Search results for "Percept"
showing 10 items of 3839 documents
Representation of time intervals in the right posterior parietal cortex: implications for a mental time line
2009
Space and time interact with each other in the cognitive system. Recent studies indicate the posterior parietal cortex (PPC) as the neural correlate of spatial-temporal interactions. We studied whether the contribution of the PPC becomes critical in tasks requiring the performance of spatial computations on time intervals. We adopted an integrated neuropsychological and transcranial magnetic stimulation (rTMS) approach, presenting behavioural timing tasks to both healthy subjects and right-brain-damaged patients with and without evidence of spatial neglect. rTMS of the right PPC of healthy subjects induced a lateralised bias during a task requiring setting the midpoint of a time interval. T…
Functional MRI of galvanic vestibular stimulation with alternating currents at different frequencies.
2004
Abstract Functional MRI was performed in 28 healthy volunteers to study the effects of galvanic vestibular stimulation with alternating currents (AC-GVS) of different frequencies on brain activation patterns. The aims of this study were (1) to identify specific areas within the vestibular cortical network that are involved in the processing of frequency-specific aspects by correlation analyses, (2) to determine the optimal frequency for stimulation of the vestibular system with respect to perception, and (3) to analyze whether different frequencies of AC-GVS are mediated in different cortical areas or different sites within the vestibular cortex. AC-GVS was performed using sinusoidal stimul…
Perceiving numbers alters time perception.
2008
The representation of time, space and numbers are strictly linked in the primate's cognitive system. Here we show that merely looking at number symbols biases a temporal judgment on their duration depending upon the number's magnitude. In a first experiment, a group of healthy subjects was submitted to a time estimation task, requiring to judge whether the duration of a test stimulus was longer or shorter than that of a previous reference fixed stimulus (digit 5; duration 300 ms). Test stimuli were the digits 1, 5 and 9 ranging between 250 and 350 ms. The main results showed that temporal perception was biased according to the magnitude expressed by the digit: low digits (i.e. 1) leading to…
The Bandwidth of VWM Consolidation Varies With the Stimulus Feature: Evidence From Event-Related Potentials
2018
Our previous work suggests that 2 colors can be consolidated into visual short-term memory (VSTM) in parallel without a loss of memory precision, whereas consolidation of 2 orientations is performed in a strictly serial manner. Those experiments compared VSTM performance for simultaneously and sequentially presented stimuli. However, there is still controversy about whether the bandwidth for consolidation is determined by the type of information. To further investigate this issue, here we measured electroencephalography while participants attempted to consolidate 1, 2 or 4 simultaneously presented colors (Experiment 1) or orientations (Experiment 2) under limited presentation times. We used…
The Development of Perceptual Sensitivity to Second-Order Facial Relations in Children
2010
This study investigated children's perceptual ability to process second-order facial relations. In total, 78 children in three age groups (7, 9, and 11 years) and 28 adults were asked to say whether the eyes were the same distance apart in two side-by-side faces. The two faces were similar on all points except the space between the eyes, which was either the same or different, with various degrees of difference. The results showed that the smallest eye spacing children were able to discriminate decreased with age. This ability was sensitive to face orientation (upright or upside-down), and this inversion effect increased with age. It is concluded here that, despite early sensitivity to conf…
Differences in pitch between tones affect behaviour even when incorrectly identified in direction.
2001
The ability to detect differences between simultaneously presented contra- and ipsilesional stimuli but not to identify the former on neurological patients with the symptom termed 'extinction' has given rise to the hypothesis that extinguished stimuli have impaired access to attentive processing but are detected pre-attentively. Such a dissociation found in normal participants with experimentally degraded sensory information, and its absence in equivalent tasks in terms of the amount of information required has, however, led to an alternative hypothesis that the lesser amount of information required to perform same/different judgements is sufficient to explain this dissociation. In the pres…
Experimental and methodological factors affecting test-retest reliability of amygdala BOLD responses.
2018
Previous studies reported poor to fair test-retest reliability of amygdala BOLD responses to emotional stimuli. However, these findings are very heterogeneous across and within studies. The present study sought to systematically examine experimental and methodological factors that contribute to this heterogeneity. Forty-six young subjects were scanned twice with a mean test-retest interval of 7 weeks. We compared amygdala reliability across three tasks: A face-matching task, passive viewing of emotional faces, and passive viewing of emotional scenes. We also explored whether extraction of physiological noise can affect the stability of amygdala responses. We assessed test-retest reliability…
Dissociation of emotional processes in response to visual and olfactory stimuli following frontotemporal damage.
2005
Contemporary neuropsychological studies have stressed the widely distributed and multicomponential nature of human affective processes. Here, we examined facial electromyographic (EMG) (zygomaticus and corrugator muscle activity), autonomic (skin conductance and heart rate) and subjective measures of affective valence and arousal in patient TG, a 30 year-old man with left anterior mediotemporal and left orbitofrontal lesions resulting from a traumatic brain injury. Both TG and a normal control group were exposed to hedonically valenced visual and olfactory stimuli. In contrast with control subjects, facial EMG and electrodermal activity in TG did not differentiate among pleasant, unpleasant…
Prism adaptation and neck muscle vibration in healthy individuals: Are two methods better than one?
2013
Studies involving therapeutic combinations reveal an important benefit in the rehabilitation of neglect patients when compared to single therapies. In light of these observations our present work examines, in healthy individuals, sensorimotor and cognitive after-effects of prism adaptation and neck muscle vibration applied individually or simultaneously. We explored sensorimotor after-effects on visuo-manual open-loop pointing, visual and proprioceptive straight-ahead estimations. We assessed cognitive after-effects on the line bisection task. Fifty-four healthy participants were divided into six groups designated according to the exposure procedure used with each: 'Prism' (P) group; 'Vibra…
Detection and distraction effects for threatening information in social phobia and change after treatment.
2007
This work examines differences in the detection and distraction by social-threatrelated information between a social phobia group (SP; N533) and a normal control group (NC; N532). The change obtained after psychological treatment is also studied for the SP group. A paper-and-pencil visual search task is used, in which the emotional valence of the ‘‘target’’ (social threat, physical threat, and neutral words) and ‘‘distractor’’ (social threat, physical threat, neutral, and nonsense words) verbal stimuli is manipulated. Results indicate that there are no differences in the detection of social-threat targets between SP and NC participants. However, the performance of SP individuals is more imp…