Biomedical subjects

B C Wheeler

Publications and source records attributed to B C Wheeler.

26 records · Page 2Linked to original sources

PubMed1989

A high-speed multichannel neural data acquisition system for IBM PC compatibles.

An inexpensive 32-channel data acquisition system has been constructed for use in acquiring neuroelectric data from a multiple element electrode array. Direct memory access (DMA) techniques allowed a maximum aggregate sampling rate of 652 ksamples/s, or 20.4 ksamples/s on 32 channels. The 8-bit analog-to-digital (A/D) conversion circuitry lies on a single plug-in card installed in an IBM PC-compatible AT & T 6300 Plus personal computer, although the card may be used in an IBM PC with no reduction in sampling performance. Data have been taken from 32 points on the surface of the rat hippocampal slice preparation. Assembly language graphics routines permitted rapid display of raw and processed data. Signal processing routines can be executed and results can be displayed to provide rapid feedback to an experimenter.

Action Potentials↗

PubMed1988

High-resolution alignment of action potential waveforms using cubic spline interpolation.

A cubic spline interpolation technique is applied to the problem of aligning action potential waveforms. Interpolation is an attractive alternative to sampling at many times the Nyquist rate in order to reduce errors caused by asynchronous sampling of rapidly changing waveforms. Alignment is achieved by locating the peak of the interpolated waveform, which can be found by solving a quadratic equation. The waveform is then reconstructed for comparison with existing templates. The technique was tested using simulated noisy, randomly arriving waveforms, the interpolated signal and alignment time errors being computed as functions of the signal/noise ratio. The spline technique is superior in accuracy to sampling at eight-times the Nyquist rate and is comparable to a Fourier-transform-based interpolation algorithm. It is computationally efficient, requiring approximately five multiplications per sample point. The interpolation concept is extended to the principal component technique for separation of action potential waveforms. The energy function is interpolated and used to align the waveforms, after which the interpolated coefficients can be used for high speed classification. The technique shows an improvement in both alignment error and effective signal/noise ratio in comparison with sampling or interpolation to a voltage peak.

Action Potentials↗

PubMed1988

Multisite hippocampal slice recording and stimulation using a 32 element microelectrode array.

A technique has been developed in which a planar array of 32 microelectrodes, arranged in a 4 by 8 pattern with 200 micron separation, is used to record from and stimulate the hippocampal slice preparation at multiple sites. Control of media flow past the tissue is critical to observe signals and preserve viability. Active suppression circuitry is used to prevent device saturation due to large stimulation artifacts. The field potentials recorded are spatially unique and provide a 2-dimensional description of the underlying population activity in the various pyramidal strata and subpopulations. Multisite stimulation is also possible with the array, permitting the experimenter to quickly stimulate and record from brain slices in many spatial patterns.

Animals↗

PubMed1988