Meta-analysis of the association between suicidal ideation and later suicide among patients with either a schizophrenia spectrum psychosis or a mood disorder.

OBJECTIVE: Recent studies of patients with a mix of psychiatric diagnoses have suggested a modest or weak association between suicidal ideation and later suicide. The aim of this study was to examine the extent to which the association between expressed suicidal ideation and later suicide varies according to psychiatric diagnosis. METHOD: A systematic meta-analysis of studies that report the association between suicidal ideation and later suicide in patients with 'mood disorders', defined to include major depression, dysthymia and bipolar disorder, or 'schizophrenia spectrum psychosis', defined to include schizophrenia, schizophreniform disorder and delusional disorder. RESULTS: Suicidal ideation was strongly associated with suicide among patients with schizophrenia spectrum psychosis [14 studies reporting on 567 suicides, OR = 6.49, 95% confidence interval (CI) 3.82-11.02]. The association between suicidal ideation and suicide among patients with mood disorders (11 studies reporting on 860 suicides, OR = 1.49, 95% CI 0.92-2.42) was not significant. Diagnostic group made a significant contribution to between-study heterogeneity (Q-value = 16.2, df = 1, P < 0.001) indicating a significant difference in the strength of the associations between suicidal ideation and suicide between the two diagnostic groups. Meta-regression and multiple meta-regression suggested that methodological issues in the primary research did not explain the findings. Suicidal ideation was weakly but significantly associated with suicide among studies of patients with mood disorders over periods of follow-up of <10 years. CONCLUSION: Although our findings suggest that the association between suicidal ideation and later suicide is stronger in schizophrenia spectrum psychosis than in mood disorders this result should be interpreted cautiously due to the high degree of between-study heterogeneity and because studies that used stronger methods of reporting had a weaker association between suicidal ideation and suicide.

Simulated electrocortical activity at microscopic, mesoscopic, and global scales.

Simulation of electrocortical activity requires (a) determination of the most crucial features to be modelled, (b) specification of state equations with parameters that can be determined against independent measurements, and (c) explanation of electrical events in the brain at several scales. We report our attempts to address these problems, and show that mutually consistent explanations, and simulation of experimental data can be achieved for cortical gamma activity, synchronous oscillation, and the main features of the EEG power spectrum including the cerebral rhythms and evoked potentials. These simulations include consideration of dendritic and synaptic dynamics, AMPA, NMDA, and GABA receptors, and intracortical and cortical/subcortical interactions. We speculate on the way in which Hebbian learning and intrinsic reinforcement processes might complement the brain dynamics thus explained, to produce elementary cognitive operations.

Ovarian responses in gonadotrophin-releasing hormone-treated anoestrous ewes: follicular and endocrine correlates with luteal outcome.

The relationships between the development of antral follicles (growing from 3 to > or = 5 mm diameter), hormone secretion (luteinizing hormone (LH), follicle-stimlating hormone (FSH), oestradiol and progesterone), ovulation and the formation of luteal structures in response to gonadotrophin-releasing hormone (GnRH) were examined in 24 anoestrous Western White Face ewes (May-July). Ewes were monitored by transrectal ovarian ultrasonography for 34 days, commencing 15 days before the administration of GnRH. Following treatment with GnRH, 83% (20/24) of ewes ovulated. Twenty-five per cent of all ewes (6/24) subsequently had normal (full-life span) corpora lutea (CL), 37% (9/24) had inadequate CL, 17% (4/24) had both normal and inadequate CL, 17% (including three of four anovular ewes and one ewe with inadequate CL) formed luteinized follicles and only 4% (1/24) did not ovulate or produce any luteal structure. None of the variables of follicular growth (follicles reaching > or = 5 mm diameter) differed between follicles that either ovulated or failed to ovulate and there was no evident correlation between the age or stage of development of ovulatory sized antral follicles and the type of luteal structure formed, except for luteinized unovulated follicles; these follicles all emerged within 3 days of GnRH injection. Mean serum concentrations of FSH and oestradiol before treatment did not differ (P>0.05) between ewes with different ovarian responses, but peaks of fluctuations in serum concentrations of FSH in daily samples were higher in ewes that produced normal CL compared with ewes with inadequate CL. After GnRH treatment, oestradiol secretion was higher in ewes that formed luteinized unovulated follicles than in all ewes with inadequate CL (P<0.05). The peak concentration of the GnRH-induced LH surge was higher and the interval from GnRH to peak LH discharge was shorter in ewes with inadequate CL compared with ewes that had normal CL after ovulation (P<0.05). In conclusion, ovulatory sized antral follicles at a similar stage of their life span can give rise to either normal or inadequate CL and a proportion of these follicles do not ovulate in response to GnRH in seasonally anoestrous ewes. This suggests differences in ovarian follicular responsiveness to gonadotrophic stimuli. Both the amplitude of episodic elevations in daily serum FSH concentrations and the characteristics of the pre-ovulatory LH surge may be important for luteogenesis following ovulation.

Toward an integrated continuum model of cerebral dynamics: the cerebral rhythms, synchronous oscillation and cortical stability.

Continuum models of cerebral cortex with parameters derived from physiological data, provide explanations of the cerebral rhythms, synchronous oscillation, and autonomous cortical activity in the gamma frequency range, and suggest possible mechanisms for dynamic self-organization in the brain. Dispersion relations and derivations of power spectral response for the models, show that a low frequency resonant mode and associated travelling wave solutions of the models' equations of state can account for the predominant 1/f spectral content of the electroencephalogram (EEG). Large scale activity in the alpha, beta, and gamma bands, is accounted for by thalamocortical interaction, under regulation by diffuse cortical excitation. System impulse responses can be used to model Event-Related Potentials. Further classes of local resonance may be generated by rapid negative feedbacks at active synapses. Activity in the gamma band around 40 Hz, associated with large amplitude oscillations of pulse density, appears at higher levels of cortical activation, and is unstable unless compensated by synaptic feedbacks. Control of cortical stability by synaptic feedbacks offers a partial account of the regulation of autonomous activity within the cortex. Synchronous oscillation occurs between concurrently excited cortical sites, and can be explained by analysis of wave motion radiating from each of the co-active sites. These models are suitable for the introduction of learning rules-most notably the coherent infomax rule.

Synchronous oscillation in the cerebral cortex and object coherence: simulation of basic electrophysiological findings.

A lumped continuum model for electrocortical activity was used to simulate several established experimental findings of synchronous oscillation which have not all been previously embodied in a single explanatory model. Moving-bar visual stimuli of different extension, stimuli moving in different directions, the impact of non-specific cortical activation upon synchronous oscillation, and the frequency content of EEG associated with synchrony were considered. The magnitude of zero lag synchrony was primarily accounted for by the properties of the eigenmodes of the travelling local field potential superposition waves generated by inputs to the cortex, largely independent of the oscillation properties and associated spectral content. Approximation of the differences in cross-correlation observed with differently moving bar stimuli, and of the impact of cortical activation, required added assumptions on (a) spatial coherence of afferent volleys arising from parts of a single stimulus object and (b) the presence of low-amplitude diffuse field noise, with enhancement of cortical signal/noise ratio with respect to the spatially coherent inputs, at higher levels of cortical activation. Synchrony appears to be a ubiquitous property of cortex-like delay networks. Precision in the modelling of synchronous oscillation findings will require detailed description of input pathways, cortical connectivity, cortical stability, and aspects of cortical/subcortical interactions.

Running addiction: measurement and associated psychological characteristics.

Runners frequently become addicted to running and continue to run even when it is detrimental to their health. In the present study a paper and pencil test to measure running addiction, the running addiction scale (RAS) was constructed and evaluated and used to investigate the psychological correlates of running addiction. The RAS, symptom check list, locus of control scale, commitment to running scale (CR), and a questionnaire about the individual's running habits and degree of addiction were administered to 32 male and 15 female runners. The results suggest that the RAS is reliable and valid, correlating with self-rated addiction. The CR score was correlated with self-rated addiction for males but not for females suggesting that the RAS and CR measure different characteristics and that for female runners commitment to running can occur without addiction. Large gender differences were found in the correlations between the RAS, CR, run frequency, and run duration with the personality, mood, and locus of control scores. Running addiction was found to be associated with high frequency of running and with positive personality characteristics but not with mood enhancement, while the duration of running was found to be associated with mood enhancement. These results suggest that the benefits of running to mood may be obtained without addiction.