Fellous lab

Welcome!

Our research interests include the neurobiology of learning and emotional memory and the mechanisms and roles of neuromodulation in large neural networks. We use a multi-disciplinary approach that includes in vitro, in vivo and computational techniques.

Current research has largely focused on single neurons. With the advent of multiple electrodes recording and imaging techniques on the one hand, and the development of large scale computational modeling techniques on the other, it has become clear that cortical processing does not simply rely on the computations of a few individual neurons, or on the static encoding of information by a few cells. Neural processing relies on the dynamic exchange of information between cell assemblies. How this communication is achieved reliably on time scales of few tens of milliseconds is still largely unknown.

The primary focus of our research program is on understanding how large populations of cells can efficiently communicate across brain regions using notoriously noisy communication channels (action potentials and synapses). We focus on the hippocampus and cortex, during spatial tasks in rodents. What are the constraints that sources of unreliability impose on the communication between neurons, and between cell assemblies? How is memory formed, consolidated and recalled?

The secondary focus is on understanding how communication pathways can be dynamically re-configured to reflect the changes in processing priorities that are dictated by particular behavioral contexts. These behavioral contexts are associated with various endogenous neuromodulators such as dopamine (DA, reinforcement learning, emotion), norepinephrine (NE, heightened attention), acetylcholine (ACh, sleep and memory) or serotonin (5HT, motivation and emotion). How do these neuromodulators modify the input-output responses of neurons, and their signal processing characteristics? How do they affect synaptic communication? How do these substances change the flow of information? We focus on the reward system, and on the role of dopamine in positively motivated tasks.

The experimental aspects of this research are conducted using a combination of in vitro and in vivo techniques in the rat. We use state of the art neurophysiology techniques that include two-way real-time brain-machine interfaces and "hyperdrives" that consist of multi-electrodes capable of recording from over 100 neurons simultaneously in the behaving animal. The theoretical aspects of the work involves the use of computational modeling techniques to simulate the activity of single cells and network of interconnected cells. These computer simulations aim at reproducing and explaining the experimental data, and generate predictions that can in turn be tested experimentally.