Journal of Integrative Neuroscience

The data of frequency properties of single neurons in the auditory midbrain center, central nucleus of the inferior colliculus and morphologic aspects of its functional ordering are reviewed. On the basis of reconstruction of single units frequency receptive fields and morphophysiologic mapping of their location within the frequency-band lamina of the central nucleus the model of spectral coding by auditory midbrain neurons is developed. The main structural basement of spectral coding in the auditory midbrain is the tonotopic organization of its central nucleus as well as the order in its morphological structure expressed in alternation of layers of disc-shaped neurons and neuropil. The main neural mechanism of spectral coding is a critical bands mechanism. The critical bandwidth is controlled by inhibitory disc-shaped neurons which constitute an essential part of the population of the central nucleus disc-shaped cells.

Goldfish are known to exhibit motor asymmetry due to functional asymmetry of their Mauthner neurons that induce the turns to the right or left during free swimming. It has been previously found that if the less active neuron is subjected to prolonged aimed visual stimulation via its ventral dendrite, the motor asymmetry of goldfish is inverted, testifying that this neuron becomes functionally dominant, while the size of the ventral dendrite under these conditions is reduced 2–3 times compared to its counterpart in mirror neuron. Earlier it has been also revealed that training optokinetic stimulation induces adaptation, a substantial resistance of both fish motor asymmetry and morphofunctional state of Mauthner neurons against prolonged optokinetic stimulation. The aim of this work was to study the cellular mechanisms of the effect of an unusual visual afferent input on goldfish motor asymmetry and Mauthner neuron function in norm and under adaptation. It was shown that serotonin applied onto Mauthner neurons greatly reduces their activity whereas its antagonist ondansetron increases it. Against the background of visual stimulation, serotonin strengthens functional asymmetry between neurons whereas ondansetron smoothes it. Taken together these data suggest the involvement of serotonergic excitatory synaptic transmission in the regulation of Mauthner neurons by vision. Ultrastructural study of the ventral dendrites after prolonged optokinetic stimulation has revealed depletions of numeral axo-axonal synapses with specific morphology, identified by means of immunogold label as serotonergic ones. These latter in turn are situated mainly on shaft boutons, which according to specific ultrastructural features are assigned to axo-dendritic inhibitory synapses. Thus, the excitatory serotonergic synapses seem to affect Mauthner neuron indirectly through inhibitory synapses. Further, it was morphometrically established that adaptation is accompanied by the significant decrease of active zones dimensions in both serotonergic and inhibitory synapses. Finally, it was determined in model experiments that the interaction of globular actin with glycine, a main inhibitory neurotransmitter supposedly directly and chronically affecting the ventral dendrite, results in actin filaments formation. It is assumed that glycine-induced cytosolic actin polymerization is a cause of reduction in the ventral dendrite size under stimulation. Thus, it was established that a rather small group of synapses situated on an individual dendrite of the neuron determines the execution of the important form of animal behavior.

In this work, the investigation of network activity of mirror neurons systems in animal brains depending on experience (existence or absence performance of the shown actions) was carried out. It carried out the research of mirror neurons network in the C57/BL6 line mice in the supervision task of swimming mice-demonstrators in Morris water maze. It showed the presence of mirror neurons systems in the motor cortex M1, M2, cingular cortex, hippocampus in mice groups, having experience of the swimming and without it. The conclusion is drawn about the possibility of the new functional network systems formation by means of mirror neurons systems and the acquisition of new knowledge through supervision by the animals in non-specific tasks.

The paper presents a review of electrophysiological data which indicate the integrative mechanisms of information coded in the human and animal peripheral skin receptors. The activity of the skin sensory receptors was examined by applying various natural stimuli. It was revealed that numerous identical receptors respond to various stimuli (mechanical, temperature, and pain ones), but the spike patterns of these receptors were found to be specific for each stimulus. The description of characteristic structures of spike patterns in the cutaneous nerve fibers in response to five major modalities, namely: "touch", "pain", "vibration/breath", "cold", and "heat", is being presented. The recordings of the cutaneous physical state revealed a correlation between the patterns of spatiotemporal skin deformation and the receptors activity. A rheological state of the skin can be changed either in response to external temperature variation or by the sympathetic pilomotor activation. These results indicate that the skin sensory receptors activity may be considered as an integrative process. It depends not only on the receptors themselves, but also on the changes in the surrounding tissue and on the adaptive influence of the central nervous system. A new framework for the sensory channel system related to the skin is proposed on the basis of experimental results.

Neurophysiological mechanisms of recognition of verbal and nonverbal stimuli have been studied. It was determined that subjects solved nonverbal tasks faster and more effectively with their left hands, while they used two strategies of recognition to solve verbal tasks (fast reactions with right and left hand). Analysis of spectral characteristics of EEG revealed that mechanisms of both anterior and posterior attention systems were simultaneously involved in the process of effective recognition of nonverbal stimuli and ineffective recognition of verbal stimuli. Analysis of the event-related potentials (ERPs) showed that ineffective recognition of verbal and nonverbal stimuli resulted in an increase in the amplitude of sensory components of ERPs (N1m, P1m), while effective recognition increased the amplitude of cognitive components of ERPs (P2m, P3m).

A new method for identification of stages in arithmetic task solving has been presented. Solving of addition tasks induced formation of EEG foci in delta–theta-band were formed in fronto-central and parietal regions of the left hemisphere and in parietal-temporal and frontal areas of right hemisphere. In multiplication tasks, delta–theta-foci were formed in frontal, central and parietal regions of the left hemisphere as well as in temporal areas of the right hemisphere. When solving addition tasks, the coherence asymmetry was increased in left hemisphere between frontal, parietal and temporal areas in delta–theta-band as well as between frontal and parietal regions in alpha-band. The neurophysiological mechanisms of complex addition and multiplication arithmetic task solving is discussed.

In the present study, we describe a new method for estimation of distractor effect at image viewing. Dynamics of gaze fixation duration was compared at presentation of distractor during recognition of two types of target stimuli: fading-in contour images and black static cross. Circular blue distractor was applied to a target stimulus at some fixation points during initial stages of image recognition. All stimuli were presented in the center of computer screen inside the foveal part of the vision field. Subjects received the following instructions: to fixate their gaze on target image, recognize target stimulus as quick as possible and press the keyboard button to stop a trial. Our experiments have shown that (i) the median of the distractor effect (increase of fixation duration) was significantly less in trials with fading-in contour images, than in trials with cross image presentation (415 and 610 ms, p < 0.05); (ii) fixation duration without distractors had no significant difference between fading-in image trials (390 ± 10 ms) and cross image trials (438 ± 22 ms); (iii) mean recognition time for fading-in images was significantly more than for cross image (13.9 ± 4.3 s, and 2.47 ± 0.84 s). Possible prospective to use the presented method are discussed.

A mathematical model is developed to describe and investigate interstitial branching of axonal networks during nervous system development. The model under consideration describes axonal network growth in which the concentration of axon guidance molecules controls axon's growth and interstitial branching from axon shaft. Numerical simulations show that in the model framework axonal networks branch similarly to real neural networks in vitro.

Fish have highly developed vision that plays an important role in detecting and recognizing objects in different forms of visually guided behavior. All of these behaviors require high spatial resolution. The theoretical limit of spatial resolution is determined by the optics of the eye and the density of photoreceptors. However, further in the fish retina, each bipolar cell may collect signals from tens of photoreceptors, and each ganglion cell may collect signals from tens to hundreds of bipolar cells. If we assume that the input signals in this physiological funnel are simply summed, then fine gratings that are still distinguishable at the level of cones should not differ from the homogeneous surface for the ganglion cells. It is therefore generally considered that the resolution of the eye is determined not by the density of cones, but by the density of ganglion cells. Given the size of the receptive field of ganglion cells, one can conclude that the resolving power at the output of the fish retina should be ten times worse than at its input. But this contradicts the results of behavioral studies, for, as it is known, fish are able to distinguish periodic gratings at the limit of resolution of the cones. Our electrophysiological studies with extracellular recording of responses of individual ganglion cells to the motion of contrast gratings of different periods showed that the acuity of ganglion cells themselves is much higher and is close to the limit determined by the density of cones. The contradiction is explained by the fact that ganglion cells are not linear integrators of the input signals, their receptive fields being composed of subunits with significantly smaller zones of signal summation where nonlinear retinal processing takes place.

The review deals with the morphology, physiology, topography, and central projections of direction-selective cells of the accessory optic system in vertebrates.