Abstract
ABSTRACT. Hemispheric lateralization of movement control diminishes with age; whether this is compensatory or maladaptive is debated. The authors hypothesized that if compensatory, bilateral activation would lead to greater intermanual transfer in older subjects learning tasks that activate the cortex unilaterally in young adults. They studied 10 young and 14 older subjects, learning a unimanual visuomotor task comprising a feedforward phase, where there is unilateral cortical activation in young adults, and a feedback phase, which activates the cortex bilaterally in both age groups. Increased intermanual transfer was demonstrated in older subjects during feedforward learning, with no difference between groups during feedback learning. This finding is consistent with bilateral cortical activation being compensatory to maintain performance despite declining computational efficiency in neural networks.
Highlights
On one hand it has been proposed that this reflects additional recruitment of functioning neural networks to compensate for declining computational efficiency with age, thereby maintaining performance levels—the Hemispheric Asymmetry Reduction in Older Adults (HAROLD) model (Cabeza, 2002) or delaying and slowing the rate of age related decline—the Compensation-Related Utilization of Neural Circuits Hypothesis (CRUNCH) proposal (Reuter-Lorenz & Cappell, 2008)
Despite the continued debate (Grady, 2013), there is still no consensus on which hypothesis is correct. This may be because overrecruitment of brain activity can be interpreted as compensatory when there is a positive correlation between cortical activity and behavior (McIntosh et al, 1999), when this correlation is negative (Vincent, Kahn, Snyder, Raichle, & Buckner 2008) and even when performance in older adults is impaired (Zarahn et al, 2007), using the argument that the performance might have been even worse without the overrecruitment
Our finding of a significantly increased intermanual transfer for the distance index in the elderly, despite an overall lower performance level, is consistent with the proposal that age related bilateral activation involves recruiting functioning neural networks that are shared by either hand during performed of the task, facilitating transfer of skill between hands
Summary
Increased bilateral brain activation in older subjects during tasks where in the younger adult unilateral activation predominates, is a ubiquitous finding across a wide range of sensorimotor and cognitive tasks and has been demonstrated using a diverse range of techniques (e.g., Cabeza, 2002; Grady, 2013; Graziadio, Basu, Zappasodi, Tecchio, & Eyre, 2010; Hutchinson et al, 2002; Inuggi et al, 2011; Mattay et al, 2002; McGregor, Craggs, Benjamin, Crosson, & White, 2009; Naccarato et al, 2006; Sailer, Dichgans, & Gerloff, 2000; Ward & Frackowiak, 2003; Ward, Swayne, & Newton, 2008; Wu & Hallett, 2005; Yordanova, Kolev, Hohnsbein, & Falkenstein, 2004). We propose that distinguishing between these hypotheses may become clearer in situations where bilateral activation of neural networks during one task potentially conveys an advantage in performance of another function Superior performance of this other function in older adults would indicate bilateral cortical activation recruits functioning neural networks relevant to the task, thereby providing strong evidence in support of compensatory mechanisms rather than being a consequence of an inability to suppress inappropriate neural processing. When motor learning is accomplished with one limb, the ability to perform the same task with the untrained limb can improve (Pereira, Raja, & Gangavalli, 2011; Perez, Wise, Willingham, & Cohen, 2007; Shea, Kovacs, & Panzer, 2011) This phenomenon is best illustrated by skilled movements such as writing, which are normally learnt by and performed only. Our hypothesis was that the elderly subjects would have significantly greater intermanual transfer of motor learning for the first component but not for the second, where intermanual transfer of the motor skill would be similar to or less than that of the young adults
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
