RESUMEN
BACKGROUND: Transcranial magnetic stimulation (TMS) combined with electromyography (EMG) has widely been used as a non-invasive brain stimulation tool to assess excitation/inhibition (E/I) balance. E/I imbalance is a putative mechanism underlying symptoms in patients with schizophrenia. Combined TMS-electroencephalography (TMS-EEG) provides a detailed examination of cortical excitability to assess the pathophysiology of schizophrenia. This study aimed to investigate differences in TMS-evoked potentials (TEPs), TMS-related spectral perturbations (TRSP) and intertrial coherence (ITC) between patients with schizophrenia and healthy controls. MATERIALS AND METHODS: TMS was applied over the motor cortex during EEG recording. Differences in TEPs, TRSP and ITC between the patient and healthy subjects were analysed for all electrodes at each time point, by applying multiple independent sample t-tests with a cluster-based permutation analysis to correct for multiple comparisons. RESULTS: Patients demonstrated significantly reduced amplitudes of early and late TEP components compared to healthy controls. Patients also showed a significant reduction of early delta (50-160â¯ms) and theta TRSP (30-250ms),followed by a reduction in alpha and beta suppression (220-560â¯ms; 190-420â¯ms). Patients showed a reduction of both early (50-110â¯ms) gamma increase and later (180-230â¯ms) gamma suppression. Finally, the ITC was significantly lower in patients in the alpha band, from 30 to 260â¯ms. CONCLUSION: Our findings support the putative role of impaired GABA-receptor mediated inhibition in schizophrenia impacting excitatory neurotransmission. Further studies can usefully elucidate mechanisms underlying specific symptoms clusters using TMS-EEG biometrics.
Asunto(s)
Excitabilidad Cortical , Electroencefalografía , Potenciales Evocados Motores , Corteza Motora , Esquizofrenia , Estimulación Magnética Transcraneal , Humanos , Estimulación Magnética Transcraneal/métodos , Esquizofrenia/fisiopatología , Masculino , Femenino , Adulto , Electroencefalografía/métodos , Corteza Motora/fisiopatología , Potenciales Evocados Motores/fisiología , Excitabilidad Cortical/fisiología , Inhibición Neural/fisiología , Persona de Mediana Edad , Electromiografía/métodos , Adulto JovenRESUMEN
Undoped semi-insulating GaAs were implanted with 500 MeV Ne ions. Monte Carlo simulation revealed that the largest concentration of vacancies induced was around the end of the Ne ion range. Positron Annihilation measurement showed that after lower dose implantation, divacancies were formed, which coexisted with monovacancies. On increasing the dose, all the monovacancies changed to divacancies. The temperature dependence of positron lifetime suggested the existence of negatively charged antisites GaAs. Near infra-red spectra were also measured to study the implantation induced amorphous layers.