Integration of spatial and social memory in hippocampus CA2 and medial entorhinal cortex

Sosiale interaksjoner er av grunnleggende betydning for mennesker, og andre mennesker spiller en viktig rolle i mange av våre minner. I lang tid har man vært klar over at hjerneområdet hippocampus er viktig for at vi skal danne episodiske minner fra våre liv. Slike minner består av mange komponenter, hva skjedde, hvor og når. Hippocampus mottar informasjon fra "grid celler" i entorhinal cortex som utgjør stedsansen. Denne spatiale (romlige) komponenten av minnene våre har vært undersøkt grundig, men vi vet lite om hvordan nervecellene koder sosial informasjon. En liten del av hippocampus, kalles CA2 og det er foreslått at dette området spiller en sentral rolle for sosiale minner. Vi skal derfor registrere aktiviteten fra i hjerneceller i CA2 og entorhinal cortex for å finne ut hvordan sosiale minner kodes i hjernen.

Social interactions are important for humankind and often a central element of our autobiographical memories. However, the neural representations underlying social memories are poorly understood. The hippocampal formation is essential for encoding of episodic memories in mammals, combining information in space and time, keeping episodes apart and in their correct context. A mostly overlooked part of the hippocampus, the subfield CA2, may have a special role integrating social information into our memories. It has a unique anatomical positioning receiving both information about social interactions from the hypothalamus and spatial information from medial entorhinal cortex (MEC). Thus, we hypothesize that the CA2 integrates social and spatial information. In SocialBrain, we will conduct simultaneous recordings of neural activity from the CA2 and its input regions during social memory tasks and object memory tasks for comparison. This will be combined with targeted perturbations of brain activity using optogenetics and chemogenetics. It is unknown if the grid cells in MEC are modulated by social interactions. We will first investigate if the spatial code of grid cells in MEC is affected by social interactions. We will examine how social memories are represented in CA2 and if they depend on spatial input from MEC, oscillatory input from medial septum and neuromodulatory input from paraventrucular nucleus. This research will also bring insight about impaired social interactions in e.g. psychiatric disorders and will be the initiation of translational studies.