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H Scheich

Publications and source records attributed to H Scheich.

At least 109 records · Page 6Linked to original sources
PubMed1985

Ascending reticular activating system in the rat: a 2-deoxyglucose study.

The autoradiographic [14C]2-deoxyglucose (2-DG) method was used to map ascending pathways which are influenced by arousing electrical stimulation of the midbrain reticular formation (RET) in alert rats. The major finding was that RET stimulation produces selective patterns of metabolic activation and suppression in discrete brain regions. The regions activated were limited to specific intralaminar, medial and anterior thalamic nuclei, and to the entire auditory system. Conversely, a large suppression of 2-DG uptake was observed in most of the cerebral cortex, limbic and extrapyramidal structures, whereas at the same time some brain regions were left unaffected. Striking similarities were found between the functional pathways affected differentially by RET stimulation and well-defined cholinergic pathways which originate in the midbrain tegmentum. Structures which showed metabolic activation are part of the dorsal cholinergic pathway, whereas the regions suppressed are part of the ventral cholinergic pathway and its higher-order projections. The results support the conclusion that cholinergic pathways represent the thalamic and extrathalamic divisions of the reticular activating system. Our observations provide the first anatomical demonstration that RET stimulation has widespread and differential effects on cerebral metabolism. They also support the concept that arousing electrocortical desynchronization involves reticular activation of thalamocortical neurons, which in turn have widespread suppressive influences on cortical metabolism.

Afferent Pathways↗
PubMed1985

Ultrastructural localization of the calcium-binding protein parvalbumin in neurons of the song system of the zebra finch, Poephila guttata.

The distribution of parvalbumin (PV) within neurons of the vocal motor nucleus hyperstriatum ventralepars caudalis (HVc) was investigated in the forebrain of adult male zebra finches by means of light and electron microscopy using the indirect immunoperoxidase technique. Parvalbumin-reaction product was located in the amorphous material of perikarya, dendrites and nuclei, and associated to microtubuli, postsynaptic densities and intracellular membranes; it was found in some axons and Gray type-2 boutons, but rarely in type-1 boutons and never in the Golgi apparatus. These observations suggest that parvalbumin may regulate calcium-dependent processes at the postsynaptic membrane and in the cytosol. Furthermore, the partial association of parvalbumin to microtubuli points to an involvement in calcium-dependent tubular functions. Calcium currents and microtubular assembly or transport may be relevant for the known functions of HVc in song learning.

Animals↗
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↗
PubMed1984

2-Deoxyglucose accumulation parallels extracellularly recorded spike activity in the avian auditory neostriatum.

In a combined 2-deoxyglucose (2-DG) and electrophysiological study, the congruence between metabolic activity and extracellularly recorded spike activity patterns has been examined in the auditory cortex analogue, field L, of chicks. Using tone stimuli we demonstrate a match of stripes of 2-DG labeling to electrode tracks yielding neurons with the same best frequency. Since 2-DG activity is thought to reflect chiefly input activity of neurons there appears to be a close input-output link for tone responses in field L.

Animals↗
PubMed1984

Classical conditioning enhances auditory 2-deoxyglucose patterns in the inferior colliculus.

The [14C]2-deoxyglucose (2-DG) method in conjunction with a heart rate conditioning paradigm was used to investigate whether associative pavlovian conditioning of an acoustic stimulus (CS) with an aversive reticular stimulus (US) would result in a learning-induced metabolic response within the rat inferior colliculus (IC). The data show that: (1) the arousal level of the animal can result in a sensitization of the IC to subsequent auditory stimuli, and (2) the overlapping area of spatial representation of US and CS within the IC selectively develops an enhanced metabolic response during training and as a result of learning. Our results support the conclusion that within the same neuronal space of the IC there is representation not only of the physical parameters of a stimulus but also of its learned behavioral significance.

Acoustic Stimulation↗
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↗