RESUMEN
An online changepoint detection procedure based on conditional expectiles is introduced. The key contribution is threefold: nonlinearity of the underlying model improves the overall flexibility while a parametric form of the unknown regression function preserves a simple and straightforward interpretation; The conditional expectiles, well-known in econometrics for being the only coherent and elicitable risk measure, introduce additional robustness-especially with respect to asymmetric error distributions common in various types of data; The proposed statistical test is proved to be consistent and the distribution under the null hypothesis does not depend on the functional form of the underlying model nor the unknown parameters. Empirical properties of the proposed real-time changepoint detection test are investigated in a simulation study and a practical applicability is illustrated using the Covid-19 prevalence data from Prague.
RESUMEN
The LCOT is a self-administered test designed to assess olfactory deficits. Altogether, 525 subjects contributed to the validation. Elderly participants were well represented in this sample. In a validation study (study 1), 407 healthy and 17 anosmic volunteers between 15 and 91 years of age underwent threshold, supraliminal detection, and identification testing. Cutoff values for normosmia and hyposmia were calculated and applied in a second study in a group of patients with smell complaints and in a group of Alzheimer patients with age-matched controls. Incidence of smell deficit was estimated at 5.6% in the healthy population of study 1, and at 16% in the elderly control group of study 2. Assessment of the ability of each subtest to discriminate between groups showed that LCOT is relevant to differentiating between perception and identification deficits and between Alzheimer's and hyposmic patients.
RESUMEN
Executive dysfunctions have long been considered a common feature of schizophrenia. However, due to their extreme heterogeneity, it is not clear whether these impairments take place at a particular level of executive functioning or non-specifically affect various aspects of behavioural control. To answer this question, we used an experimental paradigm based upon a multistage model of prefrontal executive function. This model postulates that cognitive control is organized in three hierarchically ordered control processes, operating with respect to the perceptual context (sensory and contextual controls) or the temporal episode in which the person is acting (episodic control). Twenty-four patients with schizophrenia and 24 non-psychiatric controls participated in two distinct experiments designed to separately assess each of these three levels of control. The results indicate that both sensory and episodic dimensions of cognitive control were spared in schizophrenic patients, but that they showed great difficulty in contextual conditions, as the selection of the appropriate response among competitive ones required taking into account information related to perceptual context. Contextual control can be considered as a set of executive processes mediating the hierarchical organization of behaviour. Patients' deficit in cognitive control therefore reflects a specific problem in the hierarchical control of action, leading to the selection of inappropriate behavioural representations for ongoing action plans. We also showed that this impairment was a good predictor of disorganization syndrome scores, suggesting that these clinical manifestations might result from a deficit in the combination or selection of hierarchically organized action representations.