Biomedical subjects

L I Frantsevich

Publications and source records attributed to L I Frantsevich.

21 records · Page 2Linked to original sources

PubMedDate not supplied

[Reactions of the directionally sensitive optical interneurons of insects to movement of a two-dimensional pattern].

The reactions to movements of two-dimensional patterns with the same average spatial period were compared in electrophysiological experiments. Directionally-sensitive neurons in connectives of dragonflies (fam. Libellulidae) were 1.5--2 times more sensitive to movement of "dissected" patterns (checkerboards, lattice of circles, stochastic pattern) than to vertical stripes. The power of optic signal in high-frequency domain in dissected patterns is 1.4--1.8 times higher, than in a striped pattern. It is assumed that high-frequency spatial filtering in dragonflies is provided by strong lateral inhibition in retinotopic projection. Dissected and striped patterns elicited identical reactions in directionally-sensitive neurons of the dronefly Eristalis tenax; the same was stated for the locomotory optokinetic reaction of the earty-boring dung beetle Geotrupes stercorosus.

Animals↗

PubMedDate not supplied

[Visual interneurons, sensitive to the size of objects and the direction of their movement in dragonflies of the genus Sympetrum].

Experiments have been made on 4 dragonfly species -- Sympetrum vulgatum, S. flaveolum, S sanguineum, S. danae. A pair of neurons was found in the thoracic ganglia and connectives, which has symmetrical contralateral receptive fields. These neurons are selectively sensitive to swift upward motion of a target of 3--10 degrees in size. This type of response was originally described by Zenkin and Pigarev [1, 2]. The receptive field, 120X25 degrees in size, is oriented horizontally from the medial rim of the eye. The center of sensitivity has the following polar coordinates: 15 degrees laterally from the medial plane and 20 degrees above the equatorial one. The relation of detecting properties of the observed neurones to key stimuli which trigger hunting behaviour is discussed. It is suggested that filtration of single and small optic stimuli by specialized detector neurons results not from the processes in the own receptive field of the neuron, but from the interaction with other neurons which are sensitive to motion of large objects and complex patterns.

Animals↗

PubMedDate not supplied

[Size of the binocular zone of the field of vision of insects].

The insects selected for measurements-- predators and anthophiles -- presumably possessed the ability of binocular estimation of distances. The margins of visual field and of the binocular zone in a compound eye could be traced by means of ophthalmological methods, such as observation of a pseudopupil or of a glow of ommatidia lit from inside. Predators as well as males of flies and drones, which intercept a point target against the sky, have the smallest binocular zone. They could not discover the distance to a target by binocular vision. Anthophiles have a broad binocular "window" pointing in antero--ventral direction; their binocular zone encloses 20--25% of facets. Predators hunting amidst the vegetation have the largest binocular zone (30--75%). The binocular zone of the eyes in the insects of large and middle size consists of 2--9 thousand of ommatidia.

Animals↗