Comparison of neuronal response pattern in the rat somatosensory cortex during active and passive vibrissae movements

A comparative study of neuronal response in separate cortical columns of the somatosensory cortex (the barrel field area) was made in unanesthetized partially curarized white rats under various circumstances: during passive deflection of immobile vibrissa, unhindered volitional sweeping movement of the vibrissae, and during movement induced by stimulating the motor cortex and facial muscles. Differences in the response of the same neurons emerged under these different experimental situations. Different groups of neurons — responding before, during, and after volitional vibrissa movements were observed. Such response is thought to be triggered by different afferent trains reaching cortical column neurons from sources including the motor cortex, the vibrissa follicle receptors, and facial muscles.Institute of Neurocybernetics, State University, Rostov-on-Don. State University, Simferopol. Translated from Neirofiziologiya, Vol. 22, No. 2, pp. 235–242, March–April, 1990.     

Spatial perception and vestibulomotor responses in man

A study was made on normal human subjects, using a stabilograph to investigate changes in posture produced in response to transcutaneous galvanic stimulation of the right labyrinth. Results were obtained for different head positions and under the illusion of head and trunk rotation produced by stimulating (vibrating) the gulteus maximus muscle. In the absence of illusion of movement, the direction of the vestibulomotor response was determined by the position of the head in relation to the feed: with the normal head position, the body swayed on a frontal plane, and on a sagittal plane when the heat turned through 90°. Vestibulomotor responses were sagittally oriented, as with real head turning, when illusory head and trunk turning through 90° was produced by vibration. When the illusion of head rotation (in relation to the feet) was not produced by this stimulus, the direction of the postural response was not produced by this stimulus, the direction of the postural response was determined by the real orientation of the head. It is concluded that the spatial perception system plays a major part in controlling spatially oriented vestibulomotor responses.Institute for Research into Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 18, No. 6, pp. 779–787, November–December, 1986.     

Changes in the direction of vestibulomotor response in the course of adaptation to protracted static head turning in man

Vestibulomotor response during the course of adaptation to prolonged (10 min) static head turning to the furthest limit was investigated in healthy subjects standing upright with the eyes closed. The head was either actively or passively maintained in this position. The sensation of a decline in the angle of head turning was experienced during adaptation to the position by five of the 12 subjects tested. Error in appreciating this angle ranged up to 70–80°. Matching changes occurred in the direction of vestibulomotor response to electrical stimulation of the vestibular apparatus. When true and perceived head position conflict, direction of vestibulomotor response thus matches spatial perception rather than actual orientation of the head.Institute for Research into Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 21, No. 2, pp. 210–217, March–April, 1989.     

Changes in vestibular postural response determined by information content of visual feedback

Electrical unipolar monoaural stimulation of the labyrinth led to body sway mainly on a frontal plane in normal human subjects in a standing position. Early and late stages of response with latencies of 120–200 and 200–500 msec respectively changing in size in accordance with conditions of visual control were distinguished in the stabilographic response. Maximum response was recorded when the eyes were closed. Response declined upon opening the eyes, fixing the gaze on a static target, and with visual feedback according to stabilograms. The early and late components declined by 10–20 and 50–70% respectively in all cases. Fixing the gaze, in darkness, on an illuminated light spot stationary in relation to the head had no effect on level of response. Once the expected direction of body sway had been imparted, a significant and almost identical decrease of 70–80% in both components took place with the gaze fixed, however. Early and late components of vestibulomotor response are thought to be mediated by regulatory mechasisms with differing time courses and functional connections.Institute of Research into Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vo. 22, No. 1, pp. 80–87, January–February, 1990.     

Postural responses to vibrostimulation of the neck muscle proprioceptors in man

Postural responses to vibrostimulation (50–100 Hz, 0.5 mm, 4–8 sec) of muscles of the back surface of the neck were studied in healthy subjects. In the sitting position, vibrostimulation evoked local displacements (backward head deflection), but global postural responses (forward inclination of the whole body) developed in the standing position. The amplitude of the evoked body inclination was dependent upon the site of the vibrostimuli application along the vertebral column. Asymmetrical application of vibrostimuli to the muscles of the right or left neck side was accompanied by development of a lateral component in the postural response. Changes in the spatial orientation of the head led to the changes in postural response direction: head turning to the right resulted in right-side body deviation during vibration, and vice versa. Illusions of head bend caused by habituation to its static turning were accompanied by precisely the same changes in the direction of body deviation. It is assumed that neck-evoked motor events are mediated via central mechanisms that are involved in perception of the head and body position in space.Translated from Neirofiziologiya, Vol. 25, No. 2, pp. 101–108, March–April, 1993.     

Proprioceptive endings in the myotomes of the pickerel (Teleostei: Esocidae)

Simple spray nerve endings of axons with a large diameter (15 μm) were located in the stratum compactum overlying the myotomal muscles in the pickerels, Esox niger and E. americanus . Based on the location of these nerve endings within the interwoven collagenous fibre matrix comprising the stratum compactum, and on the lack of reactivity to cholinesterase treatment, it is suggested that the endings are sensory in function and may be used as proprioceptors. These putative proprioceptors may aid the pickerel in monitoring the position of the body, (1) during ambush prey capture where the pickerel must lie motionless with as little disturbance in the water column as possible, and (2) in counteracting unwanted hydrodynamic forces such as pitch or roll brought about by sudden stopping of forward movement immediately following prey capture. This is the first report of proprioceptive endings associated with locomotor musculature in teleost fishes.     

Impact of movement tempo on bar velocity and time under tension in resistance exercises with different external loads

The goal of the study was to determine the differences between volitional and maximal movement tempo during resistance exercise. Ten healthy men volunteered for the study (age = 26.4 ± 4.8 years; body mass = 93.8 ± 9.6 kg; barbell squat one-repetition maximum (1RM) = 175 ± 16.7 kg; bench press 1RM = 140.5 ± 26.8 kg). In a randomized order, the participants performed six sets of the barbell squat and the bench press exercise at progressive loads from 40% to 90%1RM (step by 10%) under two testing conditions: with volitional movement tempo or with maximal movement tempo. The three-way repeated measures ANOVA showed a statistically significant multi-interaction effect for time under tension (p < 0.001), peak bar velocity (p = 0.04) and for mean bar velocity (p < 0.001). There was also a statistically significant main effect of movement tempo for time under tension (p < 0.001), peak bar velocity (p < 0.001) and for mean bar velocity (p < 0.001). The post hoc analysis for main effect of tempo revealed that time under tension was significantly longer for volitional compared to maximal tempo (0.84 vs 0.67 s, respectively), peak bar velocity was significantly higher for maximal compared to volitional tempo (1.24 m/s vs 0.90 m/s, respectively), and mean bar velocity was significant higher for maximal compared to volitional tempo (0.84 m/s vs 0.67 m/s, respectively). The presented results indicate that there were significant differences between volitional and maximal movement tempos in time under tension and bar velocity (peak and mean), as well as significant differences in those variables between the two exercises. Therefore, the velocity of movement and time under tension is related to movement tempo, external load and type of exercise used.     

The effect of short-term changes in body mass distribution on feed-forward postural control

It was recently shown that short-term changes in the whole body mass and associated changes in the vertical position of the center of mass (COM) modify anticipatory postural adjustments (APAs) [Li X, Aruin AS. The effect of short-term changes in the body mass on anticipatory postural adjustments. Exp Brain Res 2007;181:333–46]. In this study, we investigated whether changes in the body mass distribution and related changes in the anterior–posterior COM position affect APA generation. Fourteen subjects were instructed to catch a 2.2 kg load with their arms extended while standing with no additional weight or while carrying a 9.08 kg weight. Adding weight to a backpack, front pack or belly pocket was associated with an increase of the whole body mass, but it also involved changes in the anterior–posterior (A/P) and vertical positions of the COM. Electromyographic activity of leg and trunk muscles, body kinematics, and ground reaction forces were recorded and quantified within the typical time intervals of APAs. APAs were modified in conditions with changed body mass distribution: increased magnitude of anticipatory EMG activity in leg and trunk muscles, as well as co-activation of leg muscles and decreased anticipatory displacement of the COM in the vertical direction, were seen in conditions with increased body mass. Changes in the COM position induced in both A/P and vertical directions were associated with increased anticipatory EMG activity. In addition, they were linked to a co-activation of muscles at the ankle joints and significant changes in the center of pressure (COP) position. Modifications of the COM position induced in the A/P direction were related to increased anticipatory EMG activity in the leg and trunk muscles. At the same time, no significant differences in anticipatory EMG activity or displacement of COP were observed when changes of COM position were induced in the vertical direction. The study outcome suggests that the CNS uses different strategies while generating APAs in conditions with changes in the COM position induced in the anterior–posterior and vertical directions.     

Rotational optokinesis in reptiles and its bearing on pupillary shape

Summary Members of all orders of reptiles rotate the optic bulb to compensate for changes in pitch of the head. The eye rotates through 20–30° in snakes and turtles, 50° in crocodiles and 60° in rhynochocephalians. The eye fully compensates for changes in pitch of the head over about 1/2 the range of its response. This response is largley mediated by vestibular position reflexes. It is relatively independent of the visual horizon, body proprioceptors and temperature.Rotation of the eye bulb can be related to pupillary shape and to the reported organization of the visual projections to the optic tectum. Regardless of head position, reptiles orient their eyes to keep the horizon under close inspection.This work was supported by NSF grants GB-3702 and GB-6303.     

Human postural responses to different frequency vibrations of lower leg muscles

We analyzed human postural responses to muscle vibration applied at four different frequencies to lower leg muscles, the lateral gastrocnemius (GA) or tibialis anterior (TA) muscles. The muscle vibrations induced changes in postural orientation characterized by the center of pressure (CoP) on the force platform surface on which the subjects were standing. Unilateral vibratory stimulation of TA induced body leaning forward and in the direction of the stimulated leg. Unilateral vibration of GA muscles induced body tilting backwards and in the opposite direction of the stimulated leg. The time course of postural responses was similar and started within 1 s after the onset of vibration by a gradual body tilt. When a new slope of the body position was reached, oscillations of body alignment occurred. When the vibrations were discontinued, this was followed by rapid recovery of the initial body position. The relationship between the magnitude of the postural response and frequency of vibration differed between TA and GA. While the magnitude of postural responses to TA vibration increased approximately linearly in the 60-100 Hz range of vibration frequency, the magnitude of response to GA vibration increased linearly only at lower frequencies of 40-60 Hz. The direction of body tilt induced by muscle vibration did not depend on the vibration frequency.     

Evaluation of the EMG-force relationship of trunk muscles during whole body tilt

The study was aimed at the identification of the electromyography (EMG)-force relationship of five different trunk muscles. EMG-force relationships differ depending on changes in firing rate and the concurrent recruitment of motor units, which are linear and S-shaped, respectively. Trunk muscles are viewed as belonging to either the local or global muscle systems. Based on such assumptions, it would be expected that these functionally assigned muscles use different activation strategies. Thirty-one healthy volunteers (16 women, 15 men) were investigated. Forces on the trunk were applied with the use of a device that gradually tilts the body to horizontal position. Rotation capability enabled investigation of forward and backward as well as right and left sideward tilt directions. Surface EMG (SEMG) of five trunk muscles was taken. Root mean square (rms) values were computed and relative amplitudes, according to the measured maximum amplitudes, were calculated individually. Back muscles were characterized by a linear SEMG-force relationship during forward tilt. Abdominal muscles showed an S-shaped polynomial SEMG-force relationship for backward tilt direction. Sideward tilt directions evoked lesser SEMG levels with polynomial curve characteristics for all investigated muscles. Therefore, the SEMG-force relationship possibly is also subject to force vector in relation to fiber direction.     

Influence of adequate vestibular stimulation on locomotor activity in the guinea pig forelimb muscles. Tilting in relation to the longitudinal axis

The influence of adequate vestibular stimulation occurring as the animal tilted around longitudinal axis on locomotor activity of the forelimb muscles was investigated during experiments on guinea pigs decerebrated at precollicular level. Locomotor activity was produced by electrical stimulation of the mesencephalic locomotor region. An increase in extensor EMG activity was observed when the animal shifted its weight onto the limb ipsilateral to the tilt during the "standing" phase and a reduction in flexor activity during the swing phase. The reverse of these changes was seen in the activity of antagonist muscles in the contralateral limb. It was found that changes in muscular locomotor activity exceeded those observed during animal movements by 60–40° in the extensors and 40–20° in the flexors during cyclic sinusoidal tilting in the 0.02–0.4 Hz range. The mechanisms underlying vestibular control of locomotor activity are discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 4, pp. 534–541, July–August, 1987.     

Coding proprioceptive information to control movement to a target: Simulation with a simple neural network

When the stick insect walks, the middle and rear legs step to positions immediately behind the tarsus of the adjacent rostral leg. Previous reports have described this movement to a target as a relationship between the tarsus positions of the two legs in a Cartesian coordinate system. However, leg proprioceptors measure the position of the target leg in terms of joint angles and leg muscles bring the tarsus of the moving leg to the proper end-point by establishing appropriate angles at the joints. Representation of this task in Cartesian coordinates requires non-linear coordinate transformations; realizing such a transformation in the nervous system appears to require many neurons. The present simulation using the back-propagation algorithm shows that a simple network of only nine units — 3 sensory input units, 3 motor output units, and 3 hidden units — suffices. The simulation also shows that an analytic coordinate transformation can be replaced by a direct association of joint configurations in the moving leg with those in the target leg.     

Visual control of steering in locust flight: the effects of head movement on responses to roll stimuli

The contribution of head movement to the control of roll responses in flying locusts (Locusta migratoria) has been examined (i) on a flight balance, recording the angles through which the locust turns when following an artificial horizon; (ii) by recording activity in a pair of flight muscles in restrained conditions; and (iii) by observations on free flying locusts. Responses were compared when the head was free to turn about the thorax, as normal, and when the head was waxed to the thorax, blocking any relative motion between the two (head-fixed). These experiments suggest that the major signal generating corrective roll manoeuvres is the visual error between the angle of the head and the horizon, rather than a signal that includes a measure of the head-thorax angle.

Masseter muscle activity during vestibular stimulation in man

Experimental data report that vestibular afferents affect trigeminal system activity. The aim of this work was to evaluate whether static vestibular stimulation affects the excitability of trigeminal motoneurons in man. In order to assess this, voluntary EMG activity of masseter muscles as well as duration and latency of the early and late components of EMG exteroceptive silent period were evaluated while keeping the subject in vertical position and during 20 degrees static tilt. The experiments were performed on ten adult subjects with no orofacial, neurologic and otologic disorders. Each subject sat on a chair, which kept the complex head-jaw-neck-trunk and the limbs securely fixed, in order to minimize any interference due to the activation of somatosensory and proprioceptive afferents from these districts. The subjects were instructed to contract masseter muscles at 25% of their maximum bite force and the isometric force monitoring was used as visual feedback. Exteroceptive silent period (ESP) of masseter EMG was elicited by electrically stimulating the inferior inter-incisal gum. Results showed that static vestibular stimulation induced asymmetrical responses on voluntary masseter muscle activity, which was reduced to 70.3 +/- 16.1% (mean +/- S.D.) of the control value during ipsilateral tilt and increased to 128.8 +/- 13.0% during contralateral tilt. The duration of the early (ESP1) and late (ESP2) silent periods was also affected: during ipsilateral tilt ESP1 and ESP2 duration increased to 130.0 +/- 3.5% and to 122.1 +/- 2.1% of control, respectively; during contralateral tilt it was reduced to 76.8 +/- 1.2% and to 83.0 +/- 1.7% of control, respectively. On the contrary, changes in latencies were not significant. These data evidenced an asymmetrical effect exerted on trigeminal motor activity by static tilt. Since the influence of all receptors which could be activated by static tilt, except that arising from the macular ones, was minimized in this study, it is likely that the observed effects, induced by static tilt on masseter muscle activity, were of macular origin.     

On the invariance of visual stimulus efficacy with respect to variable spatial positions

Summary In the fly,Calliphora erythrocephala, visual stimuli presented in an asymmetrical position with respect to the fly elicit roll or tilt movements of the head by which its dorsal part is moved towards the light areas of the surroundings (Figs. 4–7). The influence of passive body roll and tilt (gravitational stimulus) on the amplitude of these active head movements was investigated for two types of visual stimuli: (1) a dark hollow hemisphere presented in different parts of the fly's visual field, and (2) a moving striped pattern stimulating the lateral parts of one eye only.The response characteristics of the flies in the bimodal situation in which the gravitational stimulus was paired with stimulation by the dark hollow hemisphere can be completely described by the addition of the response characteristics for both unimodal situations, i.e. by the gravity-induced and visually induced characteristics (Figs. 8, 9). Therefore, the stimulus efficacy of the dark hollow hemisphere is independent of (=invariant with respect to) the flies' spatial position. The advantage of this type of interaction between gravity and visual stimulation for the control of body posture near the horizontal is discussed.In contrast, the efficacy of moving patterns depends on (=non-invariant with respect to) the spatial position of the walking fly. Regressive pattern movements exhibit their stronger efficacy with respect to progressive ones only when the gravity receptor system of the legs is stimulated. The stronger efficacy of downward vs upward movements can only be demonstrated when the flies are walking horizontally, independently of whether the leg gravity receptor system is stimulated by gravity or not (Fig. 10).The results are discussed with respect (1) to the invariance and non-invariance of the efficacy of visual stimuli with respect to the direction of the field of gravity, (2) to the formation of reference lines by the gravitational field which are used by the walking fly to determine the orientation of visual patterns, and (3) to the possible location of the underlying convergence between gravitationally and visually evoked excitation. As all types of head responses occur only in walking flies, we also discussed the possible influences of some physiological processes like arousal, proprioceptive feedback during walking and various peripheral sensory inputs on the performance of behavioural responses in the fly (Fig. 11).     

Proprioceptive reflex interactions with central motor rhythms in the isolated thoracic ganglion of the shore crab

Summary Experiments were carried out on an isolated central nervous system preparation of the shore crab,Carcinus maenas, comprising the fused thoracic ganglion complex with two proprioceptors of one back leg still attached. These, the thoracic-coxal muscle receptor organ and the coxo-basal chordotonal organ, monitor movement and position of the first and second joints, respectively. Motor activity was recorded extracellularly from the central cut ends of the nerves innervating the promotor and remotor muscles of the thoracic-coxal joint, and the levator and depressor muscles of the coxal-basal joint of the same leg. Simultaneous intracellular recordings were made from central processes of individual motoneurones of each muscle.In the absence of any sensory input, the isolated ganglion exhibited rhythmic bursting in the motor nerve roots, with a slow, usually irregular cycle period of 5–50 s.Both receptor organs had both intra-joint and inter-joint effects on the rhythmically active preparation. In most cases the coxo-basal receptor organ had the greater effect.Resistance reflexes initiated by each of the joint proprioceptors were modulated by the rhythmic activity.It may be concluded that, while the isolated thoracic ganglion of the crab is capable of generating rhythmic motor output, proprioceptive feedback from the two basal joints is important in shaping the motor patterns underlying locomotion. Inappropriate reflexes which would impede active movements about these joints are modulated or reversed so as to permit and even reinforce intended locomotory movements.     

Ventilatory response to phasic contraction and passive movement in graded anesthesia

The ventilatory response to electrically induced contraction (EIC) and passive movement (PM) of hindlimb muscles at different levels of anesthesia was studied in 11 chloralose-urethan anesthetized dogs with and without rhizotomy. The level of anesthesia was assessed by corneal reflexes and measurements of the ventilatory response to hypercapnia. Muscle contraction was induced by electrically stimulating the peripheral cut ends of the sciatic and femoral nerves for 4-5 min, and PM was induced manually at the same frequency and amplitude as during EIC. In spinal intact dogs (n = 7), initial rapid increases in minute ventilation (VE) during EIC and PM were found in both light and deep anesthesia. Further increases in VE above the initial rise were seen during EIC but not PM. The initial rapid increases in VE did not differ between the two anesthetic levels. The steady-state ventilatory response during EIC decreased as anesthesia deepened but did not do so during PM. Rhizotomy (n = 4) abolished the initial rapid increase in VE during EIC and PM and the steady-state VE response to PM at both anesthetic levels. These results suggest that the transitional ventilatory response is neurally mediated from the muscles and not affected by the level of general anesthesia. Additionally, the anesthesia-induced reduction of ventilatory response may be due to depression of responsiveness to CO2 rather than to the inspiratory motoneuron pathway.     

Efferent activity in the phrenic nerve during startle reflex in chloralose anesthetized cats

Efferent activity was investigated in the phrenic nerve during startle reflex manifesting as somatic nerve discharges (lower intercostal nerves and the nerve endings) in chloralose anesthetized cats. Inhibition (usually of short duration, lasting 23–36 msec) of inspiration activity was found to be the main component of response in the phrenic nerve in the shaping of "low threshold" startle reflex produced by acoustic and tactile stimuli and stimulation of low threshold peripheral afferents. Reflex discharge prevailed amongst the response patterns produced in the phrenic nerve by stimulating high threshold afferents, i.e., early (propriospinal) and late (suprasegmental, arising from stimulating intercostal nerve) or late only (when stimulating the hindlimb nerves). Two patterns of late response could be distinguished, one on inspiration (found in roughly 3 out of 4 experiments) and other on exhalation — the respiratory homologs of somatic startle reflex. Response pattern is described throughout the respiratory cycle. Structure and respiratory modulation of reflex responses produced in the phrenic nerve by stimulating bulbar respiratory structure are also examined. Possible neurophysiological mechanisms underlying phrenic response during the shaping of startle reflex are discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 4, pp. 473–482, July–August, 1987.     

Vestibular reafference shapes voluntary movement

The vestibular organs in the inner ear are commonly thought of as sensors that serve balance, gaze control, and higher spatial functions such as navigation. Here, we investigate their role in the online control of voluntary movements. The central nervous system uses sensory feedback information during movement to detect and correct errors as they develop. Vestibular organs signal three-dimensional head rotations and translations and so could provide error information for body movements that transport the head in space. To test this, we electrically stimulated human vestibular nerves during a goal-directed voluntary tilt of the trunk. The stimulating current waveform was made identical to the angular velocity profile of the head in the roll plane. With this, we could proportionally increase or decrease the rate of vestibular nerve firing, as if the head were rotating faster or slower than it actually was. In comparison to movements performed without stimulation, subjects tilted their trunk faster and further or slower and less far, depending upon the polarity of the stimulus. The response was negligible when identical stimulus waveforms were replayed to stationary subjects. We conclude that the brain uses vestibular information for online error correction of planned body-movement trajectories.