Toshihiko Maekawa

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.

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.

Auditory gating deficit to human voices in schizophrenia: A MEG study

BACKGROUND Patients with schizophrenia have auditory gating deficits; however, little is known about P50 auditory gating to human voices and its association with clinical symptoms. We examined the functioning of auditory gating and its relationship with the clinical symptoms in schizophrenia. METHODS Auditory evoked magnetoencephalography responses to the first and the second voices stimuli were recorded in 22 schizophrenia patients and 28 normal control subjects. The auditory gating ratios of P50m and N100m were investigated and P50m-symptom correlations were also investigated. RESULTS Patients showed significantly higher P50m gating ratios to human voices specifically in the left hemisphere. Moreover, patients with higher left P50m gating ratios showed more severe auditory hallucinations, while patients with higher right P50m gating ratios showed more severe negative symptoms. CONCLUSIONS The present study suggests that schizophrenia patients have auditory gating deficits to human voices, specifically in the left hemisphere and auditory hallucinations of schizophrenia may be associated with sensory overload to human voices in the auditory cortex.

Altered face inversion effect and association between face N170 reduction and social dysfunction in patients with schizophrenia

OBJECTIVE There is accumulating evidence that schizophrenics may have deficits in facial recognition, which has been related to disease-specific disturbances in normal social interaction. Neurophysiologically, face inversion results in an amplitude increase of the event-related potential (ERP) component N170. This face inversion effect (FIE) presumably reflects a disruption of face-specific configuration processing. The present study investigated FIE and the associations between social functioning and N170 in patients with schizophrenia. METHODS The subjects consisted of 15 schizophrenics and 15 controls. Event-related potentials (ERPs) to upright and inverted neutral faces and cars were recorded. The relationships between the Social Functioning Scale (SFS) scores and N170 amplitude to upright faces or cars were also evaluated. RESULTS Normal controls exhibited a significant FIE of the N170 amplitude, while schizophrenics showed no FIE. In both normal controls and schizophrenics, no inversion effect was observed for car stimuli. For face stimuli, schizophrenics showed significant bilateral N170 reduction; additionally, in schizophrenics, but not in controls, the SFS was significantly correlated with N170 amplitudes to upright faces. CONCLUSIONS These results indicate face-specific configuration processing deficits and significant associations between face-N170 reduction and social dysfunction in schizophrenia. SIGNIFICANCE Abnormal face-specific configuration processing may underlie some of the social dysfunctions in schizophrenia.

Preattentive visual change detection as reflected by the mismatch negativity (MMN)--evidence for a memory-based process.

The aim of this study was to test the hypothesis that visual mismatch negativity (vMMN) is based on memory trace formation. Special care was taken to distinguish between memory mismatch and rareness effect. Subjects were seated in front of a monitor and asked to listen to a story. The standard sequence block consisted of nine consecutive 24-vane windmill patterns with an 800-ms inter-stimulus interval. The deviant sequence block consisted of one 24-vane pattern with eight six-vane patterns. Inter-train intervals (ITIs) varied among 1, 6, and 12s in the changing ITI experiment, while the deviant stimulus occupied the eighth position in the sequence. In the changing order experiment, the position of the deviant stimulus was varied among the second, fourth and eighth position with a 12-s constant ITI. vMMN was ascertained from the difference in responses to standard and deviant stimulus. vMMN appeared in the occipital region 150-300 ms after stimulus onset. It was significantly modulated by the ITI, and more than four preceding stimuli were needed to reinstate the implicit memory trace. These results suggest that memory-based change detection underlies vMMN. Therefore, vMMN is useful to study visual sensory memory function.

Differentiation between bipolar disorder and schizophrenia revealed by neural oscillation to speech sounds: an MEG study

OBJECTIVES   Psychiatrists have long debated whether bipolar disorder (BP) and schizophrenia (SZ) are the clinical outcomes of discrete or shared causative processes. SZ shows significantly delayed peak latencies of the evoked neural oscillation (eNO) power and reduced eNO power to speech sounds in the left hemisphere in comparison to normal controls (NC), suggesting deficits in the fast mechanism for identifying speech sounds for SZ. The current study tested the hypothesis that the eNO to speech sounds could be differentiated between BP and SZ patients. METHODS   The magnetoencephalographic data of 11 BP, 12 SZ, and 15 NC subjects were evaluated, and we analyzed the eNO power and phase-locking in 20-45 Hz to speech sounds and pure tones in the left hemisphere. RESULTS   The major findings were that: (i) BP subjects exhibited larger eNO power to speech sounds compared to NC and SZ; (ii) SZ subjects showed delayed eNO and phase-locking to speech sounds specifically in the left hemisphere; and (iii) no significant differences were observed in the response to pure tones among the three groups. CONCLUSIONS   The present study showed that different patterns in eNO to speech sounds are present in BP, SZ, and NC subjects. The eNO to speech sounds in the left hemisphere is a potential index to distinguish BP and SZ.

Auditory and Visual Mismatch Negativity in Psychiatric Disorders: A Review

Event-related potentials (ERPs) provide an objective index of neurocognitive abnormality or dysfunction in neuropsychiatric disorders. Auditory mismatch negativity (aMMN), which was discovered in the 1980s, is one unique type of ERP. Several lines of evidence suggest that it reflects auditory preattentive (automatic) information processing and the function of glutamatergic N-methyl-D-aspartate receptors. Many studies also have suggested that aMMN is a promising biomarker for some psychiatric disorders such as schizophrenia. Prospective studies combining analyses of several biomarkers, including aMMN, in schizophrenia patients from the prodromal period, are underway. Meanwhile, the existence of a visual counterpart of aMMN (vMMN) has been disputed, and a genuine vMMN was only confirmed in the last decade. Thus, there have been a relatively small number of vMMN studies compared with studies of aMMN, and the mechanism underlying vMMN is still unclear. However, it is well known that abnormal auditory and visual sensory information processing is present in psychiatric disorders, and vMMN is an important component of ERPs studied in psychiatric patients. The aim of this review is to provide an overview of recent aMMN and vMMN findings in several psychiatric disorders, including schizophrenia, major depression, Alzheimer’s disease, and developmental disorders. In doing so, we highlight their potential use as biomarkers of psychiatric disorders.

Altered visual information processing systems in bipolar disorder: evidence from visual MMN and P3

Objective: Mismatch negativity (MMN) and P3 are unique ERP components that provide objective indices of human cognitive functions such as short-term memory and prediction. Bipolar disorder (BD) is an endogenous psychiatric disorder characterized by extreme shifts in mood, energy, and ability to function socially. BD patients usually show cognitive dysfunction, and the goal of this study was to access their altered visual information processing via visual MMN (vMMN) and P3 using windmill pattern stimuli. Methods: Twenty patients with BD and 20 healthy controls matched for age, gender, and handedness participated in this study. Subjects were seated in front of a monitor and listened to a story via earphones. Two types of windmill patterns (standard and deviant) and white circle (target) stimuli were randomly presented on the monitor. All stimuli were presented in random order at 200-ms durations with an 800-ms inter-stimulus interval. Stimuli were presented at 80% (standard), 10% (deviant), and 10% (target) probabilities. The participants were instructed to attend to the story and press a button as soon as possible when the target stimuli were presented. Event-related potentials (ERPs) were recorded throughout the experiment using 128-channel EEG equipment. vMMN was obtained by subtracting standard from deviant stimuli responses, and P3 was evoked from the target stimulus. Results: Mean reaction times for target stimuli in the BD group were significantly higher than those in the control group. Additionally, mean vMMN-amplitudes and peak P3-amplitudes were significantly lower in the BD group than in controls. Conclusions: Abnormal vMMN and P3 in patients indicate a deficit of visual information processing in BD, which is consistent with their increased reaction time to visual target stimuli. Significance: Both bottom-up and top-down visual information processing are likely altered in BD.

Detection of retroperitoneal hemorrhage by transesophageal echocardiography during cardiac surgery.

PurposeTo present a case of massive retroperitoneal hemorrhage during cardiopulmonary bypass (CPB) which was detected using transesophageal echocardiography (TEE).Clinical featureA 50-yr-old man suffering from severe mitral regurgitation (MR) was admitted for mitral valvuloplasty. After the beginning of CPB, the volume in the reservoir was noticed to be gradually decreasing. Although venous cannulation had been properly performed, TEE showed an echo free space around the liver, the spleen and in front of the abdominal aorta showed intraabdominal hemorrhage. After cardiac surgery, emergency laparotomy revealed about 5,000 ml of blood in the retroperitoneal space probably as a result of femoral artery cannulation prior to CPB. Hemostasis was achieved, and the patient made complete cardiac and neurological recovery. Retrospective review of the TEE imaging revealed that the kidneys were surrounded by blood bilaterally confirming the diagnosis of retroperitoneal hemorrhage.ConclusionRetroperitoneal hemorrhage during CPB is rare, but may be lethal. Transesophageal echocardiography is a useful monitor not only to evaluate cardiac performance, but also to detect unexpected intraabdominal bleeding during cardiac surgery.RésuméObjectifPrésenter le cas d’une hémorragie rétropéritonéale massive pendant la circulation extracorporelle (CEC), détectée à l’aide de l’échocardiographie transoesophagienne (ETO).Éléments cliniquesUn homme de 50 ans, souffrant de régurgitation mitrale sévère, a été admis pour une valvuloplastie mitrale. Après le début de la CEC, on a noté que le volume du réservoir baissait graduellement. Bien qu’on ait correctement réalisé la mise en place d’une canule veineuse, l’ETO a montré un espace libre d’écho autour du foie, de la rate et, en avant de l’aorte abdominale, indiquant la présence d’une hémorragie intra-abdominale. Après la cardiochirurgie, la laparotomie d’urgence a révélé la présence d’environ 5 000 ml de sang dans l’espace rétropéritonéal, le résultat probable de l’introduction d’une canule dans l’artère fémorale avant la CEC. L’hémostase a été rétablie et le patient a connu une récupération cardiaque et neurologique complète. Létude rétrospective des images de l’ETO a révélé que les reins étaient bilatéralement entourés de sang, ce qui confirme le diagnostic d’hémorragie rétropéritonéale.ConclusionL’hémorragie rétropéritonéale est rare pendant la CEC, mais elle peut être fatale. L’échocardiographie transoesophagienne est un moniteur utile non seulement pour évaluer le rendement du coeur, mais aussi pour détecter des saignements intra-abdominaux inattendus pendant la cardiochirurgie.

Preattentive dysfunction in patients with bipolar disorder as revealed by the pitch-mismatch negativity: A magnetoencephalography (MEG) study

Mismatch negativity (MMN) and its magnetic counterpart (MMNm) are thought to reflect an automatic process that detects a difference between an incoming stimulus and the sensory memory trace of preceding stimuli. In patients with schizophrenia, an attenuation of the MMN/MMNm amplitude has been repeatedly reported. Heschls gyrus (HG) is one of the major generators of MMN and the functional alteration of HG has been reported in patients with bipolar disorder. The present study investigated the pitch‐MMNm in patients with bipolar disorder using whole‐head 306‐ch magnetoencephalography (MEG).