PubMed Health⌕ Search

Biomedical subjects

R Bruyer

Publications and source records attributed to R Bruyer.

At least 19 recordsLinked to original sources
PubMed1992

[Memory disorders and symptoms of frontal dysfunction in 29 patients operated on for an aneurysm of the anterior communicating artery].

Twenty-nine patients operated for an aneurysm of the anterior communicating artery have been submitted to short-term and long-term memory tests and to tests said to be sensitive to frontal lobe dysfunction; anosognosia was also studied. Their performance, as compared to that of 29 matched control subjects, revealed: (a) that this neurological condition induces often memory deficits (with anosognosia) and, even more often, signs of frontal dysfunction; (b) that these deficiencies are not homogeneous, however; and (c) that the classical amnesic syndrome can be observed in some cases. It appears useful to make an in-depth analysis of memory deficits of this kind of patients to reach a better understanding of normal memory processes.

Adult↗
PubMed1991

Covert face recognition in prosopagnosia: a review.

Prosopagnosia, a spectacular face agnosia, is generally detected and discussed on the basis of explicit or overt performance of the subjects. However, recent observations suggest that an overt response is probably not sufficient to determine what is and what is not preserved in the cognitive processing of faces by prosopagnosia. Indeed, signs of covert knowledge have been evidenced in some, but not all, subjects, indicating that they are still able to use representations they cannot use overtly. Empirical data, showing that the nature of prosopagnosia is a more complex phenomenon than has been thought and that the processing models should be adjusted accordingly, are reviewed.

Agnosia↗
PubMed1991

Influence of physical and semantic information in a categorisation task of fragmented forms.

Two experiments were carried out to investigate the influence of structural and semantic information in the categorisation of visual forms. In experiment 1 the stimuli were pairs of 'well structured' or 'poorly structured' fragmented forms differing in structural properties including convexity, collinearity, and closure of the elements, and in their 'nameability'. The influence of structural and semantic information was tested by means of a task involving the presentation to both visual hemifields separately of stimuli having within-category physical similarity. For well structured forms, subjects were asked to judge if two sequentially presented forms belonged to the same semantic category. For poorly structured forms, subjects were required to decide if two stimuli belonged to the same previously learnt category of forms. For the two types of stimuli, one category was composed of physically similar items, and the other was composed of physically dissimilar items. The results show a marked advantage for the category composed of physically similar forms when the stimuli are well structured but no differences between the two categories when the stimuli are poorly structured. This suggests a facilitation in the computation of global shape information for forms having collinear and closed elements. The only effect of semantic information was a tendency towards a right visual field advantage for same-category pairs of well structured forms. The pattern of results for well structured fragmented forms (experiment 1) and forms in which fragments had been joined in order to complete the contour (experiment 2) were similar, suggesting that structured incomplete forms can be processed in the same way as forms having a continuous contour. Hypotheses about the organisational processes of forms are proposed in the discussion.

Adult↗
PubMed1991

A clinical test battery of face processing.

This paper proposes a clinical tool to investigate face processing by brain-injured patients. A test battery is described, which is organized according to the cognitive model of face recognition proposed by Bruce and Young (1986), as well as Ellis' (1981) suggestion of an early facial decision stage. The battery consists of 6 basic tests tapping several loci of the cognitive architecture, together with 13 optional subtests provided to explore in greater depth defects eventually detected by means of the basic tests. The performances of 72 normal subjects are described and the battery is then illustrated by the analysis of performance by a prosopagnosic subject.

Adult↗
PubMed1990

The field-by-length effect in word processing: a failure to confirm.

It has been shown that the left hemisphere superiority for processing words applies only to long words by Young and Ellis (1985). These authors defined the length as the number of letters. Bruyer and Janlin (1989) compiled supporting evidence by contrasting the number of letters and the physical size of the stimuli: Short words were made as long as "long" words by the use of blank spaces between the letters. In the present study, another control was used: The physical size of the stimuli was manipulated by means of the viewing distance (nearer short words were as long as the long words). Thirty-six subjects were submitted to 720 trials in which two words appeared for 150 ms, one in each visual hemifield. The subject reported the two words in a defined order. The results did not clearly support the previous studies.

Analysis of Variance↗
PubMed1989

Lateral differences in lexical access: word length vs. stimulus length.

A. W. Young and A. W. Ellis (1985, Brain and Language, 24, 326-358) have shown that visual length of stimuli is a major determinant of lateral differences in word processing. They suggest that the right hemisphere must first code the words in graphemic form and, therefore, is affected by the word length. They demonstrated that visual length is best defined as the number of letters. The present experiment was conducted with 36 normal subjects to test this definition of the visual length by contrasting the number of letters and the physical length in the visual field. Spaces were inserted in the short words (4-letter) so that they matched the physical length of the long words (7-letter). Our results replicated those of Young and Ellis and confirmed that visual length can be defined by the number of letters. In addition, the imagery value of the words tended to affect this Hemifield x Length effect, a result not obtained by Young and Ellis.

Adult↗
PubMed1989

Attention and brain damage: a clinical study of response latency under various degrees of uncertainty.

Wyns and Bruyer in 1988 proposed a visual attention test that is easy to use and sensitive both to the age of the subjects and the level of uncertainty about the response required. This test was designed as a fine gauge of attention deficits in brain-damaged subjects with poorly structured complaints. We present here a preliminary application of the test to a group of 48 such persons. Analysis of response accuracy indicated that 27 subjects were deficient in this respect. Of the 21 remaining subjects whose reaction times were analyzable, only one-third appeared as entirely normal.

Attention↗
PubMed1989

Effects of age, brain damage, and task complexity on the sensitivity of reaction time to the delay between the warning signal and the stimulus.

Four age groups of normal subjects were given a visual reaction time task with three levels of uncertainty. The speed of response improved when the interval between the auditory warning signal and the imperative visual stimulus increased in the range from 1 to 3 s. This delay effect decreased when the level of uncertainty was increased, irrespective of the age. This phenomenon was globally reiterated in two control experiments. A set of 21 brain-injured subjects with clinical complaints concerning attention was also given the test. These subjects were also able to benefit from the delay. The benefit was affected neither by the task complexity nor by the slowness of the reaction times.

Adolescent↗
PubMed1988

Level of uncertainty and brain damage: a reaction time test of attention for clinical use.

The goal of this study was to search for effects of aging on visual reaction-time task designed to evidence subtle attentional disturbances in brain-injured subjects. Experiment I showed that the speed of response was affected by the level of task complexity (simple versus two-choice versus four-choice reaction times, with a forced response), irrespective of age. A main effect of age and effects of the responding finger and/or of the spatial location of the stimulus also emerged. Experiment II showed that the complexity effect was not an artifact resulting from the order of the conditions, and Exp. III, by means of a go/no-go procedure, showed that the effect of the location of the stimulus in Exp. I was due to central cognitive operations dealing with the choice of the response finger rather than with visuospatial operations about the stimulus.

Adolescent↗
PubMed1988

Brain asymmetries in face processing: a critical review of electrophysiological studies from a psychological point of view.

The few studies dealing with physiological (EEG, VEP) brain asymmetries in the processing of faces by neurologically intact subjects are critically reviewed from a psychological point of view. It emerges that a more careful selection of the cognitive tasks is needed, along with more prudent statistical planning. The difficulties of comparing physiological and behavioral asymmetries are also emphasized.

Brain↗
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↗