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Biomedical subjects

A Iwanami

Publications and source records attributed to A Iwanami.

At least 37 records · Page 2Linked to original sources
PubMed1997

Behavioral and P3 amplitude enhancement in schizophrenia following feedback training.

In order to clarify the remediability of behavioral and electrophysiological abnormalities in schizophrenia, hit rate, reaction time, and P3 amplitude from auditory event-related potentials were evaluated before and after feedback training of a task in 14 schizophrenics and 12 age-matched normal controls. Although mean changes in the three indices due to the training were nonsignificant in both schizophrenic and normal control groups as a whole, the changes in hit rate and reaction time correlated significantly with the P3 amplitude change in the schizophrenic (r = 0.60 and -0.58, respectively) but not in the normal control group. The P3 amplitude change also correlated with the P3 amplitude before the training only in the schizophrenic group (r = -0.68), suggesting that the training was more effective for the schizophrenic patients with marked P3 amplitude reduction. The observed P3 amplitude increase due to training may represent an electrophysiological correlate of a remediable aspect of behavioral deficits in schizophrenics, which may underlie the effectiveness of nonpharmacological treatments.

Adult↗
PubMed1997

Auditory event-related potentials in panic disorder.

To investigate the psychophysiological features of panic disorder (PD), we recorded auditory event-related potentials (ERPs) in 12 patients with PD meeting the DSM-IV criteria and in 12 age-matched normal controls. The ERPs were recorded during a standard two-tone discrimination task (oddball task). The probabilities of the rare target (1200 Hz) and frequent non-target tones (1000 Hz) were 15 and 85%, respectively. The subjects were required to press a button in response to the rare target tones. Scalp electroencephalograms were recorded from Fz, Cz, Pz, C3, and C4. The State-Trait Anxiety Inventory and Manifest Anxiety Scale scores were assessed for clinical evaluation. Analysis of variance revealed that the N1 and N2 amplitudes for target tones and the N1 amplitude for non-target tones were significantly larger in the PD patients than those in the controls. The two groups did not differ significantly in P3 latency and amplitude. The larger N1 and N2 amplitudes in the PD patients are suggestive of alteration of early information processing in PD.

Adult↗
PubMed1996

Plasma vanillylmandelic acid level as an index of psychological stress response in normal subjects.

The relationships between psychological stress responses and plasma levels of vanillylmandelic acid (VMA), 3-methoxy-4-hydroxyphenylglycol (MHPG), homovanillic acid (HVA), and 5-hydroxyindolacetic acid (5-HIAA) were investigated in normal volunteers. Two questionnaires were used to measure stress: the Psychological Stress Response Scale (PSRS) and the State-Trait Anxiety Inventory (STAI). Plasma levels of VMA--but not MHPG, HVA, and 5-HIAA--showed significant positive correlations with PSRS emotional and cognitive-behavioral stress and STAI state anxiety. Significant positive correlations were also found between plasma levels of VMA and MHPG and psychological stress responses measured repeatedly in a longitudinal study of an Olympic swimmer. Plasma VMA measurements, which reflect the level of activity of the peripheral sympathetic nervous system, may provide a useful biochemical index of psychological stress responses in normal subjects.

Adult↗
PubMed1996

Event-related potential correlates of functional hearing loss: reduced P3 amplitude with preserved N1 and N2 components in a unilateral case.

A female patient exhibiting functional hearing loss in her left ear demonstrated reduced amplitude of P3 component in event-related potentials (ERP) to left monaural stimulation, with preserved N1 and N2 components to stimulation of either ear. This result suggested that stimuli in the affected ear were conducted successfully up to the auditory cortex but that further processing in higher brain regions was 'repressed'. Event-related potential examination for such hysterical disorders could be useful in clarifying their brain mechanism and offer a useful diagnostic clue to its nature.

Adult↗
PubMed1996

Impairment of inhibition of unattended stimuli in schizophrenic patients: event-related potential correlates during selective attention.

Auditory event-related potentials (ERPs) were recorded during a dichotic listening task in 18 remitted schizophrenic patients and in 18 age-matched controls. The subjects were instructed to press a button in response to the target tones applied to one designated ear. In schizophrenic patients, P300 amplitude for attended target was significantly smaller than in controls. Schizophrenic patients also exhibited reduced positive potentials between 200 and 400 ms in ERPs for unattended nontarget. These results suggested that schizophrenic patients lack the ability to inhibit unattended or irrelevant stimuli, in addition to impairment of 'context closure' in the information processing.

Adult↗
PubMed1996

P300 component of event-related potentials in passive tasks.

Auditory P300 components were recorded in two kinds of passive tasks (a sequence task and a novel task) and were compared to that in a standard oddball task. The P300, the amplitude of which was largest at Pz, was elicited in the two passive tasks. The P300 amplitude in the two passive tasks was not significantly smaller than that in the oddball task. No significant correlation was found between either the P300 latency or the P300 amplitude in the oddball task and those in the two passive tasks. These results suggested that the psychological significance of the P300 component in the passive tasks is different from that in the oddball task; however, the P300 in passive tasks is a useful tool in studying information processing in severely mentally ill subjects.

Adult↗
PubMed1995

Increased neuronal firing in the rat auditory cortex associated with preparatory set.

Extracellular single neuronal firings were recorded in the auditory cortex of rats (n = 4) performing a visual reaction-time task with a warning tone (10 kHz, 10 ms duration), which preceded the imperative light stimulus by an interstimulus interval (ISI) of 1.4 s. Thirty-six neuronal firings were evoked by the warning tone, with the peak latency being between 15 and 55 ms. Among them, nine neurons (25%) showed an increased firing frequency following the evoked response during the ISI, which was, in average, 2.5 times as high as the firing frequency during the baseline period. When the tones were presented independent of the imperative stimulus, such sustained increase in neuronal firing was not observed. Activation of the sensory cortex during the ISI may constitute one of the neuronal modulations related to preparatory set.

Acoustic Stimulation↗
PubMed1995

Effects of metamfetamine on auditory P3 component of event-related potentials in rats.

Three rats were trained with an oddball paradigm, in which 5 kHz frequent and 10 kHz target rare tones were presented with a probability of 0.8 and 0.2. Pressing the lever within 2 s following the onset of the target tones was rewarded with a drop of food paste. Long latency event-related potentials (ERPs) corresponding to those in humans could be recorded in rats. After the administration of metamfetamine (0.2 mg/kg), the amplitude of surface and intracortical N1 increased, indicating an augmentation of the primary cortical response. Surface P3 showed a decrease of amplitude, accompanied by an increase of intracortical negativity. These alterations of ERPs may be caused by the dysregulation of central noradrenergic system.

Amphetamines↗
PubMed1995

Reduced attention-related negative potentials in methamphetamine psychosis.

Auditory event-related potentials were recorded during a dichotic syllable discrimination task in 16 unmedicated patients who were in the residual state following the remission of acute methamphetamine (MAP) psychosis, and in 16 age-matched normal controls. The subjects were instructed to press a button in response to the target syllables applied to one designated ear. In the patients with MAP psychosis, the area of attention-related negative potentials was significantly smaller than that in the normal controls. The two groups did not differ significantly in P300 amplitude or latency. These results suggest that patients with MAP psychosis show impairment of selective attention, although they have less cognitive deficit than schizophrenic patients.

Adult↗
PubMed1994

Event-related potentials during an auditory discrimination task in rats.

Event-related potentials (ERPs) during an auditory discrimination task were recorded both on the surface and at a depth of the auditory cortex in rats. Ten-kilohertz rare and 5-kHz frequent tones were used with the probabilities of 0.2 and 0.8. Lever pressing within 2 s, following the onset of the rare tone, was rewarded with food paste. In the performing condition, the surface ERPs for the rare tones consisted of P30, N50, P80, N130, and P290 components. Only the surface P30 and N50 showed a polarity reversal at the intracortical electrode, suggesting that these components are generated in the auditory cortex. The P290 was elicited in the performing condition but not in the resting condition, showing its task-relevancy. These results suggest that auditory ERPs similar to those in humans can be recorded in rats during an active discrimination task.

Acoustic Stimulation↗
PubMed1994

P300 component of event-related potentials in methamphetamine psychosis and schizophrenia.

To examine psychophysiological features of MAP psychosis and schizophrenia, P300 component of event-related potentials during an oddball paradigm were recorded in 25 MAP psychotics and 25 schizophrenics. P300 component was evaluated using baseline-to-peak measurement and principal component analysis. P300 amplitude in MAP psychotics was smaller at Fz and Cz region than in the controls. Unlike schizophrenics, P300 amplitude in MAP psychotics was not smaller at Pz region than in the controls. P300 latency in MAP psychotics and schizophrenics were delayed. These results indicated that MAP psychotics have some biological changes in their central nervous system after the remission of acute psychotic state.

Adult↗
PubMed1994

Patients with methamphetamine psychosis admitted to a psychiatric hospital in Japan. A preliminary report.

To examine the clinical characteristics of methamphetamine (MAP) psychosis in Japan, we evaluated 104 patients with MAP psychosis (80 men and 24 women) admitted to the closed psychiatric units of Tokyo Metropolitan Matsuzawa Hospital between 1988 and 1991. There has recently been a steep increase in the number of admissions for MAP psychosis, reflecting the growth of the epidemic of MAP abuse in Japan. Although more than half of the patients were discharged within one month, 16 patients were hospitalized for more than 3 months. Most of the patients showed paranoid psychotic state similar to schizophrenia, consistent with previous reports. Despite the abstinence from MAP and antipsychotic medication, psychotic symptoms tended to persist in some of the patients. The etiological role of MAP psychosis in the development of long-lasting psychotic state was discussed.

Adolescent↗
PubMed1994

N1 component derived from the temporal region during an auditory passive event-related potential paradigm in schizophrenics.

Event-related potentials (ERPs) were recorded at the Cz, W1 (Wernicke's area), and W2 (contralateral to Wernicke's) regions in 27 schizophrenics during an auditory passive sequence paradigm similar to that employed by Polich. N1 component for frequent tones was analyzed. In schizophrenics, the difference between the ERP waveforms at W1 and W2 was larger than that in controls, and N1 latency at W1 was significantly shorter than that at W2. To examine the similarity between interhemispheric waveforms, Person product-moment correlation coefficient (Interhemispheric Correlation Coefficient, IHCC) was calculated, time point by time point, between the ERP waveforms at W1 and at W2. The mean IHCC for schizophrenics was significantly lower than that for controls. In schizophrenics, the low IHCC group had more severe psychopathology and a longer duration of illness. These results suggest that the hemispheric imbalance of the temporal lobe is characteristic of schizophrenia.

Acoustic Stimulation↗
PubMed1993

Event-related potentials in methamphetamine psychosis during an auditory discrimination task. A preliminary report.

Auditory event-related potentials (ERPs) during a syllable discrimination task were recorded from 15 patients suffering from methamphetamine (MAP) psychosis after the remission of acute psychotic symptoms, and from 15 normal age-matched controls. Subjects were instructed to press a button in response to the target syllables applied to one designated ear. In MAP psychotics, the attention-related negative components (Nd) area was reduced and P300 latency was delayed compared with normal controls. MAP psychotics and controls did not differ significantly in P300 amplitude. These findings suggest that MAP psychotics show some impairment in the auditory information processing.

Adult↗
PubMed1992

Distributions of the Nd and P300 in a normal sample.

To obtain objective criteria for assessing the attentional and cognitive functioning of psychiatric populations, we attempted to standardize values of two components in Event-Related Potentials (ERPs), namely the attention-related negative potential (Nd) and the P300, in normal populations. The study consisted of 100 healthy volunteers (50 females, 50 males) who were given the task of making dichotic syllable discriminations requiring key-press responses. Their ages ranged between 18 and 59 years (mean +/- S.D., 32.3 +/- 11.3 years). Nd was found to be maximum in the Fz region, P300 being maximum in the Pz region. The means and standard deviations of Nd and P300 areas in their maximum regions were 554.1 +/- 307.8 microV ms and 2148.5 +/- 1248.5 microV ms, respectively. The transformation plot for symmetry indicated the suitable power of transformation to be 1/2 for both Nd and P300 distributions. After being transformed into square-root values, the distribution patterns of Nd and P300 areas were examined. When the lower limit of normal values was tentatively assigned to mean -2 S.D. using square-root transformed data for both Nd and P300, 97% of the subjects were found to display values above the lower normal limit for Nd, and 98% for the P300. Neither, Nd nor P300 areas correlated with age, while P300 latencies displayed a weak positive correlation with age. Females displayed relatively larger values than males for Nd and P300 areas and P300-peak amplitudes. However, the differences between females and males were not statistically significant. Females and males showed nearly equal P300-peak latencies.

Adolescent↗
PubMed1992

Shortening of N1 and P3 latencies in event-related potentials observed coincidentally with clinical improvement during nootropic medication in a demented patient: specific effect of nicergoline.

Event-related potentials, measured eight times in a patient in the early stages of dementia, demonstrated that clinical symptoms, especially loss of motivation, improved coincidentally with a shortening of reaction time, N1 latency, and P3 latency during nicergoline medication among three nootropics prescribed. Such a longitudinal study design was considered to be useful for quantifying and objectively comparing effects of various nootropics noninvasively.

Aged↗