontal deterioration and amplifies the decline on measures of executive functioning (b) higher fitness levels augment the effects of shorter durations of hormone treatment and ameliorate the declines associated with prolonged hormone treatment.

The extent to which cortical plasticity is retained in old age remains an understudied question, despite large social and scientific implications of such a result. Neuroimaging research reports individual differences in age-related activation, thereby educing speculation that some degree of plasticity may remain throughout life. We conducted a randomized longitudinal dual-task training study to investigate if performance improvements (a) change the magnitude or pattern of fMRI activation, thereby suggesting some plasticity retention in old age and (b) result in a reduction in asymmetry and an increase in age differences in fMRI activation as a compensatory model of performance-related activation predicts. Performance improvements were correlated with an increase in hemispheric asymmetry and a reduction in age differences in ventral and dorsal prefrontal activation. These results provide evidence for plasticity in old age and are discussed in relation to an alternative argument for the role of reduced asymmetry in performance improvements.

Although training-induced changes in brain activity have been previously examined, plasticity associated with executive functions remains understudied. In this study, we examined training-related changes in cortical activity during a dual task requiring executive control. Two functional magnetic resonance imaging (fMRI) sessions, one before training and one after training, were performed on both a control group and a training group. Using a region-of-interest analysis, we examined Time x Group and Time x Group x Condition interactions to isolate training-dependent changes in activation. We found that most regions involved in dual-task processing before training showed reductions in activation after training. Many of the decreases in activation were correlated with improved performance on the task. We also found an area in the dorsolateral prefrontal cortex that showed an increase in activation for the training group for the dual-task condition, which was also correlated with improved performance. These results are discussed in relation to the efficacy of training protocols for modulating attention and executive functions, dual-task processing, and fMRI correlates of plasticity.

The size of the functional field of view (FFOV) predicts driving safety in older adults ( Owsley et al., 1998), and practice-related changes in the FFOV may transfer to driving safety ( Roenker, Cissell, Ball, Wadley, & Edwards, 2003). We used functional magnetic resonance imaging (fMRI) and behavioral measures to examine how practice with the FFOV task changes older adults' attentional function. Behavioral data collected outside of the MRI revealed that participants in the training group showed larger improvements across conditions than did those in the control group. fMRI data revealed training-related changes in activation in a number of brain regions. In the right precentral gyrus and right inferior frontal gyrus, increases in activation between fMRI sessions correlated positively with increases in accuracy between behavioral sessions. Practice with the FFOV task improves older adults' attentional function by increasing their recruitment of regions traditionally associated with orienting visual attention.

We provide a brief review of the literature on exercise effects on brain and cognition. To this end, we focus on both prospective and retrospective human epidemiological studies that have examined the influence of exercise and physical activity on cognition and dementia. We then examine the relatively small set of human randomized clinical trials that have, for the most part, focused on exercise training effects on cognition. Next, we discuss animal research that has examined the molecular, cellular, and behavioral effects of exercise training. Finally, we conclude with a summary and brief discussion of important future directions of research on fitness cognition and brain.

BACKGROUND:The present study examined whether aerobic fitness training of older humans can increase brain volume in regions associated with age-related decline in both brain structure and cognition. METHODS:Fifty-nine healthy but sedentary community-dwelling volunteers, aged 60-79 years, participated in the 6-month randomized clinical trial. Half of the older adults served in the aerobic training group, the other half of the older adults participated in the toning and stretching control group. Twenty young adults served as controls for the magnetic resonance imaging (MRI), and did not participate in the exercise intervention. High spatial resolution estimates of gray and white matter volume, derived from 3D spoiled gradient recalled acquisition MRI images, were collected before and after the 6-month fitness intervention. Estimates of maximal oxygen uptake (VO2) were also obtained. RESULTS:Significant increases in brain volume, in both gray and white matter regions, were found as a function of fitness training for the older adults who participated in the aerobic fitness training but not for the older adults who participated in the stretching and toning (nonaerobic) control group. As predicted, no significant changes in either gray or white matter volume were detected for our younger participants. CONCLUSIONS:These results suggest that cardiovascular fitness is associated with the sparing of brain tissue in aging humans. Furthermore, these results suggest a strong biological basis for the role of aerobic fitness in maintaining and enhancing central nervous system health and cognitive functioning in older adults.

Laboratory based training studies suggest that older adults can benefit from training in tasks that tap control aspects of attention. This was further explored in the present study in which older and younger adults completed an adaptive and individualized dual-task training program. The testing-the-limits approach was used [Lindenberger, U., & Baltes, P. B. (1995). Testing-the-limits and experimental simulation: Two methods to explicate the role of learning in development. Human Development, 38, 349-360.] in order to gain insight into how attentional control can be improved in older adults. Results indicated substantial improvement in overlapping task performance in both younger and older participants suggesting the availability of cognitive plasticity in both age groups. Improvement was equivalent among age groups in response speed and performance variability but larger in response accuracy for older adults. The results suggest that time-sharing skills can be substantially improved in older adults.