Biomedical subjects
Publications and source records attributed to W J Heetderks.
Cortical signals might provide a potential means of interfacing with a neuroprosthesis. Guidelines regarding the necessary control features in terms of both performance characteristics and user requirements are presented, and their implications for the design of a first generation cortical control interface for a neuroprosthesis are discussed.
Over the past decade, many laboratories have begun to explore brain-computer interface (BCI) technology as a radically new communication option for those with neuromuscular impairments that prevent them from using conventional augmentative communication methods. BCI's provide these users with communication channels that do not depend on peripheral nerves and muscles. This article summarizes the first international meeting devoted to BCI research and development. Current BCI's use electroencephalographic (EEG) activity recorded at the scalp or single-unit activity recorded from within cortex to control cursor movement, select letters or icons, or operate a neuroprosthesis. The central element in each BCI is a translation algorithm that converts electrophysiological input from the user into output that controls external devices. BCI operation depends on effective interaction between two adaptive controllers, the user who encodes his or her commands in the electrophysiological input provided to the BCI, and the BCI which recognizes the commands contained in the input and expresses them in device control. Current BCI's have maximum information transfer rates of 5-25 b/min. Achievement of greater speed and accuracy depends on improvements in signal processing, translation algorithms, and user training. These improvements depend on increased interdisciplinary cooperation between neuroscientists, engineers, computer programmers, psychologists, and rehabilitation specialists, and on adoption and widespread application of objective methods for evaluating alternative methods. The practical use of BCI technology depends on the development of appropriate applications, identification of appropriate user groups, and careful attention to the needs and desires of individual users. BCI research and development will also benefit from greater emphasis on peer-reviewed publications, and from adoption of standard venues for presentations and discussion.
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(1) A means of describing the response of neural populations based on principal component analysis is presented. The analysis produces response descriptions that indicate whether two states are distinguishable and suggest how to best distinguish between states. (2) Analysis of slowly adapting joint receptor data from the cat knee joint indicates that the joint receptors are capable of signalling limb position in the range from 150 degrees to 180 degrees of extension during an extension movement. They also provide information which indicates whether the tibia is twisted inward or outward in this range of angles. (3) The first principal component in the response to a constant velocity extension of 8 simultaneously active units described 86% of the total mean square discharge displayed by all 8 units. The first principal component is qualitatively similar to the responses observed in slowly adapting thalamic joint units.
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An emission transaxial tomographic system using a scintillation camera as the detector is described. The unit allows accurate positioning of a scintillation camera's detector at any angle around a patient in order to obtain the multiple projection images needed for transaxial tomography, and it is capable of imaging any area of the body. The camera can also be used for all types of conventional imaging procedures. Image processing is performed by a small on-line computer. A convolution algorithm and a mathematical technique for approximate absorption correction are used to obtain high-resolution and high-contrast images with good quantitative accuracy. The operation of the system is described and representative phantom and patient studies are presented to illustrate the capabilities of the system.
The neural activity in the medial articular nerve is partitioned on the basis of conduction velocity by correlation techniques. Because of the small number of cat knee joint units (two to ten) responding under a prescribed set of rotational conditions, it is possible to partition and simultaneously study the units' responses to periodic joint articulation waveforms.