The Neurodynamic Decision Variable in Human Multi-Alternative Perceptual Choice

The neural dynamics underpinning binary perceptual decisions and their transformation into actions are well studied, but real-world decisions typically offer more than two response alternatives. How does decision-related evidence accumulation dynamically influence multiple action representations in humans? The heightened conservatism required in multiple compared to binary choice scenarios suggests a mechanism which compensates for increased uncertainty when multiple choices are present by supressing baseline activity. Here, we tracked action representations using corticospinal excitability during four and two-choice perceptual decisions, and modelled them using a sequential sampling framework. We found that the predictions made by leaky competing accumulator models in order to accommodate multiple choices (i.e. reduced baseline activity to compensate increased uncertainty) were borne out by dynamic changes in human action representations. This suggests a direct and continuous influence of interacting evidence accumulators, each favouring a different decision alternative, on downstream corticospinal excitability during complex choice

Design of a pulse power supply unit for micro-ECM

Electrochemical micro-machining (μECM) requires a particular pulse power supply unit (PSU) to be developed in order to achieve desired machining performance. This paper summarises the development of a pulse PSU meeting the requirements of μECM. The pulse power supply provides tens of nanosecond pulse duration, positive and negative bias voltages and a polarity switching functionality. It fulfils the needs for tool preparation with reversed pulsed ECM on the machine. Moreover, the PSU is equipped with an ultrafast overcurrent protection which prevents the tool electrode from being damaged in case of short circuits. The developed pulse PSU was used to fabricate micro-tools out of 170 μm WC-Co alloy shafts via micro-electrochemical turning and drill deep holes via μECM in a disk made of 18NiCr6. The electrolyte used for both processes was a mixture of sulphuric acid and NaNO3 aqueous solutions.The research reported in this paper is supported by the European Commission within the project “Minimizing Defects in Micro-Manufacturing Applications (MIDEMMA)” (FP7-2011-NMP-ICT-FoF-285614

Detecting and correcting partial errors: Evidence for efficient control without conscious access

Appropriate reactions to erroneous actions are essential to keeping behavior adaptive. Erring, however, is not an all-or-none process: electromyographic (EMG) recordings of the responding muscles have revealed that covert incorrect response activations (termed "partial errors") occur on a proportion of overtly correct trials. The occurrence of such "partial errors" shows that incorrect response activations could be corrected online, before turning into overt errors. In the present study, we showed that, unlike overt errors, such "partial errors" are poorly consciously detected by participants, who could report only one third of their partial errors. Two parameters of the partial errors were found to predict detection: the surface of the incorrect EMG burst (larger for detected) and the correction time (between the incorrect and correct EMG onsets; longer for detected). These two parameters provided independent information. The correct(ive) responses associated with detected partial errors were larger than the "pure-correct" ones, and this increase was likely a consequence, rather than a cause, of the detection. The respective impacts of the two parameters predicting detection (incorrect surface and correction time), along with the underlying physiological processes subtending partial-error detection, are discussed

Visibilité et présence de l’image dans l’espace ecclésial

Cet ouvrage met au cœur de son propos une interrogation simple : dans l’organisation complexe de l’espace de l’église médiévale, les emplacements choisis pour les images qui ornent les murs et les objets n’offrent pas toujours la possibilité de voir celles-ci, d’en déchiffrer le contenu. Certaines semblent réservées à des groupes de l’assemblée stationnant dans des espaces spécifiques, d’autres ne sont pas visibles depuis les principales zones affectées aux fidèles ou aux clercs, d’autres encore sont situées trop haut. Le rapport, a priori évident, entre représentation et visibilité se trouve donc souvent démenti, appelant alors une nouvelle notion, celle de présence. Analyser la tension existant entre ces trois catégories – figuration, visibilité et présence – implique une étude croisée des œuvres figurées, des monuments et des sources écrites. Les notions de mobilité et de fixité permettent également de prendre en compte les multiples jeux d’échelles à l’œuvre dans ce lieu rituel qu’est l’église, impliquant des objets, des manuscrits, des dispositifs liturgiques, des gestes, des déplacements physiques, dialoguant avec un décor appliqué au corps même du monument, épousant l’immobilité de l’architecture. Les cinq chapitres thématiques qui organisent ce volume mettent en regard différents cas issus de l’Occident médiéval et de l’Orient byzantin, selon une chronologie longue (de l’Antiquité tardive à la fin du Moyen Âge), dans une volonté de décloisonner les disciplines et les aires géographiques afin de tirer tous les enseignements d’une approche transversale de l’image médiévale

Prior intention can locally tune inhibitory processes in the primary motor cortex: direct evidence from combined TMS-EEG

International audienceHuman subjects are able to prepare cognitively to resist an involuntary movement evoked by a suprathreshold transcranial magnetic stimulation (TMS) applied over the primary motor cortex (M1) by anticipatory selective modulation of corticospinal excitability. Uncovering how the sensorimotor cortical network is involved in this process could reveal directly how a prior intention can tune the intrinsic dynamics of M1 before any peripheral intervention. Here, we used combined TMS-EEG to study the cortical integrative processes that are engaged both in the preparation to react to TMS (Resist vs. Assist) and in the subsequent response to it. During the preparatory period, the contingent negative variation (CNV) amplitude was found to be smaller over central electrodes (FC1, C1, Cz) when preparing to resist compared with preparing to assist the evoked movement whereas a-oscillation power was similar in the two conditions. Following TMS, the amplitude of the TMS evoked-N100 component was higher in the Resist than in the Assist condition for some central electrodes (FCz, C1, Cz, CP1, CP3). Moreover, for six out of eight subjects, a single-trial-based analysis revealed a negative correlation between CNV amplitude and N100 amplitude. In conclusion, prior intention can tune the excitability of M1. When subjects prepare to resist a TMS-evoked movement, the anticipatory processes cause a decreased cortical excitability by locally increasing the inhibitory processes