Functional organization of a photoperiodic brain system

The neurofunctional system, which receives a photoperiod, is a photoperiodic brain system. As a part of chronoperiodic system of organism it is involved in perception and transfer of information about the main external Zeitgeber to the peripheral tissues. Such role of photoperiodic system allows it not only synchronize the chronorhythms of different somatic and visceral functions, but also realize the coordination and the modulation of adaptation mechanisms to the stressors influence. The present review is focused on the ways of conduction of photoperiodic information, role of suprachiasmatic nuclei of hypothalamus in endogenous oscillation of chronorhythms and pineal gland as a neuroendocrinal transducer; and also on characteristics of circadian and circannual parts of photoperiodic system. Special attention is given to vegetative part of photoperiodic system and melatonin--"the hormone of dark". It is supposed that adenosine, one of the humoral elements of photoperiodic system, is involved in transfer of duration of the light part of photoperiod. Due to presented data we have come to the conclusion that septohippocampal system is one of the center for saving photoperiodic information.     

Functional organization of the human auditory cortex

We investigated the functional organization of the human auditory cortex using a novel electrophysiological recording technique combined with an advanced brain magnetic resonance imaging (MRI) technique. Tonotopic mapping data were obtained during single unit recording along the Heschl’s gyrus. Most of the units studied (73%) demonstrated sharply tuned excitatory responses. A tonotopic pattern was observed with the best frequencies systematically increasing as more medial-caudal recording sites were sampled. Additionally, a new auditory field along the posterior aspect of the superior temporal gyrus has been identified using a high spatial resolution direct recording technique. Results obtained during electrical stimulation demonstrate functional connectivity between the primary auditory cortex and the auditory field in the posterior superior temporal gyrus.     

Functional organization and structure of the serotonergic neuronal network of terrestrial snail

The extension of knowledge how the brain works requires permanent improvement of methods of recording of neuronal activity and increase in the number of neurons recorded simultaneously to better understand the collective work of neuronal networks and assemblies. Conventional methods allow simultaneous intracellular recording up to 2-5 neurons and their membrane potentials, currents or monosynaptic connections or observation of spiking of neuronal groups with subsequent discrimination of individual spikes with loss of details of the dynamics of membrane potential. We recorded activity of a compact group of serotonergic neurons (up to 56 simultaneously) in the ganglion of a terrestrial mollusk using the method of optical recording of membrane potential that allowed to record individual action potentials in details with action potential parameters and to reveal morphology of the neurons rcorded. We demonstrated clear clustering in the group in relation with the dynamics of action potentials and phasic or tonic components in the neuronal responses to external electrophysiological and tactile stimuli. Also, we showed that identified neuron Pd2 could induce activation of a significant number of neurons in the group whereas neuron Pd4 did not induce any activation. However, its activation is delayed with regard to activation of the reacting group of neurons. Our data strongly support the concept of possible delegation of the integrative function by the network to a single neuron.     

Functional brain network mapping with dual regression

正Functional magnetic resonance imaging(fMRI)is an in-vivo non-invasive technique for measuring brain activity with excellent spatial and good temporal resolution.Without performing explicit tasks,resting-state fMRI(rfMRI)is widely used to map the functional connectivity network(FCN),which refers to a large-scale network of interdependent or functionally connected brain regions and it could be detected by using different algorithms(Zuo and     

Functional integrative levels in the human interactome recapitulate organ organization

Interactome networks represent sets of possible physical interactions between proteins. They lack spatio-temporal information by construction. However, the specialized functions of the differentiated cell types which are assembled into tissues or organs depend on the combinatorial arrangements of proteins and their physical interactions. Is tissue-specificity, therefore, encoded within the interactome? In order to address this question, we combined protein-protein interactions, expression data, functional annotations and interactome topology. We first identified a subnetwork formed exclusively of proteins whose interactions were observed in all tested tissues. These are mainly involved in housekeeping functions and are located at the topological center of the interactome. This ‘Largest Common Interactome Network’ represents a ‘functional interactome core’. Interestingly, two types of tissue-specific interactions are distinguished when considering function and network topology: tissue-specific interactions involved in regulatory and developmental functions are central whereas tissue-specific interactions involved in organ physiological functions are peripheral. Overall, the functional organization of the human interactome reflects several integrative levels of functions with housekeeping and regulatory tissue-specific functions at the center and physiological tissue-specific functions at the periphery. This gradient of functions recapitulates the organization of organs, from cells to organs. Given that several gradients have already been identified across interactomes, we propose that gradients may represent a general principle of protein-protein interaction network organization.     

Structuro-functional organization of the fiber network in the human Achilles tendon

Owing to a complex morphological investigation of the human Achilles tendon, it was possible to distinguish four levels of the structural-functional organization of its fibrous elements and to reveal some regularities of their structure that recur at all the levels. Thus, collagenous molecules, microfibrillae, fibrillae and fibers have a wavy-spiral conformation. This spatial form is stabilized by a complex or a system of transversal connections corresponding to the given level of the organization. In order to maintain integrity (the structural-functional unity) of each level, certain substances of polysaccharide nature take part. Along the course of the long tendinous axis, a re-distribution (branching) of the fibrillar elements is observed at all the levels of the structural-functional organization.     

Functional organization of the cortico-reticular system of the brain in response to physical loads

An estimation was carried out by factor analysis method of informative value of alpha-like rhythm, EEG theta-rhythm, local cerebral blood filling and oxygen tension (pO2) in estimation of functional state of cerebral structures under submaximal physical loads. Experiments were carried out on 35 rabbits with electrodes chronically implanted in the sensorimotor cortex and reticular formation. The obtained values were processed by a variant of factor analysis--a method of main components. For interpretation of factor loads matrix an orthogonal turn of factor axes was carried out according to varimax criterion. It has been established that informative value of the parameters depends on the brain structure where the given parameters were defined. Dynamics of pO2 and the theta-rhythm mostly influence the changes in other parameters. The states of structures before and during the period of physical load after-effect are mostly characterized by the brain local blood filling and less by the theta-rhythm amplitude.     

Functional organization of limbic brain structures during conditioned reflex activity in the dog

In experiments on 3 dogs it was shown that instrumental defensive conditioned reflex (CR) to electrical stimulation of the hippocampus is generalized within the limbic system (LS). The rate of generalization depended on the place of testing stimuli in LS. Stimulation of the medial parts of LS at the stage of stabilized initial reflex did not produce the generalized CRs, while they appeared distinctly in response to stimulation of the lateral parts of LS. In the process of elaboration of heterogeneous CRs (defensive and alimentary) to electrical stimulation of the hippocampus, generalized conditioned reactions from some brain structures appeared in both situations to the same degree while from other structures--with considerable differences. These data point to a possible participation in the genesis of the generalized CRs both of signal and reinforcing brain mechanisms.     

Functional differentiation of human brain progenitor cells

Stem cells and progenitor cells derived from the developing human brain have been shown to differentiate into neurons and astrocytes. However, few studies have examined the functional, physiological properties of these differentiated neurons and astrocytes. In this study we have used immunocytochemistry in combination with electrophysiology to examine protein machinery and functional properties of neurons and astrocytes differentiated from human brain progenitor cells (hBPCs).Our results show that serum induces mainly astrocytic phenotype cells that express GFAP and have physiological properties that are typical of astrocytes. hBPCs differentiated with BDNF and PDGF develop mainly into neurons expressing mature neuronal proteins MAP-2, synaptobrevin II and vesicular glutamate transporter I in the process, plus a small population of GFAP-positive radial cells. Based on electrophysiology of BDNF/PDGF-treated cells two classes of cell were identified. Class I cells have functional neuronal properties, including functional voltage-gated Na(+) and K(+) currents, functional AMPA receptors and the ability to generate action potentials. A smaller subpopulation of cells (Class II cells) expresses GFAP and exhibit functional properties of astrocytes, including linear current-voltage relationship and dye-coupling.     

Functional organization of a neural network for aversive olfactory learning in Caenorhabditis elegans

Many animals use their olfactory systems to learn to avoid dangers, but how neural circuits encode naive and learned olfactory preferences, and switch between those preferences, is poorly understood. Here, we map an olfactory network, from sensory input to motor output, which regulates the learned olfactory aversion of Caenorhabditis elegans for the smell of pathogenic bacteria. Naive animals prefer smells of pathogens but animals trained with pathogens lose this attraction. We find that two different neural circuits subserve these preferences, with one required for the naive preference and the other specifically for the learned preference. Calcium imaging and behavioral analysis reveal that the naive preference reflects the direct transduction of the activity of olfactory sensory neurons into motor response, whereas the learned preference involves modulations to signal transduction to downstream neurons to alter motor response. Thus, two different neural circuits regulate a behavioral switch between naive and learned olfactory preferences.     

Dependence of the organization of human brain electrical activity on hemispheric dominance

In healthy subjects, in a state of relative rest, with different individual profiles of asymmetry (20 right-handed and 10 left-handed subjects), a greater conjunction of electrical brain processes (estimated by mean EEG coherence levels) has been found in the dominant hemisphere as compared to the subdominant one, more distinctly expressed in the right-handed subjects. The maximum degree of interhemispheric asymmetry of the EEG coherence is observed in the posterior associative cortical areas. Specific interhemispheric theta-range differences are revealed as compared with other EEG frequency bands. Greater values are obtained of the correlation of the EEG symmetrical hemispheres points in the whole frequency band and in alpha- and beta-ranges in the right-handed subjects than in the left-handed ones.     

Functional brain organization of global and local visual perception: an ERP study

Adult subjects were asked to recognize a hierarchical visual stimulus (a letter) while their attention was drawn to either the global or local level of the stimulus. Event-related potentials (ERP) and psychophysical indices (reaction time and percentage of correct responses) were measured. An analysis of psychophysical indices showed the global level precedence effect, i.e., the increase in a small letter recognition time when this letter is a part of incongruent stimulus. An analysis of ERP components showed level-related (global vs. local) differences in the timing and topography of the brain organization of perceptual processing and regulatory mechanisms of attention. Visual recognition at the local level was accompanied by (1) stronger activation of the visual associative areas (Pz and T6) at the stage of sensory features analysis (P1 ERP component), (2) involvement mainly of inferior temporal cortices of the right hemisphere (T6) at the stage of sensory categorization (P2 ERP component), and (3) involvement of prefrontal cortex of the right hemisphere at the stage of the selection of the relevant features of the target (N2 ERP component). Visual recognition at the global level was accompanied by (1) pronounced involvement of mechanisms of early sensory selection (N1 ERP component), (2) prevailing activation of parietal cortex of the right hemisphere (P4) at the stage of sensory categorization (P2 ERP component) as well as at the stage of the target stimulus identification (P3 ERP component). It is suggested that perception at the global level of the hierarchical stimulus is related primarily to the analysis of the spatial features of the stimulus in the dorsal visual system whereas the perception at the local level primarily involves an analysis of the object-related features in the ventral visual system.     

Functional brain organization of global and local visual perception: Analysis of event-related potentials

Event-related potentials (ERP) of the brain and psychometric indices (reaction time and percentage of correct responses) were studied in adult subjects during recognizing hierarchical visual stimuli (letters), while the subject’s attention was drawn to either the global or the local level of the stimulus. The psychophysical indices demonstrated the global precedence effect, i.e., an increased recognition time of a small letter, which was a part of an incongruent stimulus. The ERP component analysis demonstrated that differences in the regulatory mechanisms of attention and timing and topography of brain organization during processing of visual information depended on the level of recognizing the hierarchical stimulus (global vs. local). Visual recognition at the local level was accompanied by a stronger activation of visual associative areas (P _z and T ₆) at the stage of sensory feature analysis (P1 ERP component), as well as by the predominant involvement of the temporal inferior cortex of the right hemisphere (T ₆) at the stage of sensory categorization (the P2 ERP component) and of the frontal cortex of the right hemisphere at the stage of selection for the relevant target features (the N2 ERP component). Visual recognition at the global level was accompanied by significant involvement of the early sensory selection (the N1 ERP component) and predominant activation of the parietal cortex of the right hemisphere (P ₄) at the stage of sensory categorization (the P2 ERP component), as well as at the stage of identification of the target stimulus (the P3 ERP component). Perception of a stimulus at the global level is assumed to depend mostly on the analysis of its spatial features in the dorsal visual system, whereas perception at the local level involves analysis of the object-related features in the ventral visual system.