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F Gonzalez-Aguilar

Publications and source records attributed to F Gonzalez-Aguilar.

5 recordsLinked to original sources
PubMed1981

Late spreading of excitation in the lateral geniculate nucleus following visual deafferentation is independent of the size of retinal lesions.

Late spreading of excitation occurs in the lateral geniculate nucleus following partial retinal lesions. The extent of spreading remained the same when reducing the size of the lesions to one fifth. This is incompatible with the idea that the spreading could be caused by displacement of normal cells into the deafferented area as a consequence of transneuronal volume reduction.

Afferent Pathways↗
PubMed1981

Time-dependent decrease in the extent of visual deafferentation in the lateral geniculate nucleus of adult cats with small retinal lesions.

Small, round photocoagulator lesions of 3-6 degrees (0.6-1.2 mm) diameter were placed nasally on the retina of adult cats. Histological controls proved the complete destruction of all retinal layers within the lesions. Changes in lesion size by shrinkage of the retinal scar did not exceed 0.1 mm or 0.5 degrees. At different times after photocoagulation, single cells were recorded in layers A and A1 of the contralateral lateral geniculate nucleus (LGN) with tungsten microelectrodes. Acute lesions of this size completely deafferented single LGN cells in layer A whose receptive field (RF) area was within the lesion. Thirty days and more after coagulation, light-excitable cells were detected in the originally deafferented LGN region, with RFs in the immediate surround of the retinal lesion. The spontaneous activity and light excitability of these neurons were altered. The representation of 3-4 degrees retinal lesions at 20 degrees horizontal eccentricity was found to be completely filled in by excitation in the LGN. Excitation had spread from the unsevered parts of the retina into the region of deafferentation. Single cells with signs of multiple activation from more than one border region of the retinal lesion were occasionally detected.

Animals↗
PubMed1980

A functional sign of reorganization in the visual system of adult cats: lateral geniculate neurons with displaced receptive fields after lesions of the nasal retina.

High-intensity photocoagulator lesions placed nasally to the optic disc one eye destroyed all retinal layers and led to visual deafferentation of the lateral part of layer A in the contralateral lateral geniculate nucleus (LGN) of adult cats. The retino-geniculate topography was determined with vertical tungsten microelectrode penetrations through LGN layers A and A1 before and at different times after photocoagulation. Before the 20th day a border of light excitability was found in layer. A corresponding to the normal projection of the lesion onto the LGN. Deviations from the normal topographical organization were evident 30 days and later after photocoagulation. Cells were recorded within the deafferented part of layer A near to the border of deafferentiation which had receptive field (RF) centers displaced by more than two degrees of visual angle with respect to the normal retinotopy. During formation of the retinal scar no identifiable points on the retina were displaced in the same direction as the RF centers. The histological control of the retinal lesions proved that there was no potentially excitable tissue left to account for a spread of excitation into the lesion. Latency measurements after electrical stimulation of the optic tract and the visual cortex suggested a retinal input and a projection into the visual cortex for the LGN cells with displaced receptive field centers. RF center displacements up to five degrees at the border of the lesions indicated a lateral spread of excitation within the LGN up to 250 micron beyond normal.

Animals↗
PubMed1980

[Changes in the cat's visual system following retinal lesions. A functional reorganization in the mature central nervous system (author's transl)].

Layers of the lateral geniculate nucleus (LGN) of mature cats were completely or partially deafferentated by precisely defined photocoagulation of the retina. Single neuron recordings were performed with microelectrodes from an experimentally modified layer and compared with neurons from a normally innervated layer in the same animal. The spontaneous activity of cells after monocular deafferentation was severely reduced in the beginning and increased subsequently without reaching normal values within ten weeks. At this time the pattern of excitation and inhibition after light stimulation of the nondominant unsevered eye had completely changed. Twenty-seven days and later after coagulation of a part of the nasal retina light-excitable cells with displaced receptive fields were found in the LGN in the border region of the partial visual deafferentation. This indicated a lesion-induced lateral expansion of excitation by up to 200 microns within the LGN. Small, round retinal lesions initially caused a complete visual deafferentation of a certain region in the LGN. After 30 days and later visual excitation from the normally innervated surrounding was observed in cells which were not light-excitable during the first days after coagulation. Thus, while the retinal lesion itself did not substantially change, its representation within the LGN was distinctly reduced. The results indicate lesion-induced reorganization in the subcortical visual system of the adult cat. This might enable the system to a certain degree of compensation after loss of visual inputs. The transferability of these results to human pathophysiology has to be critically considered.

Animals↗