Distractor-induced saccade trajectory curvature reveals visual contralateral bias with respect to the dominant eye.

The functional consequences of the visual system lateralization referred to as "eye dominance" remain poorly understood. We previously reported shorter hand reaction times for targets appearing in the contralateral visual hemifield with respect to the dominant eye (DE). Here, we further explore this contralateral bias by studying the influence of laterally placed visual distractors on vertical saccade trajectories, a sensitive method to assess visual processing.

Dorsolateral prefrontal cortex hyperactivity during inhibitory control in children with ADHD in the antisaccade task.

Children with ADHD show significant deficits in response inhibition. A leading hypothesis suggests prefrontal hypoactivation as a possible cause, though, there is conflicting evidence. We tested the hypoactivation hypothesis by analyzing the response inhibition process within the oculomotor system.

Age related prefrontal compensatory mechanisms for inhibitory control in the antisaccade task.

Cognitive decline during aging includes impairments in frontal executive functions like reduced inhibitory control. However, decline is not uniform across the population, suggesting individual brain response variability to the aging process. Here we tested the hypothesis, within the oculomotor system, that older adults compensate for age-related neural alterations by changing neural activation levels of the oculomotor areas, or even by recruiting additional areas to assist with cognitive performance.

Asymmetry in visual information processing depends on the strength of eye dominance.

Unlike handedness, sighting eye dominance, defined as the eye unconsciously chosen when performing monocular tasks, is very rarely considered in studies investigating cerebral asymmetries. We previously showed that sighting eye dominance has an influence on visually triggered manual action with shorter reaction time (RT) when the stimulus appears in the contralateral visual hemifield with respect to the dominant eye (Chaumillon et al. 2014).

Saccadic Adaptation in 10-41 Month-Old Children.

When saccade amplitude becomes systematically inaccurate, adaptation mechanisms gradually decrease or increase it until accurate saccade targeting is recovered. Adaptive shortening and adaptive lengthening of saccade amplitude rely on separate mechanisms in adults. When these adaptation mechanisms emerge during development is poorly known except that adaptive shortening processes are functional in children above 8 years of age.

Development and learning of saccadic eye movements in 7- to 42-month-old children.

From birth, infants move their eyes to explore their environment, interact with it, and progressively develop a multitude of motor and cognitive abilities. The characteristics and development of oculomotor control in early childhood remain poorly understood today. Here, we examined reaction time and amplitude of saccadic eye movements in 93 7- to 42-month-old children while they oriented toward visual animated cartoon characters appearing at unpredictable locations on a computer screen over 140 trials.

Cognitive deterioration and functional compensation in ALS measured with fMRI using an inhibitory task.

Amyotrophic lateral sclerosis (ALS) is characterized by degeneration of upper and lower motor neurons, resulting in progressive weakness and muscle atrophy. Recent studies suggest that nondemented ALS patients can show selective cognitive impairments, predominantly executive dysfunction, but little is known about the neural basis of these impairments. Oculomotor studies in ALS have described deficits in antisaccade execution, which requires the implementation of a task set that includes inhibition of automatic responses followed by generation of a voluntary action.

Developmental improvements in voluntary control of behavior: effect of preparation in the fronto-parietal network?

The ability to prepare for an action improves the speed and accuracy of its performance. While many studies indicate that behavior performance continues to improve throughout childhood and adolescence, it remains unclear whether or how preparatory processes change with development. Here, we used a rapid event-related fMRI design in three age groups (8-12, 13-17, 18-25years) who were instructed to execute either a prosaccade (look toward peripheral target) or an antisaccade (look away from target) task.

Impaired executive function signals in motor brain regions in Parkinson's disease.

Recent evidence has shown that patients with Parkinson's disease (PD) often display deficits in executive functions, such as planning for future behavior, and these deficits may stem from pathologies in prefrontal cortex and basal ganglia circuits that are critical to executive control. Using the antisaccade task (look away from a visual stimulus), we show that when the preparatory 'readiness' to perform a given action is dissociated from the actual execution of that action, PD patients off and on dopamine medication display behavioral impairments and reduced cortical brain activation that cannot be explained by a pathology related to dysfunction in movement execution. Rather, they show that the appropriate task set signals were not in place in motor regions prior to execution, resulting in impairments in the control of subsequent voluntary movement.

Preparatory neural networks are impaired in adults with attention-deficit/hyperactivity disorder during the antisaccade task.

Adults with attention-deficit/hyperactivity disorder (ADHD) often display executive function impairments, particularly in inhibitory control. The antisaccade task, which measures inhibitory control, requires one to suppress an automatic prosaccade toward a salient visual stimulus and voluntarily make an antisaccade in the opposite direction. ADHD patients not only have longer saccadic reaction times, but also make more direction errors (i.

Spatial transfer of adaptation of scanning voluntary saccades in humans.

The properties and neural substrates of the adaptive mechanisms that maintain over time the accuracy of voluntary, internally triggered saccades are still poorly understood. Here, we used transfer tests to evaluate the spatial properties of adaptation of scanning voluntary saccades. We found that an adaptive reduction of the size of a horizontal rightward 7 degrees saccade transferred to other saccades of a wide range of amplitudes and directions.

Adaptation of voluntary saccades, but not of reactive saccades, transfers to hand pointing movements.

Studying the transfer of visuomotor adaptation from a given effector (e.g., the eye) to another (e.

Oculomotor plasticity: are mechanisms of adaptation for reactive and voluntary saccades separate?

Saccadic eye movements are permanently controlled and their accuracy maintained by adaptive mechanisms that compensate for physiological or pathological perturbations. In contrast to the adaptation of reactive saccades (RS) which are automatically triggered by the sudden appearance of a single target, little is known about the adaptation of voluntary saccades which allow us to intentionally scan our environment in nearly all our daily activities. In this study, we addressed this issue in human subjects by determining the properties of adaptation of scanning voluntary saccades (SVS) and comparing these features to those of RS.

Long-lasting modifications of saccadic eye movements following adaptation induced in the double-step target paradigm.

The adaptation of saccadic eye movements to environmental changes occurring throughout life is a good model of motor learning and motor memory. Numerous studies have analyzed the behavioral properties and neural substrate of oculomotor learning in short-term saccadic adaptation protocols, but to our knowledge, none have tested the persistence of the oculomotor memory. In the present study, the double-step target protocol was used in five human subjects to adaptively decrease the amplitude of reactive saccades triggered by a horizontally-stepping visual target.

Self-generated saccades do not modify the gain of adapted reactive saccades.

The gain of reactive saccades was manipulated in 17 subjects using a target-jump paradigm. Following adaptation three sub-groups were formed: (1) rest 15 min in the dark, eyes closed; (2) perform self-generated saccades for 15 min; (3) perform reactive saccades for 15 min. The series of saccades were the same in groups 2 and 3 (amplitude, sequence), except that group 3 performed fewer saccades (same number as the lowest number of saccades performed by one subject in group 2).

Retention of saccadic adaptation in humans.

In the present study, we tested in human subjects the persistence of the oculomotor changes resulting from saccadic adaptation up to 19 days after exposure to the double step target protocol. The main results indicate that the reduction of saccade gain related to the adaptation session (mean gain change of 5 subjects = 22 +/- 4.7%) was partially but significantly retained after 1 day and 5 days (mean amount of retention = 36 +/- 17% and 19.

Transfer of adaptation from visually guided saccades to averaging saccades elicited by double visual targets.

The adaptive mechanisms that control the amplitude of visually guided saccades (VGS) are only partially elucidated. In this study, we investigated, in six human subjects, the transfer of VGS adaptation to averaging saccades elicited by the simultaneous presentation of two visual targets. The generation of averaging saccades requires the transformation of two representations encoding the desired eye displacement toward each of the two targets into a single representation encoding the averaging saccade (averaging programming site).

Eye position specificity of saccadic adaptation.

Purpose: The accuracy of saccadic eye movements is maintained throughout life by adaptive mechanisms. With the double-step target paradigm, eight human subjects were investigated to determine whether saccadic adaptation depends only on the eye-displacement vector, or also on eye position as a context cue when two saccades of identical vector are adapted simultaneously.

Methods: First, bidirectional adaptations (BDAs) of horizontal saccades of the same vector were induced in a single training phase.

Adaptation of saccadic eye movements: transfer and specificity.

The present study was designed to test whether the adaptation of saccadic eye movements depends only on the eye displacement vector of the trained saccade or also on eye position information. Using the double-step target paradigm in eight human subjects, we first induced in a single session two "opposite directions adaptations" (ODA) of horizontal saccades of the same vector. Each ODA (backward or forward) was linked to one vertical eye position (12.