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G J Dörrscheidt

Publications and source records attributed to G J Dörrscheidt.

9 recordsLinked to original sources
PubMed2000

Sound localization with eccentric head position.

This study investigates the influence of head-to-trunk position on auditory localization in humans. Various methods of head pointing, of two-alternative forced choice, and hand pointing were employed. Head-pointing toward actual sound sources in darkness, by using only the subjective median plane of the head as a reference, resulted in systematic underestimations of target eccentricity. The deviations of the terminal head position from the target shifted with a mean slope of approximately 0.1 degrees per degree change in head position. A corresponding shift in the localization of virtual sound sources (presented via headphones during eccentric head positions) was demonstrated by requiring forced-choice (left or right) responses with respect to the subjective median plane of the head. Head pointing toward remembered auditory targets in darkness resulted in undershoots similar to those found with actual targets. However, when a visual marker of the actual median plane of the head was additionally presented to the subject during these tasks (by a laser attached to the head that projected a spot onto a screen), sound localization was fairly accurate. Localization of eccentric auditory targets by using a swivel hand pointer also showed systematic errors similar to those found with head pointing in darkness when the head was simultaneously oriented toward the sound. When the head remained in alignment with the trunk, hand pointing resulted in overshooting responses. These results may be related to neural processes, presumably in the posterior parietal cortex, that transform auditory and visual spatial coordinates into a common, trunk-centered, frame of reference.

Adult↗
PubMed1998

Spatial-tuning properties of auditory neurons in the optic tectum of the pigeon.

We studied the auditory neurons in the optic tectum of the unanesthetized pigeon, using single-unit recordings and acoustic free-field stimulation. Most units showed spatial tuning, with best areas located in the contralateral hemifield. All units responded also to visual stimuli, the auditory best areas being in rough alignment with visual receptive fields.

Acoustic Stimulation↗
PubMed1998

Development of single- and two-tone responses of anteroventral cochlear nucleus neurons in gerbil.

Responses of anteroventral cochlear nucleus (AVCN) neurons in developing gerbils were obtained to single-tone stimuli, and two-tone stimuli elicited by best frequency probes presented over a range of intensities. Neurons displayed Type I, Type I/III, and Type III receptive field patterns. Best frequencies ranged from 1.5 to 10.0 kHz. Two-tone suppression (2TS) was first observed in 5 of 16 neurons examined at 14 dab. and in all neurons examined in gerbils aged 15 to 60 dab. Suppression areas grew larger, and discharge rate reductions became greater with age. Features of the two-tone responses that were highly correlated with single-tone responses across age groups include maximum rate reductions and suppression area thresholds. The intensity level of the CF probe-tone also influenced these features of 2TS. Maximum rate reductions to below spontaneous rate levels of activity were common across age groups. Results suggest that the cochlear amplifier is present and fundamentally adult-like by 15 dab for the regions of the cochlea coding the mid frequencies in gerbil. Over the subsequent week, contributions to the developing two-tone responses by the cochlear amplifier increase slightly. Two-tone responses are influenced by central inhibitory mechanisms as early as 14 dab.

Acoustic Stimulation↗
PubMed1994

Growth of central nervous system auditory and visual nuclei in the postnatal gerbil (Meriones unguiculatus).

The objective of the present study was, by using the Mongolian gerbil (Meriones unguiculatus) as an animal model, to provide data on the growth dynamics of central auditory and visual nuclei and to relate the growth of these structures to the growth of the entire brain. So far, no such systematic study has been performed in any mammalian species. The knowledge of the rates of development of central nervous sensory structures might be useful for understanding the contribution of the central nervous system to maturation of sensory processing. Increases in volumes of nuclei and changes in their shape were analyzed for animals at the day of birth (P0); at postnatal days P7, P15, P22, P28; and in the third month (P90). The auditory nuclei investigated were the cochlear nucleus, the superior olivary complex, the nuclei of the lateral lemniscus, the inferior colliculus, and the medial geniculate body. From the visual system, the superior colliculus and the lateral geniculate body were studied. At P15 (shortly after the onset of central auditory responsiveness), the volumes of all auditory nuclei examined reached only 60-70% of their adult sizes; i.e., they showed considerable growth afterwards. At the same time (shortly before the animals open their eyes), the visual nuclei had almost reached their adult sizes (superior colliculus, 91%; lateral geniculate nucleus, 97%). These data demonstrate that different sensory nuclei contribute in highly different fashions to brain growth. There are system-specific differences in growth dynamics between central auditory and visual nuclei. However, the absolute growth of nuclei in both sensory systems relates to the brain regions. The data do not support the idea of a peripheral-to-central gradient in the growth of central auditory nuclei.

Aging↗
PubMed1992

Setting complex tasks to single units in the avian auditory forebrain. I: Processing of complex artificial stimuli.

In the auditory forebrain (field L) of the European starling (Sturnus vulgaris), single unit responses were recorded for a wide range of complex stimuli, comprising different forms of amplitude and frequency modulation. About two-third of the units locked to sinusoidal modulation regardless of whether frequency (SFM) or amplitude (SAM) was modulated. On average, however, frequency led to stronger synchronization. Both the proportion of phase locking and its mean strength showed a low-pass dependence on modulation frequency. The lower efficiency of amplitude modulation is also visible in unit responses when SAM is combined with (random) frequency modulation. For the assessment of response strength and its comparison across the tested repertoire of complex stimuli, a new index (REX) is introduced which primarily weighs similarity of the spike trains in identically repeated stimulus runs. Applied to a set of 311 field L neurons, also this approach discloses the two stimulus classes lacking frequency modulation (pure tone and SAM) as the least effective. A new measure for response latency, the Effective Response Delay (ERD), based on the spike-triggered analysis of responses to randomly frequency-modulated sounds (RFM), reflects physiological delays better than conventional latency. So, ERD correction of SAM and SFM Period Histograms allowed to disclose response effective stimulus ranges independent of modulation frequency.

Acoustic Stimulation↗
PubMed1992

Setting complex tasks to single units in the avian auditory forebrain. II. Do we really need natural stimuli to describe neuronal response characteristics?

The response characteristic of auditory forebrain neurons in the European starling was established both with artificial stimuli (AS) and a conspecific territorial song as a natural stimulus (NS1). Applying experimenter-centred statistical methods for response detection and for scaling response strength, and spike-triggered analyses for the delimitation of the key sound parameters (spectrotemporal receptive field STRF, Aertsen et al. 1980) the study aimed at disclosing differences in the processing of the two stimulus classes, AS and NS. With the STRF as reference, we find congruence (1) in the best frequency with those determined under sweep and bandpass noise stimulation, (2) in response latency, and (3) in response-intensity dependence, further similarity in the overall frequency characteristic. Partitioning the song into 42 acoustically defined segments allowed to further delimit the response criteria under natural stimulation. They are easily understood from the AS response characteristics: (1) In the neuronal sample as a whole, long segments are more effective than short and, among the short, loud segments are more effective than faint; (2) Units showing their best excitatory response to AS in a certain frequency band are most probably excited by segments with a high proportion of their power concentrated upon or near this band; (3) Units with a slow (build-up) AS response react to a lower number of song segments than those dynamically following AS transients. Our data give no hint towards adaptive, feature detection properties of single neurons in field L. Instead, these neurons appear to base their response solely on the short-time spectrotemporal structure of the stimulus, irrespective of its natural or artificial origin.

Acoustic Stimulation↗
PubMed1987

Tonotopic organization and functional characterization of the auditory thalamus in a songbird, the European starling.

1. The diencephalic auditory nucleus of the European starling, the nucleus ovoidalis, shows rostrocaudal and dorsoventral diameters of 500-800 microns and a mediolateral diameter of 800-1000 microns. This small and sharply delimited nucleus is composed of densely packed neurons. 2. Its tonotopic organization consists of evenly spaced isofrequency contours, with best frequencies decreasing ventrally. The frequency range was found to be 150 Hz to 7030 Hz. 3. Apart from tonotopic organization, other characteristics of single units demonstrate the uniformity of the neuronal population. Units have high spontaneous activities (mean 61 pps; Fig. 4a), and show mainly stimulus correlated tonic discharge patterns. In most cases, excitatory frequency bands are enclosed by inhibitory frequency bands. 4. Single units were tested, applying various stimulus classes differing in time structure (BPN, sine, FM up, FM down, SFM, SAM) but sharing a common frequency band. All neurons tested responded to all classes. Evaluation of stimulus class preference, however, revealed that BPN and SFM caused the strongest responses, whereas FM and SAM were less effective. 5. Comparison of the single unit responses in the ovoid nucleus with those known for avian auditory forebrain and midbrain centres strongly suggests a relay function for the diencephalic nucleus.

Animals↗
PubMed1978

A reversible method for sound analysis adapted to bio-acoustical experiments.

The paper describes a method of sound analysis, 'modulation analysis', its implementation on a minicomputer PDP12 and some aspects of its application in bioacoustical experiments. Modulation analysis reversibly resolves a given sound signal into time-courses of amplitude and carrier frequency. Since time is preserved as the independent variable the method provides a suitable basis for the computer modification of sounds. Problems of practical performance are discussed with regard to sounds of birds and insects. Further, the use of sound modification in a neurophysiological study of the hearing system of birds is described.

Animals↗