Examinando por Autor "Conde-Ocazionez, Sergio A."

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  • Publicación
    Acceso abierto
    Cross-frequency phase-amplitude coupling between hippocampal theta and gamma oscillations during recall destabilizes memory and renders it susceptible to reconsolidation disruption
    (2020-08-12) Radiske, Andressa; Gonzalez, Maria Carolina; Conde-Ocazionez, Sergio A.; Rossato, Janine I.; Köhler, Cristiano A.; Cammarota, Martín; Neuro Ciencias
    Avoidance memory reactivation at recall triggers theta-gamma hippocampal phase amplitude coupling (hPAC) only when it elicits hippocampus-dependent reconsolidation. However, it is not known whether there is a causal relationship between these phenomena. We found that in adult male Wistar rats, silencing the medial septum during recall did not affect avoidance memory expression or maintenance but abolished hPAC and the amnesia caused by the intrahippocampal administration of reconsolidation blockers, both of which were restored by concomitant theta burst stimulation of the fimbria–fornix pathway. Remarkably, artificial hPAC generated by fimbria–fornix stimulation during recall of a learned avoidance response naturally resistant to hippocampus-dependent reconsolidation made it susceptible to reactivation-dependent amnesia. Our results indicate that hPAC mediates the destabilization required for avoidance memory reconsolidation and suggest that the generation of artificial hPAC at recall overcomes the boundary conditions of this process.
  • Publicación
    Acceso abierto
    Dengue in Santander State, Colombia: fluctuations in the prevalence of virus serotypes are linked to dengue incidence and genetic diversity of the circulating viruses
    (2019-11-05) Carreño, María Fernanda; Jiménez-Silva, Cinthy Lorena; Rey-Caro, Luz Aida; Conde-Ocazionez, Sergio A.; Flechas-Alarcón, María Camila; Velandia, Sindi Alejandra; Ocazionez, Raquel Elvira; Neuro Ciencias
    objectiveTo investigate the link between fluctuations in the prevalence of dengue virus (DENV)serotypes and the number of dengue cases in the metropolitan area of Bucaramanga, Santander State,Colombia, in the 2007–2010 and 2014–2017 periods.methodViruses were isolated from febrile patient samples by direct application to C6/36-HT cellsand typed using monoclonal antibodies. We performed autocorrelation and cross-correlation analysesto determine whether fluctuations in the prevalence of DENV serotypes and dengue cases werecorrelated. Full envelope (E) gene sequences were employed to examine the genetic diversity ofserotypes circulating by using a phylogenetic approach.resultsAll four dengue virus serotypes were detected. DENV-1 was the dominant serotype in bothperiods followed by DENV-3 or DENV-2 depending on the period; DENV-4 was the least prevalentvirus in both periods. Cross-correlation analyses suggest a temporal relation between the fluctuationsin the prevalence of DENV serotypes, which were almost simultaneous (lag=0) or related to recentpast fluctuations (lag>1.0) in the number of dengue cases. Data suggest that a sustainedpredominance of DENV-1, an increase of the DENV-4 prevalence, and a switch from DENV-3 toDENV-2 could be linked to an outbreak. Circulating viruses were grouped into Genotype V, Asia/American III and II for DENV-1, -2, -3 and -4, respectively; intragenotypic diversity was detected.conclusionsThe present work highlights the need of comprehensive studies on dynamics of DENV inColombia to understand transmission of dengue and evaluate the effectiveness of a vaccination programme.
  • Publicación
    Acceso abierto
    Reactivation-dependent amnesia for object recognition memory is contingent on hippocampal theta–gamma coupling during recall
    (2021-12-15) Gonzalez, Maria Carolina; Radiske, Andressa; Conde-Ocazionez, Sergio A.; Rossato, Janine I.; Bevilaqua, Lia R. M.; Cammarota, Martín; Neurociencias
    Hippocampal dopamine D1/D5 receptor-dependent destabilization is necessary for object recognition memory (ORM) updating through reconsolidation. Dopamine also regulates hippocampal theta and gamma oscillations, which are involved in novelty and memory processing. We found that, in adult male rats, ORM recall in the presence of a novel object, but not in the presence of a familiar one, triggers hippocampal theta-gamma coupling. Hippocampal theta-gamma coupling (hPAC) does not happen when ORM destabilization is prevented by blocking D1/D5 receptors, but artificial hPAC generation during recall in the presence of a familiar object enables the amnesic effect of reconsolidation inhibitors. Therefore, hPAC controls ORM destabilization, and its modulation could increase reconsolidation-based psychotherapy efficacy.
  • Publicación
    Acceso abierto
    Spatial clustering of orientation preference in primary visual cortex of the large rodent agouti
    (2021-01-22) Ferreiro, Dardo N.; Conde-Ocazionez, Sergio A.; Patriota, Joao H.N.; Souza, Lua C.; Oliveira, Moacir F.; Wolf, Fred; Schmidt, Kerstin E.; Neurociencias - UDES
    All rodents investigated so far possess orientation-selective neurons in the primary visual cortex (V1) but – in contrast to carnivores and primates – no evidence of periodic maps with pinwheel-like structures. Theoretical studies debating whether phylogeny or universal principles determine development of pinwheels point to V1 size as a critical constraint. Thus, we set out to study maps of agouti, a big diurnal rodent with a V1 size comparable to cats’. In electrophysiology, we detected interspersed orientation and direction-selective neurons with a bias for horizontal contours, corroborated by homogeneous activation in optical imaging. Compatible with spatial clustering at short distance, nearby neurons tended to exhibit similar orientation preference. Our results argue against V1 size as a key parameter in determining the presence of periodic orientation maps. They are consistent with a phylogenetic influence on the map layout and development, potentially reflecting distinct retinal traits or interspecies differences in cortical circuitry.