The goal of this clinical trial is to systematically investigate two prominent factors in teenagers' daily life: Caffeine and sleep restriction (SR) and their combined influence on sleep, cognition, and behavior in healthy adolescents. The main questions it aims to answer are: The effects of caffeine under conditions of SR and SE: * on sleep pressure and sleep continuity. * on BOLD activity differences in reward related areas during a reward task (monetary incentive delay task) and on reaction times (behavioral aspect) in the same task. * on BOLD activity differences during a risk taking task (wheel of fortune task) and on risky decision-making (behavioral aspect) in the same task. Participants will be either in the SR or SE condition (between-subject). The protocol consists of 2x of approximately one week in which a participant will receive caffeine or placebo (within-subject) at the last two evenings. The experiment consists of an ambulatory and a laboratory phase: * The ambulatory phase consists of 5 nights, including 3 stabilization nights (8h sleep opportunity) prior to 2 nights consisting of either SR with 6h sleep opportunity or SE with 9.5h sleep opportunity. Participants will wear an actiwatch and fill out sleep diaries during this period. * The laboratory phase will be the 6th evening, night and morning of the protocol and will be spent in our lab. Participants will do the following: * treatment (caffeine vs. placebo) intake * saliva sampling * drug screening * cognitive tests, including risk-taking and reward task * filling in questionnaires (sleep diary, sleep quality, sleepiness, mood, expectancy) * waking and sleep with EEG The next day, participants will undergo an fMRI scan, including the following: * resting-state scan * structural scan * arterial spin labeling scan * reward task scan * risk-taking task scan Around the scan, participants will fill out/undergo: * saliva sampling * questionnaires (reward task, mood, sleepiness, expectancy)
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Nighttime Sleep SWA
Timeframe: Laboratory night week 1
Nighttime Sleep SWA
Timeframe: Laboratory night week 2
BOLD activity during reward processing
Timeframe: fMRI session week 1
BOLD activity during reward processing
Timeframe: fMRI session week 2
BOLD activity during risk-decision making (RDM)
Timeframe: fMRI session week 1
BOLD activity during risk-decision making (RDM)
Timeframe: fMRI session week 2