The patterns of changes in physiological and psychophysiological indices in operators with a three-shift working day under various work conditions

In the pulp and paper industry, intense operator activity has been demonstrated to cause fatigue in bleachers and chlorinators at different times of shift work (day, evening, and night). In all the operators, the tests for sensorimotor coordination revealed an increase in the number of errors and changes in the index of coordination; in addition, in chlorinators, fatigue was accompanied by feeling unwell and low activity (the WAM test). The diurnal rhythm of physiological functions against the background of work activity was determined from changes in the body temperature (in bleachers), heart rate, blood pressure, and sensorimotor coordination. The presence of harmful chemical substances (chlorine and chlorine dioxide) in the air negatively influenced the psychophysiological state of the chlorinators.     

Reflection of temporal parameters of an optical stimulus in unitary responses of the sensomotor and visual cortex in cats

Unit activity in the visual (area 17) and sensomotor (areas 4 and 6) cortex in response to an optical stimulus up to 1000 msec in duration was investigated by extracellular recording in acute experiments on cats anesthetized with chloralose (70 mg/kg body weight). Comparative analysis of the types of unitary responses and the durations of the intervals of functional changes showed that: 1) The number of neurons generating on-off responses was about 25% in the visual cortex and 100% in the sensomotor cortex; 2) the intervals of functional changes of the neurons were equal in length to the time intervals of on-off discharges; 3) together with a single time range (200–500 msec), for each area studied specific ranges also exist: from 0 to 200 msec for the visual cortex and from 500 msec and more for the sensomotor cortex; 4) the latent period of after-discharge is equal to the duration of the intervals of functional changes. The results were analyzed from the standpoint of reflection of temporal parameters of optical stimuli by neurons of the sensomotor cortex.A. A. Zhdanov Leningrad State University. Translated from Neirofiziologiya, Vol. 7, No. 4, pp. 365–371, July–August, 1975.     

The second rhythm and brain slow wave potentials reflecting physiological condition in humans

In 4-hour experiments, dynamics of second brain potentials and the parameters of a conventionally negative wave, were studied. Along with growing fatigue, the amplitude of the second brain potentials was found to increase with a simultaneous increase in correlation relationships among the second oscillations registered in different areas which fact may serve as a diagnostic sign when controlling functional condition in humans. Velocity of a simple sensomotor response turned out to depend on coincidence with a current phase of the second brain potentials. The shortest time of response corresponded to responses against the background of a positive phase of the second oscillations. In fatigue, the dependence is enhanced.     

Health hazard among cash register operators and the effect of improved working conditions.

The health condition of female cash register operators in relation to their working conditions was investigated. A questionnaire study revealed that cash register operators more frequently complained of general fatigue, headache, sleeplessness, and low back pain than female office machine operators or other female workers. Dullness and pain in the shoulder, arm, hand, and fingers especially on the right side were characteristic of cash register operators. Physical examinations in 1973 showed that 31.3% of 371 cash register operators suffered from muscle rigidity or tenderness; 13 were severely afficted and, 69 operators had to be either laid off, reassigned to other jobs, or given shorter working hours. Occupational cervicobrachial disorders were suggested to have been caused by repetitive upper limb motions combined with static load, an unfavorable working environment, and mental stress. Implementation of some improvements including shorter operation time, worker rotation, and adoption of electronic registers proved effective in reducing the number of sufferers of cervicobrachial disorders found during the 1975 physical examinations. But the improvements were not effective enough to alleviate fatigue of the neck, shoulder, and back due presumably to sustaining upper limbs while operating the keyboard.     

The effect of leucine enkephalin on the development of a convulsive afterdischarge in the sensorimotor cortex of rats]

The application of leucin-enkephalin solution (LEU) (2 micrograms/2 microliters) on stimulated region of sensomotor cortex did not influence threshold of direct and transcallosal cortex responses (DR and TCR). On coupling of repeated electrostimulation train (RET) (duration of impulse--0.1 ms; duration of train--10 s; frequency--10/s) with application of LEU (after every odd train) the changes of DR and TCR in course of even trains and latency of afterdischarge appearance were such as in control ones. Simultaneously LEU effectively depressed short posttetanic potentiation of DR and TCR and potentiation of amplitude and duration AD, evoked by RET. It is suggested that LEU released from neurons in the course of RET does not participate in initiation of seizure in sensomotor cortex. A possible role of LEU in sensomotor cortex is limitation of intensity and duration of seizures and prevention of status epilepticus.     

Evaluation of the professional qualities of operators working with computer displays

The influence of spatio-temporal factors (spatial heterogeneity of distribution of the numbers sought for in the matrix of data, processes of learning and development of fatigue, periodic attention oscillations) of the character of solving the task of searching the numbers in a matrix of 176 three-figure numbers (16 lines, 11 columns) was studied in 39 operators. The possibility was shown to use the characteristics obtained for evaluation of professionally important abilities of an operator working at the display.     

Hypothalamic influences on unit activity in the cat sensomotor cortex

Experiments on unanesthetized, immobilized cats showed different effects of individual hypothalamic nuclei on spontaneous unit activity in the sensomotor cortex. Compared with the posterior hypothalamic nucleus (PHN) and its anteromedial region (AMH), in response to stimulation of the lateral hypothalamic nucleus (LHN) changes in spontaneous activity were more frequently found. The ratio between activation and inhibitory responses was 36 and 36% for AMH, 51 and 30% for LHN, and 47 and 28% for PHN. An approximately equal number of sensomotor neurons (27–34%) gave tonic responses. Phasic changes in spontaneous activity were observed more often in response to stimulation of LHN, less frequently to stimulation of AMH and PHN. Responses of "nonpyramidal" neurons to stimulation of AMH and LHN were identical. "Pyramidal" units were more sensitive to LHN stimulation. Variations in hypothalamic effects depending on the type of response of sensomotor neurons to sensory stimuli were detected. Cells with tonic responses were more susceptible to influences of LHN and AMH than cells which responded by phasic changes in spontaneous activity to sensory stimuli. Fewer still positive responses were recorded in areactive neurons.Medical Institute, Chita. Translated from Neirofiziologiya, Vol. 4, No. 2, pp. 115–122, March–April, 1972.     

Changes in movement variability and task performance during a fatiguing repetitive pointing task

Changes in neuromuscular strategies employed with fatigue during multi-joint movements are still poorly understood. Studies have shown that motor variability of individual joints increases when performing upper limb tasks to fatigue, while movement parameters related to the task goal remain constant. However, how the inter-limb coordination and its variability change during specific movement phases with fatigue is still unclear. The aim of this study was to assess the effects of neck-shoulder fatigue on shoulder and elbow kinematic variabilities, shoulder-elbow coordination and its variability, and endpoint characteristics during different phases of a forward pointing movement. Nineteen healthy young adults continuously performed a repetitive pointing task until fatigue (Borg rating of 8/10). Changes in elbow-shoulder coordination through the movement were assessed using the continuous relative phase and statistical nonparametric mapping methods. At the end of the task, muscle fatigue was evidenced by significant increases in anterior deltoid (+13%) and biceps brachii (+30%) activity. Shoulder horizontal abduction, elbow flexion variability and shoulder-elbow coordination variability were increased with fatigue at different moments of the movement cycle (shoulder: during the first 17% and most of the second half movement, elbow: from 73% to 91%, coordination: almost the whole movement). However, movement timing errors and endpoint spatial variability were mostly preserved, even with fatigue. We showed that increased variability with fatigue is not only observed in the fatigued joint (shoulder), but also in the elbow and shoulder-elbow coordination, and may have a goal of preserving global task performance.     

Response of sensorimotor cortex neurons to weak disturbances of the magnetic field in Wistar rats. Cytochemical study

The influence of weak disturbances (up to 300 microT) of natural magnetic field on the protein metabolism in neurons of sensomotor cortex (layers III and V) in Wistar rats upon learning in a complex maze was studied. It was found that sensomotor neurons were very sensitive to weak disturbances of magnetic field. The protein content increased, while the nucleus-cytoplasm ratio and osmotic state of neurons remained unchanged. The specificity of neuron's reaction manifested itself in a sharp increase of nucleus and cytoplasm dimensions. In associative neurons (layer III), both the nucleus and cytoplasm were involved in the response; in efferent neurons (layer V), only nuclear parameters changed. The variance coefficients of all parameters of protein metabolism in sensomotor neurons, independently of their functional properties, were much higher than in control, which resulted in a wide diversity of cytochemical response.     

Functional asymmetry of the brain and effectiveness of sensorimotor function of oral cavity organs]

It has been established that in healthy persons functional brain asymmetry positively influences the effective performance of sensomotor function of oral cavity organs. Individual brain asymmetry is of considerable importance, the higher it is, the quicker the final results of sensomotor function are achieved. The character of brain asymmetry (right hand or left hand) does not practically influence the performance of sensomotor functions.     

Biogenic amines in brain structures of rats of different zoo-social rank during immobilization stress]

The content of monoamines and their metabolites in different parts of the brain: mesencephalic reticular formation, locus coeruleus, sensomotor cortex was studied by high-performance liquid chromatography in rats with different zoo-social position. Content of dopamine and serotonin in the brain structures studied was found to be different in dominants and subdominants. Maximal changes of monoamines under immobilization stress were observed in dominants.     

Spatial organization of direct connections of the sensomotor cortex with the rhombencephalon and spinal cord in the cat

The distribution and ultrastructure of terminals of corticofugal fibers in the rhombencephalon and spinal cord of the cat were studied by light and electron microscopy at various times (4–6 days) of experimental degeneration after extensive or local (about 3 mm in diameter) destruction of the sensomotor cortex. Definite topographical organization of corticofugal projections in the nuclei of the dorsal columns and in the spinal cord was detected by the Fink — Heimer method. After local destruction of the lateral zones of the sensomotor cortex, maximal foci of degeneration were found in the nucleus of Burdach and the lateral basilar region of the cervical segments; after local destruction of the medial zones of the sensomotor cortex maximal foci of degeneration of corticofugal fibers were observed in Goll's nucleus and the lateral basilar region of the lumbar segments. The results show that even an extremely localized area of the cat sensomotor cortex forms two separate systems of descending corticospinal fibers. The first projects into the dorsolateral and dorsomedial parts of the intermediate zone, chiefly contralaterally, whereas the second projects bilaterally into both dorsolateral and ventromedial parts of the intermediate zone. The possible physiological significance of this duality of projections is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 8, No. 2, pp. 126–133, March–April, 1976.     

Dynamics of instrumental reflex changes following transection of the corticospinal tract and ablation of the cerebral cortex sensorimotor region in rats

Unilateral transection of bulbar pyramid performed prior to ablation of the ipsilateral sensomotor cortex was shown to facilitate recovery of operant conditioning and compensatory processes in rats. There was no such corticofugal plasticity in ablation of the sensomotor cortex alone. The phenomenon may be explained by switching of descending influences on the cortico-rubrospinal system through participation of the loop: corticorubral projection--red nucleus--inferior olive--cerebellum--thalamus--cerebral cortex.     

Ultrastructural changes in the neuropile of the sensorimotor cortex during long-term protein-calorie deficiency

The effect of alimentary (protein-caloric) deficiency on the brain sensomotor cortex of mice was studied during their postnatal development. It was found that malnutrition of mice from day 10 to day 40 of postnatal period brought about the most remarkable changes in synaptic junctions located on the dendritic spines. They manifested destruction of the spine apparatus, reduction of the width of synaptic slits and of postsynaptic membranes. Dystrophic and destructive alterations are frequently encountered in dendrites, axon terminals, and myelinized axons, indicating the reduced compensatory functions of the CNS.     

Corticofugal influences on postsynaptic processes in rubrospinal neurons in the cat brain

Composite and unitary EPSPs of red nucleus neurons evoked by stimulation of the sensomotor and association parietal cortex and nucleus interpositus of the cerebellum were studied in acute experiments on cats anesthetized with pentobarbital. A monosynaptic connection was shown to exist between not only the sensomotor, but also the association cortex, and rubrospinal neurons, in which unitary EPSPs appeared during stimulation of the association cortex after a latent period of 1.5–2.7 msec, with a peak rise time of 1.1–3.1 msec and an amplitude of 0.22–0.65 mV. Analysis of the temporal characteristics of the unitary EPSP suggested that synapses formed by fibers from the association cortex occupy a position nearer the soma than synapses formed by axons of sensomotor cortical cells.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 16, No. 1, pp. 67–74, January–February, 1984.     

Long-lasting changes of irritability in the somatosensory cortex of rabbits following tetanic stimulation of the tooth pulp]

Tetanic stimulation of the tooth pulp produced long lasting increases in potentials released by stimulation of the tooth pulp with single stimuli in the sensomotor cortex of rabbits. Stimulation with 200 impulses/sec for 5 sec produced changes of irritability that are demonstrable for 10-50 min depending on the intensity of stimulation. The lower rate limit for producing such changes is 25 impulses/sec. At a rate of 200 impulses/sec, a stimulation time of 25 msec was necessary to produce these changes. The postexcitatory depression occuring after single stimuli within 10-40 msec was increased by tetanic stimulation, whereas facilitation observed 5 msec after single stimuli was unaffected.     

The mechanism of interaction between the thalamic posterior lateral nucleus and the sensomotor cortex in rabbits

The thalamic posterior lateral nucleus was shown to exert phasic and tonic effects on the function of sensomotor cortex: the former in the form of pulvinar-cortical responses, and the latter in the form of foci of increased or decreased excitability. The findings suggest an inhibitory tonic effect of the sensomotor cortex on neuronal network of the posterior lateral nucleus.