Vol 73, No 5 (2023)

The problem of frequency coding is closely related to the studies of inhibitory transmission as a factor of neural network plasticity. The rewiew presents basic mechanisms of inhibitory control of spatio-temporal pattern of neural activity during signal processing. Current views are analyzed in respect of dynamic synapses, their instability and variation within the ongoing activity. The results presented here demonstrate that short-term plasticity operates with the combined contribution of excitatory and inhibitory synapses. The role of GABAergic potentials in modulation of intracellular messenger’s activity is discussed, including those implicated in postsynaptic modifications of excitatory and inhibitory transmission. The main topics concerning the molecular mechanisms centered on the lateral diffusion of GABA_A receptors. The data of many reports argue for coordinating role of actin cytoskeleton. It is proposed that postsynaptic mechanisms underlying GABA_A plasticity may be activated in result of fast adaptation of actin cytoskeleton and associated proteins to disbalance between excitation and inhibition.

The influence of temporal characteristics of mask presentation on performance in basic and superordinate image categorization tasks was investigated in young healthy subjects using a forward masking model. The masks could be congruent, noncongruent, or semantically neutral to the stimulus images. In the first series of experiments, the influence of stimulus onset asynchrony (SOA, the time interval between the onset of the mask and the onset of the stimulus) was studied. SOA varied from 100 to 350 ms in steps of 50 ms, whereas mask duration remained unchanged and equaled 100 ms. In the second series, the influence of mask duration was investigated. It varied from 100 to 250 ms in steps of 50 ms, while SOA remained constant at 250 ms. It was found that superordinate categorization was performed faster. This could be due to the fact that superordinate categorization involves a low-frequency information of stimulus description that is rapidly transmitted through the magnocellular visual pathway. The basic categorization was more sensitive to the temporal properties of the mask and its category. Changes in SOA had a stronger effect than those in mask duration. Assuming that SOA changes affect the early perceptual phase of stimulus processing, the sensitivity of this phase to irrelevant information seems to be reflected in the stronger influence of SOA changes on basic categorization compared to superordinate categorization.

A group of 20 healthy subjects (11 males and 9 females) performed a selective auditory attention task in a dichotic listening paradigm with different levels of perceptual load. Analysis of brain activation patterns measured with fMRI during selective listening to fusion speech with distractors of varying strengths revealed statistically significant sex differences in the topography of cortical activity. “Female > male” effects dominated in the left superior temporal gyrus and the left pre and postcentral gyrus; while the most pronounced “male > female” effects were found in the left islet, shell and frontal lobule. Statistically significant effects were also obtained by comparing activation patterns according to the level of task complexity: It was shown that masking with a female speaker’s voice caused greater activation of additional high-level information processing areas. The findings indicate the presence of sexual dimorphism in the organization of the selective auditory attention system.

The paper considers the synergetic effects manifested at the cortical and muscular levels during locomotor activity showed in conditions of horizontal hanging of the lower extremities. The analysis of the synergies’ spatio-temporal structure was carried out using the data matrix factorization methods. It was found out the control of the movements’ structure is mainly realized through the three muscle synergies. The activity synchronization of the motor, associative, visual and sensorimotor regions of the cortex bilateral part is due to the specifics of performing locomotion in conditions of gravitational unloading and the associated features of receptor signaling. The identified components indicating synchronization of different areas of the right and left cortex may reflect the control processes associated with the control of alternate activation of the flexor and extensor muscles of the contralateral limb during locomotion. The data on the cortical activity spatial-temporal structuring indicate the separate management of muscle synergies through synchronization of cortical commands and the temporary organization of muscle synergies in the frequency ranges 0.30 to 8.00 Hz. Such patterns may reflect the activity of the rhythm-generating mechanism involved in the management of cyclic locomotor activity.

In behavioral experiments, we studied the ability of rhesus monkeys (Macaca mulatta) to keep in working memory visual objects that differ either in shape, or in color, or in a combination of these features. Six male rhesus monkeys performed a delayed matching-to-sample task, with three geometric shapes from a set of stimuli as samples. In the first series of experiments, these were colored figures of various shapes, in the second – circles of different colors, in the third – monochrome images of various figures from the set of stimuli. When using both features to memorize objects, the monkeys showed the maximum result, and the task of matching by color performed better than the task of matching by shape. The latter result disagrees with the data (Fehring et al., 2022), where in similar experiments, though with one sample, the opposite bias was observed. The reason for this may be the shift from local features (contours of shapes) to global ones (color) when recognizing and memorizing visual objects under conditions of a greater memory load in our study.

In vivo calcium imaging is widely used technique in neuroscience to evaluate the activity of neuronal networks. The miniscope, a single-photon miniature fluorescent microscope, has made it possible to conduct in vivo calcium imaging in freely moving animals. Various algorithms and software packages have been developed for the analysis of miniscope data. This study investigates the relationship between the sensitivity of neuron detection and the processing parameters utilized in the Minian analysis pipeline at different noise levels. To achieve this objective, we generated simulated data possessing certain attributes of an experimentally derived dataset. Simulated data was generated with various noise levels and processed through to the Minian analysis pipeline. Based on our findings, we provide recommendations for optimal values of Minian pipeline parameters depending on different noise levels. The results obtained in this study may serve as a preliminary guide for selecting appropriate parameter values during the processing of experimental data using the Minian analysis pipeline. The findings of this study are expected to be relevant to neuroscientists involved in the acquisition and processing of miniscope data.