Dysfunctional Patterns of Gamma-Band Activity in Response to Human Faces Compared to Non-Facial Stimuli in Patients with Schizophrenia

OBJECTIVE: Healthy individuals show stronger gamma-band activities (GBAs) for socially relevant stimuli (human faces) than for non-relevant ones. This study aimed to examine whether this gamma-band preference occurs in patients with schizophrenia. METHODS: EEG was recorded for 24 patients with schizophrenia and 23 healthy controls while they viewed pictures of human faces, chairs, and nature scenes. The spectral powers of high-beta (20-30 Hz) and gamma (30-80 Hz) frequencies were analyzed along 3 midline cortical regions, and phase synchronization was calculated. RESULTS: Compared to the response to non-facial stimuli, higher event related deactivation to facial stimuli was observed for the high-beta frequency across groups. For the gamma frequency, early-stage GBA was increased and late-stage GBA was decreased for all 3 stimuli in patients with schizophrenia compared to healthy controls. Preferential GBA patterns (100-200 and 200-300 ms) were found in healthy controls, but not in patients with schizophrenia. Significant correlation existed between negative symptoms and GBA in the frontal region for chair and scene stimuli. There was no significant intergroup difference in phase synchronization pattern. CONCLUSION: Our results suggest that patients with schizophrenia have deficits in the preferential pattern of GBA for human faces and the deficits in the preferential pattern were mainly influenced by over-response to socially non-relevant stimuli.

Gender Difference in Event Related Potentials to Masked Emotional Stimuli in the Oddball Task

OBJECTIVE: We investigated gender differences in event-related potential (ERP) responses to subliminally presented threat-related stimuli. METHODS: Twenty-four participants were presented with threat-related and neutral pictures for a very brief period of time (17 ms). To explore gender differences in ERP responses to subliminally presented stimuli, we examined six ERP components [P1, N170, N250, P300, Early Posterior Negativity (EPN) and Late Positive Potential (LPP)]. RESULTS: The result revealed that only female participants showed significant increases in the N170 and the EPN in response to subliminally presented threat-related stimuli compared to neutral stimuli. CONCLUSION: Our results suggest that female participants exhibit greater cortical processing of subliminally presented threat-related stimuli than male participants.

N100 Amplitude Slopes in Major Depressive Disorder, Bipolar Disorder, Schizophrenia and Normal Controls

OBJECTIVES: N100 amplitude slope(the intensity dependence of the cortical auditory evoked potentials) is widely considered as an indirect indicator of central serotonergic neurotransmission. However, there are only a few studies about N100 amplitude slopes of major psychiatric disorders. In this study, we examined N100 amplitude slope differences among major depressive disorder(MDD), bipolar disorder(BD), schizophrenia (SCZ) and normal controls(NC). METHODS: We measured the N100 amplitude slopes of 35 patients with MDD, 33 patients with BD, 27 patients with SCZ and 35 NC subjects. Amplitude differences from N1 to P2 at the five different sound intensities(55, 65, 75, 85 and 95dB) were examined at Cz electrode. The N100 amplitude slope was calculated as the linear regression of five N1/P2 peak-to-peak amplitudes across stimulus intensities. RESULTS: BD patients showed significantly reduced N100 amplitude slope compared with NC(0.54+/-0.70 vs. 0.96+/-0.72, p=0.035). N100 amplitude slope of SCZ patients was significantly reduced compared with NC(0.50 +/-0.47 vs. 0.96+/-0.72, p=0.027). N100 amplitude slope of BD patients was significantly lower than that of MDD patients(0.54+/-0.70 vs. 0.94+/-0.60, p=0.046). SCZ patients also showed significant reduction of N100 amplitude slope compared with MDD patients(0.50+/-0.47 vs. 0.94+/-0.60, p=0.036). There was no significant difference of N100 amplitude slope between MDD patients and NC(0.94+/-0.60 vs. 0.96+/-0.72, p=1.000). CONCLUSION: Interestingly, the N100 amplitude slopes of BD and SCZ were reduced compared to NC and MDD patients. Our results suggest the predictive use of N100 amplitude slope in making differential diagnoses of major psychiatric disorders. Clinical implications of N100 amplitude slope in major psychiatric disorders were discussed.

Aberrant Response of Selective Serotonin Reuptake Inhibitor in Two Patients with High N100 Amplitude Slope / 대한정신약물학회지

Serotonin is one of the most important neurotransmitters involved in the pathophysiology of depressive illness. The assessment of alteration of cerebral serotonin has been still controversial but interesting topic to study. Recently, increasing evidence has accumulated that the N100 amplitude slope reflects cerebral serotonin activity and treatment response of selective serotonin reuptake inhibitors (SSRIs). We report on two patients who showed abrupt mood changes and side effects after taking SSRI antidepressants. In both patients, aberrantly high N100 amplitude slopes were observed. Our cases suggest that the N100 amplitude slope may be a reliable indicator for predicting manic conversion and side effects in the SSRI treatment of depressive patients. Controlled studies are necessary to confirm whether a high N100 amplitude slope is a useful indicator of SSRI supersensitivity.