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Biomedical subjects

H Scheich

Publications and source records attributed to H Scheich.

At least 109 records · Page 6Linked to original sources
PubMed1984

Infrasound responses in the midbrain of the guinea fowl.

The electrophysiological audiogram of the Guinea fowl has been obtained using auditory evoked potentials from the MLD of unanesthetized birds. In restricted regions of MLD, phase-coupled responses to extreme low-frequency sinusoids (2-10 Hz) could be recorded at moderate intensities. The tonotopy of MLD extends continuously to the infrasound region at the rostrodorsal margin. Single-cell recording of infrasound responses show phase-locked firing of neurons with different phase delays for different cells.

Animals↗
PubMed1984

Functional activation in the auditory system of the rat produced by arousing reticular stimulation: a 2-deoxyglucose study.

The 2-deoxyglucose (2-DG) autoradiographic method was used to map the activity in the auditory pathway during behaviorally arousing electrical stimulation of the mesencephalic reticular formation (RET). Uptake of 2-DG during RET stimulation was compared to the effect of a frequency-modulated tone (4-5 kHz, 60 dB SPL) and to controls without stimulation. The major finding was a specific pattern of increased metabolic activation throughout the auditory pathway evoked during RET stimulation. The observed increases in 2-DG uptake were always greater in RET-stimulated rats as compared to sound-stimulated or control rats. The dorsal cochlear nucleus (DCN) showed the largest incorporation of 2-DG among the auditory nuclei of the brainstem in RET-stimulated rats. In the central nucleus of the inferior colliculus a layered pattern made of 3 discrete bands of high 2-DG uptake was visible in RET-stimulated rats. The medial geniculate (MG) and the auditory cortex (AC) also showed highly significant increases in 2-DG uptake induced by RET stimulation. The method provided correlations between classical morphological schemes of parcellation on nuclei and functionally defined areas of increased 2-DG uptake. Our observations represent the first anatomical demonstration of the activating effects of RET stimulation in a sensory system, and they support the concepts of arousing reticular mechanisms for sensory control.

Animals↗
PubMed1984

Neural substrates for tone-conditioned bradycardia demonstrated with 2-deoxyglucose. I. Activation of auditory nuclei.

The 2-deoxyglucose (2-DG) autoradiographic method was used to map the metabolic activity of auditory nuclei before, during and after conditioning. The experiment involved freely behaving rats in a Pavlovian conditioning paradigm in which a 4-5 kHz frequency modulated tone (CS) was paired with aversive electrical stimulation of the midbrain reticular formation (US). The unconditioned response was a rapid decrease in heart rate evoked by the US. Eight groups of rats were subjected to: (1) the tone CS before conditioning; (2) the US alone; (3) the paired CS-US (acquisition); (4) the tone CS after conditioning (extinction); (5) the US prior to the CS (sensitization); (6) the unpaired CS-US (pseudoconditioning); (7) the CS after pseudoconditioning; and (8) no stimulation. The major finding was the differential effect produced by the same tone before and after conditioning. The results showed that: (a) reticular mechanisms interact with incoming acoustic stimuli and modulate the response of auditory nuclei; (b) within each auditory nucleus the region of overlap of the spatial representations of CS and US developed an enhanced metabolic response during conditioning; and (c) the CS representation within the neuronal space of the tonotopic maps in all auditory nuclei, with the exception of the medial geniculate, reflected the learned behavioral value of the CS. The changes revealed by the 2-DG method represent the first anatomical demonstration of the activating effects of reticular sensitization and conditioning on a sensory system. The observations support the conclusion that auditory responses are dependent on the physical as well as on the behavioral parameters of a stimulus.

Animals↗
PubMed1983

Two columnar systems in the auditory neostriatum of the chick: evidence from 2-deoxyglucose.

In chicks, monaurally deafened at 3 weeks of age, 2-deoxyglucose labeling of the input layer L2 in the auditory neostriatum (field L) was analyzed after acoustic stimulation. Two types of stimuli were used: narrow band frequency modulations and white noise. Both stimuli provide evidence that there are bands or columns with different inputs from the contra- and ipsilateral ear, a rostral, intermediate, and caudal band, all oriented orthogonal to the isofrequency contours. The intermediate band, in addition, shows multiple alternating columns of ipsi-vs. contralateral dominant input, parallel to the isofrequency contours. Consequently, the tonotopic gradient is interrupted several times by these columns. The organization of field L bears interesting parallels to the mammalian auditory cortex and is the first evidence of columnar organization in a submammalian forebrain. The multiple interruptions of the tonotopic gradient between low and high frequencies in the intermediate band by alternating aural dominance has possible implications for understanding directional hearing, as well as for understanding formant analysis of species-specific sounds.

Acoustic Stimulation↗
PubMed1983

Linear phoneme boundaries for German synthetic two-formant vowels.

The phonetic boundaries of variable, synthetic two-formant vowels were studied in psychophysical tests. In the F1 versus F2 formant plane, vowel boundaries appeared to be straight and all but one were parallel to the formant axes. Discrimination of two of the eight German vowels examined relied within certain boundaries upon information of the frequency of the first formant (F1) independent of that of the second (F2) or vice versa. Two vertical F1 boundaries were common to six vowels and one horizontal F2 boundary was common to five vowels. Interpreted in the light of recent neurophysiological data these findings point to the existence of mechanisms of vowel recognition with independent assessment of the two formants.

Communication Devices for People with Disabilities↗
PubMed1983

Acoustic imprinting leads to differential 2-deoxy-D-glucose uptake in the chick forebrain.

This report describes experiments in which successful acoustic imprinting correlates with differential uptake of D-2-deoxy[14C]glucose in particular forebrain areas that are not considered primarily auditory. Newly hatched guinea chicks (Numida meleagris meleagris) were imprinted by playing 1.8-kHz or 2.5-kHz tone bursts for prolonged periods. Those chicks were considered to be imprinted who approached the imprinting stimulus (emitted from a loudspeaker) and preferred it over a new stimulus in a simultaneous discrimination test. In the 2-deoxy-D-glucose experiment all chicks, imprinted and naive, were exposed to 1.8-kHz tone bursts for 1 hr. As shown by the autoradiographic analysis of the brains, neurons in the 1.8-kHz isofrequency plane of the auditory "cortex" (field L) were activated in all chicks, whether imprinted or not. However, in the most rostral forebrain striking differences were found. Imprinted chicks showed an increased 2-deoxy-D-glucose uptake in three areas, as compared to naive chicks: (i) the lateral neostriatum and hyperstriatum ventrale, (ii) a medial magnocellular field (medial neostriatum/hyperstriatum ventrale), and (iii) the most dorsal layers of the hyperstriatum. Based on these findings we conclude that these areas are involved in the processing of auditory stimuli once they have become meaningful by experience.

Acoustic Stimulation↗
PubMed1982

Dendritic spine loss and enlargement during maturation of the speech control system in the mynah bird (Gracula religiosa).

Three types of neurons were identified in Golgi-Cox preparations of the telencephalic nucleus HVc of the mynah bird with the Sholl method. In a comparison of birds of 10 weeks and speech-trained birds of one year of age a reduction of dendritic spine density and an enlargement of the remaining spines was found in a large isopolar cell type. These findings are interpreted in terms of the mynah's shrinking potential with age to imitate new sounds and the stabilization of the acquired repertoire.

Age Factors↗
PubMed1981

Inputs to the torus semicircularis in the electric fish Eigenmannia virescens. A horseradish-peroxidase study.

The posterior lateral-line lobe, contrary to present belief, projects bilaterally to the torus semicircularis, although the contralateral projection is considerably more extensive. The torus also receives bilateral inputs from the medial octavo-lateralis nuclear complex, the reticular formation, a sublemniscal nucleus, and the nucleus prae-eminentialis. Unilateral inputs to the torus were found originating from the ipsilateral mesencephalic tectum and the contralateral lobus caudalis of the cerebellum. Extensive commissural systems between the right and left torus are also described for the first time.

Animals↗
PubMed1981

Connections of the olfactory bulb in the piranha (Serrasalmus nattereri).

The connections of the olfactory bulb were studied in the piranha using the Nauta and horseradish-peroxidase methods. Three olfactory tracts project to seven terminal fields in the telencephalon and one in the diencephalon, all of them bilaterally. The contralateral olfactory bulb also receives a small input. All contralateral projections decussate in the anterior commissure and are relatively weak compared to the ipsilateral projections. HRP-containing cells were found in all of the ipsilateral telencephalic aggregates receiving an olfactory tract projection; the contralateral side was free of labeled cell bodies. Although only about one fourth of the entire telencephalon receives a direct olfactory input, the high degree of differentiation of the olfactory system suggests that the piranha depends substantially on the sense of olfaction and that this species may be a good model for further studies on olfactory mechanisms.

Animals↗
PubMed1981

Neuronal discrimination of natural and synthetic vowels in field L of trained mynah birds.

The discrimination of single neurons for vowels and vowel components was analyzed in the telencephalic field L which is a layered and tonotopically organized primary auditory projection area in the bird's neostriatum. Among 250 units, 132 (53%) were responsive to at least one out of nine vowels from one German speaker. The distribution of responsiveness to n (one to nine) vowels showed that a maximum of 33 out of the 132 neurons preferred n = one vowel. The mechanisms of vowel selectivity were analyzed with five synthetic vowels composed of two formants F1 and F2 which could be presented separately. Most of the selective units also responded to F1 or F2 of the preferred vowel alone. The suppression of the vowels could be explained by formants which fell into inhibitory ranges of that unit, independently demonstrated by the pure tone response. Other units had several excitatory bands which coincided with the formants of the preferred vowel. In some cases a certain amplitude ratio of F1 versus F2 gave the strongest response. Several qualitative models of excitatory-inhibitory interaction of inputs to field L neurons are presented which explain the described selectivities. It is interesting that the distribution of vowel-selective units relates to the most superficial and most basal layer of field L where units selective for species-specific calls have previously been located in a gallinaceous bird.

Animals↗
PubMed1981

Tone-versus FM--induced patterns of excitation and suppression in the 14-C-2-deoxyglucose labeled auditory "cortex" of the guinea fowl.

The primary auditory "cortex" field L, of the Guinea fowl is a three layer tonotopically organized structure. Isofrequency planes as shown with the 2-deoxyglucose (2DG) method cut across these layers and with their second dimension extend in rostro-caudal direction. The input layer L2 exhibits "spontaneous" labeling due to high spontaneous activity of input terminals and units throughout the hearing range. The labeling is stronger locally along a rostro-caudal isofrequency contour of L2 after tone or narrow band FM stimulation. With tone stimuli the layers L1 and L3 are labeled within an isofrequency plane except for the rostral half of the field whereas frequency modulated tones do label these two layers throughout the corresponding isofrequency plane. FM stimuli in addition lead to a reduction of spontaneous labeling in frequency planes adjacent to those which are covered by the stimuli. Since these effects correlate with known inhibitory effects of such stimuli it is argued that the 2 DG method can identify the suppression of activity of neurons in suitable structures.

Animals↗
PubMed1979

Connectivity of the auditory forebrain nuclei in the guinea fowl (Numida meleagris).

Injection of tritiated leucine and proline into the nucleus ovoidalis of the Guinea Fowl (Numida meleagris) produces terminal labeling in the palaeostriatum and in three adjacent zones (field L1-L3) of the auditory neostriatum (AN). L2, situated between L1 and L3, receives the main input and corresponds to the former field L of Rose. These neuroanatomically defined zones of the auditory neostriatum are also characterized by differing properties of their neurons. Injection of radioactive material into the auditory neostriatum produces labeling of (i) a palaeostriatal, (ii) a ventral hyperstriatal, and (iii) an additional neostriatal area (Nd). Injection into the hyperstriatum ventrale reveals connections (i) to field L2, (ii) to the palaeostriatum, (iii) to Nd, and (iv) to the archistriatum. After injection into the palaeostriatum, labeling can be observed (i) in the neostriatum dorsale, (ii) in the hyperstriatum ventrale, (iii) in the archistriatum, (iv) in the diencephalic nuclei, nucleus ansae lenticularis and nucleus spiriformis lateralis, and (v) in the mesencephalic nuclei, nucleus tegmenti pedunculo-pontinus and nucleus intercollicularis. These results show that a widespread connectivity exists among primary and presumably higher order auditory areas in the forebrain of birds. Connections also exist between these auditory areas and presumed vocal-motor areas (neostriatum dorsale, archistriatum, nucleus intercollicularis).

Animals↗
PubMed1979

Functional organization of some auditory nuclei in the guinea fowl demonstrated by the 2-deoxyglucose technique.

The auditory pathway of the Guinea Fowl was labeled with [C14]2-deoxy-D-glucose after stimulation with pure tones, harmonic tones and species-specific calls. In addition to other auditory nuclei, which showed more or less uniform labeling with the present technique, the n. mesencephalicus lateralis dorsalis (MLD) of the midbrain, as well as field L and parts of the hyperstriatum ventrale in the telencephalon, showed a stripe-pattern of labeling after stimulation with a pure tone. The position and orientation of the tone-activated striped areas in field L, observed after stimulation with different tones, correspond to isofrequency contours obtained with microelectrode recordings. The labeling of the three congruent tonotopically organized layers of field L (L1, L2, and L3) was not uniform along the anterior-posterior axis of the field. Harmonic tones produced multiple reactive stripes each of which corresponded to the stripe characteristic of a particular harmonic presented as a pure tone. The species-specific Iambus-call labeled the tonotopic area of field L that corresponds to the frequency band with the highest energy of the call. The hyperstriatum ventrale generally showed a weaker pattern of labeling that, however, resembled the labeling in field L.

Animal Communication↗
PubMed1977

The jamming avoidance response in Rhamphichthys rostratus: an alternative principle of time domain analysis in electric fish.

A Jamming Avoidance Response was found in the weakly electric fish Rhamphichthys rostratus, a South American pulse-Gymnotid. The analysis of the response suggests that it requires a key stimulus which is fundamentally different from that in previously described harmonic Gymnotids. It relies on a sensitivity for the direction of phase shifts of stimulus pulses relative to the fish's own electric organ discharge rather than on a sensitivity for beating frequencies.

Animals↗
PubMed1974

Neuronal analysis of wave form in the time domain: midbrain units in electric fish during social behavior.

A fish of the genus Eigenmannia responds differently to a neighboring conspecific fish with a slightly higher frequency of the electric organ discharge than its own than to one with a slightly lower such frequency than its own. When the two frequencies are beating against each other the special wave shape of the electric organ discharge leads to asymmetries of the beat pattern which are distinct for the two cases. Midbrain neurons, called "deltaF recoders," sign and magnitude of the frequency difference on the basis of these patterns. that is, in the time rather than the frequency domain.

Action Potentials↗