The role of impulsivity in the aetiology of drug dependence: reward sensitivity versus automaticity

Journal ArticleResearch Support, Non-U.S. Gov'tCopyright © The Author(s) 2011.RATIONALE: Impulsivity has long been known as a risk factor for drug dependence, but the mechanisms underpinning this association are unclear. Impulsivity may confer hypersensitivity to drug reinforcement which establishes higher rates of instrumental drug-seeking and drug-taking behaviour, or may confer a propensity for automatic (non-intentional) control over drug-seeking/taking and thus intransigence to clinical intervention. METHOD: The current study sought to distinguish these two accounts by measuring Barratt Impulsivity and craving to smoke in 100 smokers prior to their completion of an instrumental concurrent choice task for tobacco (to measure the rate of drug-seeking) and an ad libitum smoking test (to measure the rate of drug-taking-number of puffs consumed). RESULTS: The results showed that impulsivity was not associated with higher rates of drug-seeking/taking, but individual differences in smoking uptake and craving were. Rather, nonplanning impulsivity moderated (decreased) the relationship between craving and drug-taking, but not drug-seeking. CONCLUSIONS: These data suggest that whereas the uptake of drug use is mediated by hypervaluation of the drug as an instrumental goal, the orthogonal trait nonplanning impulsivity confers a propensity for automatic control over well-practiced drug-taking behaviour.MR

Consciousness: a unique way of processing information

In this article, I argue that consciousness is a unique way of processing information, in that: it produces information, rather than purely transmitting it; the information it produces is meaningful for us; the meaning it has is always individuated. This uniqueness allows us to process information on the basis of our personal needs and ever-changing interactions with the environment, and consequently to act autonomously. Three main basic cognitive processes contribute to realize this unique way of information processing: the self, attention and working memory. The self, which is primarily expressed via the central and peripheral nervous systems, maps our body, the environment, and our relations with the environment. It is the primary means by which the complexity inherent to our composite structure is reduced into the “single voice” of a unique individual. It provides a reference system that (albeit evolving) is sufficiently stable to define the variations that will be used as the raw material for the construction of conscious information. Attention allows for the selection of those variations in the state of the self that are most relevant in the given situation. Attention originates and is deployed from a single locus inside our body, which represents the center of the self, around which all our conscious experiences are organized. Whatever is focused by attention appears in our consciousness as possessing a spatial quality defined by this center and the direction toward which attention is focused. In addition, attention determines two other features of conscious experience: periodicity and phenomenal quality. Self and attention are necessary but not sufficient for conscious information to be produced. Complex forms of conscious experiences, such as the various modes of givenness of conscious experience and the stream of consciousness, need a working memory mechanism to assemble the basic pieces of information selected by attention

Influence of Chemical Degradation and Toothbrushing on Surface of Composites

Objective: The aim of this study was to evaluate the effect of chemical degradation media associated with brushing on surface roughness (Ra) and Knoop microhardness (KHN) analyses of different composites. Materials and methods: Eighty specimens were prepared for each composite: GrandioSO (Voco), Amaris (Voco), Filtek Supreme (3M ESPE), Filtek LS (3M ESPE). The specimens were divided into four groups according to the immersion in chemical degradation media for 7 days: artificial saliva (control), heptane, 0.02 M citric acid, 70% ethanol. The surface of specimens was submitted to 10950 brushing cycles (200 gm load) in an automatic toothbrushing machine with abrasive slurry. Surface roughness and microhardness measurements were obtained at baseline, after immersion in chemical degradation media and after brushing. Data were submitted to three-way repeated measures ANOVA and Tukey’s test (p < 0.05). Results: The KHN means for composites were: Grandio (153.5± 35.9)a, Filtek Supreme (87.0 ± 24.9)b, Amaris (64.5 ± 24.5)c, LS (69.0 ± 15.3)c; for storage media: artificial saliva (97.3 ± 46.7)a, ethanol (93.3 ± 49.9)a, citric acid (95.8 ± 42.1)a, heptane (87.6 ± 36.7)b; and after treatments: after chemical degradation (104.8 ± 49.7)a, baseline (93.8 ± 42.5)b, after brushing (81.9 ± 36.5)c. The Ra results for composites were: LS (0.15 ± 0.25)a, GrandioSO (0.19 ± 0.24)ab, Filtek Supreme (0.20 ± 0.22)ab, Amaris (0.23 ± 0.37)b; for storage media: artificial saliva (0.18 ± 0.31)a, heptane (0.18 ± 0.25)a, ethanol (0.20 ± 0.26)a, citric acid (0.21 ± 0.28)a, and after treatments: brushing (0.11 ± 0.14)a, after chemical degradation (0.23 ± 0.32)b, baseline (0.24 ± 0.32)b. Conclusion: Brushing after chemical degradation reduced surface roughness values. In general, chemical degradation did not affect composites roughness, but microhardness was significantly reduced. Heptane produced the biggest reduction in composites microhardness. Clinical relevance: The food-simulating solutions and brushing simulating alter the composites properties, and these alterations are material-dependent.Department of Restorative Dentistry Institute of Science and Technology Universidade Estadual PaulistaDepartment of Restorative Dentistry Institute of Science and Technology Universidade Estadual Paulist