We examined changes in the facilitating effects on spinal motor neurons of the contralateral upper extremity during difficult movement practices. Sixteen healthy adults were randomly assigned to the ball rotation movement practice group and finger flexion–extension movement practice group. F-waves were derived from the right abductor pollicis brevis muscle during the tasks performed before and after the practice. The ball rotation movement practice group performed a task that involved a two-ball clockwise rotation with the left hand. The finger flexion–extension movement practice group performed another task that involved the flexion and extension of the left-hand fingers at a frequency of 1 Hz. The subjects practiced for three sessions of 1-min duration each. The amplitude ratio and persistence of F-wave/M-wave in the ball rotation movement practice group were lower after practice than those before practice, and no difference was observed in the finger flexion–extension movement practice group. The facilitation effects of the spinal motor neurons of the contralateral upper extremity during difficult movement decreased when the subject became proficient with the movement through practice.

Generating motor evoked potential (MEP) is sometimes difficult in cervical spondylotic myelopathy (CSM) surgery. We investigated the relationship between baseline MEP and T2 increased signal intensity (ISI). Sixty-one CSM patients with preserved lower extremity function (MMT≥4 and Nurick scale≤4) were included. They underwent CSM surgery under desflurane anesthesia. Patients were divided into ISI (−) and ISI (+) groups. Two groups were matched with propensity score. The cases that neither bilateral target muscles could generate MEP in were defined as failure. The two groups after matching were compared for baseline MEP failure. ISI (−) and ISI (+) patients were 32 and 29 respectively. Propensity score matching was performed using age, Nurick scale and JOA score as covariants. Twenty-two pairs were selected. ISI (−) group had no failure case. ISI (+) group had 5 failure cases (23%). Baseline MEP failure was more frequently observed in ISI (+) than in ISI (−) significantly. There may be a need to prepare counter-measures for baseline MEP failure in ISI (+) patients.

The changes in excitability of anterior horn cells following repetitive thumb opposition movement at different frequency were evaluated using F-wave study. Fifteen healthy subjects participated. The maximum possible number of the repetitive thumb opposition movement in 10 seconds was evaluated and was used as the maximum frequency. The 50% of the maximum frequency was named 50% maximum frequency. The F-waves were recorded from the thenar muscles following median nerve stimulation at the wrist before and after each task (maximum or 50% maximum frequency tasks). F/M amplitude ratio was used for evaluating the excitability of the anterior horn cells and was compared between before and after each task. F/M amplitude ratio after the maximum frequency task were similar to that before the task. However, F/M amplitude ratio after the 50% maximum frequency task were lower than that before. Our results suggest that the rest following repetitive thumb opposition movement at 50% maximum frequency reduces the excitability of anterior horn cells.

The amplitude of mismatch negativity (MMN) has been reported to be reduced in psychotic disorders such as schizophrenia and at-risk mental state (ARMS) who have an increased risk of developing psychotic disorders. We measured the duration MMN (dMMN) in patients with first-episode schizophrenia, chronic schizophrenia and ARMS. As results, reductions were found in dMMN and subsequent reorienting negativity (RON) amplitudes in first episode schizophrenia and chronic schizophrenia. Furthermore, the dMMN amplitude was significantly lower in the group with ARMS who later transit to schizophrenia than in the non-transition group. In recent years, there have been increasing number of reports examining the application of MMN as a tool to predict functional outcome not only diagnostic outcome in ARMS. Further clinical applications of MMN are expected.

It is well known that the amplitude of mismatch negativity (MMN), a component of event-related potentials, is attenuated in chronic schizophrenia. Although the neural basis of the MMN deficits is not fully understood, there is growing evidence that MMN amplitudes are attenuated even in the early stages of schizophrenia and that the association with cognitive function and functional outcomes and the prognostic properties vary by the stimulus condition. Because MMN is a translatable biomarker that can be measured in non-human animals, MMN studies in the early stages of schizophrenia may help to elucidate the pathophysiology of the disease and provide effective early support for patients with schizophrenia. We therefore reviewed MMN studies of the early stages of schizophrenia, such as ultra-high risk for psychosis (UHR) and first episode psychosis/schizophrenia (FEP/FES), from the perspective of progressive changes in MMN, associations with cognitive function and functional outcomes, pathophysiology, and prognosis prediction of UHR, as well as focusing on differences in stimulus conditions.