Toshiaki Onitsuka

P300 in response to the subject's own face

The P300 event‐related potentials in response to self‐relevant stimuli has been reported to be different from those to non‐target stimuli under a passive attention condition. In the present study the P300 in response to the subjects own face was examined. Twelve right‐handed volunteers served as subjects. In two separate conditions, deviant (subjects own face and red square; 30%), non‐target (two unfamiliar faces; 30% each), and target (famous face; 10%) stimuli were randomly presented on a computer screen. P300 amplitudes in response to the red square were larger than those to the unfamiliar faces, but were significantly lower than those to the subjects own face. The subjects own face in normal population may have an intense relevance to the subjects which has an additional effect over the simple orienting response.

Abnormal asymmetries in subcortical brain volume in schizophrenia

Subcortical structures, which include the basal ganglia and parts of the limbic system, have key roles in learning, motor control and emotion, but also contribute to higher-order executive functions. Prior studies have reported volumetric alterations in subcortical regions in schizophrenia. Reported results have sometimes been heterogeneous, and few large-scale investigations have been conducted. Moreover, few large-scale studies have assessed asymmetries of subcortical volumes in schizophrenia. Here, as a work completely independent of a study performed by the ENIGMA consortium, we conducted a large-scale multisite study of subcortical volumetric differences between patients with schizophrenia and controls. We also explored the laterality of subcortical regions to identify characteristic similarities and differences between them. T1-weighted images from 1680 healthy individuals and 884 patients with schizophrenia, obtained with 15 imaging protocols at 11 sites, were processed with FreeSurfer. Group differences were calculated for each protocol and meta-analyzed. Compared with controls, patients with schizophrenia demonstrated smaller bilateral hippocampus, amygdala, thalamus and accumbens volumes as well as intracranial volume, but larger bilateral caudate, putamen, pallidum and lateral ventricle volumes. We replicated the rank order of effect sizes for subcortical volumetric changes in schizophrenia reported by the ENIGMA consortium. Further, we revealed leftward asymmetry for thalamus, lateral ventricle, caudate and putamen volumes, and rightward asymmetry for amygdala and hippocampal volumes in both controls and patients with schizophrenia. Also, we demonstrated a schizophrenia-specific leftward asymmetry for pallidum volume. These findings suggest the possibility of aberrant laterality in neural pathways and connectivity patterns related to the pallidum in schizophrenia.

Cavum septi pellucidi in first-episode schizophrenia and first-episode affective psychosis: An MRI study

A high prevalence of abnormal cavum septi pellucidi (CSP) in schizophrenia may reflect neurodevelopmental abnormalities in midline structures of the brain. The relationship, however, between abnormal CSP and clinical symptoms, and with abnormalities in other limbic structures remains unclear, as does the question of whether a similar abnormality is present in affective psychosis. Seventy-four patients at their first hospitalization, 33 with schizophrenia and 41 with affective (mainly manic) psychosis, and 56 healthy control subjects underwent high-spatial-resolution magnetic resonance imaging (MRI). CSP on six slices or more on 0.9375-mm resampled coronal images was categorized as abnormal. The prevalence of abnormal CSP in both schizophrenic patients (26.1%) and affective psychosis patients (18.2%) was significantly higher than was observed in control subjects (8.2%). In schizophrenic patients only, larger CSP was significantly associated with more severe thinking disturbance and smaller left parahippocampal gyrus gray matter volumes. While the relationships between CSP ratings and clinical symptoms did not significantly differ between the two psychosis groups as assessed by the comparison of regression slopes, the association with limbic volumes appeared to be specific to schizophrenic patients. These results suggest that psychosis associated with schizophrenia and affective disorder share, at least to some extent, neurodevelopmental abnormalities involving midline structures and associated psychopathological consequences. However, the association between abnormal CSP and limbic systems may be more specific to schizophrenia.

Reduced high and low frequency gamma synchronization in patients with chronic schizophrenia

Schizophrenia has been conceptualized by dysfunctional cognition and behavior related to abnormalities in neural circuitry. The functioning of the neural circuitry can be assessed using the auditory steady state response (ASSR). Moreover, in recent years, research on high (>60 Hz) gamma band oscillations has become of increasing interest. The current study used whole-head, 306-channel magnetoencephalography (MEG) and investigated low and high gamma band oscillations with the ASSR. The subjects comprised 17 patients with schizophrenia and 22 controls. The current study investigated the MEG-ASSR elicited by click trains of 20-, 30-, 40- and 80-Hz frequencies, and symptom-ASSR associations in patients with schizophrenia. The mean power, phase-locking factor, dipole moments and source locations of the ASSR were estimated. The main findings were: (1) patients with schizophrenia showed bilaterally reduced ASSR power and dipole moments specific to the 40-Hz and 80-Hz frequencies; (2) patients with schizophrenia showed less right-greater-than-left 40-Hz ASSR power and phase-locking factor compared with healthy subjects, indicating that schizophrenics may be characterized by an abnormal asymmetry of the 40-Hz ASSR; (3) increased severity of global hallucinatory experiences was significantly associated with smaller left 80-Hz MEG-ASSR in patients with schizophrenia. The current study highlights the high and low frequency gamma abnormalities and provides clear evidence that schizophrenia is characterized by abnormalities in neural circuitry.

Abnormal Neural Oscillatory Activity to Speech Sounds in Schizophrenia: A Magnetoencephalography Study

Schizophrenia impairs many cognitive functions, and abnormalities in language processing have been proposed as one of the bases for this disorder. Previously, it was reported that different magnetoencephalography (MEG) patterns of the evoked oscillatory activity (eOA) of 20–45 Hz to speech and nonspeech sounds were evidence of a fast mechanism for the representation and identification of speech sounds in humans. The current study tested the hypothesis that the schizophrenics would show abnormal neural oscillatory activity, as measured by eOA, to speech and nonspeech sounds. Twenty patients and 23 control subjects participated in this study. MEG responses to speech and nonspeech sounds were recorded and eOA power and phase locking at 20–45 Hz were analyzed. Patients showed significantly delayed peak latencies of the eOA power and phase locking to speech sounds in the left hemisphere and to nonspeech sounds in the right hemisphere. Patients also showed a significantly reduced eOA power to speech sounds in the left hemisphere in 0–50 ms and a significantly larger eOA power to speech sounds in the left hemisphere in 100–150 ms. In addition, the analyses of the lateralization index revealed the pattern of hemispheric lateralization to be the opposite in patients. These results indicated that patients showed different characteristics of eOA compared with normal controls, probably related to deficits in a fast mechanism for identifying speech sounds. Moreover, the present study suggests that schizophrenia might be characterized by an opposite pattern of hemispheric lateralization in auditory evoked oscillations.

The effect of interstimulus intervals and between-block rests on the auditory evoked potential and magnetic field: is the auditory P50 in humans an overlapping potential?

OBJECTIVE The human auditory P50 may consist of overlapping potentials. To test this hypothesis, we manipulated interstimulus intervals (ISIs) and between-block rests, and recorded the P50, P50m, N100 and the N100m simultaneously. METHODS Subjects were 12 right-handed healthy adults. Four conditions included: (1) 1.5 s/rest, (2) 1.5 s/successive, (3) 0.5 s/rest, and (4) 0.5 s/successive. Auditory stimuli were presented a total of 880 times for each condition. Auditory evoked potentials and magnetic fields were recorded. We examined the P50, N100, P50m, N100m and dipoles of the P50m and the N100m. RESULTS There was no significant effect of the ISI on the P50 amplitudes, but the P50m amplitudes in the 0.5 s ISI conditions were significantly smaller than those in the 1.5 s ISI conditions. The N100 and the N100m amplitudes in the 0.5 s ISI conditions were significantly smaller than those in the 1.5 s ISI conditions. The N100 and the N100m amplitudes in the resting conditions were significantly larger than those in the successive conditions. The P50m dipoles were slightly deeper and more anterior than those of the N100m in primary auditory cortex. CONCLUSIONS Central structures other than supratemporal cortex contribute to the P50 and that the P50 in humans represents overlapping potentials.

Occipital lobe gray matter volume in male patients with chronic schizophrenia: A quantitative MRI study

Schizophrenia is characterized by deficits in cognition as well as visual perception. There have, however, been few magnetic resonance imaging (MRI) studies of the occipital lobe as an anatomically defined region of interest in schizophrenia. To examine whether or not patients with chronic schizophrenia show occipital lobe volume abnormalities, we measured gray matter volumes for both the primary visual area (PVA) and the visual association areas (VAA) using MRI based neuroanatomical landmarks and three-dimensional information. PVA and VAA gray matter volumes were measured using high-spatial resolution MRI in 25 male patients diagnosed with chronic schizophrenia and in 28 male normal controls. Chronic schizophrenia patients showed reduced bilateral VAA gray matter volume (11%), compared with normal controls, whereas patients showed no group difference in PVA gray matter volume. These results suggest that reduced bilateral VAA may be a neurobiological substrate of some of the deficits observed in early visual processing in schizophrenia.

Dissociable contributions of MRI volume reductions of superior temporal and fusiform gyri to symptoms and neuropsychology in schizophrenia

We sought to identify the functional correlates of reduced magnetic resonance imaging (MRI) volumes of the superior temporal gyrus (STG) and the fusiform gyrus (FG) in patients with chronic schizophrenia. MRI volumes, positive/negative symptoms, and neuropsychological tests of facial memory and executive functioning were examined within the same subjects. The results indicated two distinct, dissociable brain structure-function relationships: (1) reduced left STG volume-positive symptoms-executive deficits; (2) reduced left FG-negative symptoms-facial memory deficits. STG and FG volume reductions may each make distinct contributions to symptoms and cognitive deficits of schizophrenia.

Gender difference in right lateral prefrontal hemodynamic response while viewing fearful faces : A multi-channel near-infrared spectroscopy study

Near-infrared spectroscopy (NIRS) has been widely used to non-invasively assess brain function in various psychiatric disorders. Previous NIRS studies have extensively investigated prefrontal activation associated with cognitive tasks; in contrast, NIRS signals from prefrontal cortex in response to emotional stimuli have received little attention. We investigated spatiotemporal characteristics of hemodynamic response during an emotional activation task using fearful facial expression stimuli. We also evaluated gender difference and the relationship with anxiety-related personality traits. Subjects were 10 women and 10 men, all right-handed and matched for age, education and IQ estimated from the adult reading test. NIRS signals that are assumed to reflect regional cerebral blood volume were monitored over prefrontal regions by 52-channel NIRS. Women showed significantly increased [oxy-Hb] change relative to men in the right ventrolateral prefrontal cortex during the latter half of the task period. Frontopolar [deoxy-Hb] response correlated significantly with trait anxiety scores in the whole sample. These results suggest that gender and trait anxiety have an effect on individual variability of NIRS signals in response to emotional stimuli. This observation may help to establish NIRS as a clinical tool for monitoring prefrontal function on an individual basis.

Decreased spatial frequency sensitivities for processing faces in male patients with chronic schizophrenia

OBJECTIVE Schizophrenia impairs early visual cognitive processing. Low and high spatial frequency (LSF, HSF) visual information are differentially processed in humans. We investigated whether electrophysiological abnormalities exist in visual processing for spatial frequency (SF)-filtered neutral/emotional faces in schizophrenics. METHODS Subjects consisted of 16 male chronic schizophrenics and 23 controls. Event-related potentials (ERPs) to SF-filtered (LSF or HSF) and unfiltered (broad SF; BSF) pictures of neutral, happy, and fearful faces were recorded at 20 scalp sites. The relationships between the P100 (P1)/N170 amplitudes and the Global Assessment of Functioning (GAF) scores in patients were also evaluated. RESULTS For the P1 amplitudes at O1/O2, controls exhibited a significant LSF>BSF difference, while schizophrenics showed no LSF>BSF difference. For the N170 amplitudes at T5/T6, controls revealed a significant HSF>BSF difference, while schizophrenics showed no such difference. For the P1 latencies, controls but not schizophrenics showed a significant difference (LSF>BSF=HSF). For the N170 latencies, no significant SF differentiation was found between the two groups. For both P1 and N170 amplitudes, no significant effects of facial expressions were observed in controls and patients regardless of SFs. There were significant negative correlations between the GAF scores and the N170 amplitudes to BSF faces in schizophrenics, but not for P1 amplitudes. CONCLUSIONS Schizophrenics showed abnormal P1 and N170 responses to SF changes in faces, thus indicating decreased SF sensitivities for processing of faces. SIGNIFICANCE Abnormal early visual processing may underlie some of the deficits associated with face recognition in schizophrenia.