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PubMed1983

The effect of auditory stimulus rate on [14C]2-deoxyglucose uptake in rabbit inferior colliculus.

The relationship between auditory stimulus rate and level of [14C]2-deoxyglucose (2-DG) uptake was examined using the 2-DG technique developed by Sokoloff as an indication of glucose uptake and neural activity. Conscious restrained albino rabbits were given one monaural tone either once per second or once per minute for 45 min, or served as unstimulated controls. Autoradiographs of the inferior colliculi from these animals were compared densitometrically. It was found that the rabbits stimulated once per second had markedly elevated levels of 2-DG uptake compared to both other groups: the rabbits stimulated once per minute and to unstimulated control rabbits. In addition, the inferior colliculus autoradiographs of the rabbits stimulated with pure tones showed a distinctive banding pattern in central nucleus different from that seen in control rabbits.

Acoustic Stimulation↗
PubMed1987

[Mesencephalic locomotor region of the guinea pig].

Location of the midbrain region where electrical stimulation can evoke locomotor activity of limb muscles was determined in decerebrate guinea pig. Minimal thresholds (5-10 microA) were observed for sites in the ventromedial part of inferior colliculi, dorsolateral border of central grey and immediately dorsally to n. cuneiformis (1.8-3.0 mm rostrally to interauricular axis).

Animals↗
PubMed1985

The effects of brainstem lesions on vocalization in the squirrel monkey.

The present study is an attempt to find out the brain areas involved in the motor coordination of species-specific vocalization. For this purpose, high-frequency coagulations were placed in a systematic manner throughout the brainstem and posterior diencephalon in altogether 43 squirrel monkeys (Saimiri sciureus). The effect of these lesions on different call types elicited by electrical brain stimulation was studied spectrographically. It was found that bilateral destruction of the ventrolateral, ventroposterior and intralaminar thalamus, periventricular and rostral periaqueductal gray, ventral tegmental area of Tsai, nucl. interpeduncularis, nucl. ruber, anterodorsolateral midbrain tegmentum, superior and inferior colliculi, pontine gray, cerebral peduncles, medial pontine reticular formation, raphe and vestibular nuclei did not affect the acoustic structure of the calls tested. On the other hand, lesions in the ventrolateral midbrain involving the substantia nigra and overlying reticular formation, in the midbrain tegmentum just below the inferior colliculus, in the lateral pons and almost the whole medulla (minimal lesion size: 2.5 mm3) changed vocalization significantly. It is suggested that the latter areas are more or less directly involved in the motor coordination of vocalization, while the first are not.

Animals↗
PubMed2001

Origins of projections from the inferior colliculus to the cochlear nucleus in guinea pigs.

We used retrograde tracing techniques to examine the projections from the inferior colliculus to the cochlear nucleus in guinea pigs. Following injection of a retrograde tracer into one cochlear nucleus, labeled cells were found bilaterally in all subdivisions of the inferior colliculus. The majority of cells were located in the central nucleus and external cortex; relatively few cells were located in the dorsal cortex. Multipolar (stellate) cells were labeled in all subdivisions of the inferior colliculus. In the central nucleus, disk-shaped cells were also labeled. To determine whether individual collicular neurons send collateral projections to the cochlear nuclei on both sides, we injected different fluorescent tracers into left and right cochlear nuclei in the same animal. The inferior colliculi contained very few double-labeled cells, indicating that the projections to ipsilateral and contralateral cochlear nuclei originate from separate populations of cells.

Animals↗
PubMed1984

Electrophysiological investigations on the central innervation of the rat and guinea-pig pineal gland.

The possible influence of central nervous structures on the electrical activity of single pineal cells was investigated in rat and guinea-pig. In the rat electrical stimulation of the hippocampal formation elicited both single cell responses with different latencies and mostly long-term excitations in single pineal cells, while stimulation of the habenular nuclei caused clear orthodromical responses with different latencies, alterations in the rate of spontaneous electrical activity and evoked discharges of "silent" units. In the guinea-pig electrical stimulation of the paraventricular nucleus influenced predominantly cells in the deeper layers of the posterior part of the pineal gland. Electrical stimulation of both the superior and inferior colliculi elicited field potentials with a constant latency, indicating a functional relationship between the corpora quadrigemina and the pineal organ.

Animals↗
PubMed1975

Midbrain deafness following head injury.

A patient is described who became deaf following a head injury. Postmortem examination revealed bilateral lesions of the lateral lemnisci and inferior colliculi. The clinical pattern of midbrain deafness is examined and compared with syndromes of cortical and peripheral auditory impairment.

Audiometry↗
PubMed1980

[Use of antero- and retrograde horseradish peroxidase transport to analyze interneuronal connections of the bat auditory system].

Tpe experiment were performed on the horsseshoe-nosed bats (Rhinolophus ferrumequinum). Horseradish peroxidase (HRP) 25% solution was administered into the central nucleus of the inferior tubercles of the corpora quadrigemina. After two days, in the contralateral similar nucleus a great number of labelled multipolar neurons was revealed. Terminal axonal branchings which get into the nucleus studied via the interquadrigeminal commissure were detected near these neurons. Antero- and retrograde axonal transport of exogenic HRP made it possible to ascertain bilateral connections existing between the left and right central nuclei of the inferior colliculi. A suggestion was made on a reciprocal character of the relations, since labelled efferent terminals constantly occurred near the labelled afferent neurons.

Animals↗
PubMed1999

Differential projection patterns of superior and inferior collicular neurons onto posterior paralaminar nuclei of the thalamus surrounding the medial geniculate body in the rat.

The thalamic nuclei at the medial border of the medial geniculate body (i.e. the suprageniculate nucleus, the medial division of the medial geniculate nucleus, the posterior intralaminar nucleus and the peripeduncular nucleus) which relay sensory information to the amygdala are thought to receive convergent input from multiple sites. In order to delineate the organization of these multimodal thalamic nuclei, the locations of superior and inferior collicular neurons projecting to these nuclei were studied by means of retrograde transport methods. Small injections of the tracer Miniruby were made into single paralaminar thalamic nuclei. Injections of Miniruby into the suprageniculate nucleus labelled predominantly neurons in the stratum opticum of the superior colliculus, whereas injections into the medial division of the medial geniculate body, the posterior intralaminar nucleus and the peripeduncular nucleus labelled predominantly neurons in the deep layers of the superior colliculus. These injections also labelled neurons in the inferior colliculus. The majority of retrogradely labelled neurons were found in the external nucleus of the inferior colliculus and here predominantly in layer 2. Injections focused onto the medial division of the medial geniculate body additionally labelled magnocellular neurons in layer 3 of the external nucleus and a few neurons in the central nucleus. More ventrally located injections, focused onto the posterior intralaminar and peripeduncular nucleus, almost exclusively labelled neurons in layer 1 of the external nucleus and the dorsal part of the dorsal nucleus. After injections into the suprageniculate nucleus, only neurons in layer 2 were found. Neurons in the central nucleus of the inferior colliculus were only found after injections that involved the medial division of the medial geniculate body. The present results suggest that, despite a considerable degree of convergence in this thalamic region, each of these thalamic nuclei receives a unique pattern of projections from the superior and inferior colliculi. It appears that the thalamic nuclei may be concerned mainly, but not exclusively, with a single sensory modality, and give rise to parallel multimodal and unimodal pathways to the amygdala.

Animals↗
PubMed1987

The human auditory brain stem as a generator of auditory evoked potentials.

Data on the size, location, and orientation of human brain stem auditory nuclei are discussed here from the point of view of the potential role of these structures in generation of the brain stem auditory evoked response. Due to reduction in size of several nuclei in the human brain stem, the structures most likely to be generators of far-field potentials are the cochlear nuclei, medial olivary nuclei, dorsal lemniscal nuclei, inferior colliculi, and their axonal projections. Consideration of the anatomy of the human auditory brain stem pathway forms the basis for a model of generation of auditory evoked potentials.

Animals↗
PubMed1997

Audiogenic seizures after neck tourniquet-induced cerebral ischemia in the rat.

Development of audiogenic seizures (AGS) and their correlation with neurodegeneration were studied after 7.5 min of whole-brain ischemia. One day post-ischemia, all animals became hyperreactive and responded to auditory stimulation by generalized seizures. Neuronal necrosis developed already 6 h post-ischemia in inferior colliculi, reticular thalamic nucleus and hippocampal hilar region. Repeated ischemia did not induce any neurological changes, suggesting that the neurological effects are consequences of selective neuronal injury.

Acoustic Stimulation↗
PubMed2005

Projections from auditory cortex contact cells in the cochlear nucleus that project to the inferior colliculus.

Anterograde and retrograde tracing techniques were combined to determine whether auditory cortical axons contact cells in the cochlear nucleus that project to the inferior colliculus. FluoroRuby or fluorescein dextran was injected into auditory cortex to label cortical axons by anterograde transport. Different fluorescent tracers (Fast Blue, FluoroGold, FluoroRuby or fluorescein dextran) were injected into one or both inferior colliculi to label cells in the cochlear nucleus. After 12-15 days, the brain was processed for fluorescence microscopy and the cochlear nuclei were examined for apparent contacts between cortical axons and retrogradely labeled cochlear nucleus cells. The results suggest that axons from the ipsilateral or contralateral cortex contact fusiform and giant cells in the dorsal cochlear nucleus and multipolar cells in the ventral cochlear nucleus that project directly to the inferior colliculus. The contacts occur on cell bodies and dendrites. The target cells in the cochlear nucleus include cells that project ipsilaterally, contralaterally or bilaterally to the inferior colliculus. The results suggest that auditory cortex is in a position to exert direct effects on the monaural pathways that ascend from the cochlear nucleus.

Animals↗
PubMedDate not supplied

[Effect of destruction of the auditory centers of the brain on the range of echolocation by bats Rhinolophus ferrum-equinum (the large horseshoe-nose bat)].

Effect of the auditory cortex, internal geniculate bodies and inferior colliculus removal on echo-ranging detection of immovable wire obstacle by bats has been studied in the behavioural procedure. It is shown that destruction of the auditory cortex results in an irreversible decrease (to 74.6% of control values) in limiting detection range of obstacle by animals. Extensive destructions of internal geniculate bodies decrease limiting detection range only in the first postoperative days. In the case of the inferior colliculi + removal the limiting detection range irreversibly decreases to values equaling 38.5% of control ones. A suggestion that the obtained effects are a consequence of the auditory system sensitivity deterioration in bats is substantiated.

Animals↗
PubMed1992

Case report: neuropathology of methyl bromide intoxication.

The neuropathological findings in a man and his dog both of whom died after acute exposure to methyl bromide are presented. The dog had cerebral oedema, most marked in the depths of cortical sulci. The man survived 30 days after the initial illness and his brain contained well-defined symmetrical lesions in the mammillary bodies and inferior colliculi. He also had a peripheral neuropathy and lymphocytic thyroiditis. The pathology in the central nervous system has features resembling Wernicke's encephalopathology; the mechanism by which methyl bromide may produce such lesions is discussed.

Adult↗
PubMed1999

Transient CD15 expression reflects stages of differentiation and maturation in the human subcortical central auditory pathway.

The expression of the terminal saccharide determinant CD15 (3[a1-3]-fucosyl-N-acetyl-lactosamine) was evaluated in the central auditory system of the human developing brain by using monoclonal antibodies against this epitope. CD15 immunoreactivity was first observed in the ventral cochlear nucleus at 10 weeks of gestation, whereas the dorsal cochlear nucleus became positive from 13 weeks of gestation. In both nuclei, the intensity of immunoreactivity increased until 16 weeks of gestation and lasted until 25 weeks of gestation. In the inferior colliculi, CD15 was poorly expressed in the central nucleus from 13 to 23 weeks of gestation and later with moderate levels until birth. Within the medial geniculate nucleus, a biphasic pattern of expression was observed with peaks around 14-17 and 21-24 weeks of gestation. Heterogeneous expression in the medial geniculate nucleus, which was associated either with neurons or the neuropil, allowed distinction of subnuclei. In many of the auditory pathway structures (e.g., ventral cochlear nucleus and central nucleus of the inferior colliculus), a heterogeneous pattern of CD15 expression in the form of repeating parallel bands, possibly related to tonotopic organization, became transiently apparent around 23 weeks of gestation, whereas in the magnocellular part of the medial geniculate nucleus, a striking modular or compartmental arrangement of immunoreactive structures (which could also be associated with tonotopic organization) was also noted at about 23 weeks of gestation. We propose that the initiation of CD15 expression in each nucleus heralds the appearance of functional contacts and that high levels of neuropil labeling are related to the formation of nonstabilized synaptic contacts. Thus, transient CD15 expression in the central auditory system is possibly correlated with phases of functional plasticity in this pathway.

Aging↗
PubMed1995

Synaptic loss in the central nucleus of the inferior colliculus correlates with sensorineural hearing loss in the C57BL/6 mouse model of presbycusis.

Between 3 and 25 months of age, light and electron microscopic features of principal neurons in the central nucleus of the inferior colliculus of the C57BL/6 mouse were quantitated. This mouse strain has a genetic defect producing progressive sensorineural hearing loss which starts during young adulthood (2 months of age) with high-frequency sounds. During the second year of life, hearing is severely impaired, progressively involving all frequencies. The hearing loss was documented in the present study by auditory brainstem recordings of the mice at various ages. The cochleas from many of the same animals showed massive loss of both inner and outer hair cells beginning at the base (high-frequency region) and progressing with age along the entire length to the apex (low-frequency region). In the inferior colliculi, there was a significant decrease in the size of principal neurons in the central nucleus. There was a dramatic decrease in the number of synapses of all morphologic types on principal neuronal somas. The percentage of somatic membrane covered by synapses decreased by 67%. A ventral (high frequency) to dorsal (low frequency) gradient of synaptic loss could not be identified within the central nucleus. These synaptic changes may be related to the equally dramatic physiologic changes which have been noted in the central nucleus of the inferior colliculus, in which response properties of neurons normally sensitive to high-frequency sounds become more sensitive to low-frequency sounds. The synaptic loss noted in this study may be due to more than the loss of primary afferent pathways. It may represent alterations of the complex synaptic circuitry related to the central deficits of presbycusis.

Animals↗
PubMed2000

Word deafness after resection of a pineal body tumor in the presence of normal wave latencies of the auditory brain stem response.

We studied the case of a 48-year-old woman who had resection of a pineal body tumor in terms of postoperative audiological function. Postoperative magnetic resonance imaging disclosed partial inferior colliculi destruction and medial geniculate body degeneration. A pure tone audiogram revealed only moderate sensorineural hearing loss, but her speech perception was totally impaired. The binaural sound localization function was also impaired. The auditory brain stem response (ABR) showed waves I, III, and V to have normal latencies. The amplitude of wave III was larger than that of wave V. These results support the view that the waves of the ABR are elicited from multiple sources in the auditory brain stem nuclei and tracts. This case suggests a substantial role for the inferior colliculus and medial geniculate body in the processing of speech perception and sound localization.

Astrocytoma↗
PubMed1975

Averaged evoked potentials in cats with lesions of auditory pathway.

Averaged evoked activity was recorded from needle electrodes placed at the vertex of the calvaria and adjacent to each bulla in anesthetized cats in response to click stimuli. The portion of the response from 0 to 10 msec was analyzed. Activity during the first 3 msec was greatly reduced on the side ipsilateral to a lesion involving destruction of the cochlea or section of the eighth nerve and its blood vessels. Activity after 4 msec was greatly reduced on the side ipsilateral to destruction of the cochlear nuclei. No effect was found with destruction of both inferior colliculi. The bulla-vertex evoked responses were also compared to those recorded from the round window. The results support the premise that change in the wave-form of the early evoked potential can be used to determine site of loss of acoustic information along the auditory pathway.

Acoustic Stimulation↗
PubMed1999

Transcollicular approach to intrinsic tectal lesions.

OBJECTIVE: We used a paramedian, infratentorial-supracerebellar, transcollicular approach to resect 11 intrinsic tectal lesions, including 8 tumors and 3 hematomas, in 11 patients. The route of access to the lesions was designed to minimize the anatomic and functional damage to the surrounding structures. METHODS: Access was through one superior colliculus in each of seven patients, through one inferior colliculus in each of two patients, and through the superior and inferior colliculi of one side in each of two patients. RESULTS: Of the eight tumors, three were totally resected, four were nearly totally resected, and one was partially resected. The preoperative ocular symptoms did not change in six of these eight patients and worsened in two, and the neurological deficits, except ocular symptoms, improved in two. All three hematomas were completely removed, along with abnormal blood vessels in the wall of the hematoma cavity; all three of these patients experienced neurological improvement. CONCLUSION: We conclude that the paramedian, infratentorial-supracerebellar, transcollicular approach permits safe removal of intrinsic tectal lesions. Resection of the superior or inferior colliculus or both on one side seems to be neurologically well tolerated.

Adult↗