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At least 19 recordsLinked to original sources
PubMed1980

[Effect of destruction of the inferior colliculi on the performance of the echolocating system of horseshoe-nosed bats].

The effect of unilateral and bilateral destruction of the inferior colliculi on the auditory system sensitivity, sonar signals' parameters and the Doppler shift compensation in echoes was studied in horseshoe bats Rhinolophus ferrumequinum. Complete bilateral destruction of the inferior colliculi did not produce the auditory system disfunction, but it sharply decreased auditory sensitivity of this system which was manifested in a reduction of the maximum detection range and inability to detect a weakly sounding insect. The data obtained suggest that the inferior colliculi are immediately responsible for the maintenance of emitting frequency and that the role which various regions of inferior colliculus play in that process is different. To preserve the effect of the Doppler shift compensation it is necessary to keep intact not less than a half of the central nucleus at least of one inferior colliculus.

Animals↗
PubMedDate not supplied

[Electrophysiologic and behavioral changes in cats following section of the brachia of the inferior colliculi].

Evoked potentials to acoustic stimuli were recorded in the temporal cortical area, the medial geniculate body and the posterior lateral thalamic nucleus in acute experiments on anaesthetized cats. Section of the brachia of the inferior colliculi in an acute experiment resulted in the disappearance of potentials in the examined structures. A distinct correlation has been revealed between the recovery of evoked potentials in the cortico-thalamic auditory structures (in four to six weeks) and the possible elaboration of conditioned reactions within this time period after lesion of the inferior colliculi brachia. The involvement of the temporal area in the general brain activity appears to be one of the major conditions for the formation of new conditioned connections. Possible ways of restoration of afferent input to the temporal cortical area after lesion of the inferior colliculi brachia are discussed.

Animals↗
PubMed1998

Defective auditory recognition after small hemorrhage in the inferior colliculi.

We report the case of a male patient with a traumatic small hemorrhage partially involving the bilateral inferior colliculi without evidence of a temporal lobe lesion. He was unable to comprehend spoken words although he had intact speech production, reading and writing abilities. Comprehension of environmental sounds was also affected. Among the receptive musical abilities, discrimination of intensity, tone and rhythm were preserved, while recognition of melody was impaired. Audiometry showed normal thresholds for pure tone. Waves I-IV of brainstem auditory evoked potentials were elicited normally, whereas the wave V was elicited with reduced amplitude and prolonged latencies on both sides. The main component of middle latency auditory evoked potentials, which is evoked over both hemispheres by monaural stimulation to either side in normal subjects, was elicited only over the hemisphere contralateral to the ear receiving stimulation. Our patient's auditory findings were similar to those usually found in generalized auditory agnosia. Auditory agnosia is usually considered as a sign of a bitemporal cortical or subcortical disorder, but, in our patient, a brainstem disorder caused a disturbance of auditory recognition similar to auditory agnosia due to a bitemporal lesion. Our patient's auditory findings may belong to the category of a brainstem auditory-processing disorder brought on by a small hemorrhage in the inferior colliculi. In addition, the impairment in our patient implies that, in the neural processing of musical parameters, the decoding of intensity, tone and rhythm is accomplished at the level of inferior colliculus, whereas further cortical processing is necessary for the appropriate recognition of melody.

Auditory Perception↗
PubMed1996

Sound-evoked electrocortical desynchronization is inhibited by N omega-nitro-L-arginine methyl ester microinfused into the inferior colliculi in rats.

In previous experiments we have shown that systemic or intracerebroventricular administration of N omega-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide (NO) synthase, is able to significantly reduce sound-evoked electrocortical (ECoG) desynchronization in rats. The present experiments were aimed at identifying the site(s) of the brain through which these effects are mediated. L-NAME (200 and 300 nmol), oxyhaemoglobin (200 and 300 nmol), a NO-trapping agent, and methylene blue (100 and 150 nmol), an inhibitor of guanylate cyclase and NO synthase, given bilaterally into the inferior colliculi, but not in other relay stations of the acoustic pathway, prevented the reduction in ECoG amplitude induced by sound stimulation in rats. Significant reduction of sound-evoked ECoG desynchronization has also been observed in rats receiving injection of CGP37849 (125 and 500 pmol) and LY274614 (125 pmol), two competitive N-methyl-D-aspartate receptor antagonists into the inferior colliculi. The present results show that the inferior colliculus represents the main site where sound-evoked ECoG desynchronization is prevented by L-NAME and provide further support for the hypothesis that NO may play a role at this level in the control of the measured response.

Animals↗
PubMedDate not supplied

[Behavior of cats after unilateral section of the brachii of the inferior colliculi].

In experiments on 13 cats a unilateral section of the brachii of inferior colliculi produced a stable interhemispheric asymmetry not only in the auditory system, but in other (vestibular, visual, somatic, olfactory) analysers as well, which led to a disturbance of adequate space perception. This was manifested in orienting reactions directed only to the side of brain lesion. Animals were no more able to distinguish between the right and left troughs either by spatial or by modal cues. A complete "disregard" by the animals of the trough contralateral to the side of lesion suggests a hemispheric lateralization of conditioned connections providing for an adequate direction of the animals' running.

Animals↗
PubMed1981

Neurogenetic gradients in the superior and inferior colliculi of the rhesus monkey.

The spatiotemporal patterns of neurogenesis in the superior colliculus (SC) and inferior colliculus (IC) were analyzed by plotting the positions of heavily labeled neurons in autoradiograms from a series of rhesus monkeys that had been exposed to 3H-thymidine at various embryonic (E) days and killed either shortly thereafter or at 2-3 months postnatally. Tectal neurons in this species are generated in the ventricular and subventricular zones surrounding the mesocoele (future Sylvian aqueduct) within the first third of the 165-day gestation period. Cells destined for the SC undergo final mitosis from E30 to E56, with peak proliferation from E38 to E43. These cells exhibit only a weak ventrodorsal gradient of neurogenesis and virtually no mediolateral or rostrocaudal gradients. Genesis of the neurons of the central nucleus (CN) of the IC also occurs between E30 and E56 and peaks around E43; but in contrast to cells of the SC, CN cells exhibit distinct rostrocaudal, lateromedial, and ventrodorsal gradients of genesis. Quantitative analysis revealed that whereas neurogenesis of the SC proceeds with about equal strength along the three cardinal axes, in the CN the lateral-medial gradient is significantly stronger than the anterior-posterior gradient. In addition, both the lateral-medial and ventral-dorsal IC gradients are significantly stronger than any SC gradients. Analysis of embryos sacrificed at short intervals following 3H-thymidine injection shows that the gradients are not caused by secondary lateral cell movement or by selective cell death. Thus, these findings suggest that within the generative zone of the midbrain tectum significant regional differences exist which result in distinctive spatiotemporal patterns of proliferation for the neurons of the primate superior and inferior colliculi.

Animals↗
PubMed1984

The interconnections of the inferior colliculi through their commissure.

Much is known of the sources and manner of termination of ascending and descending input to the inferior colliculus (IC) but its commissural connections are less well understood. Most studies of the commissure have utilized small lesions or tracer deposits; while all agree that commissural axons terminating in the IC do so in its superficial and dorsomedial sectors, it is not clear where projecting cell bodies are located in the IC. The present study attempted total infiltration of the commissure of the cat IC with horseradish peroxidase (HRP) in an effort to label all neuronal somas whose axons cross in the commissure. The distribution of labeled cells after the brachium of the IC (BIC) was cut unilaterally and infiltrated with HRP was also examined to enable comparison of the locations and approximate proportions of cells projecting to the contralateral IC and medial geniculate body (MGB). The cells giving rise to commissural axons form an array tilted dorsally from caudal to rostral that spreads mediolaterally through the central nucleus into the external nucleus of the IC, but largely excludes the dorsomedial sector at posterior levels. A similar distribution of labeled cells, but with reduced numbers, is found when large HRP deposits are made in the contralateral BIC. These results, in conjunction with those from studies of the terminations of commissural axons made by others, suggest that the interconnections of the inferior colliculi through their commissure are complementary, rather than reciprocal.

Animals↗
PubMed1985

The organization of neurons in the nucleus of the lateral lemniscus projecting to the superior and inferior colliculi in the rat.

The topographic organization of neurons in the dorsal nucleus of the lateral lemniscus (DNLL) which project to the superior and inferior colliculi was studied using the retrograde horseradish peroxidase (HRP) and the fluorescent double labeling methods. Neurons projecting to the superior colliculus (SC) are situated in the rostral portion of the DNLL, whereas those to the inferior colliculus (IC) are found in the caudal area of this nucleus. These two portions are completely separated from each other and no neurons projecting to both the SC and the IC are observed. In the dorsolateral part of the rostral portion of the DNLL, neurons projecting to the ipsilateral SC are found, whereas neurons projecting to the contralateral SC are located in the central to medial part of the nucleus, but no neurons sending collateral axons to both sides of the SC were observed. Neurons located in the central part of the caudal area of the DNLL project to the ipsilateral IC and neurons in the lateral and medial parts project contralaterally to the IC. Some of the neurons in the caudal part of the DNLL have divergent axonal branching projecting to both sides of the IC. In the ventral nucleus of the lateral lemniscus, labeled neurons were observed only when the HRP was injected into the ipsilateral IC.

Animals↗
PubMed1995

Laminar organization of frequency-defined local axons within and between the inferior colliculi of the guinea pig.

We present a comprehensive description of the local (intrinsic and commissural) connections in the central nucleus of the inferior colliculi (CNICs) in guinea pig. Focal injections of the anterograde tracer biocytin were made into physiologically identified loci of the CNIC and the spatial organisation of the labeled fibres was revealed with computer-assisted three-dimensional (3-D) reconstruction. The intrinsic fibres form a series of V-shaped laminar plexuses composed of fibres bearing both terminal and en passant boutons. Each laminar plexus has a central wing located in the CNIC that extends into the dorsal cortex and an external wing located in the external cortex. The edge where the two wings intersect delimits the lateral border of the central nucleus with the external cortex. The density of labeled terminals was consistently lower in the cortices than in the CNIC. The laminar plexus connects points of similar frequency within the CNIC. Seen in 3-D, the location, orientation, shape, and area of the laminar plexus vary as a function of best frequency. The commissural fibres ending in the contralateral IC to the injection also form a laminar plexus which is symmetrical to the ipsilateral plexus. Electrolytic lesions placed in the contralateral IC at sites with best frequencies corresponding to those of the injection coincided with the terminals of the commissural fibres in most instances. Possible patterns for the organisation of these connections (point-to-point and diverging) are discussed. Three systems of peripheral axons to the laminar plexus are described: parallel, oblique, and perpendicular to the central wing. The novel parallel system has terminals in both ICs that run parallel to the central wing. It might constitute the anatomical basis for across-frequency interactions. The oblique and perpendicular systems are fibres of passage projecting to the commissure and brachium of the IC, respectively.

Acoustic Stimulation↗
PubMed2001

Cochlear electrical stimulation: influence of age of implantation on Fos immunocytochemical reactions in inferior colliculi and dorsal cochlear nuclei of the rat.

The influence of age at the time of implantation of a stimulating electrode unilaterally in the inner ear on central auditory pathways was investigated in rats deafened shortly after birth. Immunoreactivity for Fos served as a functional marker of neuronal activity. Electrodes were implanted in the left cochlea of rats aged 3 weeks or 4 months. Stimulation lasted 45 minutes, then rats were sacrificed and tissues processed for immunocytochemistry. The younger animals showed significantly more neurons with Fos immunoreactivity bilaterally in the dorsal cochlear nuclei (DCN) and inferior colliculi (IC) than the older rats or control animals with normal hearing receiving the same stimulation. Activity was more prominent in the left DCN and right IC. The results show that electrical stimulation of the inner ear is more effective in younger animals in eliciting gene expression associated with development of a functional network in the auditory pathways. This suggests that deaf children should be provided with cochlear implants as early as possible.

Age Factors↗
PubMed1981

[Ultrastructural of the neurons and synaptic architectonics of the central nucleus of the inferior colliculi in the cat brain].

In the central nucleus of the cat's brain inferior colliculus, three classes of neurons were observed. 1. Large relay neurons were distinguished by the abundance of cytoplasmic organelles. A considerable part of their perikaryon was covered by presynaptic terminals. 2. Medium sized lucent neurons having small amount of organelles. 3. Dark cells of rare occurrence in the central nucleus, which according to the number of axo-somatic synapses may be placed between type I and II neurons. In the central nucleus four type of profiles containing synaptic vesicles were distinguished. Large polymorphic endings of specific afferent fibers (type I) and small neurons (type II) contained round synaptic vesicles, while type III irregular axon terminals contained flattened and polymorphic ones. Type I, II and III terminals always appeared to be presynaptic components of synapses. Type IV terminals were found to be rare and except the polymorphic synaptic vesicles contained profiles of endoplasmic reticulum, ribosomes, microtubules, that enables them to be attributed to dendrites. Type IV terminals may be either presynaptic, or postsynaptic components of synapses.

Animals↗
PubMed1984

[Spatial characteristics of the reaction of the inferior colliculi in the cat to movement of the sound source].

The EP-series response of the inferior colliculus to clicks simulating sound source motion, reflects characteristics of this "motion" ("the motion effect", ME). ME distribution over the inferior colliculus practically coincided with the spatial distribution in cases when contralateral stimulation was more effective than the ipsilateral one. The spatial distribution in cases with no ME was identical with the distribution of cases of equal effectiveness of the contra and ipsilateral stimulations. The ME was shown to be connected with the binaural inhibitory effects and might probably be related to the activity of two main neuronal groups (the principal and multipolar ones).

Acoustic Stimulation↗
PubMed1980

[Electrophysiologic manifestations of the functional organization of the inferior colliculi of cats during binaural stimulation with different tonal signals with interaural phase differences].

The maximal activity of the inferior colliculus studied with frequency following responses was mainly observed at interaural phase differences delta phi of 180 degrees, the minimal activity at delta phi = 135-180 degrees (with contralateral delay), and the maximal asymmetry of the activity occurred mainly at delta gamma of 90-135 degrees. These values are statistically independent of both the stimulus frequency and electrode location within the inferior colliculus. These findings support observations on single unit activity and are considered as possible basis for relative estimation by the auditory system of the degree of the sound source shift from the head midline, in addition to the absolute estimation on the basis of the characteristic delay mechanism. The data obtained allow to suggest possible neurophysiological mechanisms underlying some psychophysiological phenomena concerning the shift of the fused auditory image.

Animals↗