Academic journal article The Spanish Journal of Psychology

Coding of Luminance and Color Differences on Neurons in the Rabbit's Visual System

Academic journal article The Spanish Journal of Psychology

Coding of Luminance and Color Differences on Neurons in the Rabbit's Visual System

Article excerpt

The neuronal activity in the rabbit's visual cortex, lateral geniculate nucleus and superior colliculus was investigated in responses to 8 color stimuli changes in pairs. This activity consisted of phasic responses (50-90 and 130-300 Ms after stimuli changes) and tonic response (after 300 Ms). The phasic responses used as a basis for the matrices (8 × 8) constructed for each neuron included the average of spikes/sec in responses to all stimuli changes. All matrices were treated by factor analysis and the basic axes of sensory spaces were revealed. Sensory spaces reconstructed from neuronal spike discharges had a twodimensional (with brightness and darkness axes) or four-dimensional (with two color and two achromatic axes) structure. Thus it allowed us to split neurons into groups measuring only brightness differences and the measuring of color and brightness differences between stimuli. The tonic component of most of the neurons in the lateral geniculate nucleus showed linear correlation with changes in intensities; therefore, these neurons could be characterized as pre-detectors for cortical selective detectors. The neuronal spaces demonstrated a coincidence with spaces revealed by other methods. This fact may reflect the general principle of vector coding (Sokolov, 2000) of sensory information in the visual system.

Keywords: neuronal activity, perceptual space, vector coding, color perception

Se examinaron la actividad neuronal en la corteza visual, el núcleo lateral geniculado y el collículo superior del conejo en las respuestas a 8 cambios de estímulos de color en parejas. Esta actividad consistía en respuestas fásicas (50-90 y 130-300 Ms después del cambio estimular) y respuesta tónica (después de 300 Ms). Las respuestas fásicas empleadas como una base para las matrices (8 × 8) construidas para cada neurona incluían la media de picos/segundo en respuestas a todos los cambios estimulares. Todas las matrices fueron tratadas por análisis factorial y se pusieron de manifiesto los ejes básicos de espacios sensoriales. Los espacios sensoriales reconstruidos de las descargas neuronales pico tenían una estructura bi-dimensional (con ejes de brillo y oscuridad) o de cuatro dimensiones (con dos ejes de color y dos ejes acromáticos). Así, nos permitió dividir las neuronas en grupos que sólo medían las diferencias en brillo y los que medían las diferencias entre los estímulos en color y brillantez. El componente tónico de la mayoría de las neuronas en el núcleo geniculado lateral mostraron una correlación linear con los cambios en las intensidades: de ahí, estas neuronas se podrían caracterizar como pre-detectores para los detectores corticales selectivos. Los espacios neuronales mostraron una coincidencia con los espacios revelados por otros métodos. Este hecho podría reflejar el principio general de la codificación vectorial (Sokolov, 2000) de la información sensorial en el sistema visual.

Palabras clave: actividad neuronal, espacio perceptual, codificación vectorial, percepción del color

Over many decades of studying the visual systems of humans and animals, answers were found to many questions associated with the perception of color, intensity, forms, volume, movement and other typical visual stimuli. Studies were made of the pigments in the photoreceptors of the retina, the pathways and centers of the visual analyzer, and the receptive fields of various neurons. However, questions as to how the coding of color and brightness information was accomplished and how neurons react to brightness and color differences in the visual field, at the same time forming a spectrum of chromatic sensations, remain open and unresolved to this day. The hypothesis for vector coding of information in analyzers as proposed by Professor E. N. Sokolov attempts to answer these questions (Izmailov & Sokolov, 1991; Sokolov, 2000).

Psychophysical experiments on the categorizing of colors and the correlation of color differences by humans were the basis of research for the group under the leadership of Sokolov (Sokolov & Izmailov, 1984; Izmailov, Sokolov, & Chernorizov, 1989). …

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