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First- and second-year podiatric medical students have poor sleep quality. Further research is needed to identify effective strategies to reduce stress and decrease coffee and energy drink intake to minimize their negative effect on sleep quality and academic performance in podiatric medical students.

Background:Valeriana officinalis extract (VE) is a popular herbal medicine used for the treatment of anxiety and sleep disorders. Although the anxiolytic and sedative effects are mainly attributed to the modulation of GABA-ergic transmission, the mechanism of action has not been fully investigated in humans. Noninvasive brain stimulation protocols can be used to elucidate the mechanisms of action of psychoactive substances at the cortical level in humans. In this study, we investigated the effects of a single dose of VE on cortical excitability as assessed with transcranial magnetic stimulation (TMS). Methods: Fifteen healthy volunteers participated in a double-blind, randomized, cross-over, placebo-controlled study. Subjects were required to take either 900 mg of VE (valerenic acid 0.8%) or placebo (an equal dose of vitamin E). Motor cortex excitability was studied by single and paired TMS before and at 1 h and 6 h after the oral administration. Cortical excitability was assessed using different TMS parameters: resting motor threshold, motor-evoked potential amplitude, cortical silent period, short-interval intracortical inhibition, and intracortical facilitation. Furthermore, we assessed sensorimotor integration by short-latency and long-latency afferent inhibition. Results: We found a significant reduction in ICF, without any significant changes in other TMS measures of motor cortex excitability. The amount of ICF returned to baseline value 6 h after the intake of the VE. Conclusion: A single oral dose of VE modulates intracortical facilitatory circuits. Our results in healthy subjects could be predictive markers of treatment response in patients and further support the use of pharmaco-TMS to investigate the neuropsychiatric effects of herbal therapies in humans.

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Medical education is a time of high stress and anxiety for many graduate students in medical professions. In this study, we sought to investigate the effect of academic stress on cortical excitability and plasticity by using transcranial magnetic stimulation (TMS). We tested two groups (n = 13 each) of healthy graduate medical students (mean age 33.7 ± 3.8 SE). One group was tested during a final exam week (High-stress group) while the other group was tested after a break, during a week without exams (Low-stress group). Students were required to fill the Perceived Stress Scale-10 (PSS) questionnaire. We investigated resting motor threshold (RMT), motor evoked potential (MEP) amplitude and cortical silent period (CSP). The paired-pulse stimulation paradigm was used to assess short interval intracortical inhibition (SICI) and intracortical facilitation (ICF). Long-term potentiation (LTP)-like plasticity was evaluated with paired associative stimulation (PAS-25). There was no between-group difference in cortical excitability. On the contrary, during examination period, levels of perceived stress were significantly higher (p= .036) and the amount of cortical plasticity (60 min after PAS) was significantly lower (p = .029). LTP-like plasticity (60 min after PAS) was inversely correlated with perceived stress in the High-stress group. The present study showed LTP-like plasticity was reduced by examining stress in graduate students. Our results provide a new opportunity to objectively quantify the negative effect of academic and examination stress on brain plasticity.