To achieve accurate localization of electrical sources of the human EEG and evoked potentials, the field on the scalp must be sampled at much higher spatial frequency than the 19 positions defined by the standard """"""""10- 20"""""""" locations """"""""High resolution"""""""" (64-256 channel) EEG (hrEEG) not only provides greater localization of source generators for experimental purposes but can substantially improve diagnostic and monitoring capability for diseases such as epilepsy and stroke Further, meaningful coregistration of EEG and evoked potential metrics with structural images from MRI or CT as well as functional MRI (fMRI) also requires high spatial sampling. Despite the availability of amplifier systems with large numbers of channels, the process of transducing the microvolt level cerebral electrical signals at the scalp surface remains difficult, requiring low and balanced contact impedances to achieve acceptable levels of line frequency (60 Hz) noise. Manual preparation of scalp sites using solvents, abrasives or syringe needles to match amplifier system input requirements is very time consuming and is a major impediment to hrEEG application due to the number of channels involved High system acquisition cost has also substantially inhibited the development and utilization of hrEEG. ? ? A preparation-free, high resolution EEG system will be developed that will entirely eliminate scalp site preparation without the use of costly on-head electronics, a shielded recording environment or excessive filtering that can compromise signal integrity. Setup time for clinical and experimental protocols would be reduced to the time required for physical application of electrodes and patient irritation and risk of infection from scalp puncture during abrasion will both be eliminated. In addition, the new hrEEG system will be designed to substantially lower system cost by a new type of hardware design in a highly compact form factor. The software package will feature object-oriented programmability, conferring unprecedented user control and flexibility. The proposed new system will lead to increased utilization of hrEEG for experimental and clinical applications In Phase I, the technical feasibility of a prototype hrEEG system will be evaluated in bench top tests and in human subjects at an independent, university-based EEG laboratory. ? ?
