Neuropsychobiology

Meditation is a specific consciousness state in which deep relaxation and increased internalized attention coexist. There have been various neurophysiological studies on meditation. However, the personal predispositions/traits that characterize the properties of meditation have not been adequately studied. We analyzed changes in neurophysiological parameters [EEG coherence and autonomic nervous activity using heart rate variability (HRV) as an index] during Zen meditation, and evaluated the results in association with trait anxiety (assessed by Spielberger’s State-Trait Anxiety Inventory) in 22 healthy adults who had not previously practiced any form of meditation. During meditation, in terms of mean values in all subjects, an increase in slow alpha interhemispheric EEG coherence in the frontal region, an increase in high-frequency (HF) power (as a parasympathetic index of HRV), and a decrease in the ratio of low-frequency to HF power (as a sympathetic index of HRV) were observed. Further evaluation of these changes in individuals showed a negative correlation between the percent change (with the control condition as the baseline) in slow alpha interhemispheric coherence reflecting internalized attention and the percent change in HF reflecting relaxation. The trait anxiety score was negatively correlated with the percent change in slow alpha interhemispheric coherence in the frontal region and was positively correlated with the percent change in HF. These results suggest that lower trait anxiety more readily induces meditation with a predominance of internalized attention, while higher trait anxiety more readily induces meditation with a predominance of relaxation.

<i>Background:</i> Using 7-year population-based data on Taiwan, we examined seasonal variation in violent versus nonviolent suicide, and its association with meteorological factors: ambient temperature, relative humidity, atmospheric pressure, rainfall and daily sunshine hours. <i>Methods:</i> We used Taiwan’s nationwide mortality data from 1997 to 2003, categorizing the sample decedents into two groups, violent (ICD-9-CM codes E953–E958) and nonviolent (E950–E952) suicide, based on the suicide method used. Seasonal autoregressive integrated moving average (SARIMA) modeling was used to detect seasonality of suicide, and the association of climate variables with violent versus nonviolent suicide. <i>Results:</i> The SARIMA test of seasonality was significant for both genders and the pooled sample (all p < 0.001) in violent suicide deaths, but not nonviolent suicides. Seasonal trends show a significant peak in March–May (early to late spring) for violent suicides. Increasing ambient temperature predicted increasing violent suicide rates. <i>Conclusions:</i> We conclude that seasonality exists in violent but not nonviolent suicide rates. Our findings suggest that suicide is a heterogeneous phenomenon and violent suicide may be more influenced by biochemical and chronobiological mechanisms.

<i>Objective:</i> To evaluate any correlation between plasma levels of nitric oxide metabolites (NO_x) and suicide attempt. <i>Method:</i> Plasma NO_x levels were measured in 53 patients who had recently attempted suicide, 58 nonsuicidal psychiatric patients, and 75 normal controls. The severity of suicidal behaviors was evaluated using Weisman and Worden’s Risk-Rescue Rating Scale. <i>Results:</i> Plasma NO_x levels were significantly higher in suicidal patients than nonsuicidal psychiatric patients or normal control subjects (F = 11.029, d.f. = 2, 183, p < 0.001). Among the patients with a diagnosis of major depression, suicidal depressive patients had significantly higher plasma NO_x levels than nonsuicidal depressive patients (t = –3.090, d.f. = 84, p = 0.003). <i>Conclusion:</i> Our study suggests that increased NO production in plasma is associated with suicide attempt, especially in depressive patients.

The reciprocal regulation of arginase and nitric oxide synthase (NOS) in <i>L</i>-arginine-metabolizing pathways has been demonstrated. There are various evidences of the role of the nitric oxide (NO) in several neuropsychiatric disorders including schizophrenia. However, there is no study which has investigated the role of arginase as an important part of the arginine regulatory system affecting NOS activity in schizophrenia. This study aims to investigate arginase, manganese (Mn) and total nitrite levels (a metabolite of NO) and their relationship to the arginine-NO pathway in patients with schizophrenia. Arginase activities, Mn and total nitrite levels were measured in plasma from 46 patients with schizophrenia and 32 healthy control subjects. Plasma arginase activities and Mn were found to be significantly lower and total nitrite level higher in patients with schizophrenia compared with controls. Our results suggest that the arginine-NO pathway is involved in the pathogenesis of schizophrenia.

The chronic mild stress (CMS) model of depression has high validity but has in the past been criticized for being difficult to replicate. However, a large number of recent publications have confirmed that CMS causes behavioural changes in rodents that parallel symptoms of depression. This review summarizes studies from over sixty independent research groups that have reported decreases in reactivity to rewards, and a variety of other depression-like behaviours, in rats or mice, following exposure to CMS. Together, these changes are referred to as a ‘depressive’ behavioural profile. Almost every study that has examined the effects of chronic antidepressant treatment in these procedures has reported that antidepressants were effective in reversing or preventing these ‘depressive’ behavioural changes. (The single exception is a study in which the duration of treatment was too brief to constitute an adequate trial.) There are also a handful of reports of CMS causing significant effects in the opposite direction, termed here an ‘anomalous’ behavioural profile. There are six neurobiological parameters that have been studied in both ‘anhedonic’ and ‘anomalous’ animals: psychostimulant and place-conditioning effects of dopamine agonists; dopamine D₂ receptor number and message; inhibition of dopamine turnover by quinpirole, and beta-adrenergic receptor binding. On all six measures, CMS caused opposite effects in animals displaying ‘depressive’ and ‘anomalous’ profiles. Thus, there is overwhelming evidence that under appropriate experimental conditions, CMS can cause antidepressant-reversible depressive-like effects in rodents; however, the ‘anomalous’ profile that is occasionally reported appears to be a genuine phenomenon, and these two sets of behavioural effects appear to be associated with opposite patterns of neurobiological changes.

Mirtazapine, a noradrenergic and specific serotonergic antidepressant(NaSSA), was administered on a flexible schedule in a sample of 17 drug-free patients meeting DSM-IV criteria for a major depressive episode. Sleep polygraphic recordings were performed before and during acute and chronic treatment. Severity of depression and subjective assessment of changes within different aspects of sleep were also evaluated. During the acute administration (first 2 days), mirtazapine significantly increased total sleep time, sleep efficiency, stage II, stage rapid eye movement and slow-wave sleep percentages, and decreased sleep latency and stage awake percentage. These effects persisted after 5 weeks of treatment. Subjectively, mirtazapine induced an improvement of sleep. This open, noncontrolled study suggests that mirtazapine ameliorates the sleep disturbances encountered in depressed patients both objectively and subjectively.

A wide range of studies have been published over the past two decades that involve the intersection of sleep EEG, insomnia, psychiatric illness (especially depressive disorders) and psychopharmacology. Much of value has been discovered, but there have also been false starts and contradictory results. There is in fact strong evidence that insomnia is associated with medical and psychiatric illness and that the sleepiness associated with insomnia is the cause of many accidents. Thus, the direct (visits to doctors, cost of sleeping medication, complications from use of these medications) and indirect (accidents, quality of life) costs of insomnia are enormous and constitute a major public health problem in the industrialized countries. Believing that it is now timely to assess the state of this important research area, a consensus conference was convened on June 26–28, 1998, in Porto Cervo (Italy) to attempt to clarify the important issues and findings on the clinical effect of the different classes of antidepressant drugs on sleep quality in depression. The participants’ consensus on some of the main topics is presented with the hope that this discussion and analysis will contribute to productive research in this important field.