RESUMEN
Visual evoked potentials were analyzed and general and local electroretinography carried out in 83 children and adolescents (145 eyes) aged 7 to 16 with different ocular diseases. The latencies of P100 component of evoked potentials reliably varied in different clinical groups. The role of electrophysiological studies in the differential diagnosis of pathological processes of different localization is shown, as is the role of time characteristics of evoked potentials in discrimination between the functional and organic disorders in the ocular system.
Asunto(s)
Electrorretinografía , Potenciales Evocados Visuales , Miopía/congénito , Enfermedades del Nervio Óptico/diagnóstico , Enfermedades de la Retina/diagnóstico , Adolescente , Factores de Edad , Niño , Diagnóstico Diferencial , Humanos , Miopía/diagnóstico , Enfermedades del Nervio Óptico/fisiopatología , Enfermedades de la Retina/fisiopatologíaAsunto(s)
Estado de Conciencia/fisiología , Trastornos de la Sensación/fisiopatología , Inconsciente en Psicología , Percepción Visual/fisiología , Adolescente , Adulto , Astenopía/fisiopatología , Niño , Electroencefalografía , Potenciales Evocados/fisiología , Humanos , Estimulación Luminosa/métodos , Valores de Referencia , Procesamiento de Señales Asistido por ComputadorRESUMEN
Studies of visual evoked potentials (EP) to chess field reversion in 80 children (147 eyes) aged 5 to 16 with congenital myopia have demonstrated significant deviations from the reference values of the P100 component to all the stimuli. The clinical groups with various changes in the fundus oculi were found to differ by the P100 component amplitude when chess fields with cells 112 and 56 angular min in size were shown. The number of discrepancies between the clinical vision acuity and its assessment from the threshold EP grew from 19% when no changes in the fundus oculi were seen to 54 and 61% when myopic and non-myopic changes were detectable in the fundus oculi. These data evidence that EP amplitude to chess field reversion better reflects the status of the retino-cortical route than the central vision acuity.
Asunto(s)
Potenciales Evocados Visuales , Miopía/congénito , Agudeza Visual , Adolescente , Factores de Edad , Niño , Preescolar , Humanos , Miopía/fisiopatologíaAsunto(s)
Ambliopía/fisiopatología , Potenciales Evocados Visuales/fisiología , Miopía/fisiopatología , Adolescente , Ambliopía/complicaciones , Ambliopía/congénito , Ambliopía/diagnóstico , Niño , Preescolar , Diagnóstico Diferencial , Humanos , Miopía/complicaciones , Miopía/congénito , Miopía/diagnóstico , Estimulación Luminosa , Pronóstico , Tiempo de Reacción/fisiología , Factores de Tiempo , Agudeza Visual/fisiologíaRESUMEN
Visual evoked potentials (EPs) in response to sinusoidal gratings of different contrast, with spatial frequencies of 0,5-15 cycles/grad presented in "on-off" order, were studied in six grown-up subjects with normal sight. Peak latencies of all EP components and the amplitude of the relatively early N95-130-P-120-190 complex increased with increasing spatial frequency. Presentation of low-frequency gratings led to an increase of the late EP complex (N150-230-P 210-290). The EP configuration in response to sinusoidal gratings of different spatial frequencies determined by the dominance of the early or late EP complex is supposed to reflect involvement of independent mechanisms of processing of information on low or high spatial frequency differently localized in the visual cortex.
Asunto(s)
Potenciales Evocados Visuales , Vías Visuales/fisiología , Percepción Visual/fisiología , Adulto , Humanos , Psicofísica , Tiempo de Reacción/fisiología , Factores de TiempoRESUMEN
In subjects with normal vision, differences have been detected in the reactions of the main components (P100, N150, P200) of evoked potentials recorded in the Oz and TPO leads, to homogeneous stimuli, chess fields with different sizes of cells and grids differing in area and the number of orientation stripes. The data obtained are discussed in the light of V.D. Glezer's hypothesis on specialized information processing in the visual and posterior associative cortical areas and concepts on the existence of separate channels of processing different image properties.
Asunto(s)
Corteza Cerebral/fisiología , Potenciales Evocados Visuales , Percepción Espacial/fisiología , Adolescente , Asociación , Mapeo Encefálico , Percepción de Forma/fisiología , Humanos , Orientación/fisiología , Tiempo de Reacción/fisiología , Lóbulo Temporal/fisiología , Corteza Visual/fisiologíaRESUMEN
A study was made of age peculiarities of EPs to spatially structurized stimuli in the shape of chess fields with different dimensions of their cells in children and juveniles with normal vision, aged from seven to seventeen. Heterochroneity has been established in maturation of EPs to a homogeneous and a spatially structurized stimuli. In accordance with the criterion of "maturity" of the EP to a spatially structurized stimulus, an enhanced probability of "mature" EPs appearance was observed with age, from 0.23 in seven year old to 0.75 in 11 to 17 years old. Correspondence was shown of age EP dynamics to age changes of the visual system sensitivity to deprivation.
Asunto(s)
Potenciales Evocados Visuales , Corteza Visual/fisiología , Adolescente , Factores de Edad , Ambliopía/fisiopatología , Niño , Humanos , Estimulación Luminosa/métodos , Privación Sensorial , Percepción Visual/fisiologíaRESUMEN
For the analysis of plastic rearrangements in the visual system under the influence of different conditions of adaptation and early deprivation of objective vision, VEPs to checkerboard patterns with various check sizes were studied in subjects with normal vision and with amblyopia resulting from a congenital cataract. Sensitivity of P 180-230 component to the check sizes was revealed as well as a shift of its optimum toward bigger sizes following a transition from the light to the dark adaptation. In amblyopic subjects, in response to the checkerboard patterns the amplitude of P 80-120 component significantly increased, whereas that of P 180-230 decreased, with a shift of its optimum toward bigger check sizes. Informational significance of VEP waves and possible mechanisms of amblyopia are discussed.
Asunto(s)
Ambliopía/fisiopatología , Percepción de Forma/fisiología , Privación Sensorial , Visión Ocular/fisiología , Vías Visuales/fisiología , Adolescente , Ambliopía/etiología , Catarata/complicaciones , Potenciales Evocados , Humanos , Vías Visuales/fisiopatología , Percepción Visual/fisiologíaRESUMEN
The influence of visual deprivation on the recovery cycle of the primary positive component (P1) of the visual evoked potential under conditions of dark or light adaptation was studied on eight adult unanaesthetized rabbits raised in darkness. The EP recovery cycle of visually deprived animals, studied in conditions of dark adaption, reveals a significant shortening (as compared with normal) of the initial depression period of testing responses. At the same time a significant lengthening of the facilitation phase and a sharp exaltation of the testing responses is observed. Unlike the norm, transition from dark- to light-adaptation of the deprived animals does not bring about any essential changes in the recovery cycle. An assumption is made that visual deprivation leads to a reduced effectiveness of the processes of successive inhibition. It is also assumed that enhanced excitabilty of a part of the cortical elements, apparently in the system of recurrent excitation, is likely to be one of the consequences of deprivation.
Asunto(s)
Encéfalo/fisiología , Privación Sensorial , Visión Ocular/fisiología , Percepción Visual/fisiología , Animales , Potenciales Evocados , ConejosRESUMEN
Rabbits raised in the dark revealed a significant decrease in amplitude and an increase in temporal parameters of the main components of evoked potentials (EP) to diffuse flashes under dark adaptation, as well as a facilitation of the postprimary components and intensification of the sensory after-discharge. In contradistinction to normal, the deprived animals exhibited no augmentation of the amplitude of the EP primary positive phase at higher intensity of the flahses or any significant decrease in the EP amplitude under light adaptation conditions. It is suggested that early deprivation brings about a decrease in the number of elements reacting to a specific stimulation, especially of elements working in photopic conditions; the decrease in the number of activated afferent inputs in the visual cortex due to deprivation reduces the effectiveness of the processes of successive inhibition; at the same time there is an increase of synchronic influences of the thalamic inhibitory mechanisms of the cortex.