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

Contrôle du mouvement du regard (1)

Les mouvements des yeux constituent un mode d’accès privilégié au monde qui nous entoure. Ils permettent, en plaçant les objets d’intérêt dans la partie centrale du champ visuel, d’explorer les scènes visuelles, d’en identifier les composants significatifs et d’acquérir les informations nécessaires pour pouvoir agir sur eux (préhension, évitement…). De nombreuses étapes de traitement se succèdent entre l’arrivée des photons sur la rétine et la contraction des muscles oculaires. Dans cet article, nous étudions la place du cortex pariétal dans cet enchaînement de mécanismes neurophysiologiques. Nous proposons que celui-ci soit impliqué dans la représentation de l’espace et la sélection des objets pertinents dans l’environnement, c’est-à-dire après le traitement visuel perceptif et avant l’élaboration du signal moteur

Le rôle du cortex pariétal

Les mouvements des yeux constituent un mode d’accès privilégié au monde qui nous entoure. Ils permettent, en plaçant les objets d’intérêt dans la partie centrale du champ visuel, d’explorer les scènes visuelles, d’en identifier les composants significatifs et d’acquérir les informations nécessaires pour pouvoir agir sur eux (préhension, évitement…). De nombreuses étapes de traitement se succèdent entre l’arrivée des photons sur la rétine et la contraction des muscles oculaires. Dans cet article, nous étudions la place du cortex pariétal dans cet enchaînement de mécanismes neurophysiologiques. Nous proposons que celui-ci soit impliqué dans la représentation de l’espace et la sélection des objets pertinents dans l’environnement, c’est-à-dire après le traitement visuel perceptif et avant l’élaboration du signal moteur.Eye movements constitute one of the most basic means of interacting with our environment, allowing to orient to, localize and scrutinize the variety of potentially interesting objects that surround us. In this review we discuss the role of the parietal cortex in the control of saccadic and smooth pursuit eye movements, whose purpose is to rapidly displace the line of gaze and to maintain a moving object on the central retina, respectively. From single cell recording studies in monkey we know that distinct sub-regions of the parietal lobe are implicated in these two kinds of movement. The middle temporal (MT) and medial superior temporal (MST) areas show neuronal activities related to moving visual stimuli and to ocular pursuit. The lateral intraparietal (LIP) area exhibits visual and saccadic neuronal responses. Electrophysiology, which in essence is a correlation method, cannot entirely solve the question of the functional implication of these areas: are they primarily involved in sensory processing, in motor processing, or in some intermediate function? Lesion approaches (reversible or permanent) in the monkey can provide important information in this respect. Lesions of MT or MST produce deficits in the perception of visual motion, which would argue for their possible role in sensory guidance of ocular pursuit rather than in directing motor commands to the eye muscle. Lesions of LIP do not produce specific visual impairments and cause only subtle saccadic deficits. However, recent results have shown the presence of severe deficits in spatial attention tasks. LIP could thus be implicated in the selection of relevant objects in the visual scene and provide a signal for directing the eyes toward these objects. Functional imaging studies in humans confirm the role of the parietal cortex in pursuit, saccadic, and attentional networks, and show a high degree of overlap with monkey data. Parietal lobe lesions in humans also result in behavioral deficits very similar to those that are observed in the monkey. Altogether, these different sources of data consistently point to the involvement of the parietal cortex in the representation of space, at an intermediate stage between vision and action

Implication fonctionnelle de l'aire intrapariétale latérale (LIP) et du champ oculomoteur frontal (FEF) dans l'attention visuelle sélective chez le macaque

L'attention visuelle sélective est indispensable au traitement des informations visuelles et au guidage du comportement. Cette fonction est assurée par un réseau de structures cérébrales. Durant la thèse, nous avons étudié deux aires du macaque, l'aire intrapariétale latérale (LIP) et le champ oculomoteur frontal (FEF). Ces aires, de par leurs activités neuronales, ont généralement été considérées comme participant à la réalisation de saccades oculaires. Grâce à l'inactivation réversible de LIP et FEF, nous avons mis en évidence des déficits comportementaux différents pour chacune d'elles, principalement attentionnels, et ce même sans mouvements des yeux. Ces déficits sont proches de ceux des patients négligents. Seule l'inactivation du FEF produit des déficits saccadiques. Nos résultats suggèrent que LIP n'a pas de rôle saccadique mais est impliqué dans le contrôle " top-down " de l'attention. Le FEF, en plus de son rôle saccadique, permettrait le déplacement du foyer attentionnel.LYON1-BU.Sciences (692662101) / SudocSudocFranceF

Searching for a salient target involves frontal regions

Searching for an object in a complex visual scene involves selection mechanisms. Generally, it is assumed that efficient "pop-out" search involves mainly bottom-up processing, whereas inefficient search requires pronounced top-down control over visual processing. We used functional magnetic resonance imaging in behaving monkeys to explore the functional network involved in efficient visual search. As a pop-out target automatically attracts spatial attention, we attempted to determine the regions involved in feature selection independently of the spatial allocation of attention. Therefore, monkeys were trained to perform a search task in which they had to covertly detect the presence of a salient target among distractor objects. Three tasks were used to control, as much as possible, for the spatial allocation of attention. These control tasks were matched with the search task for visual input and manual responses. Pop-out search, when compared with the control tasks, activated 3 frontal regions: frontal eye field, area 45, and a posterior portion of area 46, in addition to small activation sites in lateral intraparietal area and inferotemporal area TE. Our results show that efficient search involves frontal regions as much as visual regions and in particular that ventral prefrontal area 45 is involved in top-down control during efficient search.status: publishe

Saccadic target selection deficits after lateral intraparietal area inactivation in monkeys

We investigated the contribution of the lateral intraparietal area (LIP) to the selection of saccadic eye movement targets and to saccade execution using muscimol-induced reversible inactivation and compared those effects with inactivation of the adjacent ventral intraparietal area (VIP) and with sham injections of saline into LIP. Three types of tasks were used: saccades to single visual or memorized targets, saccades to synchronous and asynchronous bilateral targets, and visual search of a target among distractors. LIP inactivation failed to produce deficits in the latency or accuracy of saccades to single targets, but it dramatically reduced the frequency of contralateral saccades in the presence of bilateral targets, and it increased search time for a contralateral target during serial visual search. In the latter task, the observed deficits might reflect either an ispilateral bias in saccadic search strategy or an attentional impairment in locating a target among flanking distractors within the contralateral field. No effects were observed on any of these tasks after VIP inactivation. These results suggest that one important contribution of LIP to oculomotor behavior is the selection of targets for saccades in the context of competing visual stimuli

Neuronal population correlates of target selection and distractor filtering

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