Search results for "vision."
showing 10 items of 4900 documents
Pointing to a target from an upright position in human: tuning of postural responses when there is target uncertainty
2000
International audience; Human subjects performed, from a standing position, rapid hand pointings to visual targets located within or beyond the prehension space. To examine the interaction between posture and the goal-directed movement we introduced a visual double-step perturbation requiring a reprogramming of the hand movement. Trials directed towards the same spatial goal but differentiated only by the likeliness of a visual double-step were compared. The hand kinematics was not affected by the uncertainty of the visual perturbation; an increased trunk bending, however, was observed. This suggests that uncertainty constraints are integrated in a predictive manner for the optimal coordina…
Inter-joint coordination of posture on a seesaw device
2016
Even though specific adjustments of the multi-joint control of posture have been observed when posture is challenged, multi-joint coordination on a seesaw device has never been accurately assessed. The current study was conducted in order to investigate the multi-joint coordination when subjects were standing on either a seesaw device or on a stable surface, with the eyes open or closed. Eighteen healthy active subjects were recruited. A principal component analysis and a Self-Organizing Maps analysis were performed on the joint angles in order to detect and characterize dominant coordination patterns. Intermuscular EMG coherence was analysed in order to assess the neurophysiological mechan…
Unconscious response priming during continuous flash suppression.
2017
Continuous flash suppression (CFS) has become a popular tool for studying unconscious processing, but the level at which unconscious processing of visual stimuli occurs under CFS is not clear. Response priming is a robust and well-understood phenomenon, in which the prime stimulus facilitates overt responses to targets if the prime and target are associated with the same response. We used CFS to study unconscious response priming of shape: arrows with left or right orientation served as primes and targets. The prime was presented near the limen of consciousness and each trial was followed by subjective rating of visibility and a forced-choice response concerning the orientation of the prime…
High Iodine Concentration Contrast Material for Noninvasive Multislice Computed Tomography Coronary Angiography
2006
OBJECTIVE: The objective of this study was to compare intracoronary attenuation on 16-row multislice computed tomography (16-MSCT) coronary angiography using 2 contrast materials (CM) with high iodine concentration. MATERIAL AND METHODS: Forty consecutive patients (29 male, 11 female; mean age, 61 ± 11 years) with suspected coronary artery disease were randomized to 2 groups to receive 100 mL of either iopromide 370 (group 1: Ultravist 370, 370 mg iodine/mL; Schering AG, Berlin, Germany) or iomeprol 400 (group 2: Iomeron 400, 400 mg iodine/mL; Bracco Imaging SpA, Milan, Italy). Both CM were administered at a rate of 4 mL/s. All patients underwent 16-MSCT coronary angiography (Sensation 16; …
The effect of aberrations on objectively assessed image quality and depth of focus
2017
The effects of aberrations on image quality and the objectively assessed depth of focus (DoF) were studied. Aberrometry data from 80 young subjects with a range of refractive errors was used for computing the visual Strehl ratio based on the optical transfer function (VSOTF), and then, through-focus simulations were performed in order to calculate the objective DoF (using two different relative thresholds of 50% and 80%; and two different pupil diameters) and the image quality (the peak VSOTF). Both lower order astigmatism and higher order aberration (HOA) terms up to the fifth radial order were considered. The results revealed that, of the HOAs, the comatic terms (third and fifth order) ex…
The remapping of time by active tool-use
2015
Multiple, action-based space representations are each based on the extent to which action is possible toward a specific sector of space, such as near/reachable and far/unreachable. Studies on tool-use revealed how the boundaries between these representations are dynamic. Space is not only multidimensional and dynamic, but it is also known for interacting with other dimensions of magnitude, such as time. However, whether time operates on similar action-driven multiple representations and whether it can be modulated by tool-use is yet unknown. To address these issues, healthy participants performed a time bisection task in two spatial positions (near and far space) before and after an active …
Visual mismatch negativity (vMMN) is elicited with para-foveal hemifield oddball stimulation: An event-related brain potential (ERP) study.
2017
The visual mismatch negativity (vMMN) is a component of the human event-related brain potential (ERP) that indicates the automatic processing and detection of changes in the visual sensory input. The study tested whether the vMMN was observable when the visual input is restricted to one visual hemifield and, with this, only para-foveal input to one of the two primary sensory cortices in the visual system is available for stimulus processing. The vMMN was elicited by the stimulation restricted to a small portion of the visual field. This demonstrates that in general vMMN elicitation is not confined to stimulations covering a broad range of the visual field or to the propagation of sensory in…
Reliability in perimetric multichannel contrast sensitivity measurements
2014
Background: In this study, the reliability of perimetric contrast sensitivity measurements favouring the achromatic, the red-green and the blue-yellow post-receptorial mechanisms was analysed. Methods: A new technique, multichannel ATD perimetry, provides spatial and temporal stimuli favouring the detection by an achromatic mechanism (A), from a magno or parvocellular origin or by a red-green (RG) chromatic mechanism, with a parvocellular origin or a blue-yellow (BY) mechanism, with a koniocellular origin. The repeatability and reproducibility of contrast sensitivity measurements with these stimuli were studied in a group of 40 healthy subjects. The analysis was carried out on 21 testing po…
Perceptual and semantic familiarity in recognition memory: an event-related potential study
2008
Putative event-related potential correlates of perceptual and semantic bases of familiarity in recognition memory were examined with a categorized pictures recognition test. Our participants were presented, at study, with pictures of categorized objects and, at test, with either the very same pictures presented at study, different pictures of studied objects, pictures of new objects belonging to studied categories, or pictures of completely new-uncategorized objects. We found evidence for a parallel evaluation, within familiarity process, of both perceptual and semantic information. We also found new and interesting evidence for the existence of some common neural circuits involved in the F…
Anxiety symptoms among informal caregivers in 47 low- and middle-income countries: A cross-sectional analysis of community-based surveys.
2022
Background-\ud \ud There are no multi-country studies on the association between informal caregiving and anxiety from low- and middle-income countries (LMICs). Therefore, we investigated this relationship in a large predominantly nationally representative sample from 47 LMICs.\ud \ud Methods-\ud \ud Cross sectional data from the World Health Survey were analyzed. Anxiety symptoms referred to severe or extreme problems with worries or anxiety in the past 30 days.\ud \ud Information on caregiving in the past 12 months was obtained. Multivariable logistic regression analysis adjusting for age, sex, marital status, education, household size, employment, disability, and country was conducted. Da…