Probing the Human Brain: Characterizing the Highly Dimensional Neurophysiological Response of the Brain to Pulses of Electrical Current

Britni Crocker, Massachusetts Institute of Technology

Electrical stimulation of the brain is an important clinical tool for therapy and diagnosis. The most visible application of electrical stimulation is therapeutic brain stimulation, such as deep brain stimulation, in which patients receive electrical pulses through implanted electrical devices to alleviate symptoms related to neurological disease. Clinicians also use electrical brain stimulation to map the cortex before brain surgery, for patients who will have either a malignant or an epileptogenic region of brain tissue removed. This electrical stimulation can be used to inform neurosurgeons on which areas of the cortex are responsible for essential motor and language tasks. This latter form of electrical stimulation is usually done in conjunction with neurophysiological recordings and provides a unique opportunity to study the mechanisms of electrical stimulation in the brain.

From predictions of the Hodgkin-Huxley-type models, the general consensus within the neuroscience community is that electrical stimulation primarily activates axons. This microscopic understanding of stimulation has not easily translated into clinical utility, as neurologists primarily diagnose and treat neurological phenomena that occur on a much larger scale. The larger-scale mechanisms of electrical stimulation have yet to be thoroughly studied in humans.

Here we present preliminary results from two patients who, as part of their clinical course, have electrodes implanted on the surface of their brain. In particular, we have recorded signals during standard clinical mapping stimulation and during electrical stimulation paradigms of our own design. Initially, we focus on analyzing five domains of electrophysiological response: the time domain, the frequency domain, the spatial domain, the network domain, and the discrete domain of individual action potentials.

Abstract Author(s): Ronan D. Kilbride, Emad N. Eskandar, Sydney S. Cash