Nous avons analysé l'activité de population au sein du cortex visuel primaire en vue de comprendre (i) les mécanismes mis en jeu lors de l'intégration de l'information visuelle suite à un mouvement oculaire, et inversement (ii) de l'influence du traitement effectué au niveau de V1 sur la génération d'un mouvement oculaire.1. Nous avons enregistré des saccades de fixation, et mis en relation, essai par essai, ces mouvements avec la représentation de la position d'un stimulus local dans V1. Après une saccade de fixation, l'activité se déplace de façon cohérente dans V1. Le décours temporel des réponses au niveau des foyers pre- et post-saccadiques montre une dynamique biphasique. La taille du foyer d'activité augmente. Nous proposons que le comportement des populations de neurones s'explique par deux phénomènes principaux : (i) La réponse suppressive précoce attribuable à la décharge corollaire (ii) de connections latérales qui réactiveraient le foyer pre-saccadique.2. Nous avons enregistré l'OFR, et cherché à savoir si la réponse de V1 l'influençait. Les latences VSD précèdent les latences OFR. Il n'existe pas de corrélation à l'essai unique. Nous avons montré que la force et la dynamique des réponses de V1 n'étaient pas prédictives de l'OFR. La distance de la périphérie à un effet sur la réponse VSD, mais pas sur l'OFR. La dynamique de propagation de cette suppression, nous avons montré deux phases : une précoce sur l'ensemble de la carte, et une plus périphérique tardive. Nous proposons que la suppression précoce soit originaire de projections en retour de structures comme MT et MST, alors que la suppression plus lente s'explique par les connections horizontales. / We analyzed population activity in V1 to understand (i) the consequence of eye movements on integration of visual information, and (ii) the influence of the processing performed at the level of V1 on the generation of eye movements.1. We recorded fixational saccades, relating, trial-by-trial, these eye movements with the representation of the position of a local stimulus in V1. After a fixational saccade, activity moves consistently in V1. However, the time-course of responses display a biphasic dynamic. This results in a global increase of the extent of cortical activity representing the local stimulus. We propose that the behavior of populations of neurons studied is explained by the contribution of two main phenomena: (i) an early suppressive response that could be attributed to the corollary discharge and (ii) the lateral connections generating lateral interactions between pre and post-saccadic lci of activity.2. We recorded the ocular following response, determining whether the response of V1 influences the oculomotor response. We studied the contrast response function of the population V1 activity and the OFR. The dynamics of CRF for a local stimulus are similar and shifted in time. We found no correlations between the single trial latencies between V1 and the OFR. At the chosen scale, surround suppression was found to be distance-dependent only in V1. The dynamics of the surround suppression shows two phases: an early suppression present over a wide cortical area, and a later peripheral spread. We propose that the early surround suppression originates from feedback from MT and MST, while the later is explained by the horizontal connections.

Until recently induced gamma-band activity (GBA) was considered a neural marker of cortical object representation. However, induced GBA in the electroencephalogram (EEG) is susceptible to artifacts caused by miniature fixational saccades. Recent studies have demonstrated that fixational saccades also reflect high-level representational processes. Do high-level as opposed to low-level factors influence fixational saccades? What is the effect of these factors on artifact-free GBA? To investigate this, we conducted separate eye tracking and EEG experiments using identical designs. Participants classified line drawings as objects or non-objects. To introduce low-level differences, contours were defined along different directions in cardinal color space: S-cone-isolating, intermediate isoluminant, or a full-color stimulus, the latter containing an additional achromatic component. Prior to the classification task, object discrimination thresholds were measured and stimuli were scaled to matching suprathreshold levels for each participant. In both experiments, behavioral performance was best for full-color stimuli and worst for S-cone isolating stimuli. Saccade rates 200–700 ms after stimulus onset were modulated independently by low and high-level factors, being higher for full-color stimuli than for S-cone isolating stimuli and higher for objects. Low-amplitude evoked GBA and total GBA were observed in very few conditions, showing that paradigms with isoluminant stimuli may not be ideal for eliciting such responses. We conclude that cortical loops involved in the processing of objects are preferentially excited by stimuli that contain achromatic information. Their activation can lead to relatively early exploratory eye movements even for foveally-presented stimuli.