Frontopolar Cortex and Motivation in Healthy Older Adults

Motivation represents a core aspect of goal-directed behavior as it determines how much effort individuals are willing to invest to reach their goals. While research on effort-based decision-making focuses mainly on effort preferences in younger adults, loss of motivation might be a key component of the apathetic tendencies frequently seen in older adults. However, an open question refers to which brain mechanisms underlie motivational processes in older adults. The investigators have recently shown that the frontopolar cortex plays a crucial in motivating the exertion of rewarded effort in younger adults. The goal of the current study is to determine whether frontopolar cortex plays a crucial role for motivation also in older adults and may thus be a promising target for improving the motivation deficits in healthy aging. Participants perform computer-based experimental tasks measuring the propensity to exert cognitive or physical effort for monetary rewards. During task performance, participants receive anodal or sham transcranial direct current stimulation (tDCS) over their frontopolar cortex. The study tests whether tDCS over frontopolar cortex allows modulating participants' motivation to engage in rewarded effort.

Motivation represents a core aspect of goal-directed behavior as it determines how much effort individuals are willing to invest to reach their goals. While research on effort-based decision-making focuses mainly on effort preferences in younger adults, loss of motivation might be a key component of the apathetic tendencies frequently seen in older adults. However, an open question refers to which brain mechanisms underlie motivational processes in older adults. The investigators have recently shown that the frontopolar cortex plays a crucial in motivating the exertion of rewarded effort in younger adults (Soutschek et al., 2018, Biological Psychiatry). The goal of the current study is to determine whether frontopolar cortex plays a crucial role for motivation also in older adults and may thus be a promising target for improving the motivation deficits in healthy aging. 30 older participants (65-80 years) perform computer-based experimental tasks measuring the propensity to exert cognitive or physical effort for monetary rewards. During task performance, participants receive 1 mA anodal or sham transcranial direct current stimulation (tDCS) over their frontopolar cortex. The study tests whether tDCS over frontopolar cortex allows modulating participants' motivation to engage in rewarded effort.

Eligibility Criteria:
Inclusion Criteria:

* Age 65-80 years
* Informed consent as documented by signature
* Normal or corrected-to-normal vision
* Cognitive and language ability to understand study content and procedure
* Normal cognitive functioning (assessed by MMST)
* BDI-II score \< 20

Exclusion Criteria:

* Negative response to TMS/tDCS in past
* History of seizure
* History of stroke or heart attack
* History of head injury
* Psychiatric or neurological disorder
* Metal in body/head
* Implanted medical products like pacemaker, medical pumps, heart catheter
* Headache
* Tinnitus
* Currently taking medication affecting the central nervous system
* Insufficient sleep in preceding night
* Excessive consumption of alcohol within last 24 hours