Effort-based reward task, a behavioral measure to study negative symptoms in schizophrenia

Negative symptoms in schizophrenia, and specifically amotivation/apathy, have been correlated with impaired general functioning. Its neurobiological basis are thought to rely on an aberrant reward system. To study the association of reward deficits and negative symptoms, 25 schizophrenia patients and 35 controls underwent a new reward behavioral task. Briefly, patients had to choose a level of effort (1 to 3), each one corresponding to a progressively increasing number of required button presses and 3 different probabilities to win an economic reward. We compared the chosen effort between groups and correlated this output with the score of the Brief negative symptoms scale in the group of patients. Patients chose less effort than controls but without reaching significance level (mean patients effort: 2.49 vs controls: 2.76, P = 0.064). A negative correlation was found between BNSS score and effort chosen for the maximum reward corrected by sex (t: −0.021, P = 0.045). When the group of patients was split according to negative symptoms score, patients with more negative symptoms (BNSSS score > 23) chose significantly less effort than patients with less negative symptoms and controls (Fig. 1). Our reward task correlates well with negative symptoms. Thus, it could offer a behavioral measure of negative symptoms. It could be a good instrument to study the neurobiological basis of negative symptoms using functional techniques.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Can we predict the response in the treatment of epilepsy with vagus nerve stimulation?

Despite the introduction of new antiepileptic drugs and advances in the surgical treatment of epilepsy, an important group of patients still remains uncontrolled by any of these methods. The relatively recent introduction of vagus nerve stimulation is yet another possible treatment for refractory epilepsy. This safe, simple, and adjustable technique reduces the number of seizures and multiple publications support its increasing efficacy and effectiveness, with few adverse effects. The goal of our study is to determine the efficacy of this procedure and the factors predicting a response, particularly in the presence of a temporal lobe discharge on the video electroencephalogram (video-EEG) and magnetic resonance imaging (MRI) lesions. We undertook a retrospective study of all the patients with refractory epilepsy who underwent implantation of a vagus nerve stimulator between 2003 and 2009, and with a minimum follow-up of 6 months. The statistical analysis was done with SPSS for Windows. The stimulator was implanted in 40 patients, of whom 38 had a minimum follow-up of 6 months. In one patient, the device had to be removed due to infection, so the series comprised 37 patients. These were divided into different groups, according to the epidemiologic, clinical, radiologic, and electroencephalographic data. In addition, an analysis of the response was performed. The efficacy of the procedure was established according to the reduction in the mean seizure frequency. The baseline value of these seizures was 80.97 ± 143.59, falling to 37 ± 82.51 at the last revision. The response rate (reduction in seizures ≥ 50 %) at 6 months was 51.4 %, with 62.2 % of the patients showing this reduction at the last evaluation. Significant differences in the response were seen for the variables: baseline frequency of seizures, temporal lobe discharge on VideoEEG and MRI lesions. The mean time to response was 10 months in patients with lower rate of seizures versus 25 months of those with the higher rate (p = 0.024), and the response at 6 months was higher (p = 0.05). Patients with temporal lobe discharge alone or in combination with discharges over other regions had a mean time to response of 11 months versus 26 months in those without temporal discharge (p = 0.037). In the analysis of the MRI, we had seen that at the last revision, 82.4 % of the patients with lesion had achieved response versus 45 % without lesion (p = 0.02). Vagus nerve stimulation reduces the frequency of seizures. A temporal lobe discharge on the video-EEG is an indicator of an early response and the presence of an MRI lesion indicates a late response. Patients with fewer rates of seizures have a better prognosis.

Recurrent arrival of oil to Galician coast: the final step of the Prestige deep oil spill

Yearly monitoring in one of the most affected coastal zones by the Prestige oil spill, namely Nemiña and O Rostro beaches (NW Spain), has been carried out since 2004. Topographic data of beaches revealed seasonal altimetric changes up to 4m that would prevent the on shore persistence of oil. However, surficial and subsurficial oil was detected in the intertidal area of both beaches in all campaigns. The hydrocarbon analysis confirmed that this oil corresponded to the Prestige oil, even nine years after the accident. Tar balls were highly biodegraded suggesting that the oil was accumulated on the subtidal sediments for a long time and transported to the coast by the action of waves. The present work provides new evidence of the long term persistence of deep oil spills from wrecks in marine areas where the hydrodynamic conditions play a twofold key role, in determining the exposed coastal area to recurrent contamination and in burying and resurfacing the oil in the intertidal zone.

Estimators and confidence intervals for the proportion using binary auxiliary information with applications to pharmaceutical studies

Estimation of a proportion is commonly used in areas such as medicine, biopharmaceutical experiments, etc. Estimation of a proportion using auxiliary information has not been investigated in the literature. Ratio estimators of the population proportion and two-sided confidence intervals based upon auxiliary information are derived in this paper. Real data extracted from the Spanish National Health Survey are used to demonstrate the application of the proposed methods in the estimation of prevalences. Results derived from simulation studies show that proposed estimators are more efficient than the traditional estimator. Proposed confidence intervals outperform the alternative methods, especially in terms of interval width. A study on patients with hypertension is also considered to calculate various estimators and confidence intervals.