Foveal crowding for large and small Landolt Cs: Similarity and Attention.

We compare the recognition of foveal crowded Landolt Cs of two sizes: brief (40 ms), large, low-contrast Cs and high-contrast (1 sec) tests at the resolution limit of the visual system. In different series, the test Landolt C was surrounded by two identical distractors located symmetrically along the horizontal or by a single distractor. The distractors were Landolt Cs or rings. At the resolution limit, the critical spacing was similar in the two series and did not depend on the type of distractor. The result supports the hypothesis that crowding at the resolution limit occurs when both the test and the distractors fall into the same smallest receptive field responsible for the target recognition. For large stimuli, at almost all separations distractors of the same shape caused greater impairment than did rings, and recognition errors were non-random. The critical spacing was equal to 0.5 test diameters only in the presence of one distracting Landolt C. This result suggests that attention is involved: When one distractor is added, involuntary attention, which is directed to the centre of gravity of the stimulus, can lead to confusion of features that are present in both tests and distractors and thus to non-random errors.

Metabotropic glutamate receptors as targets of neuromodulatory influence of nitric oxide.

A possible effect of nitric oxide (NO) on metabotropic glutamate receptor (mGluR) function in the amino acid afferent synapse was investigated in the isolated labyrinth of the frog Rana temporaria. The modification of the amplitude of responses of metabotropic glutamate receptor agonist trans-ACPD was analyzed during bath applied NO donor S-nitroso-N-acetyl-DL-penicillamine SNAP (0.1-100 µM) or nitric oxide synthase inhibitor L-NAME. It was shown that NO donor SNAP (1 µM) inhibited mGluR induced responses, and the inhibitor of NO-synthase L-NAME (100 µM) increased the amplitude of trans-ACPD evoked answers. The results suggest that NO can depress mGluR function due to modulation of functions of the endoplasmic reticulum channels.

[Hardware and software for EMG recording and analysis of respiratory muscles of human].

This paper presents a new hardware and software system that allows to not only record the EMG of different groups of the respiratory muscles, but also hold its amplitude-frequency analysis, which allows to determine the change in the contribution to the work of breathing of a respiratory muscles and detect early signs of fatigue of the respiratory muscles. Presented complex can be used for functional diagnostics of breath in patients and healthy people and sportsmen.

[Estimates of the size of inhibitory areas in crowding effects in periphery].

In psychophysical experiments we studied how surround influences recognition of test objects. The tests were low-contrast Landolt rings of the size 1.1, 1.5 and 2.3 deg. Their centers were located at 13.2 deg from the fixation point. The additional objects were similar Landolt rings or rings without gaps. The distance between the centers of the test and the additional objects varied from 2.2 to 13.2 deg. Inone experiment, the task of the observer was to identify both the test objects and the surrounding objects. In the second experiment the stimulus layout was the same, but'identification of only the test stimulus was required. In both experiments, deterioration of performance was found at all distances between the test objects and the surround, but the deterioration was more significant when the observer carried out the dual task. The data showed that the size of the inhibitory areas in our case does not comply with the Bouma low which states that the size of the interaction areas are equal to half of the eccentricity where the test is presented. Further deterioration of performance in the dual task reveals the contribution of attention into peripheral crowding effects.

[Interdependent changes of the axon and Schwann cell in the process of reactive remodeling of a myelinated nerve fiber].

Using the inverted phase-contrast microscope, the living undamaged frog sciatic nerve fibers and the fibers mechanically injured to varying degrees, were studied. It was found that the swelling of myelin incisures (MI) (of Schmidt-Lanterman) occured according to the principles similar to those controlling the changes of the myelin gap (node of Ranvier) and depended on the swelling of a Schwann cell (SC) perikaryon. It was detected that this was a single process, which which could be united in a complex of nonspecific changes of a myelinated nerve fiber. It was also demonstrated that under the action of mechanical injury and hypotonic solution, swelling of MI, nodes of Ranvier and SC perikaryon occurred without modifications of outer fiber diameter, due to the pronounced local axon thinning. Electron microscopic study of the cytoskeletal axonal structures showed that there was not a simple local contraction of an axon, but a significant local increase in the density of cytoskeletal components of the axoplasm (by 200-275%). Reactive reversible remodeling of a myelinated fiber suggests a new type of interaction between the axon and SC, the mechanism of reversible translocation of liquid axoplasmic fraction to the glial cell cytoplasm.

[Crowding-effect and attention].

We studied the influence of additional objects on recognition of the test visual objects. The test objects were stylized low-contrast letters having size 1.1, 2.1 or 4.3 ang. deg. The additional objects after 30 ms were followed by the test objects which were presented in the middle of the screen. The additional objects were digits 1-9 having size 1.3 ang. deg. The digits were presented at various distances from the centre of the screen. The observers' task was to identify both the test objects and the digits. Recognition of the test objects deteriorated when the digits were at small distances to the tests (crowding-effect). Recognition of digits deteriorated with the increasing distances from the centre of the screen; the effect was more pronounced when the tests were large. The contribution of laterals masking and attention into crowding-effect is discussed.

[Age related size invariance in perception of illusory and fragmented contours].

We investigated invariant perception to sizes of images. Observers were schoolmates of 7-17 years and adults. Two types of stimuli were used: fragmented line drawing of common objects and discs with deleted sectors, which represented illusory Kanizsa contours when discs were in particular positions. In experiments with fragmented images, we found an improvement in image recognition with observers' age, increasing up to 13-14 years. The probability of recognition of fragmented line drawings increased significantly with decreasing stimulus size for children of 7-12 years, indicating that size invariance at recognition for fragmented line drawings was absent in these children. However, size invariance was found for observers of 13-17 years and for adults in this task. At Kanizsa illusion appearance, the ratio of the separation between discs and disc diameter was smaller when we used larger disc diameters. This ratio increased with increasing age of observers. Obtained results provide evidence for the absence of size invariance when perceiving the Kanizsa illusion in our experimental conditions.

[A new property of orientation-selective neurons of the cat lateral geniculate body].

Neuronal mechanisms of description of local properties of visual object light-shadow surfaces are studied. Earlier we have shown the cat lateral geniculate body (LGB) neurons to have sensitivity to the value and direction of brightness vector in loci of object light-shadow surfaces. Further study of properties of orientational selectivity (OS) of these neurons has revealed that single LGB cells sensitive to direction of the brightness gradient vector also have the classical OS to direction of test bands. Such complex orientational sensitivity of neurons to direction of binary and light-shadow fragments of visual objects is of essential significance, in our opinion, for understanding of principles and mechanisms of object vision.

The effects of corticoliberin at different concentrations on long-term potentiation in slices of rat olfactory cortex.

Experiments were performed to investigate evoked focal potentials in slices of rat olfactory cortex. The results showed that 1 microM corticotropin-releasing factor (CRF; corticoliberin) increases the frequency of posttetanic potentiation, which had a shorter delay phase than in control experiments. Posttetanic potentiation during perfusion with 0.1 microM corticoliberin had a longer delay phase than in control experiments.

[Effect of various concentrations of corticoliberin on long-term potentiation in slides of the rat olfactory cortex]. / Vliianie razlichnykh kontsentratsii kortikoliberina na dolgovremennuiu potetsiatsiiu srezov oboniatel'noi kory mozga krys.

Perfusion of the rat olfactory cortex slices with 1 mcM corticotropin-releasing factor (CRF) increased the rate of initiation of the posttetanic potentiation. The latter had a shorter supporting phase than in the control. With the perfusion, with 0.1 mcM the potentiation had a longer supporting phase than in the control.

[Blocking of cold paralysis of physiological functions]. / Blokada mekhanizmov kholodovogo paralicha fiziologicheskikh funktsii.

For more than 100-year history of studying hypothermia a rewarming of a cooled organism was always considered as the only method of restoring the cold-paralysed physiological functions and the vital activity of an overcooled organism of homoiothermal animals and humans. The paper gives the results of applying the method developed at our Laboratory, of restoring the cold-paralysed important physiological functions after a continuous cooling of rats, without rewarming the animals.

[Functional reorganizations of the neuronal structures of the cat associative cortex after total sectioning of the corpus callosum]. / Funktsional'nye perestroiki v neironnykh strukturakh assotsiativnoi kory mozga koshki posle total'noi pererezki mozolistogo tela.

In given work results of researches functional organization of neural networks at associative cortex level in intact and after total corpus callosum section (Cc sec) of cat's brain. In result of the given researches is established, that after total Cc sec the brain is exposed significant morphological and functional changes. Is shown, that Cc sec is accompanied by infringements in act of reception of food and head orientation of the animal in space. A configuration and characteristics varies conducting ways, opportunity of an exchange the information between is lost by hemispheres, and accordingly, to receive the information from ipsilateral hemifield of vision. The structural and functional characteristics vary of neural structures of both hemispheres: asymmetry of hemispheres in size disappears, orientational and directional characteristics and decreases number of subzones in receptive fields (RF). In RF of this area occur extensive inhibitory zones. Arrangements RF in vision field main borrows contralateral hemifield of vision, in intact a brain large part RF pass in ipsilateral hemifield of vision. Thus in result of these researches is established, that the majority of neural functions of left and right hemispheres at level associative cortex, revealed on intact brain are formed for account transcallosal of connections. In conditions of isolated functioning both hemispheres there are the changes as in ways of the information processing, and in complementary ways of display of space. In result callosotomy of neuron networks in both hemispheres undergo essential changes: the hemispheres lose ability to integrate the set of the parties of subjects, disturbed an opportunity of invariant the descriptions of images, hence the description of the space information occurs on separate attributes of this information.