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Biomedical subjects

M Hoke

Publications and source records attributed to M Hoke.

At least 73 records · Page 4Linked to original sources
PubMed1978

Decoding of human compound action potentials.

The physiological formation of the action potentials is presumed to be well-known and a method of decoding these potential is therefore based on this knowledge. The method uses the reverse process, i.e. deconvolution of the recorded AP's with a unit response, and a subsequent nonlinear transformation of the obtained waveforms (sigma PST-compound PST) from the time- into the location domain (distance along the coclear partition). The transformed waveforms are called excitation patterns. Stimulus polarity seems to have only a minor influence on the excitaton patterns and it is possible to produce frquency-specific information of the coclear function. A clinical case demonstrates the concordance between the excitation patterns and the puretone audiogram.

Acoustic Stimulation↗
PubMed1978

[Frequency specific information retrieved from compound action potentials--model investigations and clinical results (author's transl)].

It is the aim of electrochleographic assessments to determine with sufficient accuracy the hearing threshold in the frequency range usually covered by subjective audiometric investigations. An optimal result would be an "objective" audiogram comparable to the subjective one. In the present paper, difficulties and limits which are arising during the retrieval of frequency specific information from compound action potentials are demonstrated on the basis of model experiments. In connection with these experiments a new approach is demonstrated which is based on the reverse process of the physiological formation of the compound action potential. As a result of this method, the excitation pattern at the level of primary auditory neurons is obtained. The efficiency of this technique is shown by means of model simulations as well as by processing derived action potentials recorded from normal hearing subjects.

Action Potentials↗
PubMedDate not supplied

Evoked magnetic responses of the human auditory cortex to minor pitch changes: localization of the mismatch field.

The neuromagnetic source localizations of the auditory M100 and the mismatch field (MMF) were studied using a large-array biomagnetometer. Standard tones of 1000 Hz and deviant tones of 1050 Hz were delivered with 90% and 10% probability, respectively. Wave forms of the derived MMF were computed by examining difference wave forms between the responses to the deviants and the responses to the standards preceding (D-P) and following (D-F) the deviants as well as to all remaining standards (D-A). The subset of standards preceding the deviants was used for a more realistic comparison with the set of deviants (having the same number of epochs and a similar signal-to-noise ratio), while the subset of standards following the deviants served to answer the question whether those standards also elicit an MMF. The MMF deflections were compared with each other, with the "native" MMF occurring in response to the deviants, and with wave M100. (The MMF as it appears in the unprocessed response to the deviants was termed "native" for an easy distinction from the "derived" MMF.) Our results demonstrate a distinct MMF deflection, corresponding in latency to the simultaneously recorded fronto-central electrical MMN. Source analysis, using a single moving dipole model, showed the same spatial localization for the native MMF and for the different derived MMFs. The MMF source location turned out to be significantly anterior, medial and inferior relative to the sources of the M100. The present data also demonstrate that a minor frequency deviation may not activate measurably different M100 generators, yet be sufficient to trigger the nearby but spatially distinct mismatch generator.

Acoustic Stimulation↗