Navegando por Autor "Ocazionez, Sergio Andrés Conde"

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Cross-frequency phase-amplitude coupling between hippocampal theta and gamma oscillations during recall destabilizes memory and renders it susceptible to reconsolidation disruption
(Society for Neuroscience, 2020-07-13) Radiske, Andressa; Gonzalez, Maria Carolina; Ocazionez, Sergio Andrés Conde; Rossato, Janine Inez; Köhler, Cristiano André; Cammarota, Martín Pablo
Avoidance memory reactivation at recall triggers hippocampal theta-gamma 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 intra-hippocampal 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 generation of artificial hPAC at recall overcomes the boundary conditions of this process.
The influence of visual inter-hemispheric connections on spiking, assembly and LFP activities, and their phase relationship during figure-ground stimulation
(Universidade Federal do Rio Grande do Norte, 2014-03-31) Ocazionez, Sergio Andrés Conde; Schmidt, Kerstin Erika; ; http://lattes.cnpq.br/4902752912395893; ; http://lattes.cnpq.br/7159531395590165; Tort, Adriano Bretanha Lopes; ; http://lattes.cnpq.br/3181888189086405; Neuenschwander, Sergio; ; http://lattes.cnpq.br/9217956361436464; Houzel, Jean Christophe; ; http://lattes.cnpq.br/0010117558043568
Since Hubel and Wiesel s pioneer finding a vast body of literature has accumulated describing neuronal responses in the primary visual cortex (V1) to different visual stimuli. These stimuli mainly consisted of moving bars, dots or gratings which served to explore the responses to basic visual features such as orientation, direction of motion or contrast, among others, within a classical receptive field (CRF). However, in the last two decades it became increasingly evident that the activity of V1 neurons can be modulated by stimulation outside their CRF. Thus, early visual areas might be already involved in more complex visual tasks like, for example, the segmentation of an object or a figure from its (back)-ground. It is assumed that intrinsic long-range horizontal connections within V1 as well as feedback connections from higher visual areas are actively involved in the figure-ground segmentation process. Their possible role has been inferred from the analysis of the spike rate variations induced by stimuli placed outside the CRF of single neurons. Although it is very likely that those connections also have an impact on the joined activity of neurons involved in processing the figure and on their local field potentials (LFP), these issues remain understudied. In order to examine the context-dependent modulation of those activities, we recorded spikes and LFPs in parallel from up to 48 electrodes in the primary visual cortex of anesthetized cats. We stimulated with composite grating and natural scene stimuli focusing on populations of neurons whose CRFs were situated on the foreground figure. In addition, in order to examine the influence of horizontal connections we removed the inter-hemispheric input of the isotopic contralateral visual areas by means of reversible cooling deactivation. We did so because i) the intrinsic horizontal connections cannot be easily manipulated without directly affecting the measured signals, ii) because inter-hemispheric connections share the major anatomical features with the intrinsic lateral network and can be seen as a functional continuation of the latter across the two hemispheres and iii) because cooling causally and reversibly deactivates input connections by temporarily silencing the sending neurons and thus enables direct conclusions on their contribution. Our results demonstrate that the figure-ground segmentation mechanism is reflected in the spike rate of single neurons, as well as in their LFP power and its phase-relationship to the spike patterns produced by the population. In addition "lateral" inter-hemispheric connections modulate spike rates and LFP power depending on the stimulation of the neurons CRF surround. Further, we observe an influence of this lateral circuit on field- field coherences between remote recording sites. In conclusion, our findings support the idea of complex figure-ground segmentation mechanism acting already in early visual areas on different time scales. This mechanism seems to involve groups of neurons firing synchronously and dependent on the LFP s phase. Our results are also compatible with the hypothesis that long-range lateral connections contribute to that mechanism
Reactivation-dependent amnesia for object recognition memory is contingent on hippocampal theta-gamma coupling during recall
(Cold Spring Harbor Laboratory, 2022-01) Gonzalez, Maria Carolina; Radiske, Andressa; Ocazionez, Sergio Andrés Conde; Rossato, Janine Inez; Bevilaqua, Lia Rejane Muller; Cammarota, Martín Pablo
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
Theta-encoded information flow from dorsal CA1 to prelimbic cortex drives memory reconsolidation
(Elsevier BV, 2025) Radiske, Andressa; Gonzalez, María Carolina; Rossato, Janine Inez; Ocazionez, Sergio Andrés Conde; Cammarota, Martín Pablo
Reconsolidation is the process by which reactivated, labile memories are restabilized. Disrupting this process induces retrograde amnesia specific to the reactivated memory, making it a promising therapeutic target for anxiety disorders rooted in maladaptive avoidance. However, the electrophysiological mechanisms underlying reconsolidation are still not fully understood, limiting its translational potential. Here, we show that inducing reconsolidation of a fear-driven avoidance memory in adult male rats increases coherent theta synchrony and directional connectivity between the dorsal CA1 region of the hippocampus and the prelimbic cortex. Optogenetic silencing of dorsal CA1 terminals in the prelimbic cortex during the reconsolidation induction window disrupted this theta coupling and led to delayed memory impairment. These findings demonstrate that reconsolidation depends on theta-mediated information transfer through the direct dorsal CA1-prelimbic pathway and suggest that monitoring or modulating this activity could inform the development of targeted interventions aimed to modify or disrupt distressing, intrusive memories

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Navegando por Autor "Ocazionez, Sergio Andrés Conde"