Parameters of voluntary effort correlates with functional state of the motor control system

The spectrum oscillations of a prolonged supported effort that was registered at isometric regimen in 3 age groups of healthy volunteers, were analyzed. Changes in distribution of spectral density of effort oscillations and distinction in distribution of spectral density as a reaction to fatigue in age groups, were shown. The revealed amplitude-frequency ranges of changes of spectral density of effort oscillations characterize activity of suprasegmental and segmental levels of motor control system fulfilling the voluntary movement control and the automatic regulation of posture. The correlates with functional state of motor control system are considered in the terms of voluntary and involuntary components of regulation. The substantial growth of activity in the central structures of motor control system in process of development of fatigue and the narrowing of the frequency range of activity of sub-cortical structures with age, were revealed.     

Neurophysiological mechanisms of voluntary attention: a review

The review is focused on attention as behavior-controlling process. Neurophysiological, electrophysiological and neuropsychological studies of different brain structures during voluntary attention are analyzed. These data show that selective voluntary attention modulates activity of sensory specific cortical zones involved in relevant signal processing. Fronto-thalamic system consisting of prefrontal cortex and thalamic mediodorsal nuclei is shown to be main source of top-down selective modulation of voluntary attention. The review proposed the hypothetical model of selective cortical activity modulation during voluntary attention based upon the available data and evidence of own electroencephalographic studies.     

Longitudinal Study of the Development of Higher Mental Functions in Primary School Children

This article presents the results of a longitudinal population-based neuropsychological study of the development of higher mental functions (HMFs) in primary school children from grades 1 through 3 at a Moscow public school (n = 84). We monitored changes in HMFs in the total sample and in groups of children with different baseline HMFs (high, medium, low), as measured in the first grade, using seven indexes that reflect individual HMF components such as executive functions (voluntary regulation of activity), serial organization of movements and actions, processing of kinesthetic, auditory, visual, and visual-spatial information, and regulation of activation, at three time points (first, second, and third grades). The study found a generally positive trend in the structural and functional components of HMFs in the children who were tested. Groups of children with different baseline levels of HMFs steadily maintained their differences in the degree of development of the HMFs at each evaluation time point, although the greatest change in HMF components was found in children with initially low scores, and the least change was in children with initially high HMF scores. Among the components with the least change was voluntary regulation—that is, the programming, regulation, and control of one's activity. The fact that children with high baseline functioning did not change significantly in a given function from first to third grades may be related to a decline in learning motivation, insofar as their learning is then occurring in the zone of actual and not proximal development.     

Peculiarities of formation of the cognitive functions in junior school children with different maturity of regulatory brain systems

To reveal the specific role of maturation of modulating, regulatory brain systems in formation of cognitive processes at the junior school age, was performed a complex electroencephalographic and neuropsychological examination of the 7–8-year-old children with different degrees of functional maturity of the regulatory systems. It has been shown that an essential factor determining formation of the higher psychic functions (HPF) at the junior school age is maturation of the fronto-thalamic system. Immaturity of this system in the 7–8-year-old children leads to a deficiency of functions of programming, regulation, and control of the activity. The most substantial changes were revealed for the components of the voluntary organization of the activity, which are connected with its selectivity both in realization of current tasks and in creation of the activity strategy. The deficiency of processes of voluntary regulation in the 7–8-year-old children with immaturity of the fronto-thalamic system is combined with a delay of development of the meaning-forming speech function. Comparison of data of the neuropsychological and electroencephalographic examination has permitted suggesting that the basis of the revealed changes in the HPF formation in the 7–8-year-old children is immaturity of the main neurophysiological mechanisms that provide a selective involvement of different cortical regions in providing their activity both in the course of its realization and during preparation to it as well as an under-development of differentiated intracortical connections in the left hemisphere.Translated from Zhurnal Evolyutsionnoi Biokhimii i Fiziologii, Vol. 40, No. 5, 2004, pp. 427–435.Original Russian Text Copyright © 2004 by Machinskaya, Semenova.To the 100-Anniversary of N. N. Traugott     

Functional maturation of the brain and formation of the neurophysiological mechanisms of selective voluntary attention in young schoolchildren

A particular role was demonstrated for functional maturation of the frontothalamic system (FTS) of the brain in forming the cerebral organization of selective voluntary attention in ontogeny. Analysis of the coherence of the rhythmic components of the EEG α range in adults and seven-to eight-and nine-to ten-year-old children showed that, if the functional state of the control structures corresponds to the age, the formation of the neurophysiological mechanisms selectively modulating cortical activity and supporting selective tuning of the cerebral structures to the cognitive task is completed by the age of seven or eight years. Unlike adults, children demonstrated no interhemispheric features of the intercenter integration of cortical zones in the prestimulus period of voluntary attention. Children with a functionally immature FTS lacked selective specific integration of cortical zones in the pretuning period. The deficit of selective modulation of cortical activity in children with a functionally immature FTS is considered as the neurophysiological factor that delays the formation of voluntary attention and voluntary control of activity and, finally, leads to learning difficulties.     

Neural correlates of voluntary breathing in humans.

To investigate the functional neuroanatomy of voluntary respiratory control, blood O2 level-dependent functional magnetic resonance imaging was performed in six healthy right-handed individuals during voluntary hyperpnea. Functional images of the whole brain were acquired during 30-s periods of spontaneous breathing alternated with 30-s periods of isocapnic hyperpnea [spontaneous vs. voluntary: tidal volume = 0.5 +/- 0.01 vs. 1.3 +/- 0.1 (SE) liters and breath duration = 4.0 +/- 0.4 vs. 3.2 +/- 0.4 (SE) s]. For the group, voluntary hyperpnea was associated with significant (P < 0.05, corrected for multiple comparisons) neural activity bilaterally in the primary sensory and motor cortices, supplementary motor area, cerebellum, thalamus, caudate nucleus, and globus pallidum. Significant increases in activity were also identified in the medulla (corrected for multiple comparisons on the basis of a small volume correction for a priori region of interest) in a superior dorsal position (P = 0.012). Activity within the medulla suggests that the brain stem respiratory centers may have a role in mediating the voluntary control of breathing in humans.     

Exercise is more effective than diet control in preventing high fat diet-induced β-amyloid deposition and memory deficit in amyloid precursor protein transgenic mice

Accumulating evidence suggests that some dietary patterns, specifically high fat diet (HFD), increase the risk of developing sporadic Alzheimer disease (AD). Thus, interventions targeting HFD-induced metabolic dysfunctions may be effective in preventing the development of AD. We previously demonstrated that amyloid precursor protein (APP)-overexpressing transgenic mice fed HFD showed worsening of cognitive function when compared with control APP mice on normal diet. Moreover, we reported that voluntary exercise ameliorates HFD-induced memory impairment and β-amyloid (Aβ) deposition. In the present study, we conducted diet control to ameliorate the metabolic abnormality caused by HFD on APP transgenic mice and compared the effect of diet control on cognitive function with that of voluntary exercise as well as that of combined (diet control plus exercise) treatment. Surprisingly, we found that exercise was more effective than diet control, although both exercise and diet control ameliorated HFD-induced memory deficit and Aβ deposition. The production of Aβ was not different between the exercise- and the diet control-treated mice. On the other hand, exercise specifically strengthened the activity of neprilysin, the Aβ-degrading enzyme, the level of which was significantly correlated with that of deposited Aβ in our mice. Notably, the effect of the combination treatment (exercise and diet control) on memory and amyloid pathology was not significantly different from that of exercise alone. These studies provide solid evidence that exercise is a useful intervention to rescue HFD-induced aggravation of cognitive decline in transgenic model mice of AD.     

Corticospinal Excitability of Trunk Muscles during Different Postural Tasks

Evidence suggests that the primary motor cortex (M1) is involved in both voluntary, goal-directed movements and in postural control. Trunk muscles are involved in both tasks, however, the extent to which M1 controls these muscles in trunk flexion/extension (voluntary movement) and in rapid shoulder flexion (postural control) remains unclear. The purpose of this study was to investigate this question by examining excitability of corticospinal inputs to trunk muscles during voluntary and postural tasks. Twenty healthy adults participated. Transcranial magnetic stimulation was delivered to the M1 to examine motor evoked potentials (MEPs) in the trunk muscles (erector spinae (ES) and rectus abdominis (RA)) during dynamic shoulder flexion (DSF), static shoulder flexion (SSF), and static trunk extension (STE). The level of background muscle activity in the ES muscles was matched across tasks. MEP amplitudes in ES were significantly larger in DSF than in SSF or in STE; however, this was not observed for RA. Further, there were no differences in levels of muscle activity in RA between tasks. Our findings reveal that corticospinal excitability of the ES muscles appears greater during dynamic anticipatory posture-related adjustments than during static tasks requiring postural (SSF) and goal-directed voluntary (STE) activity. These results suggest that task-oriented rehabilitation of trunk muscles should be considered for optimal transfer of therapeutic effect to function.     

Using voluntary motor commands to inhibit involuntary arm movements

A hallmark of voluntary motor control is the ability to stop an ongoing movement. Is voluntary motor inhibition a general neural mechanism that can be focused on any movement, including involuntary movements, or is it mere termination of a positive voluntary motor command? The involuntary arm lift, or ‘floating arm trick’, is a distinctive long-lasting reflex of the deltoid muscle. We investigated how a voluntary motor network inhibits this form of involuntary motor control. Transcranial magnetic stimulation of the motor cortex during the floating arm trick produced a silent period in the reflexively contracting deltoid muscle, followed by a rebound of muscle activity. This pattern suggests a persistent generator of involuntary motor commands. Instructions to bring the arm down voluntarily reduced activity of deltoid muscle. When this voluntary effort was withdrawn, the involuntary arm lift resumed. Further, voluntary motor inhibition produced a strange illusion of physical resistance to bringing the arm down, as if ongoing involuntarily generated commands were located in a ‘sensory blind-spot’, inaccessible to conscious perception. Our results suggest that voluntary motor inhibition may be a specific neural function, distinct from absence of positive voluntary motor commands.     

Timing of cortical excitability changes during the reaction time of movements superimposed on tonic motor activity.

Seated subjects were instructed to react to an auditory cue by simultaneously contracting the tibialis anterior (TA) muscle of each ankle isometrically. Focal transcranial magnetic stimulation of the leg area of the motor cortex (MCx) was used to determine the time course of changes in motor-evoked potential amplitude (MEP) during the reaction time (RT). In one condition the voluntary contraction was superimposed on tonic EMG activity maintained at 10% of maximal voluntary contraction. In the other condition the voluntary contraction was made starting from rest. MEPs in the TA contralateral to the stimulation coil were evoked at various times during the RT in each condition. These were compared to the control MEPs evoked during tonic voluntary activity or with the subject at rest. The RT was measured trial by trial from the EMG activity of the TA ipsilateral to the magnetic stimulus, taking into account the nearly constant time difference between the two sides. The MEPs became far greater than control MEPs during the RT (mean = 332%, SD = 44 %, of control MEPs, P < 0.001) without any measurable change in the background level of EMG activity. The onset of this facilitation occurred on average 12.80 ms (SD = 7.55 ms) before the RT. There was no difference in the onset of facilitation between the two conditions. Because MEPs were facilitated without a change in the background EMG activity, it is concluded that this facilitation is specifically due to an increase of MCx excitability just before voluntary muscle activation. This conclusion is further reinforced by the observation that MEPs evoked by near-threshold anodal stimuli to the MCx were not facilitated during the RT, in contrast to those evoked by near-threshold transcranial magnetic stimulation. However, several observations in the present and previous studies indicate that MEP amplitude may be more sensitive to alpha-motoneuron activity than to motor cortical neuron activity, an idea that has important methodological implications.     

Biofeedback modification of frontal EMG in normal subjects

We carried out a controlled study on the voluntary control of the frontalis muscle by biofeedback procedures employing 20 normal subjects. Subjects were randomly divided into two groups of 10: (1) the biofeedback group and (2) the control group. Each of the two groups received five training sessions of about 40 minutes' duration each on different days. The results obtained are as follows: (1) In the biofeedback group, mean EMG levels decreased progressively and markedly from 2. 16 muVp-p min the first session to 1.54 muVp-p min in the last session. On the contrary, the control group did not show constant decreases in EMG levels over sessions. (2) The changes in the heart rate did not correlate with the changes in EMG activity. (3) The changes in the respiratory rate correlated with the changes in EMG activity.     

Biofeedback modification of frontal EMG in normal subjects

We carried out a controlled study on the voluntary control of the frontalis muscle by biofeedback procedures employing 20 normal subjects. Subjects were randomly divided into two groups of 10: (1) the biofeedback group and (2) the control group. Each of the two groups received five training sessions of about 40 minutes' duration each on different days. The results obtained are as follows: (1) In the biofeedback group, mean EMG levels decreased progressively and markedly from 2.16µVp-p min in the first session to 1.54µVp-p min in the last session. On the contrary, the control group did not show constant decreases in EMG levels over sessions. (2) The changes in the heart rate did not correlate with the changes in EMG activity. (3) The changes in the respiratory rate correlated with the changes in EMG activity.     

Intracerebroventricular injection of ghrelin decreases wheel running activity in rats

There is an increasing interest in elucidating the molecular mechanisms by which voluntary exercise is regulated. In this study, we examined how the central nervous system regulates exercise. We used SPORTS rats, which were established in our laboratory as a highly voluntary murine exercise model. SPORTS rats showed lower levels of serum ghrelin compared with those of the parental line of Wistar rats. Intracerebroventricular and intraperitoneal injection of ghrelin decreased wheel-running activity in SPORTS rats. In addition, daily injection of the ghrelin inhibitor JMV3002 into the lateral ventricles of Wistar rats increased wheel-running activity. Co-administration of obestatin inhibited ghrelin-induced increases in food intake but did not inhibit ghrelin-induced suppression of voluntary exercise in rats. Growth hormone secretagogue receptor (GHSR) in the hypothalamus and hippocampus of SPORTS rats was not difference that in control rats. We created an arcuate nucleus destruction model by administering monosodium glutamate (MSG) to neonatal SPORTS rats. Injection of ghrelin into MSG-treated rats decreased voluntary exercise but did not increase food intake, suggesting that wheel-running activity is not controlled by the arcuate nucleus neurons that regulate feeding. These results provide new insights into the mechanism by which ghrelin regulates voluntary activity independent of arcuate nucleus neurons.     

Initial phase of maximal voluntary and electrically stimulated knee extension torque development at different knee angles.

We investigated the capacity for torque development and muscle activation at the onset of fast voluntary isometric knee extensions at 30, 60, and 90 degrees knee angle. Experiments were performed in subjects (n = 7) who had high levels (>90%) of activation at the plateau of maximal voluntary contractions. During maximal electrical nerve stimulation (8 pulses at 300 Hz), the maximal rate of torque development (MRTD) and torque time integral over the first 40 ms (TTI40) changed in proportion with torque at the different knee angles (highest values at 60 degrees ). At each knee angle, voluntary MRTD and stimulated MRTD were similar (P < 0.05), but time to voluntary MRTD was significantly longer. Voluntary TTI40 was independent (P > 0.05) of knee angle and on average (all subjects and angles) only 40% of stimulated TTI40. However, among subjects, the averaged (across knee angles) values ranged from 10.3 +/- 3.1 to 83.3 +/- 3.2% and were positively related (r2 = 0.75, P < 0.05) to the knee-extensor surface EMG at the start of torque development. It was concluded that, although all subjects had high levels of voluntary activation at the plateau of maximal voluntary contraction, among subjects and independent of knee angle, the capacity for fast muscle activation varied substantially. Moreover, in all subjects, torque developed considerably faster during maximal electrical stimulation than during maximal voluntary effort. At different knee angles, stimulated MRTD and TTI40 changed in proportion with stimulated torque, but voluntary MRTD and TTI40 changed less than maximal voluntary torque.     

Trainability of Muscular Activity Level during Maximal Voluntary Co-Contraction: Comparison between Bodybuilders and Nonathletes

Antagonistic muscle pairs cannot be fully activated simultaneously, even with maximal effort, under conditions of voluntary co-contraction, and their muscular activity levels are always below those during agonist contraction with maximal voluntary effort (MVE). Whether the muscular activity level during the task has trainability remains unclear. The present study examined this issue by comparing the muscular activity level during maximal voluntary co-contraction for highly experienced bodybuilders, who frequently perform voluntary co-contraction in their training programs, with that for untrained individuals (nonathletes). The electromyograms (EMGs) of biceps brachii and triceps brachii muscles during maximal voluntary co-contraction of elbow flexors and extensors were recorded in 11 male bodybuilders and 10 nonathletes, and normalized to the values obtained during the MVE of agonist contraction for each of the corresponding muscles (% EMG_MVE). The involuntary coactivation level in antagonist muscle during the MVE of agonist contraction was also calculated. In both muscles, % EMG_MVE values during the co-contraction task for bodybuilders were significantly higher (P<0.01) than those for nonathletes (biceps brachii: 66±14% in bodybuilders vs. 46±13% in nonathletes, triceps brachii: 74±16% vs. 57±9%). There was a significant positive correlation between a length of bodybuilding experience and muscular activity level during the co-contraction task (r = 0.653, P = 0.03). Involuntary antagonist coactivation level during MVE of agonist contraction was not different between the two groups. The current result indicates that long-term participation in voluntary co-contraction training progressively enhances muscular activity during maximal voluntary co-contraction.     

Hyperthermia and central fatigue during prolonged exercise in humans.

The present study investigated the effects of hyperthermia on the contributions of central and peripheral factors to the development of neuromuscular fatigue. Fourteen men exercised at 60% maximal oxygen consumption on a cycle ergometer in hot (40 degrees C; hyperthermia) and thermoneutral (18 degrees C; control) environments. In hyperthermia, the core temperature increased throughout the exercise period and reached a peak value of 40.0 +/- 0.1 degrees C (mean +/- SE) at exhaustion after 50 +/- 3 min of exercise. In control, core temperature stabilized at approximately 38.0 +/- 0.1 degrees C, and exercise was maintained for 1 h without exhausting the subjects. Immediately after the cycle trials, subjects performed 2 min of sustained maximal voluntary contraction (MVC) either with the exercised legs (knee extension) or with a "nonexercised" muscle group (handgrip). The degree of voluntary activation during sustained maximal knee extensions was assessed by superimposing electrical stimulation (EL) to nervus femoralis. Voluntary knee extensor force was similar during the first 5 s of contraction in hyperthermia and control. Thereafter, force declined in both trials, but the reduction in maximal voluntary force was more pronounced in the hyperthermic trial, and, from 30 to 120 s, the force was significantly lower in hyperthermia compared with control. Calculation of the voluntary activation percentage (MVC/MVC + EL) revealed that the degree of central activation was significantly lower in hyperthermia (54 +/- 7%) compared with control (82 +/- 6%). In contrast, total force of the knee extensors (MVC + force from EL) was not different in the two trials. Force development during handgrip contraction followed the same pattern of response as was observed for the knee extensors. In conclusion, these data demonstrate that the ability to generate force during a prolonged MVC is attenuated with hyperthermia, and the impaired performance is associated with a reduction in the voluntary activation percentage.     

The Zeus of Kharkov Psychology

The controversial questions of the relations between L.S. Vygotsky’s theory of development of higher mental functions and A.N. Leontiev’s activity theory are considered in the context of the theoretical principles of the research of P.I. Zinchenko. In the author’s view, these theories are mutually complementary and potentially could be combined into a single theory. A survey of the key results of the research conducted by Zinchenko in voluntary and involuntary mediated memory is presented. Thanks to the high heuristic potential of the cultural-historical and activity-based approaches, original methodologies were developed and empirical studies were performed on fundamental mnemic effects, which much later were independently “rediscovered” in cognitive psychology (including the generation effect and the depth-of-processing effect). The patterns identified by P.I. Zinchenko in the development of mediated voluntary and involuntary memory are also of great importance in the context of current research in the age-related development of memory.     

Interactions between estrogen effects and hunger effects in ovariectomized female mice. I. Measures of arousal

Measures of arousal were used to study effects of estradiol and food restriction, and their potential interactions, in ovariectomized female C57Bl/6 mice. It was hypothesized based on a proposed theoretical equation [Pfaff, D.W., 2006a. Brain Arousal and Information Theory. Harvard University Press, Cambridge, Pfaff, D.W., (Ed.), 2006b. Knobil and Neill's The Physiology of Reproduction, 3rd edition. Elsevier/Academic Press, San Diego] that each treatment would increase arousal-related behaviors and that their combination would further increase arousal behavior. Following baseline testing, animals (n=28) were divided into 3 groups that, in different experimental phases, received either estradiol (in subcutaneous capsules), restricted diet (a liquid diet providing 60% of daily caloric requirements) or a combination of those two. An automated arousal behavior monitoring system was used to measure home cage voluntary motor activity and sensory responsiveness, these being components of a new operational definition of 'generalized arousal'. Key findings: (1) During the light, all treatments reduced voluntary activity. (2) In the dark, estrogens increased, while estrogens in combination with restricted diet decreased, horizontal activity. (3) In the dark, restricted diet alone had little effect on voluntary activity, but reduced it when combined with estrogen treatment. (4) All treatments reduced responses to the olfactory stimulus. The dependence of results on time of day was unexpected. Further, different patterns of results for the three treatments suggest that estrogens and food restriction did not have equivalent or additive effects on arousal. While contrary to the main prediction, these findings are discussed in terms of the animals' adaptive preparations for reproduction [Schneider, J.E., 2006. Metabolic and hormonal control of the desire for food and sex: implications for obesity and eating disorders. Horm. Behav. 50, 562-571].     

Voluntary control of sexual responding in men and women: Implications for the etiology and treatment of sexual dysfunctions

Recent psychophysiological investigations have shown that biofeedback and operant conditioning procedures are associated with changes in genital vasomotor activity in men and women. Although the exact role played by biofeedback or operant contingencies in the establishment of genital vasomotor control has not been conclusively established, some degree of voluntary control has been reliably demonstrated over a response that is traditionally viewed as an involuntary component of the human sexual response cycle. The present article critically reviews the experimental literature pertinent to the issue of voluntary self-control of sexual responding and makes recommendations concerning future research. The implications of this literature for traditional etiological theories and treatment approaches for sexual dysfunctions are discussed. The potential of biofeedback and operant techniques for shaping genital responses, increasing discriminability, enhancing body awareness, and facilitating cognitive labeling of genital sensations are discussed as they relate to the stated goals of sex therapy.     

Cardiac sympathetic and parasympathetic activity during self-regulation of heart period.

Fourteen subjects attempted to increase and 15 attempted to decrease cardiac interbeat interval (IBI) while being provided with biofeedback of IBI, T-wave vector magnitude (TWVM), or respiratory sinus arrhythmia (RSA). Subjects in both groups showed directional change in IBI relative to a tracking control task, but the three types of feedback did not differentially affect performance. Voluntary IBI increases were associated with significant increases in TWVM and RSA, and voluntary IBI decreases were associated with significant reductions in RSA and nonsignificant reductions in TWVM. This pattern of results suggests that alterations in cardiac vagal tone are involved in voluntary IBI increase and decrease tasks. The results also suggest a role for cardiac sympathetic nervous activity in voluntary IBI increase. The role of changing respiration cycle period was also investigated.