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Biomedical subjects

H Scheich

Publications and source records attributed to H Scheich.

At least 91 records · Page 5Linked to original sources
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↗
PubMed1987

Acoustic imprinting in guinea fowl chicks: age dependence of 2-deoxyglucose uptake in relevant forebrain areas.

In 7-day-old guinea chicks play back of an imprinted acoustic stimulus was previously found to correlate with increased uptake of 2-deoxyglucose (2DG) in 3 rostral forebrain areas (HAD, LNH and MNH). Subdivisions of these areas defined by 2DG labelling may be association fields. Auditory areas did not show labelling differences between imprinted and control animals. In the present study imprinted guinea chicks of different age and with different experience were used in the 2DG experiments. Seven-day-old chicks (beyond the sensitive phase), 4-day-old (at the decline of sensitive phase) and 1- and 3-day-old chicks (within the sensitive phase) were given a 2DG injection and afterwards heard the stimulus to which they had been imprinted previously (1.8 kHz, 3 tone pips per s). While the typical labelling pattern was weak or absent in 1-4-day-old chicks the older animals consistently had high 2DG uptake in these areas. Unsuccessfully imprinted 7-day-old chicks, having all the behavioral test experience, showed no or weak labelling. These results are related to current literature on reticular activation of the relevant areas and on morphological changes there with termination of the sensitive phase. It is argued that the reticular activation of these areas, e.g. attention mechanisms are instrumental in securing imprinting success and that subsequent reorganization of the areas leads to stronger metabolic activation after the sensitive phase.

Acoustic Stimulation↗
PubMed1987

Auditory imprinting leads to differential 2-deoxyglucose uptake and dendritic spine loss in the chick rostral forebrain.

Newly hatched chicks of the domestic fowl (White Leghorn) were imprinted to an acoustic stimulus (Group I: 400 Hz, 3 bursts per s, Group II: 900 Hz, 2 bursts per s) and tested in a straight runway with loudspeakers behind two opposite goal boxes. Those chicks were considered imprinted which headed for the imprinting stimulus in an approach test and subsequently preferred it to a new stimulus (imprinting stimulus of the other group) in a simultaneous discrimination test. On day 7 after hatching (after the sensitive phase) imprinted chicks and naive controls were injected with 2-[14C]deoxyglucose (2DG) and exposed to the imprinting stimulus. Autoradiographic analysis of their brains revealed 3 well demarcated areas of increased 2DG accumulation in the rostral forebrain of imprinted chicks compared to controls: HAD in the rostral Wulst; MNH, an auditory area in the rostromedial neostriatum and hyperstriatum ventrale; LNH in the rostrolateral neostriatum and hyperstriatum ventrale. Analysis of these brain areas in 7-day-old acoustically imprinted and control animals with the Golgi-Cox method revealed a highly significant reduction of spine frequency of a large neostriatal neuron type in MNH of imprinted chicks. An additional Golgi-Cox analysis was carried out with chicks imprinted on a broody hen, i.e. on the whole spectrum of natural stimuli. In that group spine frequency of the same neuron type was between that of acoustically imprinted and control animals. A hypothesis of filial imprinting is presented which considers spine loss as a crucial mechanism.

Acoustic Stimulation↗
PubMed1986

Effects of unilateral and bilateral cochlea removal on 2-deoxyglucose patterns in the chick auditory system.

The 2-deoxyglucose (2DG) method was used to map functional activity in the auditory system of chicks that had been subjected to unilateral or bilateral cochlea removal. Following survival times of 1 day to 4 weeks, chicks were exposed to continuous white noise in the 2DG experiments. In monaural subjects nucleus angularis and nucleus magnocellularis showed faint 2DG uptake on the side contralateral to the intact ear. In the binaural nucleus laminaris, the asymmetrical and almost mirror-imaged labeling pattern (Lippe, Stewart, and Rubel: Brain Res. 196:43-58, '80) was produced. The superior olive (OS) was strongly labeled on the ipsilateral side, whereas the contralateral OS showed only a slight 2DG uptake at its medial border. The lateral lemniscus and nucleus lemnisci lateralis, pars ventralis (LLv) showed stronger activation on the contralateral side. Both Nissl stains and 2DG patterns provide evidence that nucleus ventralis lemnisci lateralis (VLV) can be subdivided into an anterior (VLVa) and a posterior (VLVp) part. Whereas VLVp is labeled only contralaterally, VLVa is labeled on both sides with similar intensity. Nucleus mesencephalicus lateralis, pars dorsalis (MLD) is strongly labeled throughout contralaterally. The ipsilateral MLD shows a defined ventral portion of high 2DG uptake. Intensity of labeling here is symmetrical to the corresponding area of the contralateral MLD. These symmetrical patterns were related to the tonotopic organization of MLD, which was mapped in intact animals by using tone stimuli. Assuming that symmetrical 2DG uptake in monaural animals indicates excitatory input from both ears (EE-cells), it appears that these EE-cells occupy a sector of each isofrequency plane in MLD. Nucleus ovoidalis (Ov) generally was stronger labeled on the contralateral side. The columnar organization of field L as seen in monaural chicks has already been described (Scheich, Exp. Brain Res. 51:199-205, '83). In bilaterally deafened chicks, MLD, Ov, and layer L2 of field L showed strong but spatially restricted 2DG accumulation in contrast to absence of labeling in peripheral nuclei. The 2DG patterns in monaural chicks are likely to reflect excitatory input within the auditory system. In addition they reveal new insights into the functional organization of some of its nuclei. In particular, they support the notion that MLD contains maps of several interaural integration mechanisms similar to field L. Labeling in the auditory system of bilaterally deafened chicks may result from descending projections or from other than auditory inputs.

Animals↗
PubMed1986

Classical conditioning of tone-signaled bradycardia modifies 2-deoxyglucose uptake patterns in cortex, thalamus, habenula, caudate-putamen and hippocampal formation.

The 2-[14C]deoxyglucose (2-DG) autoradiographic method was used to map metabolic activity in all telencephalic and diencephalic structures of the rat brain during and after classical conditioning. A trial was made of a 4-5 KHz frequency modulated tone (CS) paired with midbrain reticular stimulation (US). The unconditioned response was a rapid bradycardia elicited by the US. Alert rats were injected with 2-DG, placed in a sound-proof chamber, and subjected during 90 min to a given treatment: (1) the CS before conditioning, (2) the US alone, (3) the paired CS-US (acquisition), (4) the 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 prefrontal cortex showed discrete regions with enhanced 2-DG uptake during conditioning and pseudoconditioning. A columnar organization was well-defined in the posterior parietal cortex of rats subjected to CS-US pairing. The medial thalamus was greatly activated in all groups subjected to reticular stimulation. The dorsomedial nucleus showed its largest activation during conditioning. The lateral habenula and a caudal portion of caudate-putamen showed an overall increase in 2-DG uptake during conditioning. The hippocampal formation showed a specific pattern of metabolic activation during conditioning and after conditioning. A laminar densitometric analysis showed that 2-DG uptake was concentrated in a central band along the sides of the hippocampal fissure which corresponded to the molecular layers. Only this neuropil band of greater metabolic activity showed the learning-related changes. In addition, the hippocampal formation was the only nonauditory structure in the forebrain which clearly responded to the acquired signal value of the tone CS after conditioning. These changes revealed by 2-DG provide a first demonstration of forebrain substrates with localized metabolic alterations related to learning and reticular sensitization.

Animals↗
PubMed1986

Social stress increases [14C]2-deoxyglucose incorporation in three rostral forebrain areas of the young chick.

The 2-deoxyglucose method and EEG-recordings were used to compare forebrain activities between socially reared chicks, one remaining in the group the other being separated with preserved visual and auditory contact. During 30% of the test period, separated chicks produced distress calls and showed a typical EEG arousal pattern. The 9 Hz band of the EEG spectrum and the duration of distress calling were found to be significantly different from grouped chicks. Increased 2-deoxyglucose incorporation were found in 3 rostral forebrain areas of separated chicks, namely the hyperstriatum accessorium/hyperstriatum dorsale, the lateral neostriatum/hyperstriatum ventrale and the medial neostriatum/hyperstriatum ventrale. These same areas were previously reported to increase metabolic activity in imprinted Guinea fowl chicks, when they heared the imprinting stimulus during the 2-deoxyglucose experiment. It is argued that high metabolic activity in these areas reflects arousal and attention to relevant auditory or visual stimuli.

Animals↗
PubMed1986

Neural substrates for tone-conditioned bradycardia demonstrated with 2-deoxyglucose. II. Auditory cortex plasticity.

The 2-deoxyglucose (2-DG) method was used to map the metabolic activity of the auditory cortex (AC) during and after conditioning. Using separate groups of animals, the effects of both paired and unpaired presentations of a 4-5 kHz FM tone (CS) and midbrain reticular stimulation (US) were compared for acquisition, extinction and sensitization training. Rats with cardiac deceleration conditioned to the FM tone showed a pattern of AC metabolic activity distinctly different from that seen in control animals. The tonotopic pattern of 2-DG labeling consisted of two contiguous spindle-shaped bands corresponding to the location of neurons with best frequency response in the 4-5 kHz band width. Reticular stimulation alone or combined with the tones produced a widespread increase of 2-DG uptake. At least two types of modulatory effects appeared to interact with the tonotopic pattern. The first involved a selective enhancement of evoked activity in the AC region of convergence of CS-US effects. This effect may be related to learning because it was restricted to the conditioning group. The second effect involved a general increase in background uptake of 2-DG in AC. This effect may be related to reticular sensitization because it was common to all groups subjected to reticular stimulation. The present findings are the first anatomical demonstration of the modulatory effects of auditory learning on AC metabolic activity.

Animals↗
PubMed1986

Functional activity in the brain of socially deprivated rats produced by an active avoidance test after razobazam (Hoe 175) treatment: a 2-deoxyglucose study.

The 2-deoxyglucose (2-DG) autoradiographic method was used to map metabolic activity in the brain of socially deprivated rats during an active avoidance test. The method investigated the effects of razobazam during this learning test. The animals were socially deprivated for 5 weeks. On the first experimental day the animals were trained to avoid a footshock by jumping onto a platform. During training and testing, the total number of avoidance responses was scored. On the second day during one 2-DG session of 40 min, razobazam increased the avoidance score by 18% as compared to controls. Autoradiographs were analyzed using a two-dimensional densitometric method. The analysis of the brain structures showed a 22% reduction of optical density in the nucleus habenularis lateralis, a 25% increase in the caudal part of the nucleus accumbens, and a 13% increase in the frontal cortex in rats treated with razobazam, but no change in the amygdala. These results provide a preliminary concept to explain how the new compound razobazam produced a better learning performance in socially deprivated rats.

Animals↗
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↗