Transcranial Direct Corrent stimulation (tDCS) of the anterior prefrontal cortex (aPFC) modulates reinforcement learning and decision-making under uncertainty: A doubleblind crossover study

Reinforcement learning refers to the ability to acquire information from the outcomes of prior choices (i.e. positive and negative) in order to make predictions on the effect of future decision and adapt the behaviour basing on past experiences. The anterior prefrontal cortex (aPFC) is considered to play a key role in the representation of event value, reinforcement learning and decision-making. However, a causal evidence of the involvement of this area in these processes has not been provided yet. The aim of the study was to test the role of the orbitofrontal cortex in feedback processing, reinforcement learning and decision-making under uncertainly. Eighteen healthy individuals underwent three sessions of tDCS over the prefrontal pole (anodal, cathodal, sham) during a probabilistic learning (PL) task. In the PL task, participants were invited to learn the covert probabilistic stimulusoutcome association from positive and negative feedbacks in order to choose the best option. Afterwards, a probabilistic selection (PS) task was delivered to assess decisions based on the stimulus-reward associations acquired in the PL task. During cathodal tDCS, accuracy in the PL task was reduced and participants were less prone to maintain their choice after positive feedback or to change it after a negative one (i.e., winstay and lose-shift behavior). In addition, anodal tDCS affected the subsequent PS task by reducing the ability to choose the best alternative during hard probabilistic decisions. In conclusion, the present study suggests a causal role of aPFC in feedback trial-by-trial behavioral adaptation and decision-making under uncertainty

Expectancy to Eat Modulates Cognitive Control and Attention Toward Irrelevant Food and Non-food Images in Healthy Starving Individuals. A Behavioral Study

It is thought that just as hunger itself, the expectancy to eat impacts attention and cognitive control toward food stimuli, but this theory has not been extensively explored at a behavioral level. In order to study the effect of expectancy to eat on attentional and cognitive control mechanisms, 63 healthy fasting participants were presented with an affective priming spatial compatibility Simon task that included both food and object (non-food) distracters. The participants (N = 63) were randomly assigned to two groups: an “immediate expectancy” group made up of participants who expected to eat immediately after the task (N = 31; females = 21; age = 26.8 ± 9.6) and a “delayed expectancy” cohort made up of individuals who expected to eat a few hours later (N = 32; females = 21; age = 25.0 ± 8.0). Slower reaction times (RTs) toward the food and non-food distracters and a more pronounced effect on the RTs in the incompatible condition [i.e., the Simon effect (SE)] were noted in both groups. The effect of the food and non-food distracters on the RTs was more pronounced in the immediate with respect to the delayed expectancy group. The magnitude of the SE for the food and the non-food distracters was also greater in the immediate with respect to the delayed expectancy group. These results seem to indicate that when the expectancy to eat is short, the RTs are delayed, and the SE is more pronounced when food and non-food distracters are presented. Instead, when the expectancy to eat is more distant, the distracters have less of an effect on the RTs and the correspondence effect is smaller. Our results suggest that the expectancy to eat can modulate both attention orienting and cognitive control mechanisms in healthy fasting individuals when distracting details are competing with information processing during goal directed behavior

alexithymia psychopathology and alcohol misuse in adolescence a population based study on 3556 teenagers

Objectives: To analyze the association between alexithymia and alcohol intake during adolescence, also in relation to psychopathology, in order to identify psychological risk factors for alcohol misuse. Method: 3556 students [mean age (range) 14.5 years (11-18)] were recruited in the Padua area. Each was administered a set of three questionnaires: the Toronto Alexithymia Scale for children (TAS-20) to measure alexithymia, the Questionnaire Adolescent Saturday evening (QAS) to estimate of alcohol intake, and the Youth Self-Report (YSR 11-18) to value psychopathology. Results: Externalizing problems appeared to increase with age and with the amount of alcohol consumed, unlike internalizing problems. The prevalence of alexithymia was 18%, decreasing with age, and it was not associated with alcohol consumption, and used except in younger subjects (≤13), for whom a positive correlation was observed between alexithymia, internalizing problems and alcohol intake. Conclusions: Younger adolescents are more psycho-emotionally vulnerable (internalizing problems and alexithymia) and at a greater risk of alcohol misuse

Market Power and Collusion on Interconnection Phone Market in Tunisia : What Lessons from International Experiences

We try in this paper to characterize the state of mobile phone market in Tunisia. Our study is based on a survey of foreign experience (Europe) in detecting collusive behavior and a comparison of the critical threshold of collusion between operators in developing countries like Tunisia. The market power is estimated based on the work of Parker Roller (1997) and the assumption of "Balanced Calling Pattern". We use then the model of Friedman (1971) to compare the critical threshold of collusion. We show that the "conduct parameter" measuring the intensity of competition is not null during the period 1993-2011. Results show also that collusion is easier on the Tunisian market that on the Algerian, Jordanian, or Moroccan one

Comparative analysis of xanafide cytotoxicity in breast cancer cell lines

Xanafide, a DNA-intercalating agent and topoisomerase II inhibitor, has previously demonstrated comparable cytotoxicity to the parent drug amonafide (NSC 308847). The current study was conducted to investigate further the anti-proliferative effects of xanafide in human breast cancer cell lines, in vitro and in vivo. The in vitro activity of xanafide against MCF-7, MDA-MB-231, SKBR-3 and T47D cell lines was compared to that of paclitaxel, docetaxel, gemcitabine, vinorelbine and doxorubicin. In MCF-7, xanafide demonstrated comparable total growth inhibition (TGI) concentrations to the taxanes and lower TGI values than gemcitabine, vinorelbine and doxorubicin. MCF-7 (oestrogen receptor (ER)+/p53 wild-type) was the most sensitive cell line to xanafide. MDA-MB-231 and SKBR-3 exhibited similar sensitivity to xanafide. T47 D (ER+/p53 mutated), showed no response to this agent. The in vivo activity of xanafide was further compared to that of docetaxel in MCF-7 and MDA-MB-231 cell lines using the hollow fibre assay. Xanafide was slightly more potent than docetaxel, at its highest dose in MCF-7 cell line, whereas docetaxel was more effective than xanafide in MDA-MB-231 cell line. Our results show that there is no relationship between sensitivity of these cell lines to xanafide and cellular levels of both isoforms of topoisomerase II and suggest that ER and p53 status and their crosstalk may predict the responsiveness or resistance of breast cancer patients to xanafide

Ammonia: The neglected risk factor

AbstractThe letter deals with the article published in Translational Neuroscience 2011, 2 (4), 360–362. It emphasizes the importance of the authors' findings in relation to the role of ammonaemia in diagnosing hepatic encephalopathy

Il ruolo della corteccia prefrontale dorso laterale in un compito di apprendimento probabilistico: uno studio pilota con la tDCS

Introduzione: L’apprendimento è un processo attraverso il quale si acquisiscono nuove informazioni come risultato delle esperienze positive o negative delle nostre scelte. Compiti di apprendimento probabilistico, con stimoli associati a determinati esiti con probabilità stabilita, sono ottimi per studiare questa funzione. Molti studi suggeriscono il coinvolgimento della corteccia prefrontale e del sistema dopaminergico nell’apprendimento basato su feedback postivi e negativi. L’obiettivo di questo studio è indagare il ruolo della corteccia prefrontale dorsolaterale (DLPFC) in un compito di apprendimento probabilistico e verificare se la stimolazione transcranica di corrente continua (tDCS) può modificare la sensibilità individuale verso i feedback o la strategia di scelta. Metodo: 10 studenti sono stati sottoposti a tre sessioni di stimolazione (anodica sinistra; anodica destra; sham), mentre veniva eseguito un compito di learning probabilistico diviso in una parte di training e in una di testing. Nella fase di learning tre coppie di stimoli erano associati a differenti probabilità di ricevere feedback positivi o negativi. Nella fase di training gli stessi stimoli erano ripresentati senza feedback. Risultati: Nella fase di training, l’analisi ha evidenziato un effetto principale del tipo di stimolazione e un’interazione tra il tipo di stimolazione e tempo di esecuzione del compito: accuratezza maggiore per la stimolazione anodica sinistra è un’accuratezza è maggiore nel blocco 1 con stimolazione anodica sinistra rispetto alle altre due condizioni. Nella fase di testing non sono state osservate differenze tra apprendimento per feedback positivi e negativi e il tipo di stimolazione. Conclusioni: Questi risultati suggeriscono che i soggetti testati hanno utilizzato nella fase di training una strategia di tipo frequency matching la quale era appresa più rapidamente con l’applicazione di una corrente anodica alla DLPFC di sinistra