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Biomedical subjects

R Bruyer

Publications and source records attributed to R Bruyer.

At least 55 records · Page 3Linked to original sources
PubMed1987

Race categorization and face recognition stages in the processing of laterally displayed unknown faces.

Bruyer and Dussart (1985) have recently shown that the "race effect", i.e. the difficulty in recognizing faces issuing from an ethnic group different from that of the subject, is limited to the right visual field. They suspected familiarization to be responsible for this asymmetry. In Exp. I, we tested this hypothesis by repeating the experiment of Bruyer and Dussart with a greater number of trials. A sample of 16 subjects were given the task of recognizing black and white faces laterally displayed for 180 msec. No laterality effect appeared, and the race effect was observed to an equal degree in each hemifield at all stages of the experimental session. It could thus be that various kinds of familiarization must be distinguished. In Exp. II, with 16 new subjects, the black and white faces were mixed so that the subjects had first to perform racial categorization, then a recognition. This time, an advantage of the left field appeared, the race effect was larger in the right than in the left field, and the race effect decreased with familiarization in the left field only. Two complementary experiments with 24 and 16 subjects showed that this phenomenon was not explainable by laterality effects in the early racial decision operation, but well by a lateralized effect of tasks requirements.

Adult↗
PubMed1987

Experimenters' expectation and subjects' knowledge of hypotheses in simple reaction time to lateralized visual stimuli.

Researchers in experimental neuropsychology usually recruit "naive" normal subjects. In this preliminary study, we attempt to consider the role of such a selection. Sixty-four normal, right-handed subjects were enlisted for an experiment on simple reaction times to laterally displayed visual stimuli for which, according to the literature, no cerebral asymmetry is expected. In the course of the experiment, the subjects were "informed" about the hypothesis of the current research. Four subgroups of 16 subjects received four different kinds of information, one for each subgroup; moreover, in each subgroup, half the subjects were examined by an experimenter who hoped to modify the performance and the other half by an experimenter who supposed that information would not affect the behavior of the subjects. The results do not reveal any effect of instructions or experimenters and are discussed to plan future research.

Adult↗
PubMed1986

Lateral differences in visual processing: relative vs exclusive hemispheric specialization.

In some cases, lateral differences reveal cerebral hemispheric asymmetry in cognitive operations. Such asymmetry can indicate the absolute dominance of one hemisphere, the "dominant" hemisphere managing the task whatever the hemisphere of entry. Consequently, a commissural transfer is needed for stimuli sent to the non-dominance as only relative: the hemisphere receiving the stimulus is able to manage it, but the dominant one can do it more accurately and/or faster than the other. These two models should be able to be distinguished by means of a correlational study and a study of the stimulated hemifield X responding hand interaction. The latter is based on the assumption of contralateral control of slight distal movements. These two methods were applied to data derived from 24 right-handed normals who were given three tasks for which right visual field superiority was expected: word/non-word discrimination, vowel/consonant classification of letters, and odd/even categorization of numbers. The stimuli were displayed centrally or laterally for 150 ms. The data indicated that the right-field superiority for words resulted from a relative dominance, that the right-field advantage for numbers resulted from an absolute dominance, and that no asymmetry emerged for letters.

Adult↗
PubMed1985

Anatomical and behavioral study of a case of asymptomatic callosal agenesis.

This paper presents radiological and behavioral observations of a case of asymptomatic congenital agenesis of the corpus callosum. CT scan data indicated that a small portion of the corpus callosum might have been preserved, although this is difficult to demonstrate with the usual criteria. Nuclear magnetic resonance showed the small preserved portion on the sagittal plane. The results of the behavioral studies agree well with already published data: the agenesis of the callosum does not induce a split-brain syndrome but does cause slight motor disturbances, an improvement of the ipsilateral paths of control, and the development of extra-callosal interhemispheric pathways.

Adolescent↗
PubMed1985

Lateral differences in the race effect in face recognition.

In experimental psychology, the difficulty people have in discriminating or recognizing faces of people not included in their own ethnic group is called the "race effect." A survey of the literature reveals several hypotheses and it is suggested that a neuropsychological investigation of the race effect could help clarify the situation. In this preliminary study, black (N = 8) and white (N = 16) right-handed subjects were given the task of recognizing black and white faces, laterally displayed in the right or left visual field for 180 msec. The race effect was observed for white people for stimuli displayed in the right field only. Some hypotheses of experimental psychology are reconsidered in the light of these results.

Adult↗
PubMed1985

Are lateral differences in word processing modulated by concreteness, imageability, both, or neither?

The classic right visual field superiority for the processing of words by normal subjects is reduced when stimuli are highly imageable or concrete. Given that these two properties are correlated, imageability and concreteness are tested separately in order to decide which is determinant. In the first experiment, 16 normal subjects were given a lexical decision task with laterally visually displayed stimuli (360 items); in the second experiment, 16 other normal subjects were given a task of reading laterally displayed words (180 items). In both experiments, the usual right field advantage emerged. It was affected neither by imageability nor by concreteness in the first experiment. In the second, the right field superiority appeared, except for highly imageable words, in males only, but this interaction was not clearly interpretable. Analysis of errors suggests that the right hemisphere could be sensitive to the imageability of words and the left to their concreteness.

Adult↗
PubMed1984

Lateral differences in face processing: task and modality effects.

According to Sergent and Bindra (1981), the literature suggests that faces are better processed in the right visual field for identification tasks and in the left field for discriminative tasks. We have tried to test this hypothesis directly along with the degree of generalization in tactile modality. A sample of 16 young normal subjects were given a face identification task in the visual and tactile modalities. The faces were first associated with names and then laterally displayed for 180 msec. in the visual hemifield or haptically explored. The subjects were asked to depress one button for two stimuli and another button for the other two. Another group of 16 subjects was similarly given a discriminative task: same-different judgments were required on successive pairs of stimuli (central stimulus first and then lateral stimulus). The results agreed well with the hypothesis as regards the visual modality. The lack of laterality effects in the tactile tests could be due to procedural defects. It also appeared that the degree of familiarization with stimuli was an important variable, at least in the visual modality.

Adult↗
PubMed1984

Lateralized brain processing of faces and facial expressions: level of blurring and specificity.

Earlier papers showed that the relative impairment in response to faces and facial expressions shown by right-brain-damaged subjects was reduced by using blurred stimuli. Reanalysis of these data supports the hypothesis of differential hemispheric sensitivity to spatial frequency of inputs and shows processing of expressions partially depends on the processing of faces.

Brain Damage, Chronic↗
PubMed1983

Hemispheric differences in the voluntary inhibition of movement.

Twenty normal, twenty left-, and fifteen right-brain injured subjects, all right-handed, were assigned a sequence of voluntary inhibition of 23 movements. The inhibition lapse was recorded. Statistical analyses indicated a high performance in the normal and a deficient performance in left-brain injured subjects, no influence of the neurological symptoms on groups' achievement, a handicap in the subjects affected by a frontal lesion in the right brain, a hierarchical clustering of items varying according to the groups, and an organ-group interaction.

Brain Diseases↗
PubMed1983

A case of prosopagnosia with some preserved covert remembrance of familiar faces.

This paper presents the detailed analysis of a case of prosopagnosia in a 54-year-old male farmer following bioccipital vascular disease. In-depth clinical investigations confirmed the diagnosis of prosopagnosia and revealed the absence of any associated defect, except for a slight aspecific disturbance of the short-term memory. Further study of this case indicated that the trouble was not concerned with the class of complex visual stimuli, was not even concerned with facial expressions or unknown faces, was not a perceptual defect, but was related mainly to the operation of individualization. The memory hypothesis was thus retained and supported. Moreover, exploration of the difficulty indicated that the deficiency was limited to defective access to conscious information concerning faces and information associated with these faces (name, context, etc.), effectively stored in memory.

Agnosia↗
PubMed1983

Lateral differences for person perception: effects of task on visual processing of handwriting.

Sergent and Bindra suggested that identification of faces using few different stimuli engages mainly the left hemisphere and, conversely, that discrimination of faces using more stimuli engages mainly the right hemisphere. The present study examined whether this suggestion holds for the perception of handwriting which, like faces, authorizes the perception of "persons". Normal adults were presented stimuli consisting of a word written in various hands, laterally displayed for 180 msec. Exp. 1 (identification) was conducted with 8 subjects, who were asked to identify (push-button) four different stimuli by means of an associated first name. Exp. 2 (discrimination) was conducted with 16 subjects who were asked to make same/different judgments between a central stimulus and a lateral one under three experimental conditions, normal, mirror-reversed, and inverted presentations of both members of the pair. The results suggest that the direction of asymmetry depends more on the amount of stimuli than on the task and that familiarity with the stimuli is an important variable.

Adolescent↗
PubMed1982

[Right hemisphere lesion and directional indication in a visuoconstructive task].

We test the hypothesis that the divergences between Hecaen and Assal (1970) and Gianotti et al (1977) as regards the efficiency of indications supplied together with drawings to patients with unilateral lesion are due to the topological or directional nature of these indicators. We submit subjects with cerebral damage to a test involving copying cubes and non-significant drawings by opposing these two types of indication and also resorting to the procedure of Pillon and Lhermitte (1978). The results demonstrate that the topological or directional character of the indicators used can account for the differences between these two sets of findings. Finally, the results tend to show that the left hemisphere basically controls the manipulatory or executive side of the visuo-constructive task, whilst the right takes over its executive and perceptive aspects in conjunction.

Apraxias↗