Reconciling psychological and neuroscientific accounts of reduced motivation in aging

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 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 exploratory, independent analysis of structural brain changes, showing that the relationship between the density of frontopolar neural tissue and willingness to exert effort differs in young versus 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 lifespan.

Brain stimulation over dorsomedial prefrontal cortex modulates effort-based decision making

“…Previous research related decisions to engage in mental effort to a brain network including the dopaminergic midbrain (Westbrook et al, 2020) and prefrontal brain regions (Chong et al, 2017;Schmidt et al, 2012;Soutschek, Bagaini, et al, 2021a;Soutschek & Tobler, 2020;Vassena et al, 2017). However, less is known about the neural oscillations underlying the motivation to exert rewarded mental effort.…”

Lower motivation for rewarded mental effort in tobacco dependence.

“…For mental effort exertion (Figure 1A), participants had to cross all instances of the letter “e” in a text composed of random letter sequences (i.e., pseudowords) according to a specific rule (the two letters before and the two letters after an “e” must be consonants; Soutschek et al, 2018). Mental effort levels used in the decision task were calibrated to the individual performance level by defining the number of lines a participant could complete in a practice task of 2 min as the 20% mental effort level (Soutschek, Bagaïni, et al, 2022). For example, if a participant completed four lines within 2 min, the 20% mental effort level in the decision task required the performance of four lines of this task, whereas the 100% mental effort level required 20 lines.…”

“…To test the hypothesis of stronger mental effort aversion in tobacco dependence, we compared effort preferences between persons who smoke and persons with no smoking history in an established task measuring the willingness to exert mental effort for monetary rewards (Soutschek, Bagaïni, et al, 2022; Soutschek et al, 2018). To obtain a deeper understanding of the decision-making impairments in tobacco dependence, we examined the decision process underlying effort-based choices with drift–diffusion models (DDMs; Ratcliff, 1978; Ratcliff et al, 2016; for DDMs in the field of effort-based choice, see Soutschek, Nadporozhskaia, & Christian, 2022; Westbrook et al, 2020).…”

Metacognitive deficits are associated with lower sensitivity to preference reversals in nicotine dependence

“…Participants then performed the confidence accuracy task, the bidding task, and the precommitment task. Additionally, participants also performed (in counterbalanced order) decision tasks eliciting risk preferences 59,60 and the willingness to engage in rewarded mental effort 61,62 . Because neither effort nor risk preferences have been linked to precommitment so far, the results of the latter two tasks will be reported in a separate article focusing on how smokers trade off benefits against the costs of actions.…”