Principle of reorganizing the functional interrelations of brain structures in action on the dopamine system of dogs

In dogs, the influence of chronic administration of the agonist (L-DOPA) and antagonist (haloperidol) of central dopamine processes on functional interrelations of the brain structures was studied by dynamics of evoked potentials. Cortical-subcortical relations during formation of a motor habit are described in intact animals: basic functional regimes of central integration are singled out--sensory and motor one. Change of their equilibrium is the general principle of systemic reconstructions elicited by differently directed interferences in dopamine processes. Against the background of chronic administration of haloperidol, a sensory-motor imbalance is formed due to uniform functioning of the basal ganglia as analyzer of the signal stimulus; simultaneously the utilization of afferentation elicited by the movement is limited. A variant is revealed of intercentral relations corresponding to bradykinesia development. Under chronic administration of L-DOPA, interrelations of sensory and motor regimes become competitive; basal ganglia are provided with nontypical kinds of afferentations. Intercentral relations variant is examined corresponding to development of psycho-motor excitation. The results are discussed in connection with pathogenic and compensatory mechanisms of some symptoms of parkinsonism and schizophrenia.     

Establishment of the afferent function of the striatum in the rabbit during early ontogenesis

The study is dedicated to electrophysiological analysis of development of the caudate nucleus afferent function in rabbits in early postnatal ontogenesis. By amplitude-temporal parameters of the evoked potentials (EPs) of the caudate nucleus, recorded in response to stimulation of afferent inputs from the cortical regions (motor and limbic) and substantia nigra, similar dynamics of these afferent pathways functional maturation is revealed from the beginning of functioning (in the age of 3-5 days) to the definitive level (by the 30th day of life). The most significant changes of the amplitude-temporal parameters of the evoked potential, particularly of latencies are observed during the 3d week of postnatal life. On the basis of the obtained data, the conclusion is made on the formation of a common system of striatum sensory integration in the 3d-4th week of rabbits life. This age period is considered as critical.     

Functional topography of afferent projections of the horizontal division of the nucleus of the diagonal band in the dorsolateral neocortex of the cat

EPs recording under Nembutal anaesthesia during stimulation of the medial section of the horizontal part of the diagonal band nucleus (HNDB) shows a wide spreading of HNDB afferentation over the neocortex: from the frontal area to the medial and some posterior parts of the auditory, parietal areas and Ep zone, with the least activation of the latter three regions and activation increasing intensity correspondingly in the somatic zones II, I (SII, SI), motor and frontal cortex. Such reduction of signals flow intensity oriented both in caudal and ventral directions of the cortex goes with foci of maximal activity of these signals in the motor, parietal areas and zones of representation of various body parts in SI and SII. Traits of similarity and differences of signal's projections in the neocortex from HNDB and thalamic relay nuclei have been revealed. A hypothesis is substantiated on different mechanisms underlying peculiarities of influences of these subcortical nuclei on the cortex depending on the type of their afferent-neuronal links in the latter and their functional role in the brain activity.     

Changes in the functional parameters of the brain structures under the influence of enkephalin-like tetrapeptidamide

In complex neurophysiological and cytobiochemical study single injections of tetrapeptide amide (TPA) caused a short-term analgetic effect which manifested itself in the absence of motor reactions and EEG changes of cortical and subcortical brain structures after painful stimulation of extremities. This effect was accompanied by changes of some indices of transmitter (monoamine oxidase) and protein metabolism in the cerebral hemispheres at cellular and subcellular levels. In 30-40 min after a TPA injection, EEG suppression and absence of EPs to light flashes were observed in cortical and subcortical structures. Simultaneously motor disorders developed. The observed EEG changes had an undulatory character: on the second day EEGs were restored and on the third day--suppressed once again. This period of TPA action was accompanied by varied changes of the investigated types of metabolism. The question of the necessity of systemic approach to the study of TPA action is discussed, as such an approach allows to reveal complex neurophysiological and fine biochemical relations in the reactions of brain structures and in animal behaviour.     

Partial muting leads to age-dependent modification of motor patterns underlying crystallized zebra finch song

The crystallized structure of adult zebra finch (Taeniopygia guttata) song is modifiable if sensory feedback is altered during sound production. Such song plasticity has been studied by examining acoustic modifications to the motif; however, the underlying changes to the vocal motor patterns of these acoustic modifications have not been addressed. Adult birds in two age categories (young=90-120 days or middle aged 150-250 days) that sang crystallized song were used in the experiment. Vocal motor patterns were monitored by recording respiratory air sac pressure before, during, and after song plasticity was induced by partial or complete reduction of phonation (i.e., "partial muting"). Birds were recorded until changes in air sac pressure patterns underlying the song structure were observed (up to 160 days). Young adult birds were more likely to insert shorter duration (<125 ms) expiratory pulses (EPs) into the motif than middle-aged adults. These shorter duration EPs were produced with a unique pressure pattern relative to the intact song, and therefore appeared to be generated by novel motor gestures. Stuttering (atypical repetition of an EP) was observed when these novel EPs were inserted into the motif, regardless of age. The EP of the distance call, which is also a learned vocalization in zebra finches, showed a similar reduction in duration if EPs were also shortened in the song. The emergence of shorter duration EPs was not related to sound production, or nonspecific effects of the surgical procedure, which suggests an age-dependent neural process for song plasticity.     

Cortical-subcortical interactions and the brain functional state regulation under acute hypoxia in man

Regulation mechanisms of the brain functional state (FS) were studied in man during acute hypoxic conditions (inhalation of 8% O2 hypoxic air for 15-25 minutes). Changes in balance of the brain regulatory structures activities caused by hypoxia determine FS dynamics that is reflected in the reorganization of the EEG spatial interrelations (by data of factor and cluster analysis of EEG cross-correlation matrices), as well as translocation of intracerebral position of electrical equivalent dipole sources (EEDS) coupled with EEDS density rising in medial and basal regions of the cerebral hemisphere temporal lobes (by EEDS-tomography data). Alterations of the cortical-sub-cortical interactions show a decline in the brain activating system tone, a decrease in the neocortical inhibitory control of subcortical processes, and activation of structures of limbic and hypothalamic regions. Switching of integrative regulatory control mechanism from "cortical-thalamic" system level to "limbic-dyencephalic" one could ensure both removal of powerful unspecific components of hypoxic stress and a greater stability of essential physiological parameters of the main vital functions regulation during oxygen deficiency accumulation.     

Motor learning in man: A review of functional and clinical studies

This chapter reviews results of clinical and functional imaging studies which investigated the time-course of cortical and subcortical activation during the acquisition of motor a skill. During the early phases of learning by trial and error, activation in prefrontal areas, especially in the dorsolateral prefrontal cortex, is has been reported. The role of these areas is presumably related to explicit working memory and the establishment of a novel association between visual cues and motor commands. Furthermore, motor associated areas of the right hemisphere and distributed cerebellar areas reveal strong activation during the early motor learning. Activation in superior-posterior parietal cortex presumably arises from visuospatial processes, while sensory feedback is coded in the anterior-inferior parietal cortex and the neocerebellar structures. With practice, motor associated areas of the left-hemisphere reveal increased activity. This shift to the left hemisphere has been observed regardless of the hand used during training, indicating a left-hemispheric dominance in the storage of visuomotor skills. Concerning frontal areas, learned actions of sequential character are represented in the caudal part of the supplementary motor area (SMA proper), whereas the lateral premotor cortex appears to be responsible for the coding of the association between visuo-spatial information and motor commands. Functional imaging studies which investigated the activation patterns of motor learning under implicit conditions identified for the first, a motor circuit which includes lateral premotor cortex and SMA proper of the left hemisphere and primary motor cortex, for the second, a cognitive loop which consists of basal ganglia structures of the right hemisphere. Finally, activity patterns of intermanual transfer are discussed. After right-handed training, activity in motor associated areas maintains during performance of the mirror version, but is increased during the performance of the original-oriented version with the left hand. In contrary, increased activity during the mirror reversed action, but not during the original-oriented performance of the untrained right hand is observed after left-handed training. These results indicate the transfer of acquired right-handed information which reflects the mirror symmetry of the body, whereas spatial information is mainly transferred after left-handed training. Taken together, a combined approach of clinical lesion studies and functional imaging is a promising tool for identifying the cerebral regions involved in the process of motor learning and provides insight into the mechanisms underlying the generalisation of actions.     

Electrophysiologic analysis of the process of recognizing target and non-target stimuli in healthy and oligophrenic children

In an automatized experiment, with a computer on line, amplitude-temporal parameters of evoked potentials (EPs) to purposive and non-purposive stimuli (digits), were analyzed in normal and mental retarded children. At unilateral stimuli presentation to the left or right visual half-fields EPs were recorded simultaneously in projection, TPO, parietal and central areas of the left and right hemispheres. It has been shown that in normal children, differential involvement of projection and associative structures in the analysis of sensory information takes place in both hemispheres. The amplitudes of most EP components in the range of 100-400 ms to the purposive stimuli are higher than to the non-purposive ones. Considerable similarity of EPs developing in response to ipsi- and contralateral stimulations of visual fields ("direct" and "transmitted" EP) is observed. In mental retarded children significant changes are revealed in intra- and interhemisphere organization of the process of perception of purposive and non-purposive stimuli. In the right hemisphere structures there are no differential EP reactions to the two types of stimuli. Significant, in comparison with the norm, prolongation of the latencies of most EP components is noted, especially in the structures of the left hemisphere, to the purposive stimuli. In the process of perception, changes are seen of the integration of functions of both hemispheres. The totality of disturbances of systemic brain organization at perceptive activity in mental retarded children may reflect neurophysiological mechanisms of mental deficiency.     

Reorganization of human evoked potentials during automatization of motor reactions

Evoked electrocortical activity appearing during rhythmic stimulation and its correlation with the level of expectancy of the signal next in turn (expressed in values of reaction time), were studied in nine grown up subjects. Reorganization of auditory evoked potentials (EPs), mostly expressed during reactions preceding the stimulus or coinciding with it occurs at motor responses to rhythmical stimuli. The character of correlation between EPs and perception is satisfactorily explained by a cyclic model of the sensory information processing. Adaptive behaviour is provided by the cyclic processes promoting engrams formation and adequate pretuning to probable events.     

感觉统合训练结合常规康复训练对痉挛型脑瘫患儿平衡控制及运动功能的影响

目的:探讨感觉统合训练结合常规康复训练对痉挛型脑瘫患儿平衡控制及运动功能的影响。方法:选取2016年1月到2017年12月期间成都市妇女儿童中心医院康复科收治的痉挛型脑瘫患儿80例为研究对象,根据随机数字表法将80例患儿分为对照组(40例)和观察组(40例)。对照组患儿采用常规康复训练进行治疗,观察组患儿采用感觉统合训练结合常规康复训练进行治疗。比较两组脑瘫患儿的平衡控制功能、步态、粗大运动功能测试量表-88(GMFM-88)D区和E区的评分。结果:治疗3个月后两组患儿的Rivermead活动指数、Berg平衡量表得分均明显升高,且观察组患儿的Rivermead活动指数、Berg平衡量表得分高于对照组(P0.05)。治疗3个月后两组患儿的步行足长、步速明显增加,步宽明显减小(P0.05),且观察组患儿步行足长、步速大于对照组,步宽小于对照组(P0.05)。治疗3个月后两组患儿的GMFM-88 D区、GMFM-88 E区得分均分别明显升高(P0.05),且观察组患儿的GMFM-88 D区、GMFM-88 E区得分均分别高于对照组(P0.05)。结论:感觉统合训练结合常规康复训练可有效改善痉挛型脑瘫患儿的平衡控制功能、步态以及粗大运动功能。     

Cortical and subcortical evoked potentials and behavioral responses after destruction of the globus pallidus in CATS

Evoked potentials (EPs) to clicks were recorded in the ectosylvian and sigmoid gyri of the cortex, in the medial geniculate body, and in the median nucleus of the thalamus by means of permanently implanted electrodes in experiments on 14 cats. A motor component of the behavioral response (conditioned food reflex) developed in response to the same stimulus (clicks). In the first group of animals the region of destruction was confined to the globus pallidus. In these animals EPs to clicks appeared during the first days after the operation in all structures, although in some tests they were reduced. Meanwhile the behavioral response to clicks was absent and showed no signs of spontaneous recovery. It could be formed (retraining) later in the experiments. In the second group of animals the globus pallidus was not completely destroyed, but neighboring areas of the entopeduncular nucleus and internal capsule were coagulated. In these cats more marked changes in behavioral and electrophysiological indices were observed. EPs to clicks disappeared in some cases for 25–30 days, subsequently returning to normal. The role of the globus pallidus as a "non-specific" polymodal structure in the analysis of sensory information is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 4, No. 2, pp. 141–149, March–April, 1972.     

Brain networks for integrative rhythm formation

Background

Performance of externally paced rhythmic movements requires brain and behavioral integration of sensory stimuli with motor commands. The underlying brain mechanisms to elaborate beat-synchronized rhythm and polyrhythms that musicians readily perform may differ. Given known roles in perceiving time and repetitive movements, we hypothesized that basal ganglia and cerebellar structures would have greater activation for polyrhythms than for on-the-beat rhythms.

Methodology/Principal Findings

Using functional MRI methods, we investigated brain networks for performing rhythmic movements paced by auditory cues. Musically trained participants performed rhythmic movements at 2 and 3 Hz either at a 1∶1 on-the-beat or with a 3∶2 or a 2∶3 stimulus-movement structure. Due to their prior musical experience, participants performed the 3∶2 or 2∶3 rhythmic movements automatically. Both the isorhythmic 1∶1 and the polyrhythmic 3∶2 or 2∶3 movements yielded the expected activation in contralateral primary motor cortex and related motor areas and ipsilateral cerebellum. Direct comparison of functional MRI signals obtained during 3∶2 or 2∶3 and on-the-beat rhythms indicated activation differences bilaterally in the supplementary motor area, ipsilaterally in the supramarginal gyrus and caudate-putamen and contralaterally in the cerebellum.

Conclusions/Significance

The activated brain areas suggest the existence of an interconnected brain network specific for complex sensory-motor rhythmic integration that might have specificity for elaboration of musical abilities.     

Electrotonic transmission in the mammalian central nervous system (author's transl]

The aim of this review is to present the electrophysiological data, obtained in the mammalian central nervous system, which show that depolarisations recorded intracellularly, under certain experimental conditions can be interpreted in terms of electrotonic coupling. The results were obtained from very different structures: primary sensory nuclei, sensori-motor integration centres and motor nuclei. The association of the phenomenon of electrotonic transmission with a known ultrastructural substrate--the "gap junction"--has been defined by the term electrotonic coupling. In the cases where it has not been possible to link depolarisations with the presence of gap junctions, other possible morphological correlates have been envisaged. The functional significance of electrotonic interactions are discussed on the basis of information obtained from different experimental approaches.     

The Dynamics of Attention during Free Looking

Simple methods to study attention dynamics in challenging research and practical applications are limited. We explored the utility of examining attention dynamics during free looking with steady-state visual evoked potentials (SSVEPs), which reflect the effects of attention on early sensory processing. This method can be used with participants who cannot follow verbal instructions and patients without voluntary motor control. In our healthy participants, there were robust fluctuations in the strength of SSVEPs driven by the fixated and non-fixated stimuli (rapidly changing pictures of faces) in the seconds leading up to the moment they chose to shift their gaze to the next stimulus sequence. Furthermore, the amplitude of SSVEPs driven by the fixated stimuli predicted subsequent recognition of individual stimuli. The results illustrate how information about the temporal course of attention during free looking can be obtained with simple methods based on the attentional modulation of SSVEPs.     

The Effects of Localized Inactivation of Somatosensory Cortex,Area 2, on the Cat Motor Cortex

Direct corticocortical afferents to the primary motor cortex (MI) originate in area 2 and area 3a of the primary somatosensory cortex (SI). The functional and morphological characteristics of the two pathways indicate that they relay different sensory signals to MI. The role of area 2 in relaying peripheral information to the cat MI was studied using electrophysiological techniques. Neurons that responded to stimulation of peripheral receptive fields on the contralateral forepaw were identified in MI by extracellular recordings. In area 2 of SI, neurons with the same receptive field modality and location as those in MI were also identified. Field potentials to electrical stimulation of the peripheral receptive field were recorded at the somatotopically matched sites in both MI and SI. Neuronal activity at the recording site in area 2 was blocked by injection of lidocaine, a local anesthetic. Changes in MI and area 2 responses were monitored before and after inactivation of area 2. Neuronal activity near the injection site was abolished, and evoked potentials (EPs) in area 2 were considerably diminished immediately following the injection. In MI, spontaneous activity levels were altered at some sites, but overall these changes were not significant. MI EPs recorded in response to peripheral stimulation were altered, and various patterns of change were noted in the early and late phases of the EPs. Changes often occurred in only one phase of the response. In some EPs, both early and late phases changed, but the direction and magnitude of change in one phase were not always linked to such changes in the other phase. Both increases and decreases in the amplitude and the area of each phase were observed. The morphological characteristics of the projection were reviewed and related to the findings in the study. It is proposed that inherent features of the pathway may account for the variable patterns of change that were observed.     

Model of dynamics of the insect cellular immune system

A mathematical model for the dynamics of functioning of an insect immune subsystem is considered. It is assumed that the interaction between hemocytes and bacteria corresponds to the Volterra principle of "pair interactions": the rate at which bacteria enter the system decreases in proportion to the rate of interaction of hemocytes with bacteria. In the absence of interaction, the intrinsic dynamics of bacteria is described by the Malthus law. Dynamic regimes of the model for different values of the parameters were analyzed. In particular, it was shown that, depending on the initial values of variables and the values of the parameters, there exist two regimes, the regime of death of the organism and the regime of elimination of bacteria.     

Input-output relations of Deiters' lateral vestibulospinal neurons with different structures of the brain

It has been the goal of this review to describe the functional interrelations between Deiters' vestibular nucleus and numerous brain structures. Emphasis is placed on dynamic and integrative properties of linkages between the neurons of Deiters' nucleus and many other brain structures in order to begin considering the capabilities of the loops in the light of motor control and coordination of movement. The problem of somatotopy within the loops is also considered. Putting this information together, the possible roles of Deiters' nucleus in the control of movements are described. It is suggested that Deiters' nucleus in co-operation with cerebral cortex, cerebellum, subcortical and brainstem structures are responsible for the integration and realization of different movements.     

Analysis of stability of different regimes of heart rate dynamics by computer modeling

Computer modeling revealed the following three regimes of heart rate dynamics: linear dynamics, “1st degree chaos,” and “2nd degree chaos.” This study investigated a stability of these regimes with respect to changes in initial conditions. The results show that the greatest stability is notable for the linear regime. For this regime small errors in values of initial conditions can not sharply change the initial dynamics of RR intervals. Both nonlinear regimes of heart rate dynamics are unstable, and a degree of instability of regime “2nd degree chaos” is higher in comparison with regime “1st degree chaos.” The results of computer modeling are in agreement with experimental data pointing to the existence of a relationship between the degree of heart rate irregularity and cardiac electrical stability.     

Noise during rest enables the exploration of the brain's dynamic repertoire

Traditionally brain function is studied through measuring physiological responses in controlled sensory, motor, and cognitive paradigms. However, even at rest, in the absence of overt goal-directed behavior, collections of cortical regions consistently show temporally coherent activity. In humans, these resting state networks have been shown to greatly overlap with functional architectures present during consciously directed activity, which motivates the interpretation of rest activity as day dreaming, free association, stream of consciousness, and inner rehearsal. In monkeys, it has been shown though that similar coherent fluctuations are present during deep anesthesia when there is no consciousness. Here, we show that comparable resting state networks emerge from a stability analysis of the network dynamics using biologically realistic primate brain connectivity, although anatomical information alone does not identify the network. We specifically demonstrate that noise and time delays via propagation along connecting fibres are essential for the emergence of the coherent fluctuations of the default network. The spatiotemporal network dynamics evolves on multiple temporal scales and displays the intermittent neuroelectric oscillations in the fast frequency regimes, 1–100 Hz, commonly observed in electroencephalographic and magnetoencephalographic recordings, as well as the hemodynamic oscillations in the ultraslow regimes, <0.1 Hz, observed in functional magnetic resonance imaging. The combination of anatomical structure and time delays creates a space–time structure in which the neural noise enables the brain to explore various functional configurations representing its dynamic repertoire.     

Cervical sprouting of corticospinal fibers after thoracic spinal cord injury accompanies shifts in evoked motor responses.

The adult central nervous system (CNS) of higher vertebrates displays a limited ability for self repair after traumatic injuries, leading to lasting functional deficits [1]. Small injuries can result in transient impairments, but the mechanisms of recovery are poorly understood [2]. At the cortical level, rearrangements of the sensory and motor representation maps often parallel recovery [3,4]. In the sensory system, studies have shown that cortical and subcortical mechanisms contribute to map rearrangements [5,6], but for the motor system the situation is less clear. Here we show that large-scale structural changes in the spared rostral part of the spinal cord occur simultaneously with shifts of a hind-limb motor cortex representation after traumatic spinal-cord injury. By intracortical microstimulation, we defined a cortical area that consistently and exclusively yielded hind-limb muscle responses in normal adult rats. Four weeks after a bilateral transsection of the corticospinal tract (CST) in the lower thoracic spinal cord, we again stimulated this cortical field and found forelimb, whisker, and trunk responses, thus demonstrating reorganization of the cortical motor representation. Anterograde tracing of corticospinal fibers originating from this former hind-limb area revealed that sprouting greatly increased the normally small number of collaterals that lead into the cervical spinal cord rostral to the lesion. We conclude that the corticospinal motor system has greater potential to adapt structurally to lesions than was previously believed and hypothesize that this spontaneous growth response is the basis for the observed motor representation rearrangements and contributes to functional recovery after incomplete lesions.