Abstract
Motivation is a hallmark of healthy aging, but the motivation to engage in effortful behavior diminishes with increasing age. Most neurobiological accounts of altered motivation in older adults assume that these deficits are caused by a gradual decline in brain tissue, while some psychological theories posit a switch from gain orientation to loss avoidance in motivational goals. Here, we contribute to reconcile the psychological and neural perspectives by providing evidence that the frontopolar cortex (FPC), a brain region involved in cost–benefit weighting, increasingly underpins effort avoidance rather than engagement with age. Using anodal transcranial direct current stimulation together with effort–reward trade-offs, we find that the FPC’s function in effort-based decisions remains focused on cost–benefit calculations but appears to switch from reward-seeking to cost avoidance with increasing age. This is further evidenced by the exploratory, independent analysis of structural brain changes, showing that the relationship between the density of the frontopolar neural tissue and the willingness to exert effort differs in young vs older adults. Our results inform aging-related models of decision-making by providing preliminary evidence that, in addition to cortical thinning, changes in goal orientation need to be considered in order to understand alterations in decision-making over the life span.
Highlights
Reduced motivation to engage in demanding activities is a widespread phenomenon in aging, even in otherwise healthy individuals (Depping and Freund, 2011)
We tested the computational role of the frontopolar cortex (FPC) for motivation by assessing whether excitatory anodal FPC transcranial direct current stimulation (tDCS) increases the willingness to exert effort
While there was a non-significant trend for higher acceptance rates for physical than for mental effort, beta = 0.61, z = 1.83, P = 0.07, BF10 = 4.3, tDCS effects did not significantly differ between mental and physical effort, beta = −0.26, z = 0.64, P = 0.52, BF10 = 2.1
Summary
Reduced motivation to engage in demanding activities is a widespread phenomenon in aging, even in otherwise healthy individuals (Depping and Freund, 2011). Previous studies observed reduced willingness to engage in effortful behavior with increasing age (Hess and Ennis, 2012; Westbrook et al, 2013). These deficits might be specific for self-regarding rather than for other-regarding benefits (Beadle et al, 2015; Lockwood et al, 2021), and, some studies reported no difference in effort aversion with increasing age (Seaman et al, 2016, 2018). Higher levels of motivation are indicative of mental and physical health as well as general well-being at older ages (Mortby et al, 2011). Knowledge about the neurobiological basis of motivational deficits in older adults may foster the development of interventions for the prevention or rehabilitation of these deficits and the associated health problems
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