Cortical Neuronal Excitability and Transcallosal Inhibition in Schizophrenic Patients: Transcranial Magnetic Study

Background: Transcranial Magnetic Stimulation (TMS) is a non-invasive method of stimulating the brain that is increasingly being used in neuropsychiatric research and clinical psychiatry. Some studies have suggested that the pathophysiology of schizophrenia may involve dysfunction of excitatory and/or inhibitory neural function This study aimed to investigate the cortical neuronal excitability and the transcallosal inhibition in schizophrenic patients. Material and Methods: The study included 26 schizophrenic patients and 13 healthy volunteers, clinical evaluation and determination of motor threshold (MT) at rest (RMT) and during active contraction (AMT), motor evoked potential (MEP) amplitude, Input-output curve, cortical silent period (CSP) duration and transcallosal inhibition were done for each jubject. Results: There was significant prolongation of duration and latency of TCI as well as lengthened transcallosal conduction time. (P< 0.001, 0.003 and 0.001 respectively) in schisophernics compared with control group. Despite the absence of significant differences between schizophrenics and controls in other neurophysiological parameters (RMT, AMT, MEP or CSP), there was significant correlation between resting motor threshold and negative symptoms of schizophrenia (P = 0.003).There was significant positive correlation between the CSP duration and positive symptoms of schizophrenia (P = 0.001). There were no significant differences between paranoid and nonparanoid schizophrenia in cortical neuronal excitability or in transcallosal inhibition. Conclusion: The significant abnormalities of TCI duration and time could support the hypothesis of an abnormally functioning corpus callosum in schizophrenia. (Egypt J. Neurol. Psychiat. Neurosurg., 2007, 44(1): 313-322).