these are the brain areas we're interested in

why?....

In the early 70's John O’Keefe (Nobel Prize in PM 2014) discovered neurons in the hippocampus whose activity is tightly regulated by the animal's position in space, e.g. they store, in the brain, a map of spatial coordinates, or spatial cognitive map.

Black dots are action potentials (or spikes) emitted by one neuron as the rat freely forages for food in an arena.

This was the first evidence for the existence of cognitive maps in animals, in these case rodents, something defined decades earlier by Edward Chance Tolman who, in a series of seminal behavioral experiments using rats in mazes, concluded, against then-dominant theories, that ”animals can learn facts about the world that they could subsequently use in a flexible manner”.

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In 2006, Matt Wilson discovered that not only these maps can be formed, but they can be retrieved even though the animal is not performing the corresponding behavioral task ("offline"), lending support to the second aspect of the above postulate, that animals can subsequently use cognitive maps in a flexible manner.

Matt Wilson discovered that hippocampal place-cells, whose activity is tightly modulated by the animal's location at any given moment, can reactivate outside their selectivity context. In other words a contextual representation can be replayed..., or remembered.

We are still trying to understand how do these neurons gain their place selectivity and how is this cognitive map used by other brain areas, to govern the animal's behavior.

Cognitive maps can be retrieved "offline" whenever the animal is deliberating about future actions.

How does sensory input contribute to hippocampal place selectivity?

We use tetrodes (see Methods section) to record neural activity from individual neurons in the secondary occipital area of the brain (Oc2M), an area we've shown to integrate multi-sensory stimuli and to send inputs to HIPP. We are also using neuronal silencers, pharmacogenetics (DREADDS) and optogenetics, to interfere with this process and analyze ensuing changes in HIPP place mapping and animal behavior.

How is time represented in episodic memory?

Decades of research have shown that the hippocampus represents places and is necessary for episodic memories. Comparatively less is known about how do hippocampal neurons represent time, even though time is a fundamental component of episodic memories ("what, where and when"). To understand the encoding of time by hippocampal neurons we have developed a novel task called "waiting-to-trajectory", in which rats are rewarded for waiting for a specified amount of time, before moving towards a reward location. All the while, we record neural activity from the entorhinal-hippocampus complex and manipulate neural connections in this circuit using DREADDS and optogenetics.

How does the brain use HIPPocampal memory to guide behavior?

We record neural activity from the hippocampus and medial mesocortical areas, anterior cingulate (CG) through retrosplenial (RSC), while rats perform spatially-guided goal-directed behaviors on a maze. To causally address the mechanisms of memory retrieval in the service of goal directed behaviors we manipulate hippocampal-mesocortical connections using DREADDs and optogenetics, and monitor ensuing changes in behavior and neural dynamics during behavior.