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Biomedical subjects

N I Nezlina

Publications and source records attributed to N I Nezlina.

At least 19 recordsLinked to original sources
PubMed2004

Long-term memory, neurogenesis, and signal novelty.

According to our suggested hypothesis, long-term memory is a collection of "gnostic units," selectively tuned to past events. The formation of long-term memory occurs with the involvement of constantly appearing new neurons which differentiate from stem cells during the process of neurogenesis, in particular in adults. Conversion of precursor neurons into "gnostic units" selective in relation to ongoing events, supplemented by the involvement of hippocampal "novelty neurons," which increase the flow of information needing to be fixed in long-term memory. "Gnostic units" form before the informational processes occurring in the ventral ("what?") and dorsal ("where?") systems. Formation of new "gnostic units" selectively tuned to a particular event results from the combination of excitation of the detector for stimulus characteristics and the novelty signal generated by "novelty neurons" in the hippocampus.

Animals↗
PubMed1989

[Changes in the spreading depression wave in rats in the postresuscitation period].

Functional state of the rat brain cortex after a 10-minute arrest of blood circulation was studied by means of the spreading depression wave, the latter leading to significant energy expenditures and being accompanied by a transmitter output and changes in extra- and intracellular ion concentration. The changes in the spreading depression wave took place at different stages of the postresuscitation period (2 hours to 2 1/2 months), suggesting various pathological changes in functional state of the brain cortex induced by disturbances in neurological interrelationships.

Animals↗
PubMed1976

[Recovery of function following incomplete section of the posterior funiculi of the spinal cord].

The course of functions recovery and the changes of somatosensory cortical evoked potentials were studied in cats after incomplete dorsal funiculi section at the cervical level. The restoration of functions was more rapid and complete in animals with the partial section as compared with those with complete dorsal funiculi section. The latter had no evoked potentials recovery. Undamaged fibers were concluded to be able to send a significant afferent inflow from the periphery to the cortical somatosensory areas and, apparently, to play an important role in the process of the compensatory reorganisation.

Animals↗
PubMed1976

[Consequences of partial deafferentation of the hindlimb in cats].

The hindlimb deafferentation was found to entail disorders of the motor activity and sensitivity, as well as a decrease in the evoked activity in the cortical somatosensory areas, although in a lesser degree than transection of the same amount of dorsal roots innervating the forelimbs. Apparently, the afferent organization of the cat hindlimb is different from that of the forelimb. This accounts for preservation of a part of the afferent inflow from periphery to the cortex after partial deafferentation, as well as for the considerable rehabilitation of functions of deafferented hindlimb.

Animals↗
PubMedDate not supplied

The dynamic of thermal fields of the brain of rats in the late post-resuscitation period under stress.

The temperature topography of the cerebral cortex of rats following clinical death and resuscitation was investigated with the technique of thermoencephaloscopy. Complete restoration of the neurological status of the animals was achieved over the course of one to two days. Marked disturbances in the background thermal maps and the thermal reactions of the cerebral hemispheres induced by a stressor were identified in the remote post-resuscitation period (up to two months). A pathological mosaicism of the thermal characteristics was detected under the conditions of relative rest, as were disturbances in the dynamics of the temperature reactions of the brain and in the character of the interhemispheric asymmetries under stress. The individual character of the post-resuscitation pathology which is found both in the baseline thermal maps as well as following a functional load is emphasized. The results of the investigation point to the importance of an individual approach in the rehabilitation therapy of the post-resuscitation illness.

Animals↗
PubMedDate not supplied

The orientating reflex: the "targeting reaction" and "searchlight of attention".

A concept of the orientating reflex is presented, based on the principle of vector coding of cognitive and executive processes. The orientating reflex is a complex of orientating reactions of motor, autonomic, and subjective types, accentuating new and significant stimuli. Two main systems form the orientating reflex: the "targeting reaction" and the "searchlight of attention:" In the visual system, the targeting reaction ensures that the image of the object falls onto the fovea; this is mediated by involvement of premotor neurons which are excited by saccade command neurons in the superior colliculi. The "searchlight of attention" is activated as a result of resonance within the gamma frequency range, selectively enhancing cortical detectors and involving the reticular nucleus of the thalamus. Novelty signals arise in novelty neurons of the hippocampus. The synaptic weightings of neocortical detectors for hippocampal novelty neurons is initially characterized by high efficiency, which assigns a significant level of excitation of these neurons to the new stimulus. During repeated stimulation, the synaptic weightings of all the detectors representing a given stimulus decrease, with the result that the novelty signal becomes weaker. When the stimulus changes, it acts on other detectors, whose weightings for novelty neurons remain high, which strengthens the novelty signal. Decreases in the synaptic weightings on repetition of a standard stimulus form a trace of this stimulus in the novelty neurons - this is the "neural model of the stimulus." The novelty signal is determined by the non-concordance of the new stimulus with this "neural model," which is formed under the influence of the standard stimulus. The greater the difference between the new stimulus and the previously formed neural model, the stronger the novelty signal.

Animals↗
PubMedDate not supplied

[Forward and backward conditioning].

A discussion. The evolution of the concept of the forward and backward conditioning is traced. An attempt to define more precisely the widely distributed term such as a "feedback", is made.

Animals↗
PubMedDate not supplied

[Orienting reflex: "targeting reaction" and "searchlight of attention"].

The concept of orienting reflex based on the principle of vector coding of cognitive and executive processes is proposed. The orienting reflex to non-signal and signal stimuli is a set of orienting reactions: motor, autonomic, neuronal, and subjective emphasizing new and significant stimuli. Two basic mechanisms can be identified within the orienting reflex: a "targeting reaction" and a "searchlight of attention". In the visual system the first one consists in a foveation of a target stimulus. The foveation is performed with participation of premotor neurons excited by saccadic command neurons of the superior colliculi. The "searchlight of attention" is based on the resonance of gamma-oscillations in the reticular thalamus selectively enhancing responses of cortical neurons (involuntary attention). The novelty signal is generated in novelty neurons of the hippocampus, which are selectively tuned to a repeatedly presented standard stimulus. The selective tuning is caused by the depression of plastic synapses representing a "neuronal model" of the standard stimulus. A mismatch of the novel stimulus with the established neuronal model gives rise to a "novelty signal" enhancing the novel input. The novelty signal inhibits current conditioned reflexes (external inhibition) contributing to redirecting the behavior. By triggering the expression of early genes the novelty signal initiates the formation of the long-term memory connected with neoneurogenesis.

Animals↗
PubMedDate not supplied

[Disorder and recovery of somatic sensitivity in cats with destruction of the afferent pathways of the spinal cord].

Somatic sensitivity was studied in intact cats and in the process of functions recovery after section of the posterior columns of the spinal cord and spino-cervical tracts. The state of somatic sensitivity was estimated by the change in the thresholds of food-procuring conditioned reflexes to electrocutaneous stimulation of the anterior limb. After section of the posterior columns or the spino-cervical tracts at the level of the 2nd cervical segment, the threshold rose. It gradually decreased in parallel to the recovery of motor activity, without reaching the initial level. The section of both tracts (simultaneous or in two stages) resulted in an intensive rise of the threshold which decreased in the course of recovery of disturbed functions. Evidently only partial recovery of somatic sensitivity takes place in the process of compensation of functions following the lesion of specific afferent ways of the spinal cord, and motor activity may be achieved with a consdierable deficit of somatic sensitivity.

Animals↗
PubMedDate not supplied

[The dynamics of the brain heat fields of rats in the late postresuscitation period during stress].

By thermoencephaloscopy method the temperature relief of the rats cerebral cortex was studied after the clinical death and reanimation. The rehabilitation of the animals neurological status was completed in 1-2 days. In the remote postresuscitation period (up to 2 months), expressed disturbances were revealed of the background thermomaps and of thermal reactions of the cerebral hemispheres, evoked by the stress influence. Pathologic mosaics of thermal characteristics was revealed in conditions of relative rest and disturbance of dynamics of the brain temperature reactions and the character of interhemispheric asymmetries at stress influence. Individual character is pointed out of postreanimative pathology, which is manifest both in the background thermomaps and after the functional load. The results of the studies suggest the importance of individual approach in rehabilitation therapy of postreanimative disease.

Animals↗
PubMedDate not supplied

[Long-term memory, neurogenesis and novelty signal].

In accordance with the advanced hypothesis the long-term memory is a collection of "gnostic units" selectively tuned to experienced events. The long-term memory is continuously supplemented by new neurons differentiated from stem cells during neurogenesis (particularly, in adults). The transformation of neuronal progenitors into event-selective gnostic units is accomplished with participation of hippocampal "novelty neurons" emphasizing information inputs to be stored in the long-term memory. The formation of the gnostic units is preceded by informational processes occurring in the ventral ("what?") and dorsal ("where?") systems. The formation of a new gnostic unit selectively tuned to a particular event is a result of combination of feature-detector excitation and novelty signal generated by hippocampal novelty neurons.

Animals↗
PubMedDate not supplied

[Evoked potential as a measure of perceptive and semantic differences].

The informational significance of human perceptive and semantic evoked potentials to an abrupt change in non-verbal or verbal stimuli, respectively, is discussed. The amplitudes of perceptive and semantic evoked potentials were shown to be positively correlated with subjective estimates of differences between these stimuli. Multidimensional scaling of amplitude matrices and subjective estimates of differences after pair-wise replacement of the stimuli showed that colors and color names were encoded by excitation vectors of equal lengths in four-dimensional spherical space of colors. Color differences were shown to be equal to absolute values of their excitation vectors, whereas semantic differences in color names turned to be determined by the absolute values of vector differences between color memory traces represented as long-term memory excitation vectors. The data were summarized in the framework of cognitive spherical model.

Evoked Potentials, Auditory↗