アンサンブル活動の編成によって海馬記憶痕跡は構成される

富山大学・富生命博甲第106号・Khaled Adel Abd El-Rahman Ghandour・2019/03/26富山大

Pcdhβ deficiency affects hippocampal CA1 ensemble activity and contextual fear discrimination

Clustered protocadherins (Pcdhs), a large group of adhesion molecules, are important for axonal projections and dendritic spread, but little is known about how they influence neuronal activity. The Pcdhβ cluster is strongly expressed in the hippocampus, and in vivo Ca2+ imaging in Pcdhβ-deficient mice revealed altered activity of neuronal ensembles but not of individual cells in this region in freely moving animals. Specifically, Pcdhβ deficiency increased the number of large-size neuronal ensembles and the proportion of cells shared between ensembles. Furthermore, Pcdhβ-deficient mice exhibited reduced repetitive neuronal population activity during exploration of a novel context and were less able to discriminate contexts in a contextual fear conditioning paradigm. These results suggest that one function of Pcdhβs is to modulate neural ensemble activity in the hippocampus to promote context discrimination

Orchestrated ensemble activities constitute a hippocampal memory engram

The brain stores and recalls memories through a set of neurons, termed engram cells. However, it is unclear how these cells are organized to constitute a corresponding memory trace. We established a unique imaging system that combines Ca2+ imaging and engram identification to extract the characteristics of engram activity by visualizing and discriminating between engram and non-engram cells. Here, we show that engram cells detected in the hippocampus display higher repetitive activity than non-engram cells during novel context learning. The total activity pattern of the engram cells during learning is stable across post-learning memory processing. Within a single engram population, we detected several sub-ensembles composed of neurons collectively activated during learning. Some sub-ensembles preferentially reappear during post-learning sleep, and these replayed sub-ensembles are more likely to be reactivated during retrieval. These results indicate that sub-ensembles represent distinct pieces of information, which are then orchestrated to constitute an entire memory

Assessment of Hematotoxicity and Genotoxicity among paint Workers in Assiut Governorate: a case control study

Abstract Background Occupational exposures to hazardous chemicals in paints cause serious health hazards in painters. The present study was designed to evaluate the possibility of hematotoxic and genotoxic effects of paint chemicals among painters in Assiut Governorate, Egypt. In addition the role of oxidative stress and apoptosis in mechanism of such toxic effects were studied. Methods A case control study was performed on 50 male painters and 50 non-exposed healthy subjects, who were included as a control group after informed consent. Venous blood samples were obtained and analyzed for determination of total and differential blood count as hematotoxic markers as well as serum malondialdehyde (MDA) as an oxidant stress markers and total antioxidant enzymes. In addition, human B-cell lymphoma-2 (Bcl-2), caspase-3 and 8-hydroxyguanosine (8-OHdG) were assayed as markers of apoptosis and genotoxicity. Results There was a statistically significant difference between paint workers and controls as regard total and differential blood count, serum MDA and total anti-oxidant levels. Also, statistical significant differences in caspase-3, Bcl-2 levels and 8-OHdG were observed. Conclusions Chronic occupational exposure to paints increased the risk of hematotoxicity and genotoxicity in painters. Oxidative stress and apoptosis play a major role in such mechanism. Periodic medical examination and application of protective devices is necessary

CAT: Credibility Analysis of Arabic Content on Twitter

Data generated on Twitter has become a rich source for various data mining tasks. Those data analysis tasks that are dependent on the tweet semantics, such as sentiment analysis, emotion mining, and rumor detection among others, suffer considerably if the tweet is not credible, not real, or spam. In this paper, we perform an extensive analysis on credibility of Arabic content on Twitter. We also build a classification model (CAT) to automatically predict the credibility of a given Arabic tweet. Of particular originality is the inclusion of features extracted directly or indirectly from the author's profile and timeline. To train and test CAT, we annotated for credibility a data set of 9, 000 Arabic tweets that are topic independent. CAT achieved consistent improvements in predicting the credibility of the tweets when compared to several baselines and when compared to the state-of-the-art approach with an improvement of 21% in weighted average F-measure. We also conducted experiments to highlight the importance of the user-based features as opposed to the content-based features. We conclude our work with a feature reduction experiment that highlights the best indicative features of credibility. 2017 Association for Computational LinguisticsScopu

Sevoflurane-induced amnesia is associated with inhibition of hippocampal cell ensemble activity after learning

General anesthesia could induce amnesia, however the mechanism remains unclear. We hypothesized that suppression of neuronal ensemble activity in the hippocampus by anesthesia during the post-learning period causes retrograde amnesia. To test this hypothesis, two experiments were conducted with sevoflurane anesthesia (2.5%, 30 min): a hippocampus-dependent memory task, the context pre-exposure facilitation effect (CPFE) procedure to measure memory function and in vivo calcium imaging to observe neural activity in hippocampal CA1 during context exploration and sevoflurane/home cage session. Sevoflurane treatment just after context pre-exposure session impaired the CPFE memory, suggesting sevoflurane induced retrograde amnesia. Calcium imaging showed sevoflurane treatment prevented neuronal activity in CA1. Further analysis of neuronal activity with non-negative matrix factorization, which extracts neural ensemble activity based on synchronous activity, showed that sevoflurane treatment reduced the reactivation of neuronal ensembles between during context exploration just before and one day after sevoflurane inhalation. These results suggest that sevoflurane treatment immediately after learning induces amnesia, resulting from suppression of reactivation of neuronal ensembles