Biology subjects

Nicolas, B.

Publications and source records attributed to Nicolas, B..

4 recordsLinked to original sources

bioRxiv2024

Comparative impact of porcine reproductive and respiratory virus and swine influenza A virus infections on respiratory lymph nodes B cells and macrophages.

Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) strongly impacts the pig rearing sector due to its persistence in infected animals. Interestingly, although the PRRSV family exhibits considerable genome variability, with the PRRSV-1 and PRRSV-2 subtypes having been finally classified in two different species (Betaarterivirus suid 1 and 2). Both viruses, as well as their derived-attenuated vaccine strains, persist for months, due in part to their ability to delay the appearance of neutralizing antibodies. Thanks to extensive efforts over the past years, we have developed the capability to perform in-depth analysis of the previously poorly understood porcine inverted lymph node (LN). In this study, by comparing the early stages of LN B cell maturation upon PRRSV-1 infection to those induced upon the acute swine influenza A virus infection, we highlighted PRRSV-specific mechanisms, including the expression of PD-L1 in efferent macrophages, the induction of extrafollicular plasmocytes, and the influx of inflammatory monocytes/macrophages. Studies on PRRSV-2 infections report observations compatible with our results, that thus might be generalized to all PRRSV-strains. Moreover, these mechanisms can be compared with those used by the human immunodeficiency virus (HIV) and the murine chronic lymphocytic choriomeningitis virus (LCMV) to hijack the immune response. These similarities can be harnessed to develop new strategies to improve the development of more efficient anti-PRRSV vaccines.

immunology↗

bioRxiv2020

Evidence of shifts towards neural states of stability during the retrieval of real-life episodic memories

How does one retrieve real-life episodic memories? Here, we tested the hypothesis, derived from computational models, that successful retrieval relies on neural dynamics patterns that rapidly shift towards stable states. We implemented cross-temporal correlation analysis of electroencephalographic (EEG) recordings while participants retrieved episodic memories cued by pictures collected with a wearable camera depicting real-life episodes taking place at "home" and at "the office". We found that the retrieval of real-life episodic memories is supported by rapid shift towards brain states of stable activity, that the degree of neural stability is associated with the participants ability to recollect the episodic content cued by the picture, and that each individual elicits stable EEG patterns that were not shared with other participants. These results indicate that the retrieval of autobiographical memory episodes is supported by rapid shifts of neural activity towards stable states.

neuroscience↗

bioRxiv2020

Neurophysiological signatures in the retrieval of individual autobiographical memories of real-life episodic events

Autobiographical memory (AM) refers to recollected events that belong to an individuals past. In a classical episodic retrieval experiment in a laboratory, the events to be remembered are words or pictures that have hardly any personal relevance. While such stimuli provide necessary experimental and controlled conditions helping to advance in the understanding of memory, they do not capture the whole complexity of real-world stimuli. Recently, the incorporation of wearable cameras has allowed us to study the cognitive and neural bases of AM retrieval without active participant involvement, and they have been demonstrated to elicit a strong sense of first-person episodic recollection enhancing ecological validity. Here, we provide a new approach to understanding the retrieval of personal events, implementing a convolution network-based algorithm for the selection of the stimuli while monitoring participants memory retrieval with scalp EEG recordings over three periods of time after encoding (1 week, 2 weeks, and 6 to 12 months). We also examined an individual with a condition termed Aphantasia that provided more insights into the sensitivity of our protocol in the investigation of individual AM using real-life sequences.

neuroscience↗

bioRxiv2019

Theta rhythm supports hippocampus-dependent integrative encoding in schematic memory networks

Integrating new information into existing schematic structures of knowledge is the basis of learning in our everyday life activity as it enables structured representation of information and goal-directed behaviour in an ever-changing environment. However, how schematic mnemonic structures aid the integration of novel elements remains poorly understood. Here, we showed that the ability to integrate novel picture information into learn structures of picture associations that overlap by the same picture scene (associative network) or by the conceptually related scene information (schematic network) is hippocampus-dependent, as patients with lesions at the medial temporal lobe (including the hippocampus) were impaired in inferring novel relations between elements within these mnemonic networks but not in retrieving individual pictures in a subsequent memory test. In addition, we observed more persistent and widespread scalp electroencephalographic (EEG) theta oscillatory pattern (3-6Hz) while healthy participants encoded novel pictures related to schematic memory networks, suggesting that theta may reflect distances between elements within a representational network space. Finally, we found high similarity values for neural activity patterns elicited by novel and related events only within associative networks, thereby suggesting that neural reactivation may promote the integration of new information into existing memory networks only when direct associations within the network link their elements. These findings have important implications for our understanding of the neural mechanisms that support the development and organization of structures of knowledge.

neuroscience↗