Sangrae Kim

Event-related potential patterns and gender effects underlying facial affect processing in schizophrenia patients

This study was designed to clarify the consecutive temporal mechanisms and gender effects underlying facial affect processing in patients with schizophrenia and normal controls through electrophysiological measurements. The following four event-related potential (ERP) components were chosen as indexes of four distinct stages: P100, N170, N250, and P300. A total of 38 schizophrenia patients (22 females) and 38 normal controls (20 females) were recruited. ERPs were recorded while participants identified emotions in images of faces showing three different states: happy, fearful and neutral. The mean peak amplitude of N170 was significantly lower in schizophrenia patients than in normal controls. The mean peak amplitudes of N170 and N250 for fearful emotion were significantly higher than that for happy emotion. The latencies of N170, and P300 were longer in schizophrenia patients than in normal controls. Gender effects were found for P100 peak amplitude and N170 latency, and significant interactions with gender were found for P300 amplitudes and P100 latency. Our results provide evidences of the dysfunctional ERP patterns underlying facial affect processing in schizophrenia patients. Furthermore, the results suggest that gender could be an important controlling factor for facial affect processing in schizophrenia patients.

The loudness dependence of the auditory evoked potential (LDAEP) in schizophrenia, bipolar disorder, major depressive disorder, anxiety disorder, and healthy controls

BACKGROUND Serotonergic dysfunction in schizophrenia, bipolar disorder, major depressive disorder, anxiety disorder, and healthy controls was evaluated by measuring the activity of the loudness dependence of the auditory evoked potential (LDAEP). METHODS The 357 subjects who were evaluated comprised 55 normal controls, 123 patients with major depressive disorder, 37 with bipolar disorder, 46 with schizophrenia, 37 with panic disorder (PD), 31 with generalized anxiety disorder (GAD), and 28 with post-traumatic stress disorder (PTSD). RESULTS LDAEP was significantly stronger in healthy controls than in patients with either bipolar disorder (p=0.025) or schizophrenia (p=0.008), and significantly stronger in patients with major depressive disorder than in those with bipolar disorder (p=0.01) or schizophrenia (p=0.03). LDAEP did not differ significantly between patients with major depressive disorder and healthy control subjects (p=0.667), or between healthy control subjects and patients with anxiety disorder, including PD (p=0.469), GAD (p=0.664), and PTSD (p=0.167). CONCLUSION The findings of the present study reveal that patients with major psychiatric disorders exhibit different strengths of LDAEP according to their serotonin-related pathology. Studies controlled for psychotropic medication, menstruation cycle, and smoking are needed.

Reduced source activity of event-related potentials for affective facial pictures in schizophrenia patients

The ability to recognize facial affect is impaired in schizophrenia patients. This study compared source activities of the event-related potentials (ERPs) for affective facial pictures between schizophrenia patients and healthy controls. Twenty-three schizophrenia patients (11 females) and 24 healthy controls (12 females) were recruited. The standardized low-resolution brain electromagnetic tomography (sLORETA) source activities of four ERP components (P100, N170, N250, and P300) were compared between schizophrenia patients and healthy controls in response to fearful, happy, and neutral facial expressions. Group differences of sLORETA source activities were found only for the N170 component in response to the fearful face. Source activities in the middle frontal gyrus and inferior frontal gyrus were lower in schizophrenia patients compared to healthy controls. Source activity in the insula was lower in male schizophrenia patients compared to male healthy controls. Source activities in the superior temporal gyrus, middle temporal gyrus, insula and inferior frontal gyrus were lower in male compared to female schizophrenia patients. However, there was no gender difference on ERP source activities in the healthy controls. These results support the hypothesis that schizophrenia patients have reduced N170 current source density in response to fearful faces. The area exhibiting reduced current source density includes the frontal and temporal cortex. The present results suggest that there may be gender differences in facial affect processing in schizophrenia patients.

Dysfunctional gamma-band activity during face structural processing in schizophrenia patients

This study investigated gamma-band activity (GBA) and its phase synchrony in schizophrenia patients viewing human faces. Twenty-five schizophrenia patients were compared with 25 normal controls. Event-related potentials were recorded from all participants while they were viewing emotionally neutral faces. The spectral power and phase synchrony in the frequency band from 30 to 55 Hz were analyzed in midline electrodes (FCz, Cz, CPz, Pz, and POz). Three windows of interest, which showed discernable GBA differences between schizophrenia patients and normal controls, were selected by visual inspection: 0-100 ms (30-33 Hz), 250-300 ms (34-38 Hz), and 700-800 ms (40-45 Hz). And the phase synchrony of gamma band was analyzed. Repeated-measures ANOVA revealed that the GBA was lower in schizophrenia patients than in normal controls. Also there were significant location and time differences in GBA. GBA was significantly lower in the schizophrenia patients than in the normal controls at around 700-800 ms at the FCz electrode. The frontal (FCz) and central (Cz) GBA were significantly correlated with the number of hospitalization, and the negative symptoms of schizophrenia, respectively. The phase synchronization was significantly lower at 200-300 ms in the schizophrenia patients than in the normal controls. These findings suggest that the schizophrenia patients have impaired GBA and gamma-band synchronization during face perception. Furthermore, our results also suggest that the decreased GBA observed at the midline cortex of schizophrenia patients is closely related to their negative symptoms and disease progress.

Neuropsychological correlates of the P300 in patients with Alzheimer's disease.

OBJECTIVES The P300 is a useful psychophysiological index that reflects cognitive functions; however, the relationship between P300 indices and neuropsychological tests in Alzheimers disease (AD) patients is unclear. METHODS Thirty-one AD patients and 31 elderly normal control (NC) subjects were recruited. Age and education level were matched between the two groups. The relationship between the P300 and the Korean version of the Consortium to Establish a Registry for Alzheimers disease (CERAD-K) assessment packet (including 11 neuropsychological tests) was examined in AD patients. RESULTS Compared to the NC subjects, the AD patients exhibited significantly decreased P300 amplitudes; however, there was no significant difference between the two groups in terms of P300 latency. After a permutation-based correction for multiple tests, P300 amplitudes at the Cz and Pz electrodes were significantly correlated with performance on the word list recognition, constructional praxis, and word fluency neuropsychological tests in the AD patients. Additionally, P300 latencies at the Pz and C6 electrodes were also significantly correlated with performance on the Mini-Mental State Examination, CERAD-K version (MMSE-K), and Trail Making Test part A (TMT-A) neuropsychological tests in the AD patients. CONCLUSIONS The results suggest that the P300 is responsive to the deterioration of language, memory, and executive functions observed in AD patients. Although there was no significant difference between the AD patients and NC subjects in the P300 latency, P300 latency has been shown to reflect impaired global cognition and attention deficits associated with AD. Our results suggest that P300 indices could be used as biological markers that indicate impaired neuropsychological functions in AD patients.

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.

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.

When crowding meets binocular rivalry: Challenges for object perception

Both crowding and binocular rivalry impair object perception, but their influence on object perception has so far only been investigated in separate fields. Three experiments investigated the joint influences of crowding and rivalry on object perception (orientation discrimination). Experiment 1 investigated how crowding and rivalry influence orientation discrimination together. Experiment 2 tested whether rivalry between flankers affects crowding using an orientation discrimination task. Experiment 3 tested whether crowding affects the temporal dynamics of the rivalry between a target and a rival stimulus. In Experiment 1, judgments of target orientation were more impaired when crowding and rivalry were simultaneously induced than when they were separately induced and their effects were combined. In Experiment 2, judgments of target orientation were impaired even when flankers were undergoing rivalry, thus highlighting the importance of the presence of flankers. Experiment 3 showed that flankers presented in the neighborhood of a target undergoing rivalry shortened target dominance and prolonged target suppression. The augmented impairments of object perception found in Experiments 1 and 3 suggest that crowding and rivalry interact, presumably through signal suppression. The adverse effect of flankers shown in Experiment 2 suggests that inappropriate feature integration may have additionally contributed to this interaction.