Biomedical subjects
Publications and source records attributed to C Capron.
Four different MRI techniques of volumetric evaluation were applied in 10 healthy females and compared. The results have shown that not all techniques were interchangeable, but that the results of two groups of methods are not statistically different.
Since the first postmortem report of sex-related differences in the size of the human corpus callosum, a number of studies on sex differences have been published, but results conflicted. The aim of this review was not to assess the possible existence and magnitude of sex variations in the size of the corpus callosum but to analyze methodological differences in several studies using Magnetic Resonance Imaging to investigate the sexual dimorphism in the size of the corpus callosum. Methodological problems arise at several steps of the method: sampling, imagery techniques, and measurements. Moreover, the means of callosal areas obtained by the nine reported studies are significantly different. The hypothesis that methodoiogical differences could explain these differences is supported by statistical results. A common method for investigating sex-related differences in callosal morphology appears necessary to resolve the question of a real sexual dimorphism of the corpus callosum and its subregions.
Previous post-mortem studies (Aboitiz, F., Scheibel, A.B., Fisher, R.S., Zaidel, E., 1992. Brain Res. 598, 154-161 and Aboitiz, F., Scheibel, A.B., Zaidel, E., 1992. Brain 115, 1521-1541) have shown an inverse association between asymmetry in perisylvian areas and the size of a specific segment, the isthmus, of the corpus callosum (CC) in males. The purpose of this work was to study in vivo the association between hemispheric asymmetry and the total size of the CC in 35 right-handed subjects (16 males, 19 females; mean age 24.9 +/- 3.9). An MRI scan was performed for each subject. The area of the right (RH) and left (LH) hemispheres were measured from images in the sagittal plane and the area of the CC from images in the mid-sagittal plane. The index of hemispheric asymmetry was absolute value((LH - RH)/[(LH + RH)/2]). There was a negative correlation between the absolute value of hemispheric asymmetry and the size of the CC in males (r = -0.55, P = 0.03) but not in females (r = -0.20, P = 0.42). These findings, like those of Aboitiz et al. (Aboitiz, F., Scheibel, A.B., Zaidel, E., 1992. Brain 115, 1521-1541), suggest a sex-dependent decrease in interhemispheric connectivity with increasing hemispheric asymmetry.
A study of reaction time in six tests (speed of simple identification, simultaneous and sequential letter identification, simultaneous and sequential stimulus word matching, and semantic verification) was carried out on 130 children aged 7 to 12 years. Subjects were tested Monday, Tuesday, Thursday, and Friday, using a cross-sectional design. The answers to each of the tests are binary in nature (Yes/No) measured by the recording of a click one of the two buttons of a microcomputer. Controlled variables were age, failure, sex, and day of test. The greatest percentage of the variance produced by the data was due to the age (typically 25%). The percentage attributable to the "day of test" (typically 5%) is hence masked by the variance due to the other factors. The method proposed herein makes it possible to isolate the percentage of the variance for the variable "day of test" alone and to provide evidence for a circaseptan effect on reaction time. It used a regressive correction on predominant variables. This effect shows performance is best on Thursday and weakest on Monday, the amplitude of the weekly rhythm being related to the task.
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A dot-filling test was used to assess hand performance in two populations of French children. In the first experiment, the effect of sex, age and handedness on hand performance was examined (1742 children). Age was related to the degree of laterality, but girls were less lateralized than boys. The second experiment (200 children) showed that the surprising sex differences cannot be explained by the group testing procedure. Underlying processes leading to performance in the dot-filling task are probably different from those involved in other tests generally used for children.
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