L'influenza del sonno sull'andamento temporale della consolidazione delle abilità procedurali

Background: It is well known, since the pioneristic observation by Jenkins and Dallenbach (Am J Psychol 1924;35:605-12), that a period of sleep provides a specific advantage for the consolidation of newly acquired informations. Recent research about the possible enhancing effect of sleep on memory consolidation has focused on procedural memory (part of non-declarative memory system, according to Squire’s taxonomy), as it appears the memory sub-system for which the available data are more consistent. The acquisition of a procedural skill follows a typical time course, consisting in a substantial practice-dependent learning followed by a slow, off-line improvement. Sleep seems to play a critical role in promoting the process of slow learning, by consolidating memory traces and making them more stable and resistant to interferences. If sleep is critical for the consolidation of a procedural skill, then an alteration of the organization of sleep should result in a less effective consolidation, and therefore in a reduced memory performance. Such alteration can be experimentally induced, as in a deprivation protocol, or it can be naturally observed in some sleep disorders as, for example, in narcolepsy. In this research, a group of narcoleptic patients, and a group of matched healthy controls, were tested in two different procedural abilities, in order to better define the size and time course of sleep contribution to memory consolidation. Experimental Procedure: A Texture Discrimination Task (Karni & Sagi, Nature 1993;365:250-2) and a Finger Tapping Task (Walker et al., Neuron 2002;35:205-11) were administered to two indipendent samples of drug-naive patients with first-diagnosed narcolepsy with cataplexy (International Classification of Sleep Disorder 2nd ed., 2005), and two samples of matched healthy controls. In the Texture Discrimination task, subjects (n=22) had to learn to recognize a complex visual array on the screen of a personal computer, while in the Finger Tapping task (n=14) they had to press a numeric sequence on a standard keyboard, as quickly and accurately as possible. Three subsequent experimental sessions were scheduled for each partecipant, namely a training session, a first retrieval session the next day, and a second retrieval session one week later. To test for possible circadian effects on learning, half of the subjects performed the training session at 11 a.m. and half at 17 p.m. Performance at training session was taken as a measure of the practice-dependent learning, while performance of subsequent sessions were taken as a measure of the consolidation level achieved respectively after one and seven nights of sleep. Between training and first retrieval session, all participants spent a night in a sleep laboratory and underwent a polygraphic recording. Results and Discussion: In both experimental tasks, while healthy controls improved their performance after one night of undisturbed sleep, narcoleptic patients showed a non statistically significant learning. Despite this, at the second retrieval session either healthy controls and narcoleptics improved their skills. Narcoleptics improved relatively more than controls between first and second retrieval session in the texture discrimination ability, while their performance remained largely lower in the motor (FTT) ability. Sleep parameters showed a grater fragmentation in the sleep of the pathological group, and a different distribution of Stage 1 and 2 NREM sleep in the two groups, being thus consistent with the hypothesis of a lower consolidation power of sleep in narcoleptic patients. Moreover, REM density of the first part of the night of healthy subjects showed a significant correlation with the amount of improvement achieved at the first retrieval session in TDT task, supporting the hypothesis that REM sleep plays an important role in the consolidation of visuo-perceptual skills. Taken together, these results speak in favor of a slower, rather than lower consolidation of procedural skills in narcoleptic patients. Finally, an explanation of the results, based on the possible role of sleep in contrasting the interference provided by task repetition is proposed.

Presa di decisione in situazioni rischiose: effetto della rabbia

The current studies assessed the role of trait anger and anger expression styles on risk decision-making in adulthood, adolescence and childhood. In the first experiment 158 adults completed the STAXI-2 and an inventory consisting of a battery of hypothetical everyday decision-making scenarios. Participants were also asked to evaluate the perception of risk for each chosen option and some contextual characteristics, that are familiarity and salience for each scenario. The study provides evidence for a relationship between individual differences in the tendency to feel and express anger and risky decisions and for mediation effects of familiarity and salience appraisals. Moreover, results indicated that trait anger was predictive of risk perception and they provide evidence for a positive relationship between risk decision-making and risk perception. In the second study, we examined the relationship between specific components of anger (i.e., cognitive, affective and behavioural) and risk decision-making in adolescents. 101 subjects completed specific tasks, measuring risk decision-making, assessed using hypothetical choice scenarios, and anger, evaluated through the STAXI-CA and the MSAI-R. Results showed that adolescents higher on hostility, anger experience and destructive expression, make more risky decisions in everyday life situations. Moreover, regression analyses indicated that destructive expression of anger and hostility were predictive of adolescents’ risky decisions. In the third experiment, 104 children completed three tasks: the STAXI-CA, the MSAI-R and a task measuring risk decision-making in everyday situations. Subjects were also asked to evaluate the degree of danger, benefit, fun and fear perceived for each risky choice. Analyses indicated that: (a) risk decision-making was predicted by both trait anger and outward expression of anger; (b) destructive expression o anger was predictive of children’s risky decisions; (c) appraisal of danger fully mediated the relation between trait anger and risk; (d) perceptions of benefit, scare and fun partially mediated the relationship between trait anger and risk; and (e) appraisal of danger partially mediated the relationship between outward expression of anger and risk decision-making. The results provide evidence for a relationship between dispositional anger and risk decision-making during childhood, suggesting a possible explanation of the mechanisms below. In particular, risk decision-making can be viewed as the output of cognitive and emotive processes, linked to dispositional anger that leads children to be amused, optimistic and fearless in potentially risky situations. These findings substantiate the importance of incorporating cognitive and emotive factors in theories that seek to explain the relationship between personality traits and risk decision making across a broad range of age.

Componenti spaziali della rappresentazione cognitiva della grandezza del numero

The humans process the numbers in a similar way to animals. There are countless studies in which similar performance between animals and humans (adults and/or children) are reported. Three models have been developed to explain the cognitive mechanisms underlying the number processing. The triple-code model (Dehaene, 1992) posits an mental number line as preferred way to represent magnitude. The mental number line has three particular effects: the distance, the magnitude and the SNARC effects. The SNARC effect shows a spatial association between number and space representations. In other words, the small numbers are related to left space while large numbers are related to right space. Recently a vertical SNARC effect has been found (Ito & Hatta, 2004; Schwarz & Keus, 2004), reflecting a space-related bottom-to-up representation of numbers. The magnitude representations horizontally and vertically could influence the subject performance in explicit and implicit digit tasks. The goal of this research project aimed to investigate the spatial components of number representation using different experimental designs and tasks. The experiment 1 focused on horizontal and vertical number representations in a within- and between-subjects designs in a parity and magnitude comparative tasks, presenting positive or negative Arabic digits (1-9 without 5). The experiment 1A replied the SNARC and distance effects in both spatial arrangements. The experiment 1B showed an horizontal reversed SNARC effect in both tasks while a vertical reversed SNARC effect was found only in comparative task. In the experiment 1C two groups of subjects performed both tasks in two different instruction-responding hand assignments with positive numbers. The results did not show any significant differences between two assignments, even if the vertical number line seemed to be more flexible respect to horizontal one. On the whole the experiment 1 seemed to demonstrate a contextual (i.e. task set) influences of the nature of the SNARC effect. The experiment 2 focused on the effect of horizontal and vertical number representations on spatial biases in a paper-and-pencil bisecting tasks. In the experiment 2A the participants were requested to bisect physical and number (2 or 9) lines horizontally and vertically. The findings demonstrated that digit 9 strings tended to generate a more rightward bias comparing with digit 2 strings horizontally. However in vertical condition the digit 2 strings generated a more upperward bias respect to digit 9 strings, suggesting a top-to-bottom number line. In the experiment 2B the participants were asked to bisect lines flanked by numbers (i.e. 1 or 7) in four spatial arrangements: horizontal, vertical, right-diagonal and left-diagonal lines. Four number conditions were created according to congruent or incongruent number line representation: 1-1, 1-7, 7-1 and 7-7. The main results showed a more reliable rightward bias in horizontal congruent condition (1-7) respect to incongruent condition (7-1). Vertically the incongruent condition (1-7) determined a significant bias towards bottom side of line respect to congruent condition (7-1). The experiment 2 suggested a more rigid horizontal number line while in vertical condition the number representation could be more flexible. In the experiment 3 we adopted the materials of experiment 2B in order to find a number line effect on temporal (motor) performance. The participants were presented horizontal, vertical, rightdiagonal and left-diagonal lines flanked by the same digits (i.e. 1-1 or 7-7) or by different digits (i.e. 1-7 or 7-1). The digits were spatially congruent or incongruent with their respective hypothesized mental representations. Participants were instructed to touch the lines either close to the large digit, or close to the small digit, or to bisected the lines. Number processing influenced movement execution more than movement planning. Number congruency influenced spatial biases mostly along the horizontal but also along the vertical dimension. These results support a two-dimensional magnitude representation. Finally, the experiment 4 addressed the visuo-spatial manipulation of number representations for accessing and retrieval arithmetic facts. The participants were requested to perform a number-matching and an addition verification tasks. The findings showed an interference effect between sum-nodes and neutral-nodes only with an horizontal presentation of digit-cues, in number-matching tasks. In the addition verification task, the performance was similar for horizontal and vertical presentations of arithmetic problems. In conclusion the data seemed to show an automatic activation of horizontal number line also used to retrieval arithmetic facts. The horizontal number line seemed to be more rigid and the preferred way to order number from left-to-right. A possible explanation could be the left-to-right direction for reading and writing. The vertical number line seemed to be more flexible and more dependent from the tasks, reflecting perhaps several example in the environment representing numbers either from bottom-to-top or from top-to-bottom. However the bottom-to-top number line seemed to be activated by explicit task demands.

Metamorfismo ercinico di bassa-pressione: evoluzione tettonico-metamorfica del complesso di mandatoriccio (massiccio della Sila - Calabria)

Low-pressure/high-temperature (LP/HT) metamorphic belts are characterised by rocks that experienced abnormal heat flow in shallow crustal levels (T > 600 °C; P < 4 kbar) resulting in anomalous geothermal gradients (60-150 °C/km). The abnormal amount of heat has been related to crustal underplating of mantle-derived basic magmas or to thermal perturbation linked to intrusion of large volumes of granitoids in the intermediate crust. In particular, in this latter context, magmatic or aqueous fluids are able to transport relevant amounts of heat by advection, thus favouring regional LP/HT metamorphism. However, the thermal perturbation consequent to heat released by cooling magmas is responsible also for contact metamorphic effects. A first problem is that time and space relationships between regional LP/HT metamorphism and contact metamorphism are usually unclear. A second problem is related to the high temperature conditions reached at different crustal levels. These, in some cases, can completely erase the previous metamorphic history. Notwithstanding this problem is very marked in lower crustal levels, petrologic and geochronologic studies usually concentrate in these attractive portions of the crust. However, only in the intermediate/upper-crustal levels of a LP/HT metamorphic belt the tectono-metamorphic events preceding the temperature peak, usually not preserved in the lower crustal portions, can be readily unravelled. The Hercynian Orogen of Western Europe is a well-documented example of a continental collision zone with widespread LP/HT metamorphism, intense crustal anatexis and granite magmatism. Owing to the exposure of a nearly continuous cross-section of the Hercynian continental crust, the Sila massif (northern Calabria) represents a favourable area to understand large-scale relationships between granitoids and LP/HT metamorphic rocks, and to discriminate regional LP/HT metamorphic events from contact metamorphic effects. Granulite-facies rocks of the lower crust and greenschist- to amphibolite-facies rocks of the intermediate-upper crust are separated by granitoids emplaced into the intermediate level during the late stages of the Hercynian orogeny. Up to now, advanced petrologic studies have been focused mostly in understanding P-T evolution of deeper crustal levels and magmatic bodies, whereas the metamorphic history of the shallower crustal levels is poorly constrained. The Hercynian upper crust exposed in Sila has been subdivided in two different metamorphic complexes by previous authors: the low- to very low-grade Bocchigliero complex and the greenschist- to amphibolite-facies Mandatoriccio complex. The latter contains favourable mineral assemblages in order to unravel the tectono-metamorphic evolution of the Hercynian upper crust. The Mandatoriccio complex consists mainly of metapelites, meta-arenites, acid metavolcanites and metabasites with rare intercalations of marbles and orthogneisses. Siliciclastic metasediments show a static porphyroblastic growth mainly of biotite, garnet, andalusite, staurolite and muscovite, whereas cordierite and fibrolite are less common. U-Pb ages and internal features of zircons suggest that the protoliths of the Mandatoriccio complex formed in a sedimentary basin filled by Cambrian to Silurian magmatic products as well as by siliciclastic sediments derived from older igneous and metamorphic rocks. In some localities, metamorphic rocks are injected by numerous aplite/pegmatite veins. Small granite bodies are also present and are always associated to spotted schists with large porphyroblasts. They occur along a NW-SE trending transcurrent cataclastic fault zone, which represents the tectonic contact between the Bocchigliero and the Mandatoriccio complexes. This cataclastic fault zone shows evidence of activity at least from middle-Miocene to Recent, indicating that brittle deformation post-dated the Hercynian orogeny. P-T pseudosections show that micaschists and paragneisses of the Mandatoriccio complex followed a clockwise P-T path characterised by four main prograde phases: thickening, peak-pressure condition, decompression and peak-temperature condition. During the thickening phase, garnet blastesis started up with spessartine-rich syntectonic core developed within micaschists and paragneisses. Coevally (340 ± 9.6 Ma), mafic sills and dykes injected the upper crustal volcaniclastic sedimentary sequence of the Mandatoriccio complex. After reaching the peak-pressure condition (≈4 kbar), the upper crust experienced a period of deformation quiescence marked by the static overgrowths of S2 by Almandine-rich-garnet rims and by porphyroblasts of biotite and staurolite. Probably, this metamorphic phase is related to isotherms relaxation after the thickening episode recorder by the Rb/Sr isotopic system (326 ± 6 Ma isochron age). The post-collisional period was mainly characterised by decompression with increasing temperature. This stage is documented by the andalusite+biotite coronas overgrown on staurolite porphyroblasts and represents a critical point of the metamorphic history, since metamorphic rocks begin to record a significant thermal perturbation. Peak-temperature conditions (≈620 °C) were reached at the end of this stage. They are well constrained by some reaction textures and mineral assemblages observed almost exclusively within paragneisses. The later appearance of fibrolitic sillimanite documents a small excursion of the P-T path across the And-Sil boundary due to the heating. Stephanian U-Pb ages of monazite crystals from the paragneiss, can be related to this heating phase. Similar monazite U-Pb ages from the micaschist combined with the lack of fibrolitic sillimanite suggest that, during the same thermal perturbation, micaschists recorded temperatures slightly lower than those reached by paragneisses. The metamorphic history ended with the crystallisation of cordierite mainly at the expense of andalusite. Consequently, the Ms+Bt+St+And+Sill+Crd mineral assemblage observed in the paragneisses is the result of a polyphasic evolution and is characterised by the metastable persistence of the staurolite in the stability fields of the cordierite. Geologic, geochronologic and petrographic data suggest that the thermal peak recorded by the intermediate/upper crust could be strictly connected with the emplacement of large amounts of granitoid magmas in the middle crust. Probably, the lithospheric extension in the relatively heated crust favoured ascent and emplacement of granitoids and further exhumation of metamorphic rocks. After a comparison among the tectono-metamorphic evolutions of the different Hercynian crustal levels exposed in Sila, it is concluded that the intermediate/upper crustal level offers the possibility to reconstruct a more detailed tectono-metamorphic history. The P-T paths proposed for the lower crustal levels probably underestimate the amount of the decompression. Apart from these considerations, the comparative analysis indicates that P-T paths at various crustal levels in the Sila cross section are well compatible with a unique geologic scenario, characterized by post-collisional extensional tectonics and magmas ascent.

Difesa idraulica delle aree di pianura dalle piene al limite della prevedibilità: asta medio inferiore del Fiume Po

La Tesi si occupa dello studio della gestione delle piene al limite della prevedibilità nel tratto medio inferiore del Fiume Po attraverso una laminazione controllata in Fascia C, in linea con le linee strategiche dell'AdB-Po. A tal fine è stato realizzato un modello numerico idraulico quasi-bidimensionale del tratto studiato del Fiume con il software HEC-RAS, comprendente le Fasce A, B e C, calibrato per un tempo di ritorno di 500 anni. Sono state condotte delle simulazioni sotto l'ipotesi di argini erodibili con conseguente formazione di brecce nei punti soggetti a tracimazione (situazione attuale), e sotto l'ipotesi di argini inerodibili (teorico intervento di rivestimento e consolidamento dei tratti arginali interessati da sormonto); attraverso il confronto dei risultati si è dimostrata l'utilità della laminazione controllata in Fascia C e l'auspicabilità di nuovi studi volti all'individuazione di aree poco sensibili in cui convogliare i volumi idrici esondati.