Free Will or Not: Causality Preserved but Access to Motor Decisions Obscured

Empirical studies having addressed the free-will issue suffer from controversial methodologies and interpretations. We present a new paradigm involving a synchronization task where the time interval to synchronize with is randomly within and without subject's synchronization capabilities and ask subjects to retrospectively evaluate (Q1) which of the two occurred or (Q2) whether their motor response had had been reactive/speeded or delayed. Contrary to the non-FW view, Q1-judgments correlate with the actual duration of the synchronization interval rather than with subjects's motor response latencies. Instead of postidictively reshuffling their judgment to make it match the outcome of their actions, subjects preserve the causal chain of events having entailed them. When answering Q2 subjects' judgments also correlate with the synchronization interval, proof that they cannot decide on the intentionality of their actions. Hence the present results reveal the intrinsic duality of the free-will concept

Comparison of perceptual and motor latencies via anticipatory and reactive response times.

To compare the timing of perceptual and motor decisions, distinct tasks have been designed, all of which have yielded systematic differences between these two moments. These observations have been taken as evidence of a sensorimotor dissociation. Inasmuch as the distinction between perceptual and motor decision moments is conceptually warranted, this conclusion remains debatable, since the observed differences may reflect the dissimilarity between the stimulations/tasks used to assess them. Here, we minimize such dissimilarities by comparing response time (RT) and anticipatory RT (ART), an alternative technique with which to infer the relative perceptual decision moments. Observers pressed a key either in synchrony with the third of a sequence of three stimuli appearing at a constant pace (ART) or in response to the onset of this third stimulus presented at a random interval after the second (RT). Hence, the two stimulation sequences were virtually identical. Both the mean and the variance of RT were affected by stimulus intensity about 1.5 times more than were the mean and the variance of ART. Within the framework of two simple integration-to-bound models, these findings are compatible with the hypothesis that perceptual and motor decisions operate on the same internal signal but are based on distinct criteria, with the perceptual criterion lower than the motor one

Dental practice in digital era: quo vadimus?

Rezumat. Graţie progresului tehnologic înregistrat în ultimii ani sistemele CAD/ CAM reprezintă o certitudine practică a utilizării lor în restaurările dentare. Prin intermediul unui scaner intraoral performant în prezent există posibilitatea expedierii rapide pe cale electronică în laboratorul de tehnică dentară a unei amprente digitale de acurateţe efectuate direct în cabinet de către medic. Fluxul tehnologic digital concretizează realitatea virtuală, care debutează prin amprentarea optică a câmpului protetic în cabinet, se continuă prin utilizarea articulatoarelor virtuale și efectuarea designului 3D al reconstituirii protetice și se termină în final cu confecţionarea unei lucrări protetice reale, prin frezare sau procese de adiţie dirijate de un software dedicat. Pentru moment introducerea tehnologiei digitale ca procedură habituală de confecţionare a unei restaurări protetice este totuși grevată atât de necesitatea instruirii unui personal cu înaltă calificare profesională cât și de reducerea preţurilor de cost, deocamdată încă mult prea ridicate comparativ cu procedeele convenţionale de tehnică dentară.Summary. Due to the technological progress of last years CAD/CAM systems definitely proved to be extremely useful in tooth restorations. Using an updated intraoral scanner nowadays is possible to quickly send by e–mail to dental laboratory an accurate digital impression directly recorded in dental office by the practitioner. The digital technological flow materializes the virtual reality which begins at dental chair with optic impression of prosthetic field, goes farther by using the virtual articulators and drawing up the 3D design of prosthetic restoration, and arrives at the end–point by manufacturing the real prosthetic product, either by milling or addition process, under the control of dedicated software. However, for the time being the use of digital technology as habitual procedure to manufacturing a prosthetic restoration sets hurdles since it needs both personnel of high professional qualification and reduced costs which presently are higher as compared to conventional procedures performed in common dental laboratories

Discrete confidence levels revealed by sequential decisions

Humans can meaningfully express their confidence about uncertain events. Normatively, these beliefs should correspond to Bayesian probabilities. However, it is unclear whether the normative theory provides an accurate description of the human sense of confidence, partly because the self-report measures used in most studies hinder quantitative comparison with normative predictions. To measure confidence objectively, we developed a dual-decision task in which the correctness of a first decision determines the correct answer of a second decision, thus mimicking real-life situations in which confidence guides future choices. While participants were able to use confidence to improve performance, they fell short of the ideal Bayesian strategy. Instead, behaviour was better explained by a model with a few discrete confidence levels. These findings question the descriptive validity of normative accounts, and suggest that confidence judgments might be based on point estimates of the relevant variables, rather than on their full probability distributions

Tratamentul chirurgical al leziunilor cerebrale parenchimatoase posttraumatice. Prezentare de caz

Leziunile traumatice parenchimatoase sunt consecinţe comune a traumatismelor craniocerebrale (TCC), asociindu-se cu acestea în 8.2%. În TCC severe leziunile parenchimatoase se asociază în 13-35% cazuri. Leziunile ce prezintă massefect, ce potenţial pot induce mecanismele secundare de injurie cerebrală, ce agravează neurologic pacientul, herniază ţesutul cerebral sunt indicaţii pentru tratament chirurgical. În lucrare sunt prezentate indicaţiile actuale şi timing-ul intervenţiei chirurgicale în leziunile parenchimatoase posttraumatice. Prezentăm în acest articol un pacient cu focare gigante bilaterale de contuzie cerebrală, operat în momentul optim cu rezoluţie postoperatorie satisfăcătoare a tabloului imagistic

Rôle de l'attention et processus de décision dans la mémoire sensorielle à court terme : comparaison entre vision et audition

Ce texte est un rapport de fin de recherche issu de l'ACI cognitiqueThe project was intended to compare (for the first time to our knowledge) attentional, decisional and mnesic processes in audition and vision by means of psychophysical and neuroimaging (MRIf) techniques. While part of the project is still ongoing, the work to date yields the following conclusions: (1) the use of an attentional cue pointing to one among a number of audio and/or visual stimuli shortly before (condition ANTE) their simultaneous presentation yields comparable improvements for the audio and the visual discrimination performances; (2) for both a visual and an auditory task, a cue presented shortly after the display of these same stimuli (condition EARLY) is less effective than in ANTE but more effective than when presented 3-6 s after the stimuli offset (condition LATE); (3) the advantage of EARLY over LATE disappears when the number of simultaneously presented stimuli is below 4, suggesting similar, or even identical storage capacities of the short term memory (STM) in vision and audition; (4) in contrast with this audio-visual STM equivalence, the mnesic trace of one among 3 pure tones deteriorates significantly after 4 s in audition, while it remains unchanged for one among 3 or 6 spatial frequencies in vision; whether this difference reflects the existence of two distinct mnesic systems for the two modalities or rather different underlying intrinsic internal noises, remains to be answered. (5) In all events, the present results point to a fundamental difference between an attentional cue allowing the selection for further processing of one among several stimuli (condition ANTE) and a “mnesic cue” entailing the selection of one among a number of mnesic traces (conditions EARLY and LATE). A second series of audio-visual experiments bearing on the decision processes shows that they follow the same laws in the two modalities, namely that they (6) comply with the principle of a unique internal representation (UIR; Gorea & Sagi, 2000) as long as the stimuli do not entail an “attentional competition” and (7) as long as these stimuli are all visual or all auditory; in other words, the UIR does not apply across modalities. (8) The preliminary MRIf data are inconclusive as to the existence of a modal or of a multimodal internal representation of the sensory information.Nous présentons brièvement des recherches de psychophysique sensorielle et d'imagerie cérébrale (IRMf ) portant (à notre connaissance pour la première fois) sur la comparaison des processus attentionnels, décisionnels et mnésiques dans le traitement sensoriel auditif et visuel. Alors qu'une partie de ces travaux est en cours, ceux déjà effectués conduisent d'ores et déjà aux conclusions suivantes : (1) l'utilisation d'une amorce permettant la focalisation attentionnelle sur un parmi plusieurs stimuli auditifs et/ou visuels juste avant (condition ANTÉ) leur présentation simultanée conduit à des améliorations comparables pour ce qui est de la discrimination auditive et visuelle ; (2) en audition comme en vision, la même amorce présentée juste après (condition TÔT) la présentation de mêmes stimuli est moins efficace que dans le cas ANTÉ et plus efficace que dans une condition où l'amorce est présentée 3-6 s après la présentation des stimuli (condition TARD);(3) toutefois, en audition comme en vision la différence entre les conditions TÔT et TARD disparaît lorsque le nombre des stimuli présentés simultanément est inférieur à 4 ce qui suggère que la capacité de la mémoire à court terme est similaire, voire identique, dans les deux modalités ; (4) contrairement aux similarités ci-dessus entre les processus auditifs et visuels, la trace mnésique d'un (parmi trois) ton(s) pur(s) se dégrade notablement au bout de 4 s en audition alors qu'elle reste inchangée pour ce qui est d'une (parmi 3 ou 6) fréquence(s) spatiale(s) en vision; à ce stade il reste à déterminer si cette différence reflète l'existence de deux systèmes mnésiques à court terme en vision et en audition, ou si elle est la conséquence d'une différence entre les bruits de fond intrinsèques aux deux systèmes sensoriels ; (5) quoi qu'il en soit, l'ensemble des résultats mentionnés ci-dessus dénote une différence fondamentale entre un amorçage attentionnel conduisant à un traitement sensoriel spécifique d'un parmi plusieurs stimuli (condition ANTÉ) et un « amorçage mnésique » permettant l'isolation d'une parmi plusieurs traces mnésiques (conditions TÔT et TARD). Une seconde série d'expériences audio-visuelles portant sur le processus de décision montre que ce dernier se conforme aux mêmes lois dans les deux modalités, à savoir que (6) il respecte le principe de la représentation interne unique (riu; Gorea & Sagi, 2000) seulement dans la mesure où les stimuli présentés ne conduisent pas à une « compétition attentionnelle » et où (7) ces stimuli sont soit visuels, soit auditifs ; en d'autres termes il n'existe pas la représentation sensorielle unitaire n'est jamais intermodale. (8) à la question de la représentation modale ou multimodale des informations sensorielles (audio), les résultats préliminaires d'IRMf ont apporté une réponse ambiguë

Sensory and decisional factors in motion-induced blindness. Journal of Vision, 7(7), Article 4. Retrieved March 27, 2008, from http://www.journal ofvision.org/7/7/4/article.aspx

The processes underlying motion-induced blindness (MIB) are widely debated. Ultimately, however, they must reduce to a sensitivity drop and/or to an upward shift of the decision criterion. The first possibility was tested by assessing the detection threshold for a contrast (or luminance) increment applied to the MIB target under its visible and suppressed phases. This was performed over a whole range of reference target contrasts (yielding the standard Threshold vs. Contrast [TvC] function) with a 2AFC staircase procedure. The second possibility was tested with a Yes/No procedure, allowing the assessment of both the sensitivities (d V ) and decision criteria (c) yielded by four contrast increments applied to a fixed reference target contrast (the psychometric function). The 2AFC procedure yielded a global upward shift of the TvC function of about 5.3 dB (a factor of 1.84) under the suppressed phase. The Yes/No procedure yielded a commensurate d Vdrop (of about 0.8 A) under the suppressed phase with no change in the slope of the psychometric function and an upward shift of c of about 0.7 A. The presently observed vertical shift (in log-log coordinates) of the TvC function in the suppressed phase is indicative of a divisive inhibition occurring after the transducing stage. The invariance of the psychometric function slope under the visible and suppressed MIB phases supports this conclusion. The present experiments cannot settle the issue of whether the upward shift of the decision criteria is yet another cause of the MIB or a consequence of its underlying inhibitory process. Instead, they make clear that MIB (and perhaps other unstable perceptual phenomena) is associated with both sensory and decisional processes