Shouval Lab for Theoretical Neuroscience
My research focuses on identifying the rules by which changes in synaptic strength – believed to be the basis of learning, memory and development in the cortex – take place. These synapses are the means by which one neuron communicates with another, and changes in these weights are called synaptic plasticity. I concentrate on theoretical/ computational approaches to the study of synaptic plasticity and its implications on learning memory and development. I study synaptic plasticity at many levels, from its molecular basis to its functional implications and I believe that theoretical studies are essential for forming the link between these different levels of description. Some of the topics I currently study are:
The molecular basis of synaptic plasticity: Much is known about the molecular and physiological basis of synaptic plasticity. I carry out complex simulations of signal transduction pathways involved in synaptic plasticity, as well as analysis of the molecular dynamics of molecules such as calcium that are essential for synaptic plasticity.
Simplified cellular models of synaptic plasticity: Derivation of simplified models, either by approximating the more complex molecular models, or from first principles can help bridge the gap between the molecular level and electrophysiological experiments. Recently I derived a simple unified calcium dependent plasticity model that can account for the various induction paradigms, including spike time dependent plasticity (STDP). Both the assumptions and predicted consequences of the model can be tested experimentally.
The contribution of synaptic plasticity to receptive field development: Many properties of receptive fields in visual cortex, as well as other cortical areas are experience dependent. We have previously accounted for such properties using more traditional, rate-based models of synaptic plasticity, in visual environments composed of natural images. Currently we are examining if the unified calcium dependent model can account for the development of receptive fields as well.
Long range horizontal connections, how they affect map formation and how they are formed: Long range horizontal connections in Layers II-III of visual cortex have specific connectivity patterns. These specific connections form, at least to a certain extent, before the onset of patterned vision. We have previously concentrated on how such connections effect the structure of developing cortical maps. Since some of these connections form before eye opening we are examining how such patterns could emerge in the absence of patterned input or possibly in an activity independent manner.
Stability of long term synaptic plasticity: Synaptic plasticity, believed to be the cellular basis of learning and memory, is synapses specific. Experimentally synaptic plasticity has been shown to be stable for days, and memories can last a life time. How can a synapse specific biological processes be stable for such long periods of time? One compelling idea is the molecular switch; the validity of this idea has not been demonstrated experimentally. We are currently examining alternative ideas, that are not based on a molecular switch.