Electrophysiological underpinnings of reward processing: Are we exploiting the full potential of EEG?

Understanding how the brain processes reward is an important and complex endeavor, which has involved the use of a range of complementary neuroimaging tools, including electroencephalography (EEG). EEG has been praised for its high temporal resolution but, because the signal recorded at the scalp is a mixture of brain activities, it is often considered to have poor spatial resolution. Besides, EEG data analysis has most often relied on event-related potentials (ERPs) which cancel out non-phase locked oscillatory activity, thus limiting the functional discriminative power of EEG attainable through spectral analyses. Because these three dimensions -temporal, spatial and spectral- have been unequally leveraged in reward studies, we argue that the full potential of EEG has not been exploited. To back up our claim, we first performed a systematic survey of EEG studies assessing reward processing. Specifically, we report on the nature of the cognitive processes investigated (i.e., reward anticipation or reward outcome processing) and the methods used to collect and process the EEG data (i.e., event-related potential, time-frequency or source analyses). A total of 359 studies involving healthy subjects and the delivery of monetary rewards were surveyed. We show that reward anticipation has been overlooked (88% of studies investigated reward outcome processing, while only 24% investigated reward anticipation), and that time-frequency and source analyses (respectively reported by 19% and 12% of the studies) have not been widely adopted by the field yet, with ERPs still being the dominant methodology (92% of the studies). We argue that this focus on feedback-related ERPs provides a biased perspective on reward processing, by ignoring reward anticipation processes as well as a large part of the information contained in the EEG signal. Finally, we illustrate with selected examples how addressing these issues could benefit the field, relying on approaches combining time-frequency analyses, blind source separation and source localization

Proactive Inhibitory Control of Response as the Default State of Executive Control

Refraining from reacting does not only involve reactive inhibitory mechanisms. It was recently found that inhibitory control also relies strongly on proactive mechanisms. However, since most available studies have focused on reactive stopping, little is known about how proactive inhibition of response is implemented. Two behavioral experiments were conducted to identify the temporal dynamics of this executive function. They manipulated respectively the time during which inhibitory control must be sustained until a stimulus occurs, and the time limit allowed to set up inhibition before a stimulus occurs. The results show that inhibitory control is not set up after but before instruction, and is not transient and sporadic but sustained across time. Consistent with our previous neuroimaging findings, these results suggest that proactive inhibition of response is the default mode of executive control. This implies that top-down control of sensorimotor reactivity would consist of a temporary release (up to several seconds), when appropriate (when the environment becomes predictable), of the default locking state. This conclusion is discussed with regard to current anatomo-functional models of inhibitory control, and to methodological features of studies of attention and sensorimotor control

EMG as a key tool to assess motor lateralization and hand reaction time asymmetries

International audienceInconsistent and conflicting results about hand reaction time (RT) asymmetries have led to controversies over lateralization and hemispheric specialization for visuomotor transformations. In this paper, we propose a methodological solution to separate the central and peripheral processes that may be differently involved in simple visuomotor asymmetries. We provide empirical data from a simple RT task that suggests that fractionating RT into motor and premotor components with respect to a change in the electromyographic activity is necessary to disentangle motor and premotor lateralization patterns. These results call for a refinement of classical studies of visuomotor transformations using electrophysiologi-cal correlates of embedded but unrelated asymmetries rather than overt psychophysical measurements alone

Asymétries manuelles en temps de réaction (rôles de la planification du mouvement et de l'attention visuo-spatiale)

L'étude des mouvements rapides dirigés vers un but, qui sont à la base de nombre de gestes quotidiens et de l'ensemble des comportements impliquant une coordination perceptivo-motrice, révèle des performances manuelles souvent asymétriques. L'objectif de ce travail est de contribuer à une meilleure compréhension de ce phénomène observé dans la préparation du mouvement. Une revue de littérature relative aux relations qu'entretiennent les asymétries cérébrales et les performances manuelles a permis de soulever certaines controverses méthodologiques et théoriques. Une série d'expérimentations dans lesquelles étaient manipulées les contraintes biomécaniques du mouvement, la planification spatiale et l'attention visuo-spatiale a permis, dans un premier temps, de valider l'utilisation du paradigme de Poffenberger pour l'étude des asymétries manuelles en temps de réaction. Dans un second temps, les résultats observés suggèrent que ces asymétries manuelles observées lors de la réalisation de mouvements spatialement dirigés reposeraient, au moins en partie, sur un phénomène de dominance hémisphérique droite à la fois pour la planification spatiale et pour l'orientation de l'attention visuo-spatiale.POITIERS-BU Sciences (861942102) / SudocSudocFranceF

Etude comportementale et neurofonctionnelle des effets de la présentation d'un signal avertisseur en temps de réaction simple (alerte ou contrôle inhibiteur des automatismes visuomoteurs ?)

L'attention est généralement étudiée au moyen de tâches d'amorçage destinées à estimer dans quelle mesure un signal préparatoire va permettre d'améliorer le traitement de la cible a venir. Les interprétations de l'effet de la présentation d'un signal préparatoire neutre suggèrent en général que le signal avertisseur provoque un effet d'alerte qui améliore la réactivité générale du sujet. Toutefois, ce signal d'alerte provoque également des activations électromyographiques automatiques et non désirées susceptibles de déclencher des réponses anticipées (chapitre III). Ce phénomène justifie la nécessité d'implémentation d'un contrôle inhibiteur proactif, démontrée au chapitre IV grâce notamment à l'utilisation de l'IRMf. Une conclusion importante de ces deux premières parties expérimentales du travail est que les méthodes expérimentales classiquement utilisées dans la littérature sont très susceptibles d'être biaisées par ce phénomène qui influence considérablement les temps de réaction à la cible. Dans le chapitre V, ces considérations méthodologiques ont été mises à profit pour affiner l'analyse IRMf dans le but d'isoler les structures directement responsables de la genèse du signal inhibiteur de celles sujettes à l'inhibition. Un ensemble de structures beaucoup plus restreint que généralement observé dans les études de l'inhibition motrice (cortex préfrontal médial et cortex pariétal inférieur) a été mis en évidence. L'inhibition générée par ce réseau s'appliqueraient aux structures corticales motrices (M1) et prémotrices (AMS) ainsi qu'au putamen. Conjointement aux données électroencéphalographiques présentées au chapitre VI, ces résultats suggèrent que l'inhibition s'applique au niveau des mécanismes neuronaux responsables de l'initiation du mouvement. Il est conclu que de fortes interactions, voire d'importantes confusions, caractérisent les fonctions attentionnelle, sensorimotrice et exécutive.Questions about attention are usually addressed by cueing tasks assessing whether knowledge of stimulus related information provided in advance will improve target processing. Most current interpretations suggest that a warning stimulus provokes an alerting of the organism resulting in a faster processing of either the sensory of the motor aspects of the task. However, as shown in chapter III, warning signals trigger automatic motor activations (observed on EMG) which are likely to cause false alarms. Chapter IV provides converging behavioral and fMRI evidences that classical cueing methods entail competing processes of automatic motor activation triggered by the cue and proactive response inhibition intended to counteract these automatic responses to the cue. It is concluded that some classical protocols generally used in attention research are likely to be biased and to reveal behavioural effects that are not attentional in origin. The paradoxical warning signal effect (proactive inhibition) was found to be mediated by the medial prefrontal cortex and the inferior parietal lobule, which is consistent with a role in volitional inhibition (chapter V). This inhibition would act on motor structures which are critical for connecting the basal ganglia and appealing the neuronal processes underlying movement initiation (M1, SMA, putamen). This premotor hypotesis was further reinforced in chapter VI by the electroencephalographic analysis of this effect. It is concluded that strong interactions (even confusions) are observed within attentional, sensorimotor and executive functions.POITIERS-BU Droit Lettres (861942101) / SudocSudocFranceItalyFRI

PSORIATIC ARTHRITIS: A MULTIDISCIPLINARY APPROACH Strategic recommendations on the therapeutic management of psoriatic arthritis

National audienc

Knowledge of Results and Explicit Instruction: Efficiency of Learning the Crawl Stroke in Swimming

International audienceSpecific verbal instructions when added to simple knowledge of results during learning the crawl stroke by 4 adult novices was followed after 1 mo. of no practice by a higher index of swimming than observed for 4 novices given only the qualitative knowledge of results

Warning signals induce automatic EMG activations and proactive volitional inhibition: evidence from analysis of error distribution in simple RT

International audienc