Biomedical subjects

M Brouchon

Publications and source records attributed to M Brouchon.

4 recordsLinked to original sources

PubMed1992

Perception of optical flow in cortical blindness: a case report.

Motion perception was studied in a subject with bilateral lesion of the visual cortex, involving severe damage to cortical areas V1 and V4, but with no apparent damage to visual associative areas situated in occipito-parietal and lateral occipito-temporal (presumably V5) zones. He was able to perceive optical flow motions simulating motion in depth in "blind" parts of his visual field, provided that the stimulus-onset was temporally dissociated from its motion. Moreover, he was able to discriminate between different velocities and directions of motion. The results suggest that perimetrically "blind" parts of the visual field in this patient have true capacities to process visual motion. They are discussed in reference to the subject's ability to move freely in his environment and in reference to the role of extrastriate visual pathways in visual motion processing.

Acceleration↗

PubMed1992

Head turning versus manual pointing to auditory targets in normal subjects and in subjects with right parietal damage.

Head turning and manual pointing to auditory targets have been studied in normal subjects and in subjects with right parietal damage. Important differences were found between these two types of movement. (1) In brain-damaged subjects, audiospatial manual pointing deficit patterns and audiospatial head turning deficit patterns were dissociated. Moreover, head turning deficits tended to appear peripherally in both auditory hemifields, while manual pointing deficits tended to appear unilaterally in the left hemifield. (2) In normal subjects, at all tested eccentricities in both hemifields, head turning performances showed a characteristic undershooting of auditory targets when compared to manual pointing. Results are discussed in terms of differences between the processes underlying audio-motor tasks that involve the head and tasks that involve the hands.

Adult↗

PubMed1992

[Interhemispheric transfer in multiple sclerosis. Morphofunctional correlations].

Signs of cerebral disconnection, especially left ear suppression to dichotically presented verbal stimuli, have been reported in multiple sclerosis patients and found to be correlated to morphological atrophy of the corpus callosum on magnetic resonance imaging. To reinvestigate this issue, 26 patients satisfying criteria for definite multiple sclerosis were proposed 3 tasks aimed at evaluating interhemispheric function: a dichotic listening task, a motor finger-tapping task and a sensory transfer task. Performance at these tasks suggested impaired callosal function in MS patients, compared to normal controls. Callosal morphology was assessed on midsagittal MRI sections using a digitalised method of partition of the callosal area into 6 subregions and automatized surface measurements. Results of correlations between task performance and callosal areas showed a significant correlation between total callosal atrophy and severity of interhemispheric impairment on each functional task. Moreover, impaired motor transfer was specifically related to atrophy of the anterior callosal regions. These results suggest that MS patients may constitute a suitable population to studying interhemispheric transfer of information through the callosal commissure and that this approach may be useful in the clinical management of MS patients.

Adolescent↗

PubMed1992

[Ambulatory autonomy and visual motion perception in a case of almost total cortical blindness].

A 37-year-old man experienced cortical blindness following a bilateral stroke in the territory of the posterior cerebral arteries. Four years later, the measurement of visual field defects (Goldmann perimeter) showed persistence of bilateral blindness with a 2-degree preservation of macular vision and a perifoveal sparing between 10 to 30 degrees of eccentricity in the left inferior quadrant. Despite this visual impairment, the subject was able to perform visually-guided locomotion. Moreover he consciously perceived visual motion in the blind parts of his visual field. CT and MRI showed a lesion involving most of the striated cortex. The visual cortex located in the internal occipito-parital regions was relatively spared. The contribution of this structure to extra-striated vision of motion is discussed.

Adult↗