The sensitivity of neurons in the lateral geniculate body of the cat to the orientation vectors of brightness gradients.

We describe here a new property of visual neurons: sensitivity to the magnitude and orientation of the brightness gradient vector in a test stimulus presented in the receptive field of the neuron. The brightness gradient test image was a spot (diameter 4 degrees) on the dark background of the slide. Brightness changed linearly within the spot. The absolute value of the brightness gradient varied over the range 0.4-2.7 cd/m2 /degrees in the direction of the brightness gradient. The integral brightness in the test spot containing the gradient image was identical for different values of the brightness gradient. The numbers of spikes in the on- and off-responses of on and off neurons in the lateral geniculate body of cats depended on the orientation of the brightness gradient vector in the test stimulus. The sensitivity of neurons to the orientation of the brightness gradient vector, K (the coefficient of sensitivity), was assessed as the normalized difference between the number of spikes in neuron responses in the preferred and non-preferred orientations of the brightness gradient vector in the neuron's receptive field. The mean sensitivity coefficient for 53 cells was 0.55 +/- 0.20. A 6.7-fold decrease in the brightness gradient resulted in a 3.7-fold decrease in the coefficient of sensitivity (for the preferred direction of the orientation of the gradient vector); there was no change in the latent period of responses. The preferred orientation of the brightness gradient vector in the receptive fields of neurons coincided (to within +/-22.5 degrees) with the radial direction on the map of the field of vision in 45% of cases, and with the tangential direction in 26% of cells.

[Sensitivity of the cat lateral geniculate body neurons to orientation of the brightness gradient vector]. / Chuvstvitel'nost' neironov naruzhnogo kolenchatogo tela koshki k orientatsii vektora gradienta iarkosti.

A new property of visual neurons: their sensitivity to orientation and the vector brightness gradient, was revealed and described. Receptive fields of the lateral geniculate body neurons in the cat have preferred orientation maximum reaction (average mean of orientation sensitivity coefficient--0.55 +/- 0.20). The preferred orientation mainly has a radial or tangential trend in the visual field. Temporal characteristics of the neuronal responses were analysed. A role of inhibition processes in the orientation sensitivity is discussed.

[A quantitative assessment of the process of the reflection of the spatial-brightness properties of a stimulus by the neuronal structures in the lateral geniculate body of the cat]. / Kolichestvennaia otsenka protsessa otobrazheniia prostranstvenno-iakostnykh svoistv stimula neironnymi strukturami naruzhnogo kolenchatogo tela koshki.

Correlation between spatial brightness distribution in the test image and the spatial response distribution was estimated for the cat LGB. The correlation was found to be quite high. The data obtained corroborate the hypothesis by Podvigin and Kuperman of the topological correspondence of isophote structure family to the pattern of activity reflecting the test image.

A simple surgical method for immobilizing the cat eye.

In this article we describe a new method for surgical immobilization of the cat eye in which 3 motor nerves are simultaneously destroyed where they converge in the orbital fissure. The method depends upon inserting a special instrument 'spoon' through the soft palate into the orbital fissure.

[Relation between the spatial characteristics of the receptive fields of the superior colliculi of the cat and the rate of movement of a photic stimulus]. / Zavisimost' prostranstvennykh kharakteristik retseptivnykh polei perednikh bugrov chetverokholmiia koshki ot skorosti dvizheniia svetovogo stimula.

The receptive fields of visual cells in superficial and intermediate layers of the cat superior colliculus were investigated: their boundaries, size, shape, dependence on the velocity of stimulus. The size of the excitatory zone decreased whereas the firing rate of the cells increased when the velocity 3 +/- 180 degrees.S-1 was changed. That was typical of both directionally and non-directionally selective cells. The mechanism of directional selectivity is discussed.

[Directional selectivity of the neurons of the superior colliculi in the cat: the effect of the rate of movement of a stimulus]. / Direktsional'naia izbiratel'nost' neironov perednikh bugrov chetverokholmiia koshki: vliianie skorosti dvizheniia stimula.

Responses to stimuli moving with velocities of 3-180 degrees X sec-1 were studied in each of four axes (eight directions) separated by 45 degrees in neurons of the cat superior colliculus. 69% of units were directionally selective. In 55% of all the neurons the directional selectivity depended on stimulus velocity and was the largest for high velocities (over 10-30 degrees X sec-1). The preferred direction for some neurons was reversed with velocity increasing. The directional selectivity-velocity relationships were compared for the cat superior colliculus and visual cortex and discussed in regard to probable role of this phenomenon in the oculomotor system.