Clinic Study On P50 Sensory Gating In First-episode Schizophrenia And Their Healthy First-degree Relatives

Background and Objective: Sensory gating is the ability of the human brain to modulate its response to sensory stimuli and to filter out irrelevant stimuli, this mechanism is believed to be important for normal brain function. If sensory gating is inadequate, many irrelevant signals are transmitted and came to consciousness, which may cause all kinds of psychotic symptoms as well as cognitive deficiency. P50 sensory gating is an electropsysiological index to reflect the brain inhibition recorded by auditory evoked potential, there are two record paradigms: conditioning-testing stimulus paradigm and stimulus train paradigm. Although the two kinds of P50 sensory gating deficits have been detected in schizophrenics, whether they derive from the same mechanism remains unclear. The relationships between P50 sensory gating and psychotic symptoms, and the effects of antipsychotic medication on P50 sensory gating are also controversial. This study is design to explore: (1) the difference of the two P50 sensory gatings between the first-episode schizophrenics, their healthy relatives and normal subjects. (2) The coincidence of P50 suppression ratio in the two evoked paradigms. (3) The relationships between P50 sensory gating and psychotic symptoms, and the effects of typical and atypical antipsychotic medication on the two sensory gatings.Participants and Methods: Participants include the patients meet the criteria for schizophrenia according to the China diagnostic criteria of mental disorders-3rd edition (CCMD-3), the patient's healthy relatives and normal controls. Conditioning-testing stimulus paradigm and stimulus train paradigm are used to record the P50 auditory evoked potential, and the Positive and Negative Syndrome Scale (PANSS) and the Brief Psychiatric Rating Scale (BPRS) are used to assess the schizophrenics' symptoms.Results: The differences of P50 suppression in conditioning-testing stimulus paradigm are significantly between the first-episode schizophrenics with their healthy relatives, and with the normal controls (p<0.05) . In the stimulus train paradigm, the differences of P50 suppression also exist between the first-episode schizophrenics and their healthy relatives and the normal controls (p<0.05) , but not between the patients' healthy relatives and the normal controls (p>0.05) .By coincidence analysis of the P50 suppression ratios between the two stimulus paradigms, we found high coincidence in the normal subjects but not in the schizophrenics.The P50 suppression is not related to PANSS score and BPRS score in the conditioning-testing stimulus paradigm. But we do find relationships between P50 suppression abnormality with PANSS global severity score, and with BPRS total score, anxiety and depression score, and intension score in the stimulus train paradigm.The typical antipsychotics have obviously effects on P50 suppression in the stimulus train paradigm, but not in the conditioning-testing stimulus paradigm. The atypical antipsychotics have obviously effects on P50 suppression in both paradigms.Conclusions:1. First-episode schizophrenics and some of their healthy first-degree relatives have the P50 sensory gating deficiency which reflects brain inhibition deficit.2. There is no coincidence of the two kinds of evoked P50 suppression, which suggest that different central neuron mechanisms exist in schizophrenics.3. The conditioning-testing stimulus paradigm P50 sensory gating has no significant relationships with psychotic symptoms. The stimulus train paradigm P50 sensory gating is related to illness severity and some emotional state.4. The typical antipsychotic medication can ameliorate the P50 suppression in stimulus train paradigm, but not in the conditioning-testing stimulus paradigm. Atypical antipsychotic medication can ameliorate P50 suppression in both paradigms.All of above indicate that the conditioning-testing stimulus paradigm P50 sensory gating deficit maybe a biological trait marker linked to genetics, and the stimulus train paradigm P50 sensory gating deficit maybe a biological state marker linked to the illness state in schizophrenics.