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P Heil

Publications and source records attributed to P Heil.

40 records · Page 3Linked to original sources
PubMed1985

Quantitative analysis and two-dimensional reconstruction of the tonotopic organization of the auditory field L in the chick from 2-deoxyglucose data.

The tonotopic organization of the input layer L2 of the auditory neostriatum (field L) of chicks was analyzed using 2DG autoradiographs of serial transverse sections through this structure. In the experiments neonatal chicks were stimulated with pure tones in the frequency range between 0.1 and 2.5 kHz. The spacing of isofrequency contours, which are represented as stripes of 2DG labeling across the field, were measured on autoradiographs and on computer generated densitometric profiles. Positions of contours were determined along both the dorsolateral-ventromedial axis (tonotopic gradient) and along the rostrocaudal axis (parallel to the isofrequencies) of the field. Using these data a two-dimensional top view of the L2-layer and its tonotopic organization was reconstructed. The results demonstrate that isofrequency contours do not run parallel to each other but rather diverge from rostral to caudal. Whereas in the rostral part the spatial resolution is about 0.3 mm per octave this factor increases to 0.4 mm per octave towards the caudal border of the L2-layer. Regression analyses along the tonotopic gradient and mathematical extrapolations revealed that the tonotopic organization can be equally well described by logarithmic and power functions. The frequency range which is represented in L2 converges from rostral to caudal. In that way the rostral part of L2 is characterized by the representation of a wide frequency range with low spatial resolution, whereas in the caudal part a more confined frequency range with a higher spatial resolution is represented.

Animals↗
PubMedDate not supplied

Representation of sound onsets in the auditory system.

Sound onsets constitute particularly salient and behaviorally relevant transients and elicit vigorous responses from most auditory neurons. Here I show that response latency, precision of response timing, and response magnitude depend on dynamic properties of the stimulus envelope at onset. The joint consideration of these response parameters, and of the stimulus and neuronal properties on which they depend, suggests a point-by-point sampling, or tracking, mechanism for the onset envelope. This mechanism is characterized by an automatically adjusted sampling rate and precision of spike timing, so that it should be rather robust against changes in the dynamics of the envelope, brought about for example by changes in a signal's sound pressure level. There will be a one-to-one relationship between stimulus onset and the evoked spatiotemporal response pattern. That pattern involves both the tonotopic and the isofrequency axes of cortical maps. Such a mechanism could provide a temporal resolution of the time course of the onset envelope which is likely orders of magnitude higher than that inferred from the phase-locking capabilities of neurons in cortical fields to periodic signals and could contribute to the instantaneous coding of transients.

Acoustic Stimulation↗
PubMedDate not supplied

Intubation with transillumination: nasal or oral?

Transillumination-guided intubation is a useful back-up method when laryngoscopic intubation proves to be difficult or impossible. The Trachlight (Laerdal, N-4001 Stavanger, Norway) is suited for both nasal and oral use. Intubation times (IT) and success rates (SR) for nasal and oral intubation with the Trachlight were compared. Twenty-four medical students, inexperienced in intubation were instructed in the use of the Trachlight. A demonstration also was performed. Subsequently, they were asked to intubate a Laerdal Airway Management Trainer (Laerdal, Stavanger, Norway) using the Trachlight. Each student intubated 10 times orally and 10 times nasally (five times through the right and five times through the left nostril). The succession of the students was randomized. The intubation times were measured and the position of the tube noted. Nasal and oral intubation times for the tenth trial (steady state conditions) were compared using the rank-order test for paired observations. Oral and nasal success rates were compared using the sign test for paired observations. The differences between nasal and oral intubation concerning intubation time and the success rates were not significant. Nasal intubation with the Trachlight seems to be more difficult than the oral intubation.

Clinical Competence↗