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Z A Aleksanyan

Publications and source records attributed to Z A Aleksanyan.

9 recordsLinked to original sources
PubMed2006

Correlates of measures of voluntary force with the functional state of the motor system.

Oscillation spectra were analyzed for prolonged isometric force recorded in healthy subjects of three age groups. Changes in the distributions of spectral components of the oscillations in force were noted, along with differences in the distributions of spectral density as exhaustion developed in the age groups. The amplitude-frequency ranges of changes in the spectral densities of oscillations in force characterized the activity at the suprasegmental and segmental levels of the motor system which support the voluntary control and automatic regulation of posture during the performance of movements. Correlates of the functional state of the motor system are discussed in terms of the voluntary and involuntary components of control. A significant increase in activity in the central structures of the movement control system was seen with the development of exhaustion, along with decreases in the frequency range of the activity of subcortical structures with age.

Adolescent↗
PubMed2004

Characteristics of tremor in normal subjects and in the diagnosis and treatment of Parkinsonism.

Tensotremorography was used to record voluntary forces and to study the characteristics of the involuntary and voluntary components of isometrically recorded hand strength. The frequency ranges for changes in the spectral density of oscillations recorded here supported the existence of two suprasegmental systems associated with voluntary control and continuous regulation of force maintaining or holding a posture. Cross-correlation analysis of hand force maintained in conditions of visual feedback in normal conditions and in conditions of central disorders of the movement control system is presented.

Basal Ganglia↗
PubMed1985

A response-specific conditioned aversion to rewarding hypothalamic stimulation in rats.

Rats with hypothalamic electrodes were trained to self-stimulate by nose-poking and by licking at a dry spout. Separate groups of animals were then exposed to pairings of either self-stimulation by licking or by nose-poking with the subsequent administration of LiCl. The licking/LiCl pairing group exhibited a marked attenuation of licking maintained by hypothalamic stimulation on the first retention trial (24 h post LiCl). This effect was enhanced by a further licking/LiCl pairing. In a final cross-over trial with this group, nose-poking maintained by stimulation at the same site and intensity was found to be unaffected. With another group of animals nose-poking/LiCl pairing had no effect on self-stimulation, despite two conditioning trials. In a final cross-over trial with this group licking maintained by stimulation of the same site and intensity was also unaffected. These data indicate that the sensory properties of brain stimulation may be dependent on the behavioural context in which the stimulation occurs.

Animals↗
PubMed1979

Electrophysiological analysis of retrieval of conditioned taste aversion in rats. Unit activity changes in critical brain regions.

Gustatory discrimination testing shows that rats with an overtrained conditioned taste aversion (CTA) to isotonic LiCl stop salt intake after 1 to 2 licks at the LiCl spout and move to the adjacent water spout within 0.7 s. Activity of 526 neurones from the nucleus of the solitary tract, gustatory thalamus, gustatory cortex, lateral and ventromedial thalamus, and amygdala was recorded in naive or CTA trained rats during the above gustatory discrimination. Post-stimulus histograms (PSH) triggered by water or salt licks or by spout switching were plotted for single units. Population responses of various regions were obtained by integration of the statistically significant excitatory and inhibitory intervals in the individual PSHs. Lick related changes of unit activity were orserved in 52% and 65% of neurones in control and CTA trained rats, respectively. The CTA training increased the incidence of units in which salt licking influenced the activity less than water licking. Presentation of the aversive fluid induced inhibition of unit activity in the gustatory cortex, ventromedial hypothalamus, and amygdala and excitation in the lateral hypothalamus. The changes started 100 to 150 ms after spout switching and culminated 100 ms later. Activity of the solitary tract nucleus and gustatory thalamus was affected less consistently. The results indicate that the gustatory cortex, amygdala and hypothalamus participate in CTA retrieval but a more specific identification of the electrical correlates of memory readout and of drinking control was not possible.

Action Potentials↗
PubMed1976

Activity of neuronal populations of human subcortical structures during sleep.

Multi-unit activity of 14 subcortical structures was studied during drowsiness and sleep in patients with depth electrodes implanted in the brain for therapeutic purposes. The mean firing rate of the multi-unit activity was found to decrease during "slow-wave" sleep in each cycle. The multi-unit activity was sharply increased during paradoxical sleep. In successive sleep cycles the mean firing rate somewhat increased from cycle to cycle during slow sleep. The mean firing rate was considerably increased during wakefulness after a sufficiently logn sleep, as compared with the initial background values. Fluctuations of the mean firing rate were characteristic of paradoxical sleep. When studying simultaneously 2 or 3 structures, both uniform or different changes of the neuronal activity were possible. Changes of the firing rate in separate structures may develop a few seconds prior to the "clinical display" of the REM phase. All (or nearly all) the structures, whose activity during sleep is rather independent, are presumed to be able to be a source of the REM phase.

Brain↗