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Biomedical subjects

F Leporé

Publications and source records attributed to F Leporé.

15 recordsLinked to original sources
PubMed1981

Inter-hemispheric competition during postnatal development.

Functional asymmetries between the two sides of the brain, a well documented phenomenon in species as different as frog and man, are thought to arise from genetically determined anatomical differences which, at least in humans, may be observed in utero. Functional asymmetries can, however, be reversed after damage to one side of the brain. Here we report that rearing of kittens with the optic chiasm sectioned and one eyelid sutured during postnatal development results in a functional asymmetry in the corpus callosum, a bidirectional pathway which inter-connects the visual cortices on the two sides of the brain. Visual input originating on the side of the brain ipsilateral to the sutured eye loses the ability to influence cells on the other side of the brain. Conversely, visual input originating on the side of the brain ipsilateral to the exposed eye markedly increases its influence in the other hemisphere.

Animals↗
PubMed1981

[Interhemispheric competition during postnatal development].

The corpus callosum is a bidirectional pathway interconnecting the visual cortices on the two sides of the brain. Rearing kittens with the optic chiasm sectioned and one eyelid sutured during early development results in a functional asymmetry in this pathway. Visual input originating on the side of the brain ipsilateral to the sutured eye looses the ability to influence cells on the other side of the brain. Conversely, visual input originating on the side of the brain ipsilateral to the exposed eye markedly increases its influence in the other hemisphere. These physiologic findings are paralleled by anatomic results indicating that the terminal field of the corpus callosum is markedly expanded in the cortical hemisphere ipsilateral to the deprived eye and reduced in the other hemisphere.

Aging↗
PubMed1981

[Role of the contralateral cortex on the receptive field properties in the visual cortex of cats].

The aim of this series of experiments was to evaluate the receptive field properties of visual cells receiving part of their input the corpus callosum. Normal (control) and chiasma sectioned cats were recorded using conventional methods. The recording sites were the 17-18 border and the lateral suprasylvian (LS) cortex. The results indicated (a) the ocular dominance distribution was shifted towards the ipsilateral eye in the split chiasma cats; (b) orientation tunning and/or directional specificity were identical for the two eyes; (c) R.F. positions of binocular cells were also similar for each eye and were clustered near the vertical meridian, which they sometimes straddled; (d) R.F. sizes were larger in L.S. than in primary visual cortex but generally of equal dimensions for each eye. The results are interpreted with respect to the various functions which have been postulated for the corpus callosum.

Animals↗
PubMed1981

[The role of the corpus callosum and other commissures in the interhemispheric transfer of visual information].

In order to assess the contribution of the lateral suprasylvian area and subcortical pathways other than the corpus callosum in learning and interhemispheric transfer, a series of studies was undertaken in the cat. Groups of animals which received different types of cortical and subcortical lesions were tested for learning and interocular transfer of visual pattern discriminations. Results have shown that : 1. the lateral suprasylvian area is of equal importance in learning and transfer as areas 17, 18 and 19; 2. in the absence of the corpus callosum, other commissures could preserve interocular transfer of visual information. The results obtained on commissurotomized neonate kittens clearly support this assumption.

Animals↗
PubMed1980

Abolition of optokinetic nystagmus in the cat.

Combining a behavioral and a surgical manipulation, namely complete visual deprivation with surgical section of the optic chiasm, results in the abolition of optokinetic nystagmus in the cat. This basic optomotor reflex remains relatively unaffected by either of these manipulations performed singly.

Animals↗
PubMed1976

[Neurobehavioral study of colliculectomized monkeys].

A battery of neurological tests was administered to normal and colliculectomized monkeys to determine the effect of the lesion on visually guided behavior, acoustically guided behavior, general locomotor performance and affective behavior. The tests were given at one week and three months post-operatively. The behaviors of the animals were filmed and the results were derived from a careful analysis of the films. The operated monkeys showed important deficits on most tests. After three months a considerable improvement was noted in many functions. However, some behaviors were still totally or partially abnormal. An attempt is made to relate the completeness of the collicular resection and the duration of some of these symptoms.

Animals↗
PubMed1975

Rod and cone sensitivity in destriate monkeys.

Photopic and scotopic spectral sensitivity of rhesus monkeys was determined before and after complete removal of the striate cortex. The monkeys were required to choose between a white and a series of monochromatic stimuli distributed throughout the visible spectrum. A modified method of limits was used to determine the psychophysical point of subjective equality at which the colored and white lights were perceived as being equally bright. The preoperative results indicated that the method of testing was appropriate to determine spectral sensitivity since the curves obtained compared favorably to the theoretical sensitivity curves. Postoperatively, the scotopic sensitivity curve was normal whereas the photopic curve was completely displaced towards the scotopic curve. The results as indicating that cone information is processed by the geniculo-striate visual system whereas the extra-striate structures receive their input mainly from the rod receptors of the retina.

Adult↗
PubMed1975

Spectral sensitivity in a female Cebus Griseus.

The photopic spectral sensitivity of one female Cebus Griseus was determined to complement published results showing that this monkey did not demonstrate the red deficiency typical of most New World monkeys. A modified method of limits was used to determine S's perceived brightness of different monochromatic stimuli. The results suggest that this monkey might be a normal trichromat.

Animals↗