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bhalla at ncbs dot res dot in
Neurobiology
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The emergence of memory from multilevel neuronal computation

If we could take a picture of a memory in the brain, what would it look like? Remarkably, memory formation triggers changes at almost every level of brain function: molecular, electrical, cellular, and circuit. A picture of memory would not be complete without a view across all these scales. We want to understand how these changes work together.


First, sensory input like sound or smell, must be converted into patterns of activity in the brain. This 'representation' of information sets the stage for subsequent computations and memory storage. To use an analogy, a computer represents sound as a sequence of ones and zeroes, and once it is in that form it can be played back as music, or stored as an mp3 file. We investigate sensory representations by recording neuronal activity using fine wires in the brain, or using optical techniques to monitor hundreds of brain cells at a time. Details

Second, this activity changes during learning. We train rats and mice to recognize odors, sounds, or other stimuli, and to associate them with later events. We compare brain activity throughout the course of learning using our electrical and optical methods. These activity changes provide a glimpse of circuit changes underlying memory. Details

Third, many hidden changes occur during learning. These include changes in connections between cells in the brain circuitry. They also include changes in excitability of cells, or the state of molecules that control cellular activity. To read out these hidden changes we stimulate input cells using light (optogenetics), chemical, or electrical inputs, and monitor what happens to output cells. This uncovers changes in connections and cellular state. Details

All these events are complex and closely coupled, and we believe that it is important to keep track of them across molecular, electrical and circuit levels. We have been developing computer models to do span these levels, which are closely tied to our own experiments and data from the research community. Details

We have been developing new computational methods in order to make these multiscale models. The MOOSE project (Multiscale Object-Oriented Simulation Environment) is hosted in our lab with many collaborations around the world. Details

Overall, our work falls into the domains of systems biology and computational neuroscience, with a lively mix of experiments and computer modeling. Our lab includes people from physics, chemistry, mathematics, biology, computer science and other branches of engineering.

We are hiring Postdocs, graduate students and programmers to participate in these projects. Details