Integration of visual information for saccade production

International audienceTo foveate a visual target, subjects usually execute a primary hyp-ometric saccade (S1) bringing the target in perifoveal vision, followed by a corrective saccade (S2) or by more than one S2. It is still debated to what extent these S2 are pre-programmed or dependent only on post-saccadic retinal error. To answer this question , we used a visually-triggered saccade task in which target position and target visibility were manipulated. In one-third of the trials, the target was slightly displaced at S1 onset (so-called double step paradigm) and was maintained until the end of S1, until the start of the first S2 or until the end of the trial. Experiments took place in two visual environments: in the dark and in a dimly lit room with a visible random square background. The results showed that S2 were less accurate for shortest target durations. The duration of post-saccadic visual integration thus appears as the main factor responsible for corrective saccade accuracy. We also found that the visual context modulates primary saccade accuracy , especially for the most hypometric subjects. These findings suggest that the saccadic system is sensitive to the visual properties of the environment and uses different strategies to maintain final gaze accuracy

A new tool for the assessment of speech understanding and spatial hearing difficulties in children: the Kid-SSQ questionnaire

International audiencePURPOSE: To develop and validate a new questionnaire, the Kid-SSQ, for the rapid screening of hearing abilities in children with hearing impairment, aged 7-17 years. METHODS: The questionnaire was constructed from two existing, validated versions of the 'Speech, Spatial and Qualities of Hearing' - (SSQ) questionnaire (pediatric form and adult short-form). The 12 selected items included auditory aspects from three subscales: speech perception, spatial hearing, and qualities of hearing. This new short form was then validated in 154 children with cochlear implants (100 bilaterally, and 54 unilaterally implanted children). Construct validity was assessed by testing relationships between Kid-SSQ scores and objective clinical parameters (e.g., age at test, pure-tone audiometry-PTA threshold, speech reception threshold-SRT, duration of binaural experience). RESULTS: Completion time was acceptable for use with children (less than 10 min) and the non-response rate was less than 1%. Good internal consistency was obtained (Cronbach's α = 0.78), with a stable internal structure corresponding to the 3 intended subscales. External validity showed the specificity of each subscale: speech subscale scores were significantly predicted (r = 0.32, p < 0.001) by both 2 kHz PTA threshold (β = 0.33, p < 0.001) and SRT (β = - 0.23, p < 0.001). Children with more binaural experience showed significantly higher scores on the spatial subscale than children with less binaural experience (F(1,98) = 5.1, p < 0.03) and the qualities of hearing subscale scores significantly depended on both age and SRT (r = 0.32, p < 0.001). CONCLUSIONS: The Kid-SSQ questionnaire is a robust and clinically useful questionnaire for self-assessment of difficulties in various auditory domains

Learned rather than online relative weighting of visual-proprioceptive sensory cues

International audienc

Intensive Training of Spatial Hearing Promotes Auditory Abilities of Bilateral Cochlear Implant Adults: A Pilot Study

International audienc

A new tool for the assessment of speech understanding and spatial hearing difficulties in children: the Kid-SSQ questionnaire

International audiencePURPOSE: To develop and validate a new questionnaire, the Kid-SSQ, for the rapid screening of hearing abilities in children with hearing impairment, aged 7-17 years. METHODS: The questionnaire was constructed from two existing, validated versions of the 'Speech, Spatial and Qualities of Hearing' - (SSQ) questionnaire (pediatric form and adult short-form). The 12 selected items included auditory aspects from three subscales: speech perception, spatial hearing, and qualities of hearing. This new short form was then validated in 154 children with cochlear implants (100 bilaterally, and 54 unilaterally implanted children). Construct validity was assessed by testing relationships between Kid-SSQ scores and objective clinical parameters (e.g., age at test, pure-tone audiometry-PTA threshold, speech reception threshold-SRT, duration of binaural experience). RESULTS: Completion time was acceptable for use with children (less than 10 min) and the non-response rate was less than 1%. Good internal consistency was obtained (Cronbach's α = 0.78), with a stable internal structure corresponding to the 3 intended subscales. External validity showed the specificity of each subscale: speech subscale scores were significantly predicted (r = 0.32, p < 0.001) by both 2 kHz PTA threshold (β = 0.33, p < 0.001) and SRT (β = - 0.23, p < 0.001). Children with more binaural experience showed significantly higher scores on the spatial subscale than children with less binaural experience (F(1,98) = 5.1, p < 0.03) and the qualities of hearing subscale scores significantly depended on both age and SRT (r = 0.32, p < 0.001). CONCLUSIONS: The Kid-SSQ questionnaire is a robust and clinically useful questionnaire for self-assessment of difficulties in various auditory domains

Brain processing of visual information during fast eye movements maintains motor performance.

Movement accuracy depends crucially on the ability to detect errors while actions are being performed. When inaccuracies occur repeatedly, both an immediate motor correction and a progressive adaptation of the motor command can unfold. Of all the movements in the motor repertoire of humans, saccadic eye movements are the fastest. Due to the high speed of saccades, and to the impairment of visual perception during saccades, a phenomenon called "saccadic suppression", it is widely believed that the adaptive mechanisms maintaining saccadic performance depend critically on visual error signals acquired after saccade completion. Here, we demonstrate that, contrary to this widespread view, saccadic adaptation can be based entirely on visual information presented during saccades. Our results show that visual error signals introduced during saccade execution--by shifting a visual target at saccade onset and blanking it at saccade offset--induce the same level of adaptation as error signals, presented for the same duration, but after saccade completion. In addition, they reveal that this processing of intra-saccadic visual information for adaptation depends critically on visual information presented during the deceleration phase, but not the acceleration phase, of the saccade. These findings demonstrate that the human central nervous system can use short intra-saccadic glimpses of visual information for motor adaptation, and they call for a reappraisal of current models of saccadic adaptation

Sensory Prediction of Limb Movement Is Critical for Automatic Online Control

International audienceFast, online control of movement is an essential component of human motor skills, as it allows automatic correction of inaccurate planning. The present study explores the role of two types of concurrent signals in error correction: predicted visual reafferences coming from an internal representation of the hand, and actual visual feedback from the hand. While the role of sensory feedback in these corrections is well-established, much less is known about sensory prediction. The relative contributions of these two types of signals remain a subject of debate, as they are naturally interconnected. We address the issue in a study that compares online correction of an artificially induced, undetected planning error. Two conditions are tested, which only differ with respect to the accuracy of predicted visual reafferences. In the first, "Prism" experiment, a planning error is introduced by prisms that laterally displace the seen hand prior to hand movement onset. The prism-induced conflict between visual and proprioceptive inputs of the hand also generates an erroneous prediction of visual reafferences of the moving hand. In the second, "Jump" experiment, a planning error is introduced by a jump in the target position, during the orienting saccade, prior to hand movement onset. In the latter condition, predicted reafferences of the hand remained intact. In both experiments, after hand movement onset, the hand was either visible or hidden, which enabled us to manipulate the presence (or absence) of visual feedback during movement execution. The Prism experiment highlighted late and reduced correction of the planning error, even when natural visual feedback of the moving hand was available. In the Jump experiment, early and automatic corrections of the planning error were observed, even in the absence of visual feedback from the moving hand. Therefore, when predicted reafferences were accurate (the Jump experiment), visual feedback was processed rapidly and automatically. When they were erroneous (the Prism experiment), the same visual feedback was less efficient, and required voluntary, and late, control. Our study clearly demonstrates that in natural environments, reliable prediction is critical in the preprocessing of visual feedback, for fast and accurate movement

Social Learning as a Way to Overcome Choice-Induced Preferences? Insights from Humans and Rhesus Macaques

International audienc

On-line modication of saccadic eye movements by retinal signals

International audienceA saccade is a rapid shift of the position of the eyes (< 100 ms). Saccades are generally considered too quick to be influenced by retinal signals. To address this idea, we displaced the visual target of a rightward horizontal saccade at eye movement onset (when there is suppression of conscious perception). To prevent adaptive and learning effects to occur, jump saccades were always followed by a random series of 10 no-jump saccades. Results indicated that the target jump influenced significantly the amplitude and the peak velocity of the ongoing saccade (opposite effects were found for rightward and leftward jumps). Changes in saccade kinematics occurred as early as 50 ms after the target jump. These results show that retinal information is processed quickly during eye movements, presumably through sub-cortical pathways