Current Research Directions and Technologies at the BRAINS Center

As described in our mission statement, the Center for Brain Research and Informational Sciences provides research/learning opportunities in two areas of neuropsychology. One involves the application of microelectrode recording techniques to the study of brain function. The other, only a hope when the mission statement was written, involves the application of dense array (128 electrode) recording techniques for the electroencephalographic (EEG) study of psychological processes. The microelectrode experiments are performed with laboratory rats, whereas the EEG studies are performed with human volunteers. These methodologies afford the opportunity to study brain/behavior relationships at a range of levels, from the microscopic, local levels to the brain systems level. This report describes the specific capabilities within these research/learning methodologies offered by the BRAINS Center.

Recording the activity of the brain with microelectrodes enables us to observe the operation of individual cells or small groups of cells within the brain as a function of changes in testing conditions. Most recently, we have been studying the patterns of responses of small groups of neurons to sensory stimulation of the rat's whiskers. The possibilities offered by environmental stimulation are extremely varied, yet the brain only responds in terms of two or three types of electrical activity. Our question is straightforward: How does the brain transform environmental input so that the varied types of environmental stimulation can be represented in its electrical activity? In short, how does the brain know what the animal's whiskers are touching?

This research is of fundamental importance because, contrary to popular belief, we still do not understand how the brain represents the outside world. One fundamental question is whether to think of the brain's encoding of the outside world in terms of patterns of activity in individual neurons or in terms of patterns of activity across inter- connected networks of neurons. Our research has indicated that, at least in anesthetized animals, the latter view is the more useful one. The challenge, therefore, is to discover the transformations in that input that take place in each processing area before it is passed on for further processing. We are presently working to record from awake, behaving animals and use multiple microelectrodes to study these aspects of brain function. Therefore, in this research, we can use microelectrodes to "observe" the activity of both individual and small groups of neurons in particular parts of the brain. With an under- standing of the general scheme of a brain system, microelectrode and signal processing technologies provide the tools necessary for this "fine-grained" look into nervous system function.

Clarity does not always result from such a microscopic level of analysis. There are other occasions when psychological functions are best understood at a more macorscopic level of analysis. In addition, for studies of human psychological processes, it is often necessary to use human subjects. To complement the microelectrode research, we also use the technology of electroencephalography (EEG) to study the working brain. Currently we have two EEG systems with which we work. The first is a standard 10-20 system which uses a fabric "cap" that holds the electrodes, and is placed over the subject's head. The collection of data is controlled by a computer and software written by engineers at the BRAINS Center. Most recently, we have obtained an EEG system which uses 128 electrodes. This system, designed by Dr. Don Tucker and his associates at the University of Oregon, consists of an array of 128 silver chloride coated electrodes, each wrapped in a tiny sponge which is inserted into a plastic holder. These holders are collectively arranged in a geodesic array by polyethylene threads forming a net which fits over the head, neck, and portions of the face. This geodesic arrangement provides for even spatial distribution of electrode sites over the scalp, as well as roughly even pressure of each electrode against the scalp. The use of this large number of recording sites extends brain recordings to include sites towards the bottom of the brain . The extended recording area, along with increased recording density provided by the 128 electrode system, allow us to more precisely determine the brain area that generates a particular EEG pattern, and to precisely identify when the pattern begins. A surprising result of this new technology (often referred to as "dense array recording") is that the application of the 128 electrodes to a subject takes one-fourth the time required to apply the 19 electrode system, and, similarly, can be learned to use much more easily.

We use this EEG technology primarily to study two areas of psycho- logical function. The first involves the effects of cognitive effort on brain function. These studies involve recording "running EEG" while the subject performs various types of mental tasks. The dense array technology affords the precision in localizing brain function which is not present with the 10-20 system. However, our first experiments were with the 10-20 system, and resulted in the development of some new methods for the description and analysis of EEG activity. A report of these methods is currently under review for publication by a major professional journal. We are currently adapting these methods for use with the dense array EEG system. An exciting area of application of our studies of cognitive effort is to the effects of aging on "cognitive flexability". Several current theories of aging view this process as one of decreasing processing speed, rather than decreasing processing competence by the brain. The use of our analytical methods along with the dense array technology provides a "cutting edge" test of these cognitive theories of aging.

A second use of our EEG systems is for the study of attention in humans. Our current project is one that seeks to understand which brain areas are responsible for the processing of novelty. It is well- known that we often are not counsciously aware of much of our surroundings until some change occurrs. It is often these unexpected changes that "capture" our attention, if only for a short time. However, it seems likely that all changes are not equal, for we also simplify our world by organizing it into figures and backgrounds. Our specific question is whether novelty in backgrounds is processed by the same systems that process novel figures. Experiments using brain lesions in monkeys indicate that context is processed by different brain areas than those used to extract specific features. Therefore, it would seem that such momentary "switches" in attention caused by novelty are precisely the kind of phenomena for which the EEG is well suited. Our intention is to extend these studies to include individuals with attention deficit disorder (ADD) and certain learning disabilities.

The studies on attention use another feature of EEG analysis called Event Related Potentials (ERPs). If a display is projected onto a screen for a brief interval (250 miliseconds), and repeated many times, then a computer can be used to "overlay" the successive presentations with respect to the onset of the repeated display. These overlayed EEG patterns can then be averaged. Any part of the patterns that is consistently related to the dispaly is enhanced, and any parts not so related are "averaged out". Since each EEG electrode generates its own pattern, the comparison of these averaged patterns under different conditions enables us to accurately identify the different processing demands of different displays.

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These pages were last updated on October 8, 1996.