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H Scheich

Publications and source records attributed to H Scheich.

At least 73 records · Page 4Linked to original sources
PubMed1992

Postnatal shift of tonotopic organization in the chick auditory cortex analogue.

The existence of an ontogenetic shift of tonotopic organization throughout the auditory pathway concomitant with cochlea maturation is a matter of controversy. Using the 2-deoxyglucose method we demonstrate here for the first time the shift phenomenon in an auditory forebrain structure, field L, the auditory cortex analogue of the chick. During the first postnatal month isofrequency contours move to positions where, in younger chicks, lower frequencies (up to half an octave) are represented. This developmentally changing place code of sound frequencies at the forebrain level is similar to the one previously reported for brain stem auditory nuclei. It raises the question of constancy of frequency-related pitch perception during development and may be a complication of early auditory learning and memory.

Acoustic Stimulation↗
PubMed1991

Parvalbumin-, calretinin- and calbindin-D28k-immunoreactivity and GABA in a forebrain region involved in auditory filial imprinting.

The distribution and morphology of neurons containing the Ca-binding proteins parvalbumin (PV), calbindin-D28k (CaBP) and calretinin (CaR) are described in a rostral forebrain region (MNH) of the chick, known to be involved in auditory filial imprinting. PV immunoreactivity is chiefly a marker for numerous large to medium-sized neurons in the neostriatal part of MNH. They show patchy staining of their dendrites, but PV-positive spines are not visible. CaBP is represented in a different neuron population with on the average slightly smaller-sized somata, which carry long, spiny, CaBP-positive dendrites. In contrast to PV and CaBP, CaR immunoreactivity is a marker chiefly for neuropil in MNH but only for few stained neurons. They may be spiny and show the largest size variations. The density of CaR-immunoreactive neuropil is highest in the hyperstriatal part of MNH. Double immunostaining for PV and CaBP reveals that these proteins are expressed mostly in different neuron populations, with only few neurons containing both proteins. These neuron populations appear to form an interconnected network within MNH. A possible relationship between the expression of either Ca-binding protein and the presence of the inhibitory transmitter GABA is also examined. The GABA-antibody labels scattered, very small to medium-sized neurons and dense punctate neuropil. The comparison of the area histograms of somata reveals an overlap with all 3 Ca-binding protein containing cell populations, except for a large proportion of small GABA-positive neurons. The characteristics of immunostained neuron populations are compared to the previously described 3 Golgi-types of neurons in MNH, and possibilities of a functional implication of the proteins in MNH plasticity are examined.

Acoustic Stimulation↗
PubMed1991

Functional organization of the avian auditory cortex analogue. I. Topographic representation of isointensity bandwidth.

Bandwidth of auditory units in the chick forebrain (field L/Hv complex) was measured with isointensity tone stimuli. Isointensity bandwidth is topographically represented within the four-layered tonotopically organized structure. It declines continuously from rostrodorsal to caudoventral along the longitudinal axis of two-dimensional best frequency planes (frequency band laminae). Layer-specific differences along the radial axis are also obvious. In the input layer of field L and in Hv ON-response bandwidths are relatively broad. The narrower bandwidths of units in the two postsynaptic layers of field L are probably caused by lateral inhibition mechanisms, as derived from the different topographic representations of OFF-versus ON-response bandwidths. A quantitative comparison of the topographic representation of bandwidth is made with the geometry of the tonotopic organization of the chick auditory forebrain complex, as revealed by 2-deoxyglucose data in a former study. A number of possible input-output transformations are derived from this comparison.

Acoustic Stimulation↗
PubMed1991

Functional organization of the avian auditory cortex analogue. II. Topographic distribution of latency.

Onset latencies of units were measured at 70 dB SPL in the auditory forebrain area (field L/Hv-complex) of awake domestic chicks. Latencies ranged from 8.8 to 75 ms. Latencies of units averaged for octave bands of best frequencies (BF) declined with increasing BF. Latencies were topographically distributed in the radial but not in the longitudinal dimension of frequency band laminae (FB laminae). Latencies were shortest in the input-layer L2 and increased systematically towards the postsynaptic layers L3 and L1/Hv, respectively. This topography visualizes the spatiotemporal spread of onset excitation and reflects the hierarchical processing within the structure. It also indicates a topographical representation of temporal resolution.

Acoustic Stimulation↗
PubMed1991

Functional organization of auditory cortical fields in the Mongolian gerbil (Meriones unguiculatus): binaural 2-deoxyglucose patterns.

Unilaterally deafened (cochlear destruction) gerbils were exposed to white noise after injection of 14-C-2-deoxyglucose. The labelling patterns were compared to those of unstimulated operated animals, noise stimulated control animals and bilaterally ear plugged animals. Serial transverse, horizontal and tangential autoradiographs through the cortex were analysed. In lesioned animals, labelling was strongly reduced on the side contralateral to the lesion in the high frequency regions of A1 and the anterior auditory field (AAF). We assume that these regions correspond to the high frequency EI cell areas. Fine banding could be seen superimposed on this pattern in transverse and tangential sections. We suggest that this may be due to alternating strips of EI and EE cells orthogonal to iso-frequency contours. In the low frequency regions of A1 and AAF, labelling asymmetries were also present, but were less pronounced. We assume that these effects are due to low frequency EE cells. In sub-cortical structures, labelling was reduced in the inferior colliculus and ventral part of the medial geniculate body contralateral to the lesioned ear, but no labelling pattern was visible. We presume that the spatial separation of EE and EI inputs to these structures is not marked enough to allow labelling patterns to be seen. In the superior olivary complex, labelling was reduced on the side contralateral to the lesioned ear in the medial dendritic field of the medial superior olivary nucleus and in the nucleus of the trapezoid body. Ipsilateral to the lesioned ear, labelling was reduced in the lateral dendritic field of the medial superior olive.

Acoustic Stimulation↗
PubMed1991

Parvalbumin and calbindin-D28K immunoreactivity as developmental markers of auditory and vocal motor nuclei of the zebra finch.

The posthatch developmental profiles of parvalbumin and calbindin-D28K immunoreactivity were compared for the auditory nucleus mesencephalicus lateralis pars caudalis in the midbrain, n. ovoidalis in the thalamus, and telencephalic field L, as well as for the telencephalic vocal motor nuclei hyperstriatum ventrale pars caudalis and n. robustus archistriatalis. The two calcium-binding proteins showed specific temporal patterns of expression in each nucleus, without following an ascending or descending sequence. Calbindin-D28K immunoreactivity usually preceded parvalbumin immunoreactivity. Onset of expression, especially of parvalbumin-immunostaining, was earlier in auditory nuclei than in vocal motor nuclei. The developmental order of appearance of immunoreactivity in somata, dendrites and axons was different in various brain regions. In some structures parvalbumin or calbindin-D28K immunoreactivity occurred only transiently. The two antibodies bound to separate but spatially complementary groups of cells in the nucleus mesencephalicus lateralis pars dorsalis and n. ovoidalis, as has previously been described in visual nuclei. This pattern was maintained into adulthood. These hitherto unknown subcompartments may reflect internal functional organization in these nuclei. A transitory neostriatal zone containing parvalbumin-positive neurons and fibres was observed between the immature field L and the emerging hyperstriatum ventrale pars caudalis. Some comparative aspects are discussed as to the way in which neurons distinguished by the two Ca-binding proteins may differ in energy metabolism, activity pattern and other functional mechanisms.

Animals↗
PubMed1991

Auditory cortex: comparative aspects of maps and plasticity.

Much recent work in the field of auditory cortex analysis consists of an intensified search for complex sound representation and sound localization mechanisms using tonotopic maps as a frame of reference. Mammalian species rely on parallel processing in multiple tonotopic and non-tonotopic maps but show different degrees of unit complexity, and orderly representation of acoustic dimensions in such maps depending on the predictability of sounds in their environment. Birds appear to rely chiefly on one tonotopic map which harbours multidimensional complex representations. During development and after partial hearing loss, tonotopic organization changes in a predictable manner. Learning also modifies the spatial representation of sounds and even modifies tonotopic organization, but the spatial rules involved in this process have not yet emerged.

Animals↗
PubMed1991

Distribution of (fucogalactosyl-)epitope expressing glycoconjugates in rat brain.

Glycoconjugates are known to be concentrated in plasma membranes, especially in synaptic junctions, where they subserve various functions in neural connectivity. Here we report the cellular distribution of a new monoclonal antibody recognizing (fucogalactosyl) sequences in carbohydrate structures. The most pronounced immunoreactivity was found in fibrous astrocytes, in many parts of the brain and with lower density in various neuronal elements. This points to the expression of identical carbohydrate sequences on molecules within certain glial and neuronal elements. Previous intracerebral injections of the antibody interfered with long term memory formation. Therefore, functions mediated by corresponding glycoproteins in neurons and glia cells or even neuron-glial interactions, might be relevant for information-processing.

Animals↗
PubMed1991

Invasion of visual cortex by the auditory system in the naturally blind mole rat.

Previously we have shown that the dorsal lateral geniculate body (LGB), which is strictly visual in sighted mammals, receives a strong auditory input in the naturally blind mole rat (Spalax ehrenbergi). Here we show with the 2-deoxyglucose technique and with single-unit recordings that in this species the initially non-degenerated visual cortex, as defined by its connection with LGB, is also activated by the auditory modality. These findings suggest that cross-modal compensation may occur as a natural consequence of the degeneration of a sense organ.

Animals↗
PubMed1990

Distribution of choline acetyltransferase and acetylcholinesterase in the vocal motor system of zebra finches.

The distribution of choline acetyltransferase immunoreactivity (ChAT-IR) was surveyed in the vocal motor system of adult male and female zebra finches and was compared with the pattern of histochemical acetylcholinesterase (AChE-His). In the vocal motor system the most prominent accumulation of ChAT-IR somata was found in lobus parolfactorius (LPO) including Area X. Immunoreactive neuropil was found to be concentrated in pericellular networks of fibers in male's Area X while the corresponding area in females could not be demarcated within the LPO. The density of ChAT-IR fiber networks was much higher in LPO, paleostriatum augmentatum and in a shelf region around nucleus robustus archistriatalis (RA) than in neostriatal and hyperstriatal parts of the telencephalon. AChE positive neurons and neuropil were observed in all ChAT-IR regions and, in addition, in the vocal motor nuclei nucleus hyperstriatum ventrale pars caudalis (HVc), nucleus magnocellularis in the anterior neostriatum (MAN), nucleus interfacialis (NIF) and RA. However, none of the latter nuclei contained ChAT-IR cell bodies. They were characterized by rare ChAT-IR neuropil. MAN and RA exhibited shelf regions with a higher degree of stained fibers. The discrepancy between the localization of AChE-His and ChAT-IR can hardly be explained by different classes of ChAT isoenzymes in neurons within the basal forebrain and the neostriatal, hyperstriatal and archistriatal vocal control nuclei not detected by our antibody. On the other hand, vocal control centers while receiving cholinergic inputs, might - except for Area X - not possess cholinergic efferent projections within the telencephalon.

Acetylcholinesterase↗
PubMed1989

Auditory pathway and auditory activation of primary visual targets in the blind mole rat (Spalax ehrenbergi): I. 2-deoxyglucose study of subcortical centers.

The blind mole rat Spalax ehrenbergi is a subterranean rodent that shows striking behavioral, structural, and physiological adaptations to fossorial life including highly degenerated eyes and optic nerves and a behavioral audiogram that indicates high specialization for low-frequency hearing. A 2-deoxyglucose functional mapping of acoustically activated structures, in conjunction with Nissl/Klüver-Barrera-stained material, revealed a typical mammalian auditory pathway with some indications for specialized low-frequency hearing such as a poorly differentiated lateral nucleus and a well-developed medial nucleus in the superior olive complex. The most striking finding was a marked 2-deoxyglucose labeling of the dorsal lateral geniculate body and of cortical regions that correspond to visual areas in sighted rodents. The results render the blind mole rat a good model system for studying natural neural plasticity and intermodal compensation. In this report, we confine ourselves to the subcortical levels. The cortical level will be dealt comprehensively in a following paper.

Acoustic Stimulation↗
PubMed1989

System-specific distribution of zinc in the chick brain. A light- and electron-microscopic study using the Timm method.

The brain of young domestic chicks was investigated using a Timm sulfide silver method. Serial Vibratome sections were analyzed under the light microscope, and the localization of zinc-positive structures in selected areas was determined at the ultrastructural level. Both strong and differential staining was visible in the avian telencephalon whereas most subtelencephalic structures showed a pale reaction. The highest staining intensity was found in the nonprimary sensory regions of the telencephalon such as the hyperstriatum dorsale, hyperstriatum ventrale, hippocampus, palaeostriatum augmentatum, lobus parolfactorius and caudal parts of neostriatum. There was an overall gradient of staining intensity in neostriatal areas from rostral to caudal with the heaviest zinc deposits in the caudal neostriatum. Primary sensory projection areas, such as the ectostriatum (visual), hyperstriatum intercalatum superius (visual), nucleus basalis (beak representation), the input layer L2 of the auditory field L and the somatosensory area rostral to field L were selectively left unstained. Fiber tracts throughout the brain were free of zinc deposits except for glial cells. In electron micrographs of stained regions, silver grains were localized in some presynaptic boutons of asymmetric synpases (Gray type I), within the cytoplasm of neuronal somata and sporadically in the nucleus. The possible involvement of zinc in synaptic transmission and other processes is discussed.

Animals↗
PubMed1988

Postnatal development of parvalbumin-, calbindin- and adult GABA-immunoreactivity in two visual nuclei of zebra finches.

The characterization of neuron populations by their immunoreactivity against parvalbumin- and calbindin (28-kDa)-antisera has been used to study the postnatal development of the visual diencephalic nucleus rotundus and the mesencephalic nucleus isthmi complex in zebra finches. In nucleus rotundus, parvalbumin-immunoreactivity was restricted to the neuropil during the first 10 days and appears additionally in somata around day 12 where it remains until adulthood. Calbindin-immunoreactivity of the very scarce neuropil and the few somata, which can be observed during the first two weeks, disappears until adulthood. Thus, the adult nucleus rotundus shows an almost complementary distribution of calbindin- and parvalbumin-immunoreactive structures: the numerous, heavily parvalbumin-positive somata, which are surrounded by dense immunoreactive neuropil are in sharp contrast to the complete absence of calbindin-immunoreactive somata. Only a thin rim surrounding this nucleus contains punctate calbindin-positive neuropil. In the nucleus isthmi complex, parvalbumin and calbindin staining patterns show markedly different developmental profiles. While the density of parvalbumin-immunoreactive neuropil in the parvocellular part of the nucleus isthmi continuously increases and the somata remain unstained, the initially heavily calbindin-positive somata gradually lose their immunoreactivity during the first two weeks. In the adult nucleus isthmi complex, parvalbumin- and calbindin show nearly identical staining patterns. A comparison between the two calcium-binding proteins and GABA-immunoreactivity in adult brains revealed different relationships in the two nuclei: while in nucleus rotundus GABA-staining pattern neither resembles that of parvalbumin nor of calbindin, in the nucleus isthmi complex all three staining patterns coincide.

Animals↗
PubMed1988

Contribution of GABAergic inhibition to the response characteristics of auditory units in the avian forebrain.

1. We tested the contribution of GABAergic inhibition to the response characteristics of 213 neurons in the auditory telencephalon of chronically prepared nonanesthetized chickens. Extracellular recordings were obtained with multibarrel glass electrodes containing a tungsten wire. Auditory stimuli consisted of tones, two-tone combinations, and noise bursts presented either free field or via earphones. 2. Response properties of the neurons were studied both before and during iontophoretic application of GABA, glutamate, bicuculline methiodide (BIC), and acetylcholine. 3. During BIC application excitatory responses were facilitated. With the exception of transient off-responses, which occasionally appeared only in the BIC condition, the temporal response patterns to tone stimuli at the units' best frequency usually were unaltered. In no case was an inhibitory response component to binaurally presented pure tones antagonized by BIC. 4. BIC iontophoresis enlarged the isointensity-response areas of the vast majority of neurons in the structures of the auditory forebrain lying postsynaptic to the thalamorecipient layer L2. This effect was not obtained when neurons were depolarized to perithreshold levels with glutamate. 5. Two-tone stimulation resulted in a suppression of the excitatory response to a neuron's best frequency when the second frequency lay outside the excitatory response area. In lamina L2, the frequency range inducing two-tone suppression was narrow, and the suppressive effect was not antagonized by BIC. In the postsynaptic layers, frequencies up to three octaves from the neurons' best frequency induced two-tone suppression that was sensitive to BIC. In addition, these neurons also displayed a BIC-insensitive suppression similar to the one seen in layer L2. 6. Neurons displaying no or only a poor response to white-noise stimulation strongly responded to this wide-band stimulus during BIC iontophoresis. 7. Neurons without tone responses usually displayed clear response areas to tones during BIC application. Iontophoretic application of acetylcholine, but not glutamate, also induced such tone responses. Two-tone combinations with frequencies lying within the response areas observed in the BIC condition elicited excitatory responses after full recovery from the BIC application. 8. During BIC iontophoresis nonmonotonic intensity-response functions were converted to monotonic functions in most of the neurons studied. 9. A model of GABAergic inhibitory interactions is proposed that is based on two independent GABAergic systems.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetylcholine↗
PubMed1987

Topographic representation of periodicities in the forebrain of the mynah bird: one map for pitch and rhythm?

Coding of amplitude modulated acoustic stimuli was studied within isofrequency planes of the tonotopically organized field L, the avian analogue of the mammalian auditory cortex. The synchronization of unit responses to envelopes of sinusoidally amplitude modulated tones (AM) and repetitive noise bursts (RN) were determined as a function of envelope frequency (EF). From 249 synchronizing units, 66% were tuned to a best envelope frequency (BEF) using a synchronization criterion. BEFs varied from 0.3 to 380 Hz and showed an orderly representation within isofrequency planes orthogonal to the lamination of field L. The majority (68%) of these units had BEFs below 20 Hz down to 0.3 Hz. Thus, they were tuned to rhythms typical for animal communication sounds, speech, and music. Thirty-two % had BEFs between 20 Hz and 380 Hz and covered at least 4 of 5 octaves of the range of periodicity pitch sensation.

Acoustic Stimulation↗
PubMed1987

GABAergic inhibition increases the neuronal selectivity to natural sounds in the avian auditory forebrain.

The influence of the iontophoretically applied GABA antagonist bicuculline-methiodide (BIC) on single cell selectivity to natural sounds in the auditory forebrain was studied in awake chickens. Units in the thalamo-recipient lamina showed no clear changes in neuronal selectivity during BIC application, while cells postsynaptic to this layer displayed a clear loss of response selectivity. The results are discussed in regard to the role of GABA-mediated inhibition in auditory processing within the telencephalon.

Acoustic Stimulation↗