Functional contribution of visual features to hippocampal memory encoding

Información del proyecto

FindMEMO

Identificador del acuerdo de subvención: 800027

DOI

10.3030/800027

Proyecto finalizado el 31 Marzo 2021

Fecha de la firma de la CE 4 Mayo 2018

Fecha de inicio 1 Septiembre 2019

Fecha de finalización 31 Agosto 2021

Financiado con arreglo a

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Coste total

€ 173 076,00

Aportación de la UE

€ 173 076,00

Coordinado por

INSTITUT PASTEUR
France

Periodic Reporting for period 1 - FindMEMO (Functional contribution of visual features to hippocampal memory encoding)

Período documentado: 2019-09-01 hasta 2021-08-31

Resumen del contexto y de los objetivos generales del proyecto

Storing and recalling distinct memories are essential brain functions that play key roles in guiding our day-to-day behavior. For example, you may encounter your old school professor whom you have not seen in ten years. His hair is thinner and grayer, he wears different glasses, and has put on some weight. Nonetheless, your brain allows you to retrieve your old memories of this individual even though the inputs are altered. At the same time, you also want to create a distinct, new memory of the individual you have seen today. How can the brain allow both processes (neuronal discrimination and generalization) to occur simultaneously? A brain structure called the hippocampus is thought to be in charge of this task. However, it is still unclear how and where in the hippocampus distinct memories of similar events are formed, and surprisingly little is known about how these memory representations are then used to guide our behavior. In the reporting period of the project FindMEMO, I aimed to address this ambitious key question: How are distinct memories formed and used for behavior?

Trabajo realizado desde el comienzo del proyecto hasta el final del período abarcado por el informe y los principales resultados hasta la fecha

To address this fundamental question we have measured the activity of populations of neurons in behaving animals and combined imaging and behavioral techniques. We performed experiments of 2-photon calcium imaging, a microscopy technique that allows to observe the activity of individual identified neurons deep in the brain while mice navigate in a virtual reality environment. Mice have been trained to detect small or large differences in the virtual environment (such as a change in the angle of the stripes that cover the walls) by stopping at distinct points along the virtual track to receive a sugar water reward. These experiments have enabled to relate behavioral performance to the activity of neurons in different subregions of the hippocampus. We found that neurons in the entry station of the hippocampus, the dentate gyrus, reliably detect small and large differences between two environments. By contrast, neuronal activity in the output region, called CA1, depends on the degree of differences between environments and reflects the performance in the task. These findings suggest that the dentate gyrus attaches “tags” to different environments depending on external and internal variables, and the downstream circuit CA1 uses this information to form a new memory if the saliency of the new environment is sufficiently large. The resulting distinct memories can then be used to guide behavior.

Avances que van más allá del estado de la técnica e impacto potencial esperado (incluida la repercusión socioeconómica y las implicaciones sociales más amplias del proyecto hasta la fecha)

By linking the behavioural performance of the animal with neuronal responses in the hippocampal input and output structures, my work provided novel insight into the fundamental processes underlying memory formation. It thus reconciles a long debate by explaining why previous studies have led to controversial results about the role of hippocampal regions in memory formation.

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