The electrical interaction between artificial pacemakers and patients, with applications to electrocardiography.
Explore the source record for details and available documents.
Electrocardiography↗
Biomedical subjects
S D Arlinger
Publications and source records attributed to S D Arlinger.
Slow evoked cortical responses to linear frequency ramps in subjects with cochlear lesions.
Slow evoked cortical potentials in response to linear frequency ramps of a continuous pure tone with a 1 kHz base frequency have been recorded from ten relatively young subjects with hearing loss of cochlear origin. At small frequency ramps, the N1-latency of their responses to the three ramp durations studied (20, 100, 500 msec) was significantly longer than those of a group with normal hearing. As the ramps are made larger, the difference between the latencies of the pathological group and the normal group becomes smaller; above a certain rate of frequency change, the latency of N1 becomes smaller in the pathological cases than in the normal group. This crossover occurs at frequency change rates around 1-3 kHz/sec. It is concluded that recording of evoked cortical responses to frequency ramps may provide an additional tool in the differential diagnosis of hearing disorders.
Acoustic Stimulation↗
Bone-conducted stimulation in electrocochleography.
The mechanical vibration patterns close to the cochlea in intact skulls of human cadavers have been studied by means of a miniature accelerometer. A Radioear B70A vibrator and a Brüel & Kjaer Mini Shaker have been used, fed with filtered clicks and with short tone bursts. The tone bursts were found to be superior to the clicks with regard to the vibration spectrum. At 500 Hz a considerable distortion was observed in the accelerometer signal, also when using tone bursts. This distortion was presumably due to resonant vibrations in the skull itself, and may be a source of error not only when using stimuli of short duration as in bone-conduction ECoG but also in conventional bone-conduction audiometry. When the vibrations were applied to the exposed bone surface of the mastoid, vibration levels increased by 10-25 dB compared with when soft tissues covered the point of application. This could be of advantage in bone-conduction ECoG performed at ear surgery.
Acoustic Impedance Tests↗
Electrocochleography used as a clinical hearing test in difficult-to-test children.
Thirty difficult-to-test children have been tested with transtympanic ECoG. When possible, informal hearing tests and/or free-field testing were performed. Children in whom no action potential (AP) could be recorded were submitted to conventional radiography of the inner ear, and vestibular tests. The correlation between free-field test thresholds and AP "thresholds" was good, especially in subjects with relatively good hearing. Response amplitude increased, and latency decreased, with increasing frequency of the stimulus implying that different parts of the basilar membrane are stimulated according to the frequency of the stimulus. Input-output curves of response amplitude and latency were plotted, and three different types were distinguished. ECoG can contribute to the evaluation of peripheral hearing in difficult-to-test children, and vestibular tests should always be performed on a child with suspected deafness or sensorineural hearing loss. Conventional radiography of the inner ear, however, seems to be of little value.
Action Potentials↗
Peroperative temporary threshold shift in ear surgery. An electrocochleographic study.
TTS resulting from drilling in the temporal bone was detected by means of pre- and post-exposure ECoG recordings taken during ear surgery for chronic otitis media. The TTS obtained varied between 5 and 40 dB at 4 and 8 kHz. The correlation between duration of noise exposure and magnitude of TTS was statistically significant. The results indicate that drill-induced noise in ear surgery may result in postoperative high-tone sensorineural hearing loss, and support the view that manipulation of the ossicular chain during ear surgery causes mainly a threshold shift at the lower frequencies.
Acoustic Stimulation↗
Discrimination of frequency ramps in subjects with cochlear hearing loss.
The auditory sensitivity for detecting linear frequency sweeps of a continuous pure tone has been studied in ten young subjects with cochlear hearing loss. The mean thresholds were elevated by a factor of 2.8 as compared with a normal group over the whole range of ramp durations studied (10-500 msec). The results show that this elevation is most likely caused mainly by the cochlear lesion per se, other possible factors having only a minor effect. No clear correlations could be found between thresholds for frequency change and results of other pure tone audiometric tests. Such tests thus cannot predict a subject's frequency discrimination.
Acoustic Stimulation↗
Thresholds for linear frequency ramps of a continuous pure tone.
The human auditory sensitivity in detecting linear frequency ramps of a continuous pure tone has been studied. It is shown that for short ramp durations (less than 200 msec) discrimination depends on the difference between base and plateau frequencies, the mean threshold being about 3 Hz at 1 kHz. For longer ramp durations (greater than 200 msec), discrimination was found to be based on detection of the actual frequency sweep. No significant difference was found between thresholds for upward and downward sweeps. Expressed in Hz, the threshold for frequency change was approximately constant for base frequencies up to 1 kHz, above which it increased, reaching approximately 14 Hz at 4 kHz. There was no significant difference in the threshold for frequency change from 40 to 80 dB HL but at 20 dB HL the threshold was significantly higher than at 40 dB HL. Intra-individual variation in thresholds was found to be smaller than inter-individual variation. The results are discussed in relation to previous frequency discrimination data, where either tone pulse pairs, continuous frequency modulation or frequency ramps were used as stimuli.
Acoustic Stimulation↗
Skull distortion of bone conducted signals.
A previously essentially unknown type of distortion of bone conduction (BC) signal has been studied on the skulls of four human cadavers. The method was based on a miniature accelerometer, rigidly attached to the cranial bone, converting the skull vibration close to the cochlea into an electrical signal which was analysed with regard to harmonic distortion. The BC signals, pure tones, were presented by means of a high-quality vibrator. The distortion was found to be limited to the lower audiometric frequencies, with a maximum around 500 Hz, and of such a degree as to be able to significantly influence the results of BC audiometry. The distortion is probably caused by nonlinear mechanical properties of the human skull.
Audiometry↗
N1 latencies of the slow auditory evoked potential.
Several studies have been published concerning the relation between stimulus level and amplitude of the slow auditory evoked response. Little attention has, however, been given to the relation between level and latency of the N1 component (100-200 ms). A mathematical model of such a relation is proposed based on the assumption of an exponential relationship. The model has been tested on normally hearing subjects as well as on patients with sensorineural lesions, cochlear as well as retrocochlear. The results indicate that the proposed method of evaluating the slow evoked responses offers a way of threshold extrapolation with rather good accuracy. It also appears to be useful in determining the type of hearing loss.
Adolescent↗