Факторы модуляции памяти при лучевом воздействии на гиппокампстатья
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Дата последнего поиска статьи во внешних источниках: 8 апреля 2022 г.
Аннотация:Although the key scene of the hippocampus in memory processes is obvious, the specificity of its participation in information processingis far from being established. Current advanced neuroimaging enables to operate with precise morphometric parameters.The aim of the study was to reveal fine memory rearrangements under mechanical impact on the hippocampus by a neoplasm andradiation exposure in the course of therapy.Materials and Methods. We used a homogeneous sample of 28 patients with parasellar meningiomas adjacent to hippocampus. In 10patients (5 with left-sided and 5 with right-sided meningiomas), the tumor was located near the hippocampus but exhibited no mechanicaleffect on it. In 18 patients (10 with left-sided and 8 with right-sided tumors), the neoplasm compressed the adjacent hippocampus. Thecontrol group consisted of 39 healthy subjects. All three groups were comparable in age, education, and gender characteristics. In order tocontrol tumor growth, the patients underwent radiotherapy when the hippocampus involuntary was exposed to a dose comparable to that inthe tumor (30 sessions with a single focal dose of 1.8 Gy, total dose — 54.0 Gy).Based on the literature data on hippocampus involved in mnestic processes, a special methodology to investigate memory wasdeveloped. Incorrect responses the subjects made when identifying previously memorized images were classified as neutralizing thenovelty factor of an identified stimulus or as wrongly emphasizing its novelty.Results. At the first observation point (before radiation therapy) all groups underwent a complete standardized neuropsychologicalexamination and performed a battery of cognitive tests. The overall results of the tests assessing attention, memory, thinking processes,and neurodynamic indicators corresponded to standard values. A mild brain compression by the tumor without brain tissue destruction wasnot accompanied by focal neuropsychological symptoms and deficit manifestations in the cognitive sphere. However, as early as in the firstobservation point, the number of “pattern separation” errors in the clinical group was significantly higher than that in healthy subjects.The second observation point (immediately after radiotherapy) and the third observation point — 6 months after the treatment —showed that, in general, the patients’ cognitive sphere condition was not deteriorating, and in a number of parameters was characterized bypositive dynamics, apparently associated with some tumor reduction due to the therapy provided. However, the distribution of errors in theoriginal method significantly changed. When previously memorized stimuli were recognized, the errors neutralizing the novelty factor ofthe evaluated stimulus increased, while the number of errors with overestimating the stimuli novelty decreased.All tendencies hypothetically (according to the published data) associated with the changes in functional activity of the hippocampuswere more pronounced in the subgroup of patients with mechanical impact of the tumor on hippocampus.Conclusion. The continuous flow of impressions any person has at any moment of his activity is most likely marked by the hippocampusin a continuum “old–similar–new”. The present study has shown that mechanical impact on the hippocampus combined with radiationexposure changes the range of assessments towards the prevailing labeling “old, previously seen, already known”.