To unravel the neural mechanisms governing cognition, one must understand how different brain areas interact with one another on time scales that range from tens to several hundreds of milliseconds. Temporal resolution in the range of milliseconds is hard to achieve through imaging techniques such as fMRI. On the other hand, electrophysiological techniques used in primates provide high temporal resolution but only record from a single or at most a few tens of neurons at a time. An alternative recording technique that overcomes many of these problems is electrocorticography (ECoG) where an array of electrodes, implanted for assessment of the brain before surgery, is used to record electrical fluctuations from the surface of the human. ECoG allows electrical signals from several different brain areas to be measured simultaneously while at the same time providing temporal resolution in the millisecond range. It is thus uniquely suited for probing the neural dynamics of cognition.
With NSF support, Drs. Rajesh Rao and Jeff Ojemann of the University of Washington will examine cortical dynamics using three tasks that represent three different levels of abstraction in cognition: a motor movement task, a working memory task, and a language task. It will analyze the data using conventional spectral techniques as well as more sophisticated statistical techniques such as Independent Component Analysis (ICA) for source separation and Bayesian techniques for signal estimation. From this, they will construct biophysical models of networks of neurons and simulating cortico-cortical and cortico-thalamic feedback loops to understand the neural genesis of ECoG. If successful, this research will allow a new understanding of brain function, leading in the long term to possible remedies for cognitive deficits involving motor control, memory, or language processing.
