Randy Bruno

Associate Professor of Neuroscience

Columbia University

Randy Bruno asks the question How do real neural networks–composed of numerous different types of neurons, interconnected by complex arrangements of synapses–process information?

We have been pursuing this question in the rodent whisker-barrel system, where anatomically and functionally distinct networks (barrels and barrel columns) are clearly identifiable and the sensory transducers that provide input (whiskers) are easily controlled. I characterize the functional properties of individual neurons in anesthetized and awake animals by their the synaptic inputs and action potential outputs, recorded using both intracellular and extracellular techniques. Simultaneous filling of cells allows identification of their anatomical type and location as well their axonal projections.

A variety of paired-recording techniques permit one to test for a possible synaptic connection between two cells and study its properties. I have successfully used such approaches to determine the mechanism for propagating information between thalamus and cortex, to study receptive field generation in excitatory and inhibitory neurons, and to demonstrate micro-organization of inputs to cortical columns.

More recently, we have also been examining the anatomy of these circuits using new imaging techniques to visualize dendritic and axonal arbors of neurons and even their synaptic interconnections. These tools can be used to address fundamental questions: What is the connectivity within and between cortical layers and columns, and how is this changed by experience? To what degree are synaptic inputs compartmentalized? When do synaptic inputs act in concert?

The long-term goal for my lab is to identify the principles by which an iterated cortical circuit achieves tactile sensation and, perhaps, all modalities of sensory processing.

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