Thermoelectric response near a quantum critical point of ß-YbAlB4 and YbRh2Si2: a comparative study.

The thermoelectric coefficients have been measured down to a very low temperature for the Yb-based heavy-fermion compounds ß-YbAlB4 and YbRh2Si2, often considered as model systems for the local quantum criticality case. We observe a striking difference in the behavior of the Seebeck coefficient S in the vicinity of their respective quantum critical point (QCP). Approaching the critical field, S/T is enhanced in ß-YbAlB4, but drastically reduced in YbRh2Si2. The ratio of thermopower to specific heat remains constant for ß-YbAlB4, but it is significantly reduced near the QCP in YbRh2Si2. In both systems, on the other hand, the Nernst coefficient shows a diverging behavior near the QCP. The interplay between valence and magnetic quantum criticality and the additional possibility of a Lifshitz transition crossing the critical field under magnetic field are discussed as the origin of the different behaviors of these compounds.

Age related changes in 5-methylcytosine content in human peripheral leukocytes and placentas: an HPLC-based study.

The goal of the present study was to investigate inter-individual and age-dependent variation of global DNA methylation in human tissues. In this work, we examined 5-methyldeoxycytidine ((met)C) content by HPLC in human peripheral blood leukocytes obtained from 76 healthy individuals of ages varying from 4 to 94 years (yr), and 39 human placentas from various gestational stages. The HPLC analysis revealed a significant variation of (met)C across individuals and is consistent with the previous findings of age-dependent decrease of global methylation levels in human tissues. The age-dependent decrease of (met)C was relatively small, but statistically highly significant (p= 0.0002) in the aged group (65.9 +/- 8.9 [mean age +/- SD] yr; n = 22) in comparison to the young adult group (19.3 +/- 1.4 yr; n = 21). Males showed a subtle but statistically significant higher mean (met)C content than females. In contrast to the peripheral blood samples, DNA extracted from placentas exhibited gestational stage-dependent increase of methylation levels that appeared to inversely correlate with the expression levels of human endogenous retroviruses. These data may be helpful in further studies of DNA methylation, such as inheritance of epigenetic patterns, environment-induced changes, and involvement of epigenetic changes in disease.

Sex effects on rate of change of P300 latency with age.

OBJECTIVE: Recent MRI evidence suggests that neuroanatomic structures may change more rapidly with age in males compared with females. Sex differences for P300 latency were tested to determine whether similar results might appear for P300 latency, a neurophysiological measure sensitive to age and neurodegenerative processes. METHODS: Auditory event related potentials (ERPs) were recorded using an auditory 'oddball' to elicit the N200 and P300 components. Forty-two male and 42 female healthy normal subjects (age range 15-85 years) were entered in this study. Both linear and curvilinear correlations of N200 and P300 latency/amplitude with age were tested. RESULTS: The slope of P300 latency on age for males was steeper than for females at Pz in subjects who were 30 years of age and older. N200 and P300 latencies were inversely correlated with age in young adult males (<30 years old). CONCLUSIONS: Males may experience more rapid change of P300 latency, but not amplitude, than females in middle to old age. Further research is required to determine whether those change reflects neural pathophysiology, or is mediated by such factors as neuroanatomic differences, body temperature, or mild auditory deficits.

N2 and P3b components of the event-related potential in students at risk for psychosis.

The N2 and P3b components of event-related potentials (ERPs) were studied in students who were identified as being at high risk for psychosis on the basis of their scores on the Chapman Psychosis Proneness Scales (PPS). The Magical Ideation subscale (MIS), the Perceptual Aberration subscale (PABS), and the Social Anhedonia subscale (SAS) were administered to 2,022 undergraduate university students. To determine if there were any relationships between these psychometric instruments and electrophysiological measures, 40 high-risk students were compared with 40 age- and gender-matched control students using auditory ERPs obtained from three midline electrodes (Fz, Cz, Pz) in a standard oddball paradigm. N2 (rare stimuli) and N2b latencies were significantly longer in the high-risk than in the control subjects, and the high-risk group also evidenced significantly smaller amplitude of the P3b component. No significant correlations between scores on the PPS or its three subscales and the amplitudes or latencies of the P3b or N200 component were found. These findings suggest that the N2 and P3b ERP components might serve as trait markers for psychosis and that individuals psychometrically identified as being at high risk for psychosis have deficits in the maintenance of attention and in decision-making.

Assessment of psychosocial stressors and maladjustment among foreign students of the University of the Ryukyus.

An extensive survey of problems encountered by foreign students of the University of the Ryukyus and the resulting levels of stress was carried out in order to determine the main stressors hindering academic progress and personal adjustment. Subjectively perceived stress levels after arrival in Japan were obtained from 134 subjects through a comprehensive questionnaire for reporting specific stressors. The 30-item General Health Questionnaire (GHQ) was included to assess mental health state. Differences in scores by area of origin were also determined for the total GHQ scores and its sub-scales. The GHQ results showed that regardless of length of time in Japan, more than 60% of the subjects scored within a range usually indicative of a mental health risk. Mean scores by area of origin showed a 50% reduction over time for non-Chinese Asians and North American/Europeans, but only a reduction of 1.1% or less for Chinese, Latin American, Middle/Near Eastern and African subjects. Limitations in achievement of academic goals were reported by the greatest number of students as causing moderate to excessive stress (57.5%); most frequently reported causes were language inadequacy (55.2%), reference materials unavailable (34.3%), unfamiliarity with Japanese study methods (32.1%), and inadequate guidance from teachers/advisors (26.9%). Various social, personal and daily life problems in the non-academic setting were also reported as causing high stress levels. Most of the stressors identified are not considered inevitable and point toward directions to pursue in preventive strategies in mitigating psychological distress and maladjustment of students.

Abnormalities of auditory event-related potentials in schizophrenia prior to treatment.

BACKGROUND: P300 amplitude reduction is a consistent finding in schizophrenic patients, but it is unclear if this abnormality predates neuroleptic treatment or is present at onset of illness. METHODS: Auditory event-related potentials (ERPs), during a standard oddball paradigm, were recorded from 45 neuroleptic-naive schizophrenics, 56 drug-free, previously treated schizophrenics, and 73 healthy normal controls. Forty-seven of the schizophrenic subjects had their first episode within the past year. RESULTS: N200 amplitude did not differ among groups. P300 amplitude was significantly smaller in both neuroleptic-naive and previously treated schizophrenic groups compared to the control groups. There were no significant differences between the two schizophrenic groups in P300 amplitude. N200 and P300 latency were prolonged in previously treated schizophrenics compared to neuroleptic-naive schizophrenics and normal controls. CONCLUSIONS: The present study suggests that ERP abnormalities, especially P300 amplitude reduction, are already present prior to the administration of neuroleptic medication in the earliest stage of schizophrenia.

[Developing the portable type sleep apnea detector, and verifying the usefulness of the device].

Polysomnographic recording is indispensable in the diagnosis of sleep apnea syndrome (SAS). However, this method has a number of drawbacks, for example, subjects cannot sleep naturally like at their homes, and the methodology involved is complicated. We have now developed Portable Type Sleep Apnea Detector (PSD) that needs to equipment to provide subject's body. This study was done to verify the usefulness of this device. Subjects were 50 patients (42 male and 8 female, average and S.D. of age: 47.0 +/- 14.5), who were suspected to have SAS. Polysomnography and sleep recording using PSD were performed simultaneously. PSD consisted of three sensors for respiratory movements, a sensor for breathing sounds and a data recorder. The recorder was an 8K32 type 4-channel Handycorder (Nippon Denki Sanei, 370 mm x 115 mm x 200 mm, 7.5 kg) and the sensor for respiratory movements was a thin plate (180 mm x 100 mm). The three sensors for respiratory movements were placed between the mattress and bedsheet, hence the subjects did not feel them during sleep. A sound sensor detected breathing sounds such as snoring. We defined whether a subject is in sleep or awake by the number of body movements recorded by this device. Apnea was defined as depressed or stopped respiratory movement with no snoring for a period longer than 10 seconds. Standard polysomnography which consisted of electroencephalogram (2 channels), electrooculogram (2 channels), electromyogram (2 channels), electrocardiogram (1 channel), oral (1 channel) and nasal airflow (1 channel) and chest movements (1 channel) were performed. Sleep stages were evaluated according to the standard methods. The apnea hypopnea index (AHI) was defined as the number of apneas and hypopneas per sleep-hour. Significant correlation between each type of sleep apneas, AI and AHI as measured by two methods, was found (obstructive type: r = 0.929; p < 0.001, central type: r = 0.880; p < 0.001, mixed type: r = 0.952; p < 0.001, AI and AHI: r = 0.956; p < 0.001). It was concluded that this device is useful for screening SAS.

Transient P300 abnormality of event-related potentials following unilateral temporal lobectomy.

Event-related potentials (ERP) were recorded during auditory oddball tasks for a patient prior to and soon after left anterior temporal lobectomy. The N100 amplitude decreased bilaterally although the latency did not change after the lobectomy. The P300 amplitude decreased in the left hemisphere at 1 and 2 weeks after surgery, then recovered to the pre-operative level at 4 weeks. These findings suggest that the medial temporal structure participates in the generating system of P300.

Prevalence of senile dementia in Okinawa, Japan. COSEPO Group. Study Group of Epidemiology for Psychiatry in Okinawa.

METHODS. The prevalence of dementia was investigated in Okinawa Prefecture, Japan. In all, 3524 subjects, > or = 65 years old, were sampled randomly (urban and rural populations 61.1% and 38.9% respectively). Phase 1 of the survey was carried out by specially trained students of the Faculty of Medicine who used the Mini-Mental State (MMS) scale (interview rate: 94.3%) to screen 522 (15.8%) of the 3312 subjects for the phase 2 survey. Phase 2, conducted by psychiatrists using the Diagnostic and Statistical Manual of Mental Disorders (DSM-III-R) criteria, detected 172 cases of dementia. RESULTS. The estimated prevalence of dementia was 6.7%. For women, the rate increased sharply in the 90-99 year old group, and was 41.4%; for men in the 90-99 year old group prevalence was 21.2%. The ratio of Alzheimer-type dementia to multi-infarct dementia was 1.5:1 (men 1.2:1, women 1.7:1). The breakdown of the severity of dementia in the total cases was: mild 16.9%, moderate 30.8%, and severe 52.3%. The number of severe cases increased with age.

Effects of the dopamine-related drug bromocriptine on event-related potentials and its relation to the law of initial value.

Effects of the dopamine-related drug bromocriptine (BCT) on event-related potentials (ERP) were investigated in 18 healthy volunteers. Bromocriptine 2.5 mg or an inactive placebo was administered according to a completely randomized double-blind, cross-over design. The ERP were recorded 3 h after medication was given. Although BCT prolonged the P300 latency, it had no effect on the amplitudes of the ERP components as a whole. Bromocriptine increased the latencies of N100, P200 and P300 in the respective short-latency subject group, and decreased the latency of N200 in the long-latency subject group. It increased the amplitude of N200 in the low-amplitude subject group. It was concluded that the prolongation of P300 latency as a whole and the different responses that take place are dependent on the initial values and were recognized in the effect of a single administration of BCT 2.5 mg. The results of this study are discussed in relation to the law of initial value.

ERPs in schizophrenic patients during word recognition task and reaction times.

Event-related brain potentials (ERPs) were recorded in 28 schizophrenic patients and 26 healthy controls during a word recognition task. In each trial, stimuli consisting of S1 (word) and S2 (word or non-word) were presented. The subjects were required to indicate whether S2 was a word or a non-word by pressing buttons. For both groups, a clear N370 was elicited by S2 which were non-word or semantically unrelated to its S1. The N370 amplitude did not differ between the groups. The schizophrenics responded more slowly than the controls, and the latencies of P200 and N370 were longer for patients than for controls. However, these latencies did not differ between the groups when their reaction times were matched.

Effects of the GABA mimetic drug, sodium valproate, on event-related potentials and its relation to the law of initial value.

The effects of gamma-aminobutyric acid (GABA) mimetic drug sodium valproate (VPA) on event-related potentials (ERPs) were investigated in 18 healthy volunteers during an auditory odd ball task. VPA (200 or 400 mg) or an inactive placebo was administered according to a completely randomized double-blind, cross-over design. ERPs were recorded one hour after medication was given. VPA did not affect the latencies of N100, P200, N200 and P300. Although on the whole VPA had no effect on the amplitudes of the ERP components in the subjects, it increased the P300 amplitude in the low P300 amplitude subjects and decreased it in the high P300 amplitude subjects. This tendency toward a bidirectional response was also seen in the P200 and N200 amplitudes. It was concluded that the response which takes place being dependent on the difference in the initial values was recognized on the effect of a single administration of 200 or 400 mg VPA to ERPs. The results of this study are discussed, especially in relation to the law of initial value.

Correlation between event-related potentials and MR measurements in chronic alcoholic patients.

Event-related potentials were recorded in 25 abstinent alcoholics, and 25 gender- and age-matched controls during a two-tone discrimination (odd ball) task. All the subjects were free from medication and dextral. MR images were examined in the alcoholics. The amplitudes of N100, N200 and P300 in the alcoholics were reduced compared with those of the controls. In order to identify morphological changes responsible for ERP abnormalities, linear regression analyses were performed between ERP measures and MRI parameters. The amplitude of N100 was inversely correlated with ventricular size. The amplitudes of P300 were inversely correlated with both ventricular size and width of cortical sulci. It was suggested that the N100 abnormality was related to subcortical structure, and P300 alteration was related to both subcortical and cortical structures in the alcoholics.

Effect of the dopamine D2 antagonist sulpiride on event-related potentials and its relation to the law of initial value.

Effects of the dopamine antagonist sulpiride on event-related potentials (ERPs) were investigated during an auditory odd ball task in 18 healthy volunteers. Sulpiride (150 or 300 mg) or an inactive placebo was administered according to a completely randomized double-blind cross-over design. ERPs were recorded 1 h after medication was given. Sulpiride shortened the P200 latency for frequent stimuli, but tended to increase the N200 and P300 latencies for rare stimuli. Although on the whole sulpiride had no effect on the amplitudes of the ERP components in the subjects, it increased the P300 amplitudes in the low P300 amplitude subjects and decreased them in the high P300 amplitude subjects. This tendency for a bidirectional response was also found for the N100 and N200 amplitudes. A single administration of 150 or 300 mg sulpiride is considered to affect the ERP latencies and amplitudes in healthy subjects, the bidirectional response that takes place being dependent on the difference in the initial values. The results of this study are discussed in relation to the 'Law of initial value'.

Deviate P200 and P300 in non-patient college students with high scores on the schizophrenia scale of the Minnesota Multiphasic Personality Inventory (MMPI).

Event-related potentials (ERPs) were examined in 16 college students who had high scores on the Schizophrenia Scale of the MMPI (HSS) but were without a hereditary disposition for major psychiatric disorders. 32 sex- and age-matched college students were used as controls. Subjects whose T scores were higher than 70 were designated the HSS subjects. ERPs were recorded during an auditory oddball task. Although neither the P300 latencies nor the P200 latencies differed between the two subject groups, the amplitudes of P300 to rare stimuli and P200 to frequent stimuli were lower in the HSS subjects than in the controls. These results suggest that deficits, both in the P300-related cognitive function to rare relevant stimuli, as well as matching and/or the comparison process for irrelevant frequent stimuli, may be present in HSS subjects. The HSS subjects, especially those with a combination of P300 and P200 deficits, even though without a hereditary diathesis for schizophrenia, may constitute one type of high-risk group.

Abnormalities in event-related potentials: N100, N200 and P300 topography in alcoholics.

Event-related potentials were recorded in 30 abstinent alcoholics, and 30 gender- and age-matched controls during a two-tone discrimination (odd ball) task. All the subjects were free from medication and dextral. The amplitudes of N100, N200 and P300 in the alcoholics were reduced and the P300 latency prolonged as compared with those of the controls. A P300 amplitude reduction occurred in the left and midline frontal, and the left and midline central regions. This is the first report of the amplitude of P300 being markedly decreased in the left hemispheres of the brains of the alcoholics. The results are discussed in terms of the cognitive dysfunctions of alcoholics.

N200 component of event-related potentials in depression.

Event-related potentials (ERPs) recorded during a two-tone discrimination (oddball) task were examined in 36 drug-free depressed patients and 36 control subjects. At remission, the ERPs of 12 of the depressed patients were reexamined. In the depressed patients, although a group difference was not detected in the peak latency and amplitude of N200 to rare stimuli, the mean amplitude for the N200 latency range in the difference waves was smaller than in the control subjects. Mismatch negativity (N2a), which was elicited by rare stimuli, was reduced in amplitude; but N2b may have been evoked to frequent stimuli more in the patients than in the control subjects. Depressed subjects may have a deviance in the fully automatic cerebral mismatch process that is assumed to be related to mismatch negativity and provoke the controlled mismatch detection process (presumed to be associated with N2b) even to nontarget frequent stimuli. These findings were observed during remission; however, there was a tendency for the N2b amplitude to decrease and recover toward the level of the control subjects.

Endogenous event-related potentials in obsessive character.

Fifteen healthy subjects with obsessive character (OC) and 15 control subjects were tested for endogenous event-related potentials using the auditory odd ball paradigm. A difference was found in the peak amplitude of the P200 component in response to both stimuli; the subjects with OC had smaller amplitudes than the controls, and the mean amplitude for the 120 to 200 ms latency range was smaller (negative shift) for the OC subjects. In the OC subjects, NA appears to be markedly induced to both rare and frequent stimuli; moreover, the OC subjects may show excessive reactions to selective attention as well as to the process of pattern recognition.