Molecular Mechanisms in Perirhinal Cortex Selectively Necessary for Discrimination of Overlapping Memories, but Independent of Memory Persistence. Miranda M, Kent BA, Morici JF, Gallo F, Weisstaub NV, Saksida LM, Bussey TJ, Bekinschtein B. 2017

AUTORES Miranda M, Kent BA, Morici JF, Gallo F, Weisstaub NV, Saksida LM, Bussey TJ, Bekinschtein B.
AÑO 2017
JOURNAL eNeuro
VOLUMEN October, 2017
ABSTRACT Successful memory involves not only remembering over time but also keeping memories distinct. The ability to separate similar experiences into distinct memories is a main feature of episodic memory. Discrimination of overlapping representations has been investigated in the dentate gyrus of the hippocampus (DG), but little is known about this process in other regions such as the perirhinal cortex (Prh). We found in male rats that perirhinal brain-derived neurotrophic factor (BDNF) is required for separable storage of overlapping, but not distinct, object representations, which is identical to its role in the DG for spatial representations. Also, activity-regulated cytoskeletal-associated protein (Arc) is required for disambiguation of object memories, as measured by infusion of antisense oligonucleotides. This is the first time Arc has been implicated in the discrimination of objects with overlapping features. Although molecular mechanisms for object memory have been shown previously in Prh, these have been dependent on delay, suggesting a role specifically in memory duration. BDNF and Arc involvement were independent of delay-the same demand for memory persistence was present in all conditions-but only when discrimination of similar objects was required were these mechanisms recruited and necessary. Finally, we show that BDNF and Arc participate in the same pathway during consolidation of overlapping object memories. We provide novel evidence regarding the proteins involved in disambiguation of object memories outside the DG and suggest that, despite the anatomical differences, similar mechanisms underlie this process in the DG and Prh that are engaged depending on the similarity of the stimuli.
RESUMEN Muchas veces se asocia la pérdida de memoria con la imposibilidad de recordar items luego de un intervalo de tiempo. No obstante, la amnesia puede ocurrir porque dos experiencias o ítems fueron similares y al momento de recordarlos, se confunden. El cerebro posee mecanismos para transformar la información proveniente de experiencias similares en memorias diferenciadas que sean menos confundibles al momento de evocarlas. En este trabajo demostramos que los mecanismos moleculares involucrados en el almacenamiento de experiencias similares como memorias diferentes son similares en el dominio espacial y en el de objetos. Estos mecanismos involucran la acción del factor neurotrófico derivado de cerebro (BDNF) tanto en el hipocampo como en la corteza perirrinal, necesarios para el almacenamiento de información espacial y de objetos respectivamente. A pesar de ser dos estructuras anatómicamente muy diferentes, los mecanismos moleculares necesarios para el procesamiento de este tipo de memorias es similar.

Immediate Early Genes, Memory and Psychiatric Disorders: Focus on c-Fos, Egr1 and Arc. Francisco T Gallo, Cynthia Katche, Facundo Morici, Jorge H Medina, Noelia V Weisstaub. 2018

AUTORES Francisco T Gallo, Cynthia Katche, Facundo Morici, Jorge H Medina, Noelia V Weisstaub.
AÑO 2018
JOURNAL Frontiers 
VOLUMEN April 25, 2018
ABSTRACT Many psychiatric disorders, despite their specific characteristics, share deficits in the cognitive domain including executive functions, emotional control and memory. However, memory deficits have been in many cases undervalued compared with other characteristics. The expression of Immediate Early Genes (IEGs) such as, c-fos, Egr1 and arc are selectively and promptly upregulated in learning and memory among neuronal subpopulations in regions associated with these processes. Changes in expression in these genes have been observed in recognition, working and fear related memories across the brain. Despite the enormous amount of data supporting changes in their expression during learning and memory and the importance of those cognitive processes in psychiatric conditions, there are very few studies analyzing the direct implication of the IEGs in mental illnesses. In this review, we discuss the role of some of the most relevant IEGs in relation with memory processes affected in psychiatric conditions.
RESUMEN Mas allá de las diferencias existentes en distintos desordenes psiquiátricos, varios de ellos comparten deficits en el dominio cognitivo, incluyendo deficits de memoria. La expresión de genes como c-Fos, Egr1 y Aarc son selectivamente regulados en procesos de aprendizaje y memoria en regiones y poblaciones neuronales especificas. En esta revision discutimos el rol de algunos de los genes tempranos mas importantes en relación con procesos de memoria afectados en desordenes psiquiátricos.

5-HT2a receptor in mPFC influences context-guided reconsolidation of object memory in perirhinal cortex. Juan Facundo Morici, Magdalena Miranda, Francisco Tomás Gallo, Belén Zanoni, Pedro Bekinschtein, Noelia V. Weisstaub. 2018

AUTORES Juan Facundo Morici, Magdalena Miranda, Francisco Tomás Gallo, Belén Zanoni, Pedro Bekinschtein, Noelia V. Weisstaub.
AÑO 2018
JOURNAL eLife
VOLUMEN May 2, 2018
ABSTRACT Context-dependent memories may guide adaptive behavior relaying in previous experience while updating stored information through reconsolidation. Retrieval can be triggered by partial and shared cues. When the cue is presented, the most relevant memory should be updated. In a contextual version of the object recognition task, we examined the effect of medial PFC (mPFC) serotonin 2a receptor (5-HT2aR) blockade during retrieval in reconsolidation of competing objects memories. We found that mPFC 5-HT2aR controls retrieval and reconsolidation of object memories in the perirhinal cortex (PRH), but not in the dorsal hippocampus in rats. Also, reconsolidation of objects memories in PRH required a functional interaction between the ventral hippocampus and the mPFC. Our results indicate that in the presence of conflicting information at retrieval, mPFC 5-HT2aR may facilitate top-down context-guided control over PRH to control the behavioral response and object memory reconsolidation.
RESUMEN Las memorias dependientes de contexto pueden guiar las conductas apoyándose en experiencias pasadas mientras se actualiza la información guardada previamente a través del proceso de reconsolidación. La evocación puede darse por la presentación de calves que son comunes a distintas memorias, en esos casos, la memoria mas relevante debe ser la que sufre el proceso de actualización. En este estudio evaluamos el efecto que el bloqueo del receptor serotoninérgico 5-HT2a en la corteza pre frontal de ratas tiene sobre la reconsolidación de memorias de objetos que compiten al momento de la evocación.

Editorial: Human and Animal Models for Translational Research on Neurodegeneration: Challenges and Opportunities From South America. Ibáñez A, Sedeño L, García AM, Deacon RMJ and Cogram P. 2018

AUTORES Ibáñez A, Sedeño L, García AM, Deacon RMJ and Cogram P.
AÑO 2018
JOURNAL Frontiers Aging Neuroscience
VOLUMEN April 6, 2018
ABSTRACT Facing the alarming growth of dementia and neurodegenerative conditions has become a critical priority across the globe. Although most research on this subject is concentrated in first-world centers, growing efforts in South American countries (SACs) are affording important breakthroughs. This emerging agenda poses not only new challenges for the region, but also new opportunities for the field at large.  This Research Topic engages researchers from the world over, helping to integrate the international community of experts and to establish new challenges and developments for future investigation. We present original research in SACs, including studies assessing the interplay among genetic, neural, and behavioral dimensions of these diseases, as well as articles on vulnerability factors, comparisons of findings from various countries, and works promoting multicenter and collaborative networking. More generally, our Research Topic covers a broad scope of human research approaches (behavioral assessment, neuroimaging, electromagnetic techniques, brain connectivity, peripheral measures), animal methodologies (genetics, epigenetics, proteomics, metabolomics, other molecular biology tools), target species (human and non-human animals, sporadic, and genetic versions), and article types (mainly original research articles, but also case reports, data reports, commentaries, opinions, and reviews), all based on work conducted in SACs. Here, we summarize the main contributions included in the volume. Through this wide-ranging proposal, we hope to introduce a fresh approach to the challenges and opportunities of research on neurodegeneration across these countries, focusing on two overarching levels of evidence (human and animal research), as summarized below.
RESUMEN En esta edición especial, reunimos cientos de expertos regionales que abordan desde múltiples perspectivas los desafíos y oportunidades específicas de Sudamérica para enfrentar la demencia. Los aportes se realizan desde múltiples perspectivas, desde las políticas públicas, la investigación clínica, los modelos preclínicos en animales, y la investigación neurocientífica, entre otros.