Evoked cortical responses do not follow a rigid input-output function but are dynamically shaped by intrinsic neural properties at the time of stimulation. Recent research has emphasized the role of oscillatory activity in determining cortical excitability. Here we employed EEG-guided transcranial magnetic stimulation (TMS) during non-rapid eye movement sleep to examine whether the spontaneous Ͻ1 Hz neocortical slow oscillation (SO) is associated with corresponding fluctuations of evoked responses. Whereas the SO's alternating phases of global depolarization (up-state) and hyperpolarization (down-state) are clearly associated with fluctuations in spontaneous neuronal excitation, less is known about state-dependent shifts in neocortical excitability. In 12 human volunteers, single-pulse TMS of the primary motor cortical hand area (M1 HAND ) was triggered online by automatic detection of SO up-states and down-states in the EEG. Statedependent changes in cortical excitability were traced by simultaneously recording motor-evoked potentials (MEPs) and TMS-evoked EEG potentials (TEPs). Compared to wakefulness and regardless of SO state, sleep MEPs were smaller and delayed whereas sleep TEPs were fundamentally altered, closely resembling a spontaneous SO. However, both MEPs and TEPs were consistently larger when evoked during SO up-states than during down-states, and ampliudes within each SO state depended on the actual EEG potential at the time and site of stimulation. These results provide first-time evidence for a rapid state-dependent shift in neocortical excitability during a neuronal oscillation in the human brain. We further demonstrate that EEG-guided temporal neuronavigation is a powerful tool to investigate the phase-dependent effects of neuronal oscillations on perception, cognition, and motor control.

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Exerting self-control in a first task weakens self-control performance in a subsequent unrelated task (ego depletion). In self-control research new strategies are required to investigate the ego-depletion effect, which has recently been shown to be more fragile than previously assumed. Moreover, the relation between ego depletion and trait self-control is still unclear, as various studies have reported heterogeneous findings concerning the interplay of both variables. We addressed these lacunas by drawing on a sample of N = 120 students, who participated in two test sessions. In the first test session, we assessed trait self-control and several control variables. The second test session followed an experimental design and tested the effects of ego depletion on invested effort and cognitive performance trajectories in an ecologically valid computer-based assessment setting (i.e., a 30-minute mathematical problem-solving and reasoning test). Trait self-control was then used as a moderator of the ego-depletion effect. Combining an established ego-depletion paradigm (i.e., the sequential-task paradigm) with multilevel modeling of time-on-task and performance changes, our results indicate (1) that trait self-control predicted the motivation to solve cognitive tasks, (2) that ego depletion led to a progressive performance decrease, and (3) that the negative effect of ego depletion on performance was stronger for students with high trait self-control. Additional analyses revealed that our results could not be alternatively explained by fatigue effects. All effects were robust even after controlling for the students’ cognitive abilities, which are known to be closely related to mathematical performance. Our results provide evidence that the self-control invested in order to keep performance at a consistently high level wanes over time. By modeling progressive ego-depletion effects while considering trait self-control, we provide an alternative approach that may help future researchers to investigate the underlying mechanisms of self-control.

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