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F V Kopytova

Publications and source records attributed to F V Kopytova.

At least 19 recordsLinked to original sources
PubMed1994

Some physiological characteristics of motor cortex neurons of aged rabbits.

Neurophysiological alterations occurring in the motor cortex of aged rabbits have been examined. Experiments were performed on rabbits of three age groups: one year old (young), four to five years old (middle-aged) and six to seven years old (aged). Extracellular unit activity was recorded in the motor projection of a forelimb. Several sessions of rhythmic (2 Hz) electrocutaneous stimulation were delivered to contralateral forelimb. The neuronal activity was recorded before and after rhythmic stimulation. We also measured the firing rate during spontaneous electromyogram activity of the extensor carpi radialis. Neurons having slow spontaneous firing activity were predominant in aged rabbits as compared with young animals. In young animals the highest values of spontaneous firing rate (15-20 impulses/s) were observed in neurons related to movement. In aged rabbits spontaneous firing rate of movement-related neurons did not exceed 16 impulses/s. During spontaneous movements of extensor carpi radialis, the level of neuronal activity in young rabbits was twice as high as that in aged ones. In young rabbits after rhythmic electrocutaneous stimulation of a forelimb, 20% of recorded neurons exhibited periodic fluctuations in firing rate with the period of preceding stimulation. The repeated stimulation sessions increased the number of rhythmic firing neurons to 40-50%. In aged rabbits, patterns of firing activity of motor cortex neurons did not change significantly after several sessions of rhythmic electrocutaneous stimulation. Decreased neuronal excitability may be the cause of functional alterations in motor cortex neurons of aged rabbits.

Aging↗
PubMed1981

[Changes in the sign of the response of striopallidal neurons during elaboration of conditioned reflexes to time].

During formation of motor conditioned reflexes to time (CRT) in alert rabbits, an increase in the number of neurones with activation and diminution of the number of cells with inhibitory trace activity was revealed when the stimuli were omitted, as compared with conditioned reactions (CR) to actual stimuli pairings, as well as a change in CR and CRT signs, as compared with the sign of cell responses to control tests. The changes were more pronounced in the caudate nucleus and the putamen. In the caudate nucleus and the globus pallidus, the number of cells capable of CRT in omissions of pairings increased as compared with the number of neurones which elaborate CR to actual pairings. Differences in the CR and CRT signs may suggest a difference in mechanisms of consolidation and reproduction of trace processes during elaboration of a motor behavioural act.

Animals↗
PubMedDate not supplied

Characteristics of the trace reproduction of rhythm by neurons of the sensorimotor cortex of rabbits in the aftermath of periodic stimulation.

The trace recruitment of rhythm (TRR), an analog of the CR to time, which arises in response to prolonged electrodermal stimulation of the forelimb of the awake rabbit at a frequency of 0.5-2 Hz, was studied. The activity of 180 cells of the sensorimotor cortex before (80) and after (100) periodic stimulation for a duration of 10-20 min was recorded. The first series of rhythmical stimulation led to a brief TRR of the stimulation frequency; subsequent series formed a clear TRR which was preserved for several days. The possibility of "retraining" the neurons given a change in the rhythm of stimulation was identified. The capacity of the TRR phenomenon for extinction, prolonged maintenance, and reproduction of traces, as well as "retraining" allies it with processes analogous to the temporary connections.

Animals↗
PubMedDate not supplied

The morphofunctional characteristics of neurons of the sensorimotor cortex of aged rabbits during the trace assimilation of rhythm.

The formation of trace rhythm assimilation (an analog of the conditioned reflex to time) by neurons of the sensorimotor cortex in response to prolonged (10-20 min) electrodermal stimulation of an extremity at a frequency of 0.5-1 or 2 Hz was investigated in awake adult (5-7 months), old (54-65 months), and very old (66-85 months) rabbits. The data of the spectral analysis of the impulse activity of 460 neurons showed aged-related differences in the formation of trace rhythm assimilation by neurons: it takes place after one to two series (1st to 2nd days of the experiment) in young animals; after two to four series of periodic stimulation (2nd to 3rd days of the experiment) in the old animals; in very old animals rhythmic stimulation essentially did not result in rhythm assimilation by cortical neurons. Quantitative and qualitative morphological changes in nerve and glial cells in the sensorimotor cortex of old rabbits as compared with young rabbits were identified. It is hypothesized that deviations in the course of mnestic processes observed in animals during aging may be associated with destructive phenomena in the neocortex during normal aging.

Aging↗
PubMedDate not supplied

Cholinosensitivity as an indicator of functional differences of neurons of the cortex of young and old rabbits.

The cholinosensitivity of neurons of the motor cortex of young and old rabbits was studied. It was shown that muscarinic activation in the cells of old animals is encountered half as often than in young animals. The age-related decrease in cholinosensitivity is explained by an insufficiency of the overall activation of neurons in old animals. The change in the functional state of the cells of the motor cortex leads to the fact that the frequency of impulse activity of neurons associated with movement proves to be insufficient for the achievement of effective cortical control of motor functions.

Acetylcholine↗
PubMedDate not supplied

[Trace reactions following combination of a sensory stimulus with polarization of the visual region of the cortex].

Spontaneous activity and responses to photic flashes and tones of 133 neurones were recorded in the visual cortex during polarization of the same area (1.5 to 10 muA, 5 to 30 min) and after it (one to 52 min). Responses of cells to two unimodal stimuli of different parameters were analysed, of which one was presented repeatedly during the polarization ("positive"), and the other one to three times ("negative"). Depending on the previous "learning", 47.4% of the units responded after the polarization to "positive" photic stimulus and 37,8%--to acoustic stimulus. The trace effects of the stimuli pairings are reproduced in polarization after-effect by the action of the sensory signal alone. The recorded differences in the nature and duration of the reproduction of trace processes formed to an adequate and inadequate stimuli, are due to the dissimilar action of polarizing currents on neurones of the cortex cross-section and to different effectivity of the visual and non-visual influences related to it.

Acoustic Stimulation↗
PubMedDate not supplied

[Conditioned responses to time of hypothalamic neurons. The ventromedial nucleus].

Conditioned reactions to the time of regularly (every 30 sec.) presented pairings of an acoustic and an electrical cutaneous stimuli were studied in neurones of the hypothalamic ventromedial nucleus in an alert rabbit. Conditioned reactions of an inhibitory (81%) and activating (19%) types were elaborated in 27 out of 63 units (43%). They were significantly reproduced at six to nine omissions of stimulations at the stage of the 50th to 70th pairings. The maximum manifestation of trace processes coincides with the initial formation of a vegetative (electrocardiogram) component of the behavioral conditioned reflex to time. Significant correlation has been shown between the frequency of spikes in the pairings and their omissions, and the corresponding changes in heart rate at the same temporal intervals. This testifies to the involvement of the ventromedial nucleus structures in the formation of the vegetative component of the behavioral conditioned reflex to time. Common characteristics and peculiarities of conditioned reactions to time have been revealed in units of the hypothalamic ventromedial and perifornical nuclei in accordance with morpho-functional properties of the examined structures.

Animals↗
PubMedDate not supplied

[The characteristics of trace rhythm reproduction by the neurons of the rabbit sensorimotor cortex in the aftereffect of periodic stimulation].

Trace rhythm recruitment (TRR)--CR analogue to time was studied appearing in response to prolonged electrocutaneous stimulation of the forelimb of the alert rabbit with the frequency 0.5-1-2 Hz. The activity was recorded of 180 cells of the sensorimotor cortex before (80) and after (100) periodical stimulation during 10-20 min. The first series of rhythmic stimulation led to a short-term TRR of the stimulation frequency, the following series formed a clear TRR, preserved for several days. The possibility was revealed of "relearning" of neurones at stimulation rhythm change. The ability of TRR phenomenon of extinguishment, prolonged preservation and reproduction of traces, "relearning" brings it nearer to the processes, analogous to the temporal connection. The ability to reveal distinctly and to quantitatively estimate the characteristics of the applied stimulus fixated by the neurones, makes this model perspective for comparable study of the memory traces at the neuronal level in the animals of various ages.

Action Potentials↗
PubMedDate not supplied

[Trace rhythm recruitment by the neurons of the rabbit sensorimotor cortex in old age].

Spectral analysis (ACG and gSP) of the impulse activity of the neurones of the old rabbits sensorimotor cortex allowed to reveal a trace recruitment of the rhythm--CR analogue to time--in after-action f rhythmic stimulation. Connection was established between the number of presented series of periodic electrocutaneous stimulation and expressiveness of the trace rhythm recruitment depending on the animals age. Trace rhythm recruitment took place slower in old animals (54-56 months) than in young ones (up to 1 year), chiefly in 2-3 experimental days after 2-4 series of rhythmic stimulation and was preserved in a small percent of cases the next day after stimulation. In the background activity of a number of neurones an initial periodicity was discovered, which was intensified under the influence of stimulation by another frequency, or the initial rhythm was extinguished, and stimulation rhythm was reproduced. Periodical stimulation in very old animals (66-85 months) practically did not evoke plastic reconstructions of the cortical neurones. Under the influence of the stimulation a non-specific trace increase of the frequency of neurones background activity of the old animals was observed. The revealed characteristics of plastic neurones properties may testify to projected disturbances of mnestic processes at definite age stages of normal aging.

Action Potentials↗
PubMedDate not supplied

[The morphofunctional characteristics of the neurons in the sensorimotor cortex of old rabbits during the trace assimilation of rhythm].

Extracellular neuronal activity was recorded from 460 neurons from alert young (5-7 months), middle-aged (54-65 months) and old (66-85 months) rabbits. Trace rhythmic activity of sensorimotor cortical neurons was examined after long-lasting (10-20 min) rhythmic (0.5-2 Hz) electrocutaneous stimulation of the contralateral forelimb. Spectral analysis of spike activity showed age-related differences in capability of producing a rhythm of previous stimulation in spontaneous neuronal activity. In young animals propriate rhythmic fluctuations of firing rate appeared after the first or second sessions of stimulations (on the first experimental day), in middle-aged ones--after 2-4 sessions (on the second or third days); cortical neurons in old rabbits did not exhibit trace rhythmic activity. Significant morphological changes in glial and neuronal cells were observed in sensorimotor cortex of old rabbits. It is proposed that morphological deteriorations may be the reason of the impairement of trace processes during aging.

Aging↗
PubMedDate not supplied

[Cholinergic sensitivity as an index of the functional differences in cortical neurons in young and old rabbits].

Acetylcholine-sensitivity of motor cortex neurons was studied in the young and old rabbits. Muscarinic-type excitation in the neurons of old animals was revealed twice less frequently compared to the young ones. The age-related fall in the number of cholinoceptive neurons may be due to general decrease of neuronal activation in the motor cortex during aging. Changes in functional properties of motor cortex neurons with age may have a result that firing rate of movement related neurons becomes insufficient for the effective control of motor function.

Acetylcholine↗