Search results for " visual perception"
showing 10 items of 25 documents
Modulation of excitatory and inhibitory circuits for visual awareness in the human right parietal cortex.
2005
The balance of specific patterns of excitation and inhibition in critical regions of both hemispheres could be relevant in orienting attention over the extrapersonal space. In the present study a group of normal subjects had to detect small rectangular stimuli presented briefly on a computer screen in three different conditions: unilateral presentation either to left or right visual periphery or bilateral simultaneous presentation. Paired transcranial magnetic stimulation (TMS), was applied over the right parietal cortex 150 ms after the presentation of the visual stimuli with different inter-stimulus intervals (ISIs: 1, 3,5 and 10 ms). When paired TMS was applied 150 ms, but not 100 ms, af…
Is backward disequilibrium in the elderly caused by an abnormal perception of verticality? A pilot study
2007
International audience; OBJECTIVE: We hypothesised that backward disequilibrium (BD), defined by a posterior position of the centre of mass with respect to the base of support, could be caused by a backward tilt in the perception of verticality. METHODS: The relationship between BD, the perception of verticality, and the history of falls in 25 subjects aged 84.5+/-7.4 years was analysed. An original ordinal scale, the BD scale (BDS), was used to quantify BD. Postural (PV) and haptic verticals (HV) were measured in sagittal plane. RESULTS: BDS scores closely correlated with the number of falls (r = 0.81, p =10(-5)). The more the PV was tilted backward, the greater the BDS scores (r = -0.95, …
RELATIVISTIC COMPRESSION AND EXPANSION OF EXPERIENTIAL TIME IN THE LEFT AND RIGHT SPACE
2007
Time, space and numbers are closely linked in the physical world. However, the relativistic-like effects on time perception of spatial and magnitude factors remain poorly investigated. Here we wanted to investigate whether duration judgments of digit visual stimuli are biased depending on the side of space where the stimuli are presented and on the magnitude of the stimulus itself. Different groups of healthy subjects performed duration judgment tasks on various types of visual stimuli. In the first two experiments visual stimuli were constituted by digit pairs (1 and 9), presented in the centre of the screen or in the right and left space. In a third experiment visual stimuli were constitu…
Age-related differences in a delayed pointing of a M�ller-Lyer illusion
2003
It has been suggested that movements to visible or remembered targets are differently sensitive to the Müller-Lyer (ML) illusion. Indeed, when the target is continuously visible, movements rely on the veridical object characteristics, whereas remembered movements are thought to reflect the perceived characteristics of the object. The aim of the present study was to determine how movements to visible or remembered targets are influenced by the ML illusion in children aged 7 to 11 years old. Participants were asked to make a perceptual judgment or to point a shaft extremity of the ML configurations (Closed, Control, and Open) in three visual conditions (Closed Loop, Open Loop-0-s delay, and 5…
Developmental dissociation between visual and auditory repetition priming: The role of input lexicons
2000
Contrasting theories posit the source of verbal repetition priming in the activation of preexisting memory representations in the input lexicons or, alternatively, in the formation of new episodic memory traces. The two hypotheses predict different outcomes from the comparison of developmental rates of visual and auditory verbal repetition priming. The activation theory predicts a developmental dissociation between the early maturation of auditory priming and the later maturation of visuo-verbal priming, contingent upon the discrepant acquisition rates of the auditory and visual input lexicons. The episodic theory, instead, does not make such an assumption. We administered visual and audito…
Trains with a view to sickness
2001
This study was supported by Region Rhone-Alpes (contract ARASSH n°L099552501) and CEC Improving Human Potential: Access to Research Infrastructures HPRI-1999-CT-00025.
Remembering what but not where: independence of spatial and visual working memory in the human brain
2001
We report the neuropsychological and MRI investigation of a patient (MV) who developed a selective impairment of visual-spatial working memory (WM) with preservation not only of verbal, but also of visual shape WM, following an ischemic lesion in the cerebral territory supplied by one of the terminal branches of the right anterior cerebral artery. MV was defective in visual-spatial WM whether the experimental procedure involved arm movement for target pointing or not. Also, in agreement with the role generally assigned to visual-spatial WM in visual imagery. MV was extremely slow in the mental rotation of visually and verbally presented objects. In striking contrast with the WM deficit, MV'…
Biased postural vertical in humans with hemispheric cerebral lesions.
1998
International audience; This study was aimed at demonstrating the existence of a biased postural vertical in humans with a recent cerebral lesion. The postural vertical of patients and controls was analysed comparatively using a self-regulated balancing task, performed in sitting posture. Patients displayed a quite constant (19/22) contralesional tilt of the postural vertical (mean -2.6 degrees), varying with the severity of their spatial neglect and hemianaethesia. Eight of them showed a pathological contralesional bias (mean -5.5 degrees) as compared to normals. This result indicates an asymmetric process of somatic graviceptive information due to some cerebral lesions. When patients were…
Subliminal fear priming potentiates negative facial reactions to food pictures in women with anorexia nervosa.
2010
BackgroundTo investigate hedonic reactivity and the influence of unconscious emotional processes on the low sensitivity to positive reinforcement of food in anorexia nervosa (AN).MethodAN and healthy women were exposed to palatable food pictures just after a subliminal exposure to facial expressions (happy, disgust, fear and neutral faces), either while fasting or after a standardized meal (hungerversussatiety). Both implicit [facial electromyographic (EMG) activity from zygomatic and corrugator muscles, skin conductance, heart rate, and videotaped facial behavior] and explicit (self-reported pleasure and desire) measures of affective processes were recorded.ResultsIn contrast to healthy wo…
Saliency Based Image Cropping
2013
Image cropping is a technique that is used to select the most relevant areas of an image, discarding the useless ones. Handmade selection, especially in case of large photo collections, is a time consuming task. Automatic image cropping techniques may help users, suggesting to them which part of the image is the most relevant, according to specific criteria. We suppose that the most visually salient areas of a photo are also the most relevant ones to the users. In this paper we present an extended version of our previously proposed method, to extract the saliency map of an image, which is based on the analysis of the distribution of the interest points of the image. Three different interest…