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PubMed1981

Afferent sources of a lateral midbrain tegmental zone associated with the pinnae in the cat as mapped by retrograde transport of horseradish peroxidase.

A paralemniscal zone in the lateral midbrain tegmentum of the cat has been identified in a possible pathway from the superior colliculus to the facial nucleus that may control pinna movements (Henkel and Edward, '78). Other brainstem afferent projections to this paralemniscal zone have been mapped in the present study using the retrograde horseradish peroxidase tracing method and are discussed in three groups. First, potential sources of auditory afferents were limited mainly to the external nucleus of the inferior colliculus, the nucleus sagulum, and the dorsomedial periolivary cell group. Labeled cells in other superior olivary regions and the dorsal cochlear nucleus were apparently related to uptake of horseradish peroxidase from the axons of the lateral lemniscus. Second, afferents from several premotor regions involved in aspects of gaze control were identified. These were mainly from the nucleus prepositus hypoglossi and adjacent pontine reticular formation, but also included projections from the medial vestibular an abducens nuclei and possibly subthalamic regions such as the zona incerta and fields of Forel. Third, a relatively large group of midbrain afferents was closely related to the origin of the collicular projection to the paralemniscal zone. This group consisted of labeled cells in the periaqueductal gray matter, nucleus cuneiformis, and pretectum. The relatively sparse labeling in auditory regions that projected to the paralemniscal zone seems to indicate that the sensorimotor integration necessary to guide pinna movements does not take place primarily in the lateral midbrain tegmentum. The interaction of gaze-related sources with the pinna-related pathway is also discussed.

Afferent Pathways↗
PubMed1995

Prostacyclin receptor in the brain and central terminals of the primary sensory neurons: an autoradiographic study using a stable prostacyclin analogue [3H]iloprost.

Presence and localization of the prostacyclin receptor in the rat brain and spinal cord were examined by in vitro autoradiography using [3H]iloprost, a highly specific and stable agonist for this receptor. Density of specific binding sites for iloprost was generally high in four regions of the lower brain stem, that is, the medial and commissural subnuclei of the nucleus tractus solitarius, the area postrema, superficial layers of the spinal trigeminal nucleus caudalis and dorsal horn. Moderate density was found in the thalamus, cerebral cortex, hippocampus, striatum and dorsal cochlear nucleus. The distribution pattern was distinct from those of other prostanoid binding sites previously studied except that prostaglandin E2 binding sites were also abundant in the nucleus tractus solitarius, spinal trigeminal nucleus caudalis and dorsal horn. Even in these regions, binding sites for iloprost had several features clearly different from those for prostaglandin E2. First, within the medial and commissural subnuclei of the nucleus tractus solitarius, iloprost binding sites were distributed preferentially in the dorsal part, while those for prostaglandin E2 were located more ventrolaterally. Second, on postnatal day 0, iloprost binding sites have already been expressed in large amounts in the nucleus tractus solitarius, spinal trigeminal nucleus caudalis and dorsal horn of rats, while prostaglandin E2 binding sites are negligible at this stage. Thirdly, the binding of 10 nM [3H]iloprost in these three regions was almost completely displaced by 10 microM unlabelled iloprost but only slightly by 10 microM unlabelled prostaglandin E2. Unilateral nodose ganglionectomy or dorsal rhizotomy decreased the density of iloprost binding sites in the nucleus tractus solitarius or dorsal horn, respectively, with a greater decrease in the operated side. Ligation of the vagus either central or peripheral to the nodose ganglion resulted in an accumulation of iloprost binding sites proximal to the ligation. These results suggest that specific binding sites for iloprost, presumably prostacyclin receptor, are present in the nervous system and, in particular, that the iloprost binding sites in the nucleus tractus solitarius, dorsal horn and possibly in the superficial layers of the spinal trigeminal nucleus caudalis are produced in their sensory ganglia and transported to central terminals of the primary sensory afferents as well as to their peripheral terminals.

Animals↗
PubMed1983

Subcortical auditory and somatosensory afferents to hamster superior colliculus.

To determine whether the pattern of superior colliculus (SC) afferents seen in cat is generalizable to other mammalian species, HRP was injected into the SC of twenty hamsters (Mesocricetus auratus). After reaction with TMB, subcortical structures were examined for labeled perikarya. Although most subcortical afferents to SC were similar in cat and hamster, there were differences in auditory and somatosensory SC innervation. In hamster only two putatively auditory structures showed labeled cells, the external nucleus of inferior colliculus and nucleus of the brachium of the inferior colliculus, whereas in cat additional cells are reported in the dorsal cochlear nucleus, trapezoid and superior olivary nuclei, and nucleus of the lateral lemniscus. Again, in hamster the major trigeminal somatosensory input to SC is from spinal trigeminal nucleus caudalis whereas in cat trigeminal input is reported to be from the principalis and oralis portions of the trigeminal nucleus. Thus the hamster possesses a very restricted auditory input to and a different pattern of somatosensory innervation of the SC relative to the cat.

Afferent Pathways↗
PubMed1997

Experimental facial myokymia in cat.

INTRODUCTION: The objective of this study was to describe facial myokymia in experimental animals accompanying kainic acid affects on facial motor neurons. MATERIAL & METHODS: Anesthetized cats were injected with kainic acid into the pons adjacent to the facial nucleus. Facial movements appeared shortly after the injections and facial electromyographic potentials were recorded. Cats were killed up to 4 weeks later, the brainstems were processed histologically, and the number of neurons in the facial nucleus counted. RESULTS: Cats receiving injection of kainic acid adjacent to facial nucleus all developed spontaneous writhing movements of the face ipsilateral to the injection site, clinically resembling facial myokymia in humans. Transient facial paresis, lasting several weeks, appeared in some of the cats. Facial myokymia occurred independent of histological evidence of neuronal loss in facial nucleus, whereas facial paresis occurred in all but one of the animals with significant neuronal loss in the facial nucleus. Placing a needle into the superior olive without injecting kainic acid or injections of kainic acid into cochlear nucleus was not accompanied by facial myokymia or subsequent facial paresis. CONCLUSION: Facial movements in cats similar to myokymia in humans accompanies kainic acid injections adjacent to the nucleus of the facial nerve.

Animals↗
PubMed2002

Physiological response properties of neurons in the superior paraolivary nucleus of the rat.

The superior paraolivary nucleus (SPON) is a prominent nucleus of the superior olivary complex. In rats, this nucleus is composed of a morphologically homogeneous population of GABAergic neurons that receive excitatory input from the contralateral cochlear nucleus and inhibitory input from the ipsilateral medial nucleus of the trapezoid body. SPON neurons provide a dense projection to the ipsilateral inferior colliculus and are thereby capable of exerting profound modulatory influence on collicular neurons. Despite recent interest in the structural and connectional features of SPON, little is presently known concerning the physiological response properties of this cell group or its functional role in auditory processing. We utilized extracellular, in vivo recording methods to study responses of SPON neurons to broad band noise, pure tone, and amplitude-modulated pure tone stimuli. Localization of recording sites within the SPON provides evidence for a medial (high frequency) to lateral (low frequency) tonotopic representation of frequencies within the nucleus. Best frequencies of SPON neurons spanned the audible range of the rat and receptive fields were narrow with V-shaped regions near threshold. Nearly all SPON neurons responded at the offset of broad band noise and pure tone stimuli. The vast majority of SPON neurons displayed very low rates of spontaneous activity and only responded to stimuli presented to the contralateral ear, although a small population showed binaural facilitation. Most SPON neurons also generated spike activity that was synchronized to sinusoidally amplitude-modulated tones. Taken together, these data suggest that SPON neurons may serve to encode temporal features of complex sounds, such as those contained in species-specific vocalizations.

Acoustic Stimulation↗
PubMed1992

[Placement of intracochlear electrodes with Healon].

The cochlear implant surgeon would like to insert the electrodes into the cochlea as deep as possible. With the Nucleus Cochlear Implant Mini System 22 often he succeeds until even all 10 blind rings disappear in the cochlea. By coating the electrodes with hyaluronic acid (Healon) it will be facilitated and additionally we expect a cytoprotective effect for the cell structures of the inner ear.

Cochlear Implants↗
PubMed1992

Experience with the cochlear miniature speech processor in adults and children together with a comparison of unipolar and bipolar modes.

Following the experience with nearly 150 patients with the Nucleus cochlear implant, a more sophisticated and lighter speech processor was tested successfully in terms of better speech understanding. In order to prepare further miniaturization, the standard bipolar stimulation mode was compared with an unipolar mode. It was found that unipolar stimulation needs less energy, without decreasing speech understanding. Preconditions for supplying very young children with a cochlear implant were the use of electrically elicited stapedius reflex thresholds, obtained intraoperatively, for the fitting of the speech processor and the setup of a special rehabilitation center, where children together with their mothers could be trained in hearing and understanding by special teachers and engineers for 12 weeks, distributed over the 1st postoperative year.

Adult↗
PubMed1991

Pediatric performance with the Nucleus 22-channel cochlear implant system.

Results from 80 pediatric subjects with 12 months of experience wearing the Nucleus multichannel cochlear implant are presented. The data suggest that children demonstrate statistically and clinically significant benefit across a broad spectrum of abilities with the implant. Significant postoperative improvement was demonstrated by 66 percent (51 of 77), 63 percent (45 of 72), and 46 percent (27 of 59) of subjects tested on suprasegmental (prosodic), closed-set and open-set tests, respectively. Forty-nine percent of subjects tested improved when lipreading was combined with sound from the implant, compared with lipreading alone. Children who were deaf at an early age or who had longer duration deafness tended to demonstrate poorer performance on the more difficult perceptual tasks after 12 months of implant experience. However, preliminary evidence suggests that continued improvements by congenital and prelinguistic subjects over longer periods of time may reduce performance differences between subjects with early and later onset deafness.

Adolescent↗
PubMed1986

Origin of ascending auditory projections to the nucleus mesencephalicus lateralis pars dorsalis in the chicken.

Ascending auditory projections to the nucleus mesencephalicus lateralis pars dorsalis (MLd) were studied in white Leghorn chickens by means of unilateral injections of horseradish peroxidase into the MLd and by injections of tritiated leucine into nucleus angularis or the combined nucleus magnocellularis and nucleus laminaris. The experiments showed that nucleus angularis sends an extensive projection to the contralateral MLd and a smaller projection to the rostral pole of the ipsilateral MLd; the lagenar region contributes to these bilateral connections. Nucleus angularis also projects bilaterally to the superior olive and nucleus ventralis lemnisci lateralis and to the contralateral nucleus lemnisci lateralis pars ventralis and dorsal nucleus of the lateral lemniscus. Projections from nucleus laminaris were demonstrated to the ipsilateral superior olive, to the contralateral lemniscal nuclei and a small medial region in MLd bilaterally; the contralateral projection is much denser than the ipsilateral one. Other nuclei having ascending connections with MLd include the contralateral superior olive, the ipsilateral nucleus lemnisci lateralis pars ventralis, the contralateral nucleus ventralis lemnisci lateralis and the contralateral MLd. The ipsilateral superior olive and nucleus ventralis lemnisci lateralis also project to MLd but much more sparsely than in their contralateral projection. Although several of these findings correspond with auditory connections previously shown in the pigeon brainstem, they differ fundamentally in that we find both nucleus angularis and nucleus laminaris projecting to different areas of the MLd on both sides of the brain. In particular, our observation that the cochlear nucleus has bilateral connections with MLd demonstrates an important avian similarity with the brainstem auditory pathways of other terrestrial vertebrates.

Animals↗
PubMed1989

Non-N-methyl-D-aspartate receptors may mediate ipsilateral excitation at lateral superior olivary synapses.

Principal cells of the lateral superior olivary nucleus (LSO) are thought to receive a direct excitatory input from spherical bushy cells located in the ipsilateral ventral cochlear nucleus (VCN) and an indirect input from the contralateral VCN globular bushy cells via a secure synapse in the medial nucleus of the trapezoid body (MNTB). MNTB bushy cells project to the somata and proximal dendrites of LSO principal cells. LSO neurons display phasic 'chopper' temporal response patterns to ipsilateral tone-burst stimuli at characteristic frequency (CF), while binaural stimuli suppress this ipsilaterally evoked activity. This suppression is sensitive to interaural differences in intensity, phase and time, suggesting a role for these neurons in the localization of sound in space. In the present study, the nature of the neurotransmitter mediating fast ipsilateral excitation of LSO neurons was examined using iontophoretic application of excitant amino acid (EAA) agonists and antagonists. N-methyl-D-aspartate (NMDA) and quisqualate (QUIS) were used as agonists, while the selective NMDA receptor antagonist D. L-2-amino-5-phosphonovaleric acid (APV), and the non-selective receptor EAA antagonist cis-2,3-piperidine-dicarboxylic acid (PDA) were used to study ipsilaterally evoked neuronal responses. In 3 additional experiments the selective non-NMDA receptor antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX) replaced PDA. Ipsilateral, tone-evoked and spontaneous activities were generally enhanced by EAA agonists while partial blockade of tone-evoked, ipsilateral excitation was observed with EAA antagonists. Both PDA and DNQX more effectively blocked ipsilateral tone-evoked excitations and spontaneous activity than did the NMDA-receptor antagonist, APV.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMedDate not supplied

Autoradiographic localization of a non-reducible somatostatin analog (125I-CGP 23996) binding sites in the rat brain: comparison with membrane binding.

The regional distribution of somatostatin binding sites in the rat brain was determined by quantitative autoradiography, using 125I-CGP 23996, a non-reducible somatostatin analog. In preliminary experiments, kinetic properties of 125I-CGP 23996 binding to rat brain membranes and slide mounted frozen brain sections were compared and found similar. In addition, distribution of 125I-CGP 23996 and 125I-N-Tyr-SRIF14 binding sites on membrane prepared from 10 different rat brain structures were closely correlated (r = 0.91, 2 p less than 0.01), indicating that the non-reducible analog recognizes the same binding site as the Tyr-extended native peptide. Highest levels of 125I-CGP 23996 binding sites were found in anterior temporal, frontal and cingular cortex as well as hippocampus. Moderate levels were found in the remaining part of the limbic system including amygdala, olfactory tubercles and bed nucleus of the stria terminalis. In the brain stem, nuclei involved in the auditory system such as the ventral cochlear nucleus and the superior olive nucleus, contained high levels of 125I-CGP 23996 binding sites. The distribution of 125I-CGP 23996 binding sites roughly correlated with that of the endogenous peptide in most structures, except in the mediobasal hypothalamus.

Amygdala↗
PubMed1993

Cochlear place-frequency map in the marsupial Monodelphis domestica.

In order to determine the place-frequency map of the cochlea in the marsupial Monodelphis domestica, iontophoretic HRP-injections were made at several locations in the ventral cochlear nucleus. Prior to iontophoresis the auditory neurons at these locations were characterized electrophysiologically. The resulting distribution of retrogradely labeled cochlear spiral ganglion cells was analysed by means of a three dimensional reconstruction of the cochlea. The map was established for frequencies between 2.4 and 44.5 kHz, corresponding to positions between 95 to 14% of basilar membrane length (base = 0%). The maximum slope amounted to 1.8 mm/octave. Over the basal-most 60% of the cochlea the slope of the place-frequency map was larger than 1.5 mm/octave, further apically the slope rapidly decreased to values below 0.8 mm/octave. The shape of the cochlear place-frequency map is similar to that described in placental mammals.

Acoustic Stimulation↗
PubMed1994

Programming the cochlear implant based on electrical acoustic reflex thresholds: patient performance.

The electrical acoustic reflex threshold (EART) has been shown to be a reliable estimate of behavioral comfort levels in both child and adult cochlear implant patients. The purpose of this study was to investigate the potential for using EARTs for programming the Nucleus cochlear implant. EARTs and behavioral comfort levels were obtained from 7 adult implant patients. Two programs or "maps" were made for each patient, one based on behavioral comfort levels and one based on EARTs. Performance on open set tests of speech recognition was measured with each map. Mean data suggest that speech perception is similar with both maps. Analysis of individual data revealed that, whereas 2 subjects performed better with the C-level maps, the remaining 5 subjects tended to perform either better with the EART map or equally well with both maps. These results suggest that EARTs may be an adequate substitute for comfort levels when programming the implant for patients who are unable to make reliable psychophysical judgments.

Adult↗
PubMed1982

Uptake and transport of horseradish peroxidase by cochlear spiral ganglion neurons.

Cochlear spiral ganglion neurons in the cat have been classified as type I and type II. The type II neurons are of special interest since they are reported to provide the afferent innervation to three-quarters of the cochlear hair cells, and also because of a recent assertion that they do not project to the brain. In the present study the neuronal marker horseradish peroxidase (HRP) was utilized to re-examine these issues. HRP was injected into the intranuclear cochlear nerve root of adult cats. 18 to 48 h post-injection HRP reaction product was observed in both type I and type II neurons. The majority of labeled cells were characterized by granular reaction product, while a smaller number of cells were also diffusely filled with HRP, resulting in intense staining of the cell soma and its processes. These data indicate that the central axons of type II neurons are constituents of the cochlear nerve root at the level of the brainstem and thus do project centrally. In the organ of Corti HRP-filled fibers to both inner and outer hair cells were observed and demonstrated in electron microscopy to be afferent neurons. This intra-axonal accumulation of the HRP by outer hair cell afferents constitutes direct evidence of the functional projection of these neurons to the cochlear nucleus.

Animals↗
PubMed1990

[Cochlear implants: histological data].

We have performed a histological examination of the pars petrosa of 13 implanted patients. Morphological data were confronted with the clinical findings. The results of this study show that the nerve elements stimulated by the electrode are the cells of the spiral ganglion, and that a small number of ganglionic cells, as few as 10% of the normal figure, is compatible with auditory perception by electrical stimulation. Furthermore, all the implanted pars petrosa were the seat of a fibrosis and neo-ossification reaction around and sometimes even beyond the tip of the electrode. The trauma caused by the insertion of the electrode into the cochlea involved the sensorial cells of the organ of Corti and the dendritic populations in the lamina spiralis, but the cells of the spiral ganglion were spared. Prolonged electrical stimulation (14 years in 1 case) does not appear to have any deleterious effect on the survival of the spiral ganglion, of the cochlear nerve or of the cochlear nucleus.

Adult↗
PubMed1989

RU 24722, a new eburnamine derivative, induces selective alterations in cerebral glucose utilization in freely moving rat.

The effect of a new eburnamine derivative, RU 24722, a putative phasic activator of catecholaminergic systems on local cerebral glucose utilization was studied in freely moving rats 15 min, 90 min and 6 h after the intraperitoneal administration of the drug (25 mg/kg). Of the 53 brain regions examined, 9 exhibited significant time-dependent increases of glucose utilization (up to 45-55%). Some changes were early and transient, as in the substantia nigra reticulata and the paraventricular nuclei. Other areas showed sustained (median septal nucleus) or delayed increases of glucose utilization (lateral septum, dorsal subiculum, hippocampal fimbria, fronto-parietal motor cortex and ventral cochlear nucleus). No significant alterations of glucose utilization could be elicited in the locus coeruleus and raphe nuclei, and none of the brain regions showed a decrease in glucose consumption. Our findings suggest that RU 24722 preferentially stimulates the activity in some brain areas involved in cognitive, vegetative and locomotor functions.

Animals↗
PubMed1985

The spiral ganglion and cochlear nuclei of deafness mice.

Deafness mice (dn/dn) never develop hearing, but, except for the associated physical defects, have no other known abnormalities. For this study, cochleas and brains of five adult homozygotes (dn/dn) and five adult heterozygotes (+/dn), matched by weight and sex, were prepared for serial section light microscopy. In the homozygotes, the organ of Corti was totally degenerated basally, gradually improving toward the apex where supporting cells, border cells and pillar cells were present; however, the stria vascularis was dystrophic in the apex. The saccular macula was atrophied or dystrophic in seven of the ten homozygote ears. The homozygotes had only 23% of the number of spiral ganglion cells found in the heterozygotes, but they appeared robust. In six of the ears of each group there was clumping of apical spiral ganglion neurons. In the homozygotes, the volume of Rosenthal's canal was 121%, that of the dorsal nuclei was 90%, and that of the ventral cochlear nuclei was 63% of the comparable volumes in heterozygotes. The globular cells of the homozygote ventral cochlear nucleus were 72% of the size of those of heterozygotes. These quantitative morphological abnormalities of the homozygote spiral ganglion and cochlear nuclei may result from organ of Corti atrophy.

Animals↗
PubMed2001

Increased glutamate, GABA and glutamine in lateral geniculate nucleus but not in medial geniculate nucleus caused by visual attention to novelty.

This study is concerned with cortico-thalamic neural mechanisms underlying attentional phenomena. Previous results from this laboratory demonstrated that the visual sector of the GABAergic thalamic reticular nucleus is selectively c-fos activated in rats that are naturally paying attention to features of a novel-complex environment, and that this activation is dependent on top-down glutamatergic inputs from the primary visual cortex. By contrast, the acoustic sector of the thalamic reticular nucleus is not activated despite noise generated by exploration and c-fos activation of brainstem acoustic centers (e.g. dorsal cochlear nucleus, inferior colliculus). A prediction of these results is that the levels of the neurotransmitters glutamate and GABA, and the glutamate-related amino acid glutamine, will be increased in the lateral geniculate nucleus (LGN), but not in the medial geniculate nucleus (MGN) of rats that explore a novel-complex environment in comparison to levels of these amino acids in control rats. By means of neurochemical analysis of these amino acids (HPLC) the results of this study confirmed this prediction. The results are consistent with the previously proposed 'focal attention' hypothesis postulating that a focus of attention in the primary visual cortex generates top-down center-surround facilitatory-inhibitory effects on geniculocortical transmission via corticoreticulogeniculate pathways. The results also supports the notion that a main function of corticothalamic pathways to relay thalamic nuclei is attention-dependent modulation of thalamocortical transmission.

Animals↗