Biomedical subjects

André Dufour

Publications and source records attributed to André Dufour.

7 recordsLinked to original sources

PubMed2006

Time-on-task effect in pseudoneglect.

Neurologically normal subjects systematically misbisect space during visual line-bisection or similar tasks, generally erring to the left of the veridical center when bisecting horizontal lines, a phenomenon referred to as pseudoneglect. This phenomenon is usually interpreted as enhanced attention toward the left hemispace resulting in an overestimation of the leftward extent of a line. While most studies have examined the role of attention in spatial bias using spatial cueing methods in bisection tasks, Manly et al. (Neuropsychologia 43(12):1721-1728, 2005) proposed an original paradigm in which the participants' alertness was diminished by sleep deprivation or prolonged execution of a line-bisection task. The authors reported a significant rightward shift in attention related to declining alertness, but they did not control eye movements and, consequently, modifications of scanning and fixation strategies with fatigue cannot be ruled out in their study. Here we examine whether a diminution in alertness induced by a 60-min-long Landmark task would diminish (or even reverse) this attentional bias, when eye movements are absent. Participants performed a forced-choice judgment about the location of a transaction mark in relation to the veridical center of a horizontal line. The results confirmed a significant decrease in the leftward bias over the course of the session but, in contrast to the findings of Manly et al. (2005), we did not observe a reverse bias from the left to the right hemispace. The results are discussed within the context of the hemisphere-activation model.

Adult↗

PubMed2005

Enhanced sensitivity to echo cues in blind subjects.

Many studies have reported that blind people compensate for their visual deficit by sharpening auditory processes. Here we compare the sensitivity to echo cues between blind and sighted subjects. In the first experiment, the blind subjects were more accurate than the sighted subjects in localizing an object on the basis of echo cues. To ensure that enhanced echolocalization abilities were not only due to the fact that blind individuals are more used to consciously paying attention to echo cues and are more familiar with this kind of tasks than sighted subjects, we tested both groups of subjects in a simple azimuthal localization task of auditory stimuli. In this second experiment, we evaluated the influence of irrelevant echo signals on auditory localization by placing the subjects and the sound sources at different positions in a sound reverberant room. Results revealed that blind subjects exhibit a higher sensitivity to echo signals than sighted subjects.

Acoustic Stimulation↗

PubMed2005

Thermal comfort: multisensory interactions?

Experimentally, the effects of environmental conditions upon human capabilities have been studied most often through the imposition of a single stressor in isolation. Although it seems to be a common belief that thermal comfort can be influenced by concomitant stimulation of non-tactile sensorial modalities, few studies have succeeded in delineating non-tactile stimulations, which interact with thermal sensation and thermal comfort. Here we briefly overview neurophysiological and behavioural findings in multisensory influences on thermal sensation and thermal comfort.

Body Temperature↗

PubMed2004

The extent of visual deficit and auditory spatial compensation: evidence from self-positioning from auditory cues.

Blindfolded sighted, myopic, amblyopic, adventitiously blind and congenitally blind humans performed a self-positioning task during which they were stimulated only by auditory cues. Results showed that visually deprived subjects used auditory cues to position themselves in their environment with a greater accuracy than normal-sighted subjects. In addition, the magnitude of auditory spatial compensation was found to be strongly related to the extent of the visual deficit.

Acoustic Stimulation↗

PubMed2004

Effect of musical expertise on visuospatial abilities: evidence from reaction times and mental imagery.

Recently, the relationship between music and nonmusical cognitive abilities has been highly debated. It has been documented that formal music training would improve verbal, mathematical or visuospatial performance in children. In the experiments described here, we tested if visual perception and imagery abilities were enhanced in adult musicians compared with nonmusicians. In our main experiment, we measured reaction times of subjects who had to detect on which side of a horizontal or a vertical line a target dot was flashed. In the "imagery" condition the reference line disappeared before the target dot was presented. In order to accomplish the task, subjects had to keep a mental image of the position of the line until the dot appeared. In the "perception" condition, the procedure and stimuli were the same except that the line remained on the screen until the dot was displayed. In both groups, reaction times were shorter for horizontal compared to vertical discrimination, but reaction times were significantly shorter in musicians in all conditions. Moreover, discrimination on the vertical dimension, especially in imaging condition, seemed to be greatly improved on the long term by musical expertise. Simple and choice visual reaction times indicate that this advantage could only be partly explained by better sensorimotor integration in adult musicians.

Adult↗

PubMed2004

Perceptual encoding of fingerspelled and printed alphabet by deaf signers: an fMRI study.

We measured brain activation during the perception of fingerspelled letters, printed letters, and abstract shapes (control condition) in six congenitally, profoundly deaf signers and six normal hearing subjects. Normal hearing subjects showed essentially extrastriate activation in the fingerspelled letters and printed letters conditions whereas deaf subjects showed activation of a broader network in printed letters and fingerspelled conditions, comprising supplementary frontal and posterior areas, and the supramarginal gyrus (Brodmann Area 6). These results suggest that, on one hand, different cerebral areas in deaf and hearing subjects mediate processing of printed letters and, on the other hand, common cerebral areas are activated in deaf signers when they are engaged in processing fingerspelled or printed letters.

Brain↗

PubMed2003

Improved mental rotation by near-sighted subjects.

Several studies have shown significant correlations among factors such as sex, age, and hormone levels with performance on mental rotation tasks. To perform spatial rotation also seems to be related to cognitive abilities such as musical skills. The present experiment investigated a possible relationship for enhanced spatial abilities, as observed in near-sighted subjects, with mental rotation performance. 39 near-sighted and 21 normal-sighted subjects were tested on a mental rotation task using two-dimensional representations of three-dimensional objects. Near-sighted subjects displayed fewer errors in possible rotations than normal-sighted subjects. There was no difference in errors between groups in identification of mirror images ("impossible rotations"). Results were interpreted in terms of a relation between enhanced reliance on nonvisual information by near-sighted subjects and improved spatial representation.

Adult↗