Aging effects on the control of grip force magnitude: An fMRI study

Abstract

Functional neuroimaging techniques have allowed for investigations into the mechanisms of agerelated deterioration in motor control. This study used functional Magnetic Resonance Imaging (fMRI) to investigate age related differences in the control of grip force magnitude. Using an event-related design, fMRI scans were completed on 13 older adults, and 13 gender matched younger adults, while using their dominant hand to squeeze a rubber bulb for 4s at 10%, 40% or 70% of their maximum voluntary contraction. Both groups were able to match the relative force targets, however the older adults produced significantly lower levels of absolute force. fMRI analysis consisted of a 1) region of interest (ROI) approach to detect differences in selected motor areas within brain and 2) a voxel-wise whole brain comparison to find areas of differential activation that were not defined a priori between the older and younger group. The ROI analysis revealed that despite producing lower levels of absolute force, the older adults showed higher levels of activity predominantly in subcortical structures (putamen, thalamus and cerebellum) when compared to the younger group. The older adults also showed higher levels of activity in the ipsilateral ventral premotor cortex. A total of 19 of the 22 ROIs analyzed showed a significant main effect of the required force-level. In the majority of the ROIs that showed a significant force effect there were no significant differences in the magnitude of the blood-oxygen-level-dependent (BOLD) signal between the 10% and 40% conditions but a significantly higher BOLD signal in the 70% condition, suggesting that the modulation of brain activation with grip force may not be controlled in a linear fashion. It was also found that the older adult group demonstrate higher levels of activation in 7 areas during a force production task at higher force levels using a voxelwise analysis. The 7 clusters that showed significant differences tended to be areas that are involved in visual-spatial and executive processing. The results of this study revealed that older adults require significantly higher activation of several areas to perform the same motor task as younger adults. Higher magnitudes of the BOLD signal in older adults may represent a compensatory pattern to counter age related deterioration in motor control systems.Corresponding Author: Janice J. Eng, PT, OT, Ph.D., Professor, Department of Physical Therapy, University of British Columbia, 212-2177 Wesbrook Mall, Vancouver, BC, Canada V6T 1Z3, Janice.Eng@ubc.ca, Phone: IntroductionThe normal aging process leads to several declines of the motor system that are related to changes within the central nervous system, peripheral nervous system and the musculoskeletal system (Seidler et al., 2010). These changes have the potential to lead to decreased motor performance with aging, which has been observed in the forms of decreased coordination, increased movement variability, slower movements and difficulties with balance and gait (Seidler et al., 2...

Changes of cortico-muscular coherence: an early marker of healthy aging?

“…In particular, increased activation and involvement of a widespread motor network in elderly subjects have been suggested by means of electroencephalography (EEG; Babiloni et al 2006;Derambure et al 1993;Sailer et al 2000) and functional magnetic resonance imaging (fMRI) studies (Heuninckx et al 2005;Noble et al 2011;Ward and Frackowiak 2003). Additionally, slowing of brain dynamics has been evidenced with increasing age (Krampe 2002;Seidler et al 2010).…”

The Impact of Cognitive Fatigue on Age-related Differences in Neuromuscular Function

“…This theory suggests that with aging there is a compensatory shift in neural recruitment to accommodate cognitive challenge (Park & Reuter-Lornez, 2009;Cooper et al, 2013). While the present study focused solely on the activation of the PFC, other brain regions are involved in fatigue development, particularly in older adults (Liu et al, 2003;Clark & Taylor, 2011;Noble et al, 2011). Previous research has demonstrated a shift in activation centers in the brain to maintain neuromuscular performance during a fatiguing protocol (Liu et al, 2007).…”

“…Second, the present study monitored the PFC regions due to equipment constraints. Existing neuroimaging investigations of fatigue development suggest a shift in activation centers in the brain to compensate for fatigue-related loss in neural efficiency, particularly with the normal aging process (Liu et al, 2007;Clark & Taylor, 2011;Noble et al, 2011), future research should examine activation of motor function-related brain regions to understand age-related changes in functional brain activation patterns when individuals are physically and cognitively fatigued. Third, while all participants reported that the 60-minute working memory tasks were cognitively fatiguing, it is possible that longer exposure to such stressors may result in greater negative effects of cognitive fatigue on neuromuscular function.…”

“…However, aging is associated with an increase in type I muscle fibers that has shown to increase fatigue resistance in older adults (Yoon, Schlinder, Griffith, & Hunter, 2008;Avin & Law, 2011). Age-related changes at the CNS, particularly the brain, include reduced cerebral blood flow, loss of cortical excitability, reduction in cortical plasticity, and loss of grey matter (Clark & Taylor, 2011;Noble, Eng, Kokotilo, & Boyd, 2011). Functional brain imaging studies have shown age-related increased compensatory activation at the PFC, ipsilateral cortical motor and sensorimotor areas to maintain motor performance (Noble et al, 2011;Boudrias et al, 2012).…”

“…Age-related changes at the CNS, particularly the brain, include reduced cerebral blood flow, loss of cortical excitability, reduction in cortical plasticity, and loss of grey matter (Clark & Taylor, 2011;Noble, Eng, Kokotilo, & Boyd, 2011). Functional brain imaging studies have shown age-related increased compensatory activation at the PFC, ipsilateral cortical motor and sensorimotor areas to maintain motor performance (Noble et al, 2011;Boudrias et al, 2012). Conversely, reduced brain activity or inefficient cortical connectivity is observed in these brain regions, particularly the PFC, in older adults during fatiguing exercises (i.e.…”