Bioelectric fields can be measured on the human scalp in response to sensory stimuli and in association with cognitive tasks. Evoked potential (EP) and event related potential (ERP) scalp fields, the terms used for these bioelectric fields, are important objects in research on fundamental issues concerning sensory processing in humans. Scalp potential fields offer good temporal resolution (less than 1 ms); brain activity can be "tracked" during processing, a feature unavailable to other modalities of functional brain imaging. Magnetic field recording also supports tracking but at a cost more than 10 times that of bioelectric field recording. In most contemporary applications, bioelectric field recording has suffered from inadequate spatial sampling. Both theoretical and empirical studies suggest that the Nyquist sampling interval on the scalp is about 2.5 cm. More than 100 electrodes must be placed on the scalp to capture potential fields without risking distortion, a recording density that until recently has been out of practical reach. This proposal is made to acquire equipment for high density spatial sampling which will be used by several researchers, their graduate students and post-doctoral fellows. The research projects supported by this facility will span a wide range from engineering through sensory psychology. It will bring together a group of researchers with complimentary backgrounds and act as a catalyst for a sophisticated research program aimed at understanding how the human brain processes sensory information. These researchers are from three institutions, Southwestern Medical School (SWMS), University of Texas at Dallas (UTD) and Southern Methodist University (SMU), all located close to the proposed facility. No comparable facility exists within or near the Dallas metro area. UTD has a 32-channel "BEAM" system. SWMS has a 32-channel "homemade" recording system in operation. Neither school or the ir combination can provide the required recording equipment. It is proposed to purchase a 128-channel recording system from Electrical Geodesics Inc. (EGI), an S.B.I.R. grant-supported company under a "Beta" site agreement to reduce costs. The system, "Net Station", will include EGI's Geodesic sensor nets that allow 128 electrodes to be placed on the scalp in about 20 minutes, state of the art amplifiers, a flexible data acquisition system, and software for signal processing, convenient display of results, as well as statistical testing. These functions are vital to making the facility useful to the researchers. It is also proposed to acquire an optical disk to support the large data storage requirements of the project. A three-dimensional digitizer completes the equipment requirements allowing experimenters to record all electrode locations for adequate display and processing. Important as the equipment and software are to the success of this project, it is also recognized that the facility must provide apppopriate support staff for the researchers at least for the first few years of its operation. Thus it is proposed to hire an electrical engineer who will serve as the chief technical person. In addition, SWMS is prepared to support the salaries of the P.I., who will act as the administrative head of the facility and of a well-trained technician who will be responsible for subject scheduling, equipment maintenance and who will assist in the actual data acquisition process. During the three years of this project, the goal is to develop the facility so that it becomes a "stand alone" research resource supported by its users.
