Randy M. Bruno, Ph.D.Assistant Professor, Neuroscience
Member, The Kavli Institute for Brain Science
Area of Research
Synapses and Circuits, Cognitive/Systems Neuroscience, Theoretical Neuroscience, Sensory Physiology
Synaptic Connectivity Underlying Cortical Computation
How do real neural networks--composed of numerous different types of neurons, interconnected by complex arrangements of synapses--process information?
I 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, I 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.
Constantinople, C.M., and Bruno, R.M. (2011) Effects and mechanisms of wakefulness on local cortical networks. Neuron 69: 1061-1068.
Kuhn, B., Denk, W., and Bruno, R.M. (2008). In vivo two-photon voltage-sensitive dye imaging reveals top-down control of cortical layers 1 and 2 during wakefulness. Proc Natl Acad Sci U S A 105, 7588-7593.
de Kock, C.P., Bruno, R.M., Spors, H., and Sakmann, B. (2007). Layer- and cell-type-specific suprathreshold stimulus representation in rat primary somatosensory cortex. J Physiol 581, 139-154.
Sarid, L., Bruno, R., Sakmann, B., Segev, I., and Feldmeyer, D. (2007). Modeling a layer 4-to-layer 2/3 module of a single column in rat neocortex: interweaving in vitro and in vivo experimental observations. Proc Natl Acad Sci U S A 104, 16353-16358.
Bruno, R.M., and Sakmann, B. (2006). Cortex is driven by weak but synchronously active thalamocortical synapses. Science 312, 1622-1627.
Bruno, R.M., and Simons, D.J. (2002). Feedforward mechanisms of excitatory and inhibitory cortical receptive fields. J Neurosci 22, 10966-10975.