Bayesian analysis of trinomial data in behavioral experiments and its application to human studies of general anesthesia

Accurate quantification of loss of response to external stimuli is essential for understanding the mechanisms of loss of consciousness under general anesthesia. We present a new approach for quantifying three possible outcomes that are encountered in behavioral experiments during general anesthesia: correct responses, incorrect responses and no response. We use a state-space model with two state variables representing a probability of response and a conditional probability of correct response. We show applications of this approach to an example of responses to auditory stimuli at varying levels of propofol anesthesia ranging from light sedation to deep anesthesia in human subjects. The posterior probability densities of model parameters and the response probability are computed within a Bayesian framework using Markov Chain Monte Carlo methods.National Institutes of Health (U.S.) (Grant DP2-OD006454)National Institutes of Health (U.S.) (Grant K25-NS057580)National Institutes of Health (U.S.) (Grant DP1-OD003646)National Institutes of Health (U.S.) (Grant R01-EB006385)National Institutes of Health (U.S.) (Grant R01-MH071847

Methylphenidate in mania project (MEMAP): study protocol of an international randomised double-blind placebo-controlled study on the initial treatment of acute mania with methylphenidate.

BACKGROUND: Treatment of patients with acute mania remains a considerable medical challenge since onset of action of antimanic medication is delayed for several days. Psychostimulants could have an earlier onset of action. This assumption is based on the 'vigilance regulation model of mania' which postulates that vigilance is unstable in manic patients. Accordingly, vigilance-stabilising psychostimulants could be more useful than conventional treatment in acute mania. We present here the study protocol of a trial intended to study the efficacy and safety of methylphenidate in the initial treatment of acute mania. METHODS/DESIGN: A multi-centre, randomised, double-blind, placebo-controlled clinical trial will be conducted in 88 bipolar inpatients with acute mania. Male and female patients older than 18 years will be randomised to treatment with either methylphenidate (20 to 40 mg/day) or placebo for 2.5 days, given once or twice daily. The main outcome measure is the reduction in the Young Mania Rating Scale (YMRS) after 2.5 days of treatment. Other outcome measures include the Positive and Negative Syndrome Scale-Excited Component (PANSS-EC) the Clinical Global Impression-Bipolar Scale (CGI-BP), the Screen for Cognitive Impairment in Psychiatry (SCIP), actigraphy and the EEG-'Vigilance Algorithm Leipzig' (VIGALL). DISCUSSION: A positive study outcome of the proposed study could substantially impact our understanding of the etiopathogenesis of mania and open new treatment perspectives

Executive function deficits, rumination and late-onset depressive symptoms in older adults

Empirical evidence indicates that late-onset depression (i.e., age of onset > 60 years) is associated with executive function decline. This relationship suggests the possibility that executive dysfunction (ED) may contribute to depressive symptoms because it leads to decreased ability to inhibit ruminative thinking. This hypothesis was tested in a sample of 44 older adults reporting depressive symptoms with onset either late in adulthood or earlier in life. Consistent with hypotheses, older adults suffering from late onset, but not early onset, depressive symptoms showed an association between ED and depressive symptomatology. Furthermore, this selective relationship between ED and depressive symptomatology was mediated by ruminative tendencies. These results suggest that executive function deficits may contribute to late-onset of depressive symptoms by interfering with the ability to control ruminative thoughts