Lucas C. Parra
The City College of New York

On reading and writing the brain: Using electric field potentials to read and modulate the timing of neuronal activity

Tuesday 04th of September 2007 at 12:30pm
508-20 Evans Hall

During normal function neurons in the brain produce ionic currents that can be measured, locally and at the scalp surface, as electric field potentials. These signals provide an unique window into the temporal aspects of neuronal activity, allowing us to monitor, and indeed, modulate neuronal timing.

This talk will cover three topics: 1) To study human perception one is typically limited to non-invasive electrodes. The technical challenge is to overcome the poor signal-to-noise ratio of scalp surface potentials. The talk will present a framework for the linear analysis of functional imaging data to extract spatial and temporal information which we have used to analyze the electroencephalogram. 2) The resulting tools are remarkably successful at extracting timing information, surpassing in fact the temporal accuracy of human behavioral response. We have given a dramatic demonstration of this effect as an application of a brain-computer interface to broad-area image search, showing 400% improvement in human search performance. 3) Remarkably, electric fields have also been shown to affect the timing of neuronal activity, and in fact, have been demonstrated to have a causal effect on human behavioral response. The talk will present a mechanistic theory of how fields can affect the timing of neuronal activity and show results on slice experiments confirming the quantitative predictions that result from this theory. In summary, the talk will show that electric field potentials can be used as a tool to read and modulate the timing of neuronal activity.

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