How do neocortical circuits balance the need for plasticity and stability?

If you are like most people, your car is in constant need of a tune-up by a highly trained (and well-paid) mechanic. In contrast, you have likely made it through your life thus far without bringing your brain in for a tune-up. This is truly remarkable, because with billions of neurons interconnected with many billions of synapses, your brain is the most complex object in the known universe ~ far more complex than the internal combustion engine. Also unlike most machines your brain is constantly changing in order to adapt to a fluid environment, to store memories, and to become better able to process the kinds of sensory information it receives.

Our brains are thus faced with a fundamental challenge: they must preserve the integrity of the neural circuits that subserve behaviors over the lifetime of an organism, while at the same time allowing plastic mechanisms to shape and fine-tune their function.

Our lab studies the plasticity mechanisms that allow our brains to “tune themselves up” and remain both plastic and stable. Over the last two decades we uncovered a family of “homeostatic” plasticity mechanisms, including Synaptic Scaling, that allow neurons to adjust their excitability to maintain constant average firing rates in the face of outside perturbations.

More recently we have been probing the role of homeostatic plasticity in the experience-dependent development of the neocortex. We are specially interested in understanding how homeostatic mechanisms interact with classical forms of synaptic plasticity such as LTP/LTD to allow experience-dependent circuit refinement and learning, and in the role of sleep and other behavioral states in gating these forms of plasticity.