Biomedical subjects

M S John

Publications and source records attributed to M S John.

4 recordsLinked to original sources

PubMed2000

MASTER: a Windows program for recording multiple auditory steady-state responses.

MASTER is a Windows-based data acquisition system designed to assess human hearing by recording auditory steady-state responses. The system simultaneously generates multiple amplitude-modulated and/or frequency-modulated auditory stimuli, acquires electrophysiological responses to these stimuli, displays these responses in the frequency-domain, and determines whether or not the responses are significantly larger than background electroencephalographic activity. The operator can print out the results, store the data on disk for more extensive analysis by other programs, review stored data, and combine results. The system design follows clear principles concerning the generation of acoustic signals, the acquisition of artifact-free data, the analysis of electrophysiological responses in the frequency-domain, and the objective detection of signals in noise. The instrument uses a popular programming language (LabVIEW) and a commercial data acquisition board (AT-MIO-16E-10), both of which are available from National Instruments.

Computer Simulation↗

PubMed2000

Human auditory steady-state responses to amplitude-modulated tones: phase and latency measurements.

Human auditory steady-state responses were recorded to four stimuli, with carrier frequencies (f(c)) of 750, 1500, 3000 and 6000 Hz, presented simultaneously at 60 dB SPL. Each carrier frequency was modulated by a specific modulation frequency (f(m)) of 80.6, 85.5, 90.3 or 95.2 Hz. By using four different recording conditions we obtained responses for all permutations of f(m) and f(c). The phase delays (P) of the responses were unwrapped and converted to latency (L) using the equation: L=P/(360xf(m)). The number of cycles of the stimulus that occurred prior to the recorded response was estimated by analyzing the effect of modulation frequency on the responses. These calculations provided latencies of 20.7, 17.7, 16.1 and 16.1 ms for carrier frequencies 750, 1500, 3000 and 6000 Hz. This latency difference of about 4.5 ms between low and high carrier frequencies remained constant over many different manipulations of the stimuli: faster modulation rates (150-190 Hz), binaural rather than monaural presentation, different intensities, stimuli presented alone or in conjunction with other stimuli, and modulation frequencies that were separated by as little as 0.24 Hz. This frequency-related delay is greater than that measured using transient evoked potentials, most likely because of differences in how transient and steady-state responses are generated and how their latencies are determined.

Acoustic Stimulation↗

PubMedDate not supplied

Intracerebral sources of human auditory-evoked potentials.

Evoked potentials to brief 1,000-Hz tones presented to either the left or the right ear were recorded from 30 electrodes arrayed over the head. These recordings were submitted to two different forms of source analysis: brain electric source analysis (BESA) and variable-resolution electromagnetic tomography (VARETA). Both analyses showed that the dominant intracerebral sources for the late auditory-evoked potentials (50-300 ms) were in the supratemporal plane and lateral temporal lobe contralateral to the ear of stimulation. The analyses also suggested the possibility of additional sources in the frontal lobes.

Auditory Cortex↗

PubMedDate not supplied

Multiple auditory steady-state responses (MASTER): stimulus and recording parameters.

Steady-state responses evoked by simultaneously presented amplitude-modulated tones were measured by examining the spectral components in the recording that corresponded to the different modulation frequencies. When using modulation frequencies between 70 and 110 Hz and an intensity of 60 dB SPL, there were significant interactions between two stimuli when the carrier frequencies were closer than one half of an octave apart, with attenuation of the response to the lower carrier frequency. However, there were no significant decreases in response amplitude with four simultaneous stimuli provided the carrier frequencies differed by one octave or more. Higher intensities (70 dB SPL) resulted in greater interactions between the stimuli than when low intensities (35 dB SPL) were used. Modulation frequencies could be as closely spaced as 1.3 Hz without affecting the responses. Using broad-band noise as a carrier instead of a pure tone resulted in a significantly larger response when the stimuli were presented at the same sound pressure level. At modulation frequencies between 30 and 50 Hz, there were greater interactions between stimuli than at faster modulation frequencies. These results support the following recommendations for using multiple stimuli in evoked potential audiometry: (1) The multiple stimulus technique works well for steady state responses at frequencies between 70 and 110 Hz. (2) Up to four stimuli can be simultaneously presented to an ear without significant loss in amplitude of the response, provided the carrier frequencies are separated by an octave and the intensities are 60 dB SPL or less. (3) Bandpass noise might serve as a better carrier signal than pure tones.

Adolescent↗