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At least 235 records · Page 13Linked to original sources
PubMed1982

Functional ontogeny in the central auditory pathway of the Mongolian gerbil. A 2-deoxyglucose study.

The 2-deoxyglucose (2-DG) autoradiographic technique was used to map functional activity in the central auditory system of the mongolian gerbil, throughout the period of functional onset. Uptake of 2-DG during exposure to 105 dB SPL wide band noise (WBN) was compared to silence in adults and in neonates at 12, 14, 16 and 18 days after birth (DAB). At 12 DAB, WBN exposure increased 2-DG uptake relative to silence only in the ventral cochlear nucleus. At 14 DAB, 2-DG uptake increased during WBN in the entire cochlear nuclear complex, superior olivary complex, and ventral nucleus of the lateral lemniscus. These stimulus-evoked increases in 2-DG uptake were at adult levels. However, little or no stimulus-evoked increase was seen in higher auditory nuclei at 14 DAB. By 16 DAB, 2-DG uptake also increased during WBN exposure in the dorsal nucleus of the lateral lemniscus, inferior colliculus and medial geniculate nucleus. By 18 DAB, WBN exposure produced increases in 2-DG uptake of medullary and pontine auditory nuclei which exceeded those seen in adults. At higher levels of the pathway, increases were comparable to those seen in adults. WBN-induced increases in 2-DG uptake observed in the cochlear nuclear and superior olivary complexes of neonates were comparable in all regions at all ages, even at 12 DAB. However, the 2-DG uptake increases observed at 16 and 18 DAB were appreciably greater in those regions of the inferior colliculus and medial geniculate nucleus which respond to high frequencies.

Aging↗
PubMed1984

Visual and auditory pathways contain cholecystokinin: evidence from immunofluorescence and retrograde tracing.

The distribution of cholecystokinin (CCK) in the visual and auditory systems of the rat was studied with combined immunofluorescence and fluorescence retrograde tracing techniques. Double-labeled projection neurons in the pathway from the dorsal lateral geniculate nucleus to area 17 of visual cortex, and from the superior olive to the inferior colliculus demonstrated the presence of CCK-containing pathways in the ascending visual and auditory systems. Thus, CCK can be viewed as a neurotransmitter/neuromodulator candidate in ascending sensory systems.

Animals↗
PubMed1997

The c-Fos transcription factor in the auditory pathway of the juvenile rat: effects of acoustic deprivation and repetitive stimulation.

The expression of the inducible transcription factors (ITF) c-Fos and JunB was investigated in the dorsal cochlear nucleus (DCN), ventral cochlear nucleus (VCN) and inferior colliculus (IC) of juvenile and adult rats following deprivation and repetitive stimulation paradigms using 8 kHz tone bursts at 5 min duration and 70 dB, 90 dB or 120 dB sound pressure level (SPL). (1) During postnatal development without stimulation, c-Fos is absent in DCN and VCN from postnatal day (P) 12 to adulthood, but shows a strong expression in the IC which declines during maturation. A similar decrease was also seen in the pons. (2) Between P15 and P35 stimulation of rats with 8 kHz for 5 min at 70 dB SPL evoked expression of c-Fos in a moderate number of cells of DCN, VCN and IC. Higher sound pressure levels increased the number of c-Fos immunoreactive neurons as studied at P21. (3) Deprivation of acoustic stimulation up to P21 reduced the expression of c-Fos when rats were stimulated with 90 dB immediately after the restoration of acoustic input. In contrast to 90 dB SPL, c-Fos immunoreactivity (IR) did not significantly differ between deprived and normal rats following application of 120 dB SPL at P21. Stimulation at P28, i.e., 7 days after the end of the deprivation, evoked an increase of c-Fos only in the IC compared to otherwise normally stimulated rats. At P35, effects of the former deprivation on the c-Fos expression were not longer detectable. (4) In a repetitive stimulation paradigm, 8 kHz tone bursts 5 min in duration were applied each second day between P23 and P35 or each day between P29 and P35. When compared with acutely stimulated rats at P35, both repetitive acoustic stimulation protocols reduced the c-Fos immunoreactivity by 50%-75% in the DCN, VCN and IC. In adult 4-month-old rats, repetitive stimulation did not reduce the c-Fos immunoreactivity from its moderate levels as compared with acute stimulation. (5) In some experiments, we studied also the expression of the JunB protein. JunB paralleled the expression of c-Fos following single acoustic stimulation, but was expressed in a substantially lower number of cells. In contrast to c-Fos, however, repetitive stimulation as described in section 4 did not evoke a decrease of JunB in the lower acoustic pathway.

Acoustic Stimulation↗
PubMed1977

[Damages of the auditory pathway at brain stem level investigated by acoustically evoked potentials (author's transl)].

In 57 patients with operated expansive tumors in the postcranial fossa auditory evoked brain stem potentials were investigated. A group of 36 with neurological evidence for the brain stem compression showed significantly prolonged latencies (Fig. 1), whereas the evoked potentials were nearly normal in the preceding state of CSF circulatory disturbances (21 cases). For one patient with a neurinoma of the right trigeminal root the post-operative reduction of the pathological latency shift is demonstrated (Fig. 2). Latency evaluation of evoked brain stem potentials are used in our clinical routine for differential diagnosis of retrocochlear hearing damages.

Acoustic Stimulation↗
PubMed1992

Some forms of tinnitus may involve the extralemniscal auditory pathway.

It has previously been shown that the click-evoked responses recorded from the intracranial portion of the eighth nerve in patients with incapacitating tinnitus are not abnormal, nor is the latency of peak III of the click-evoked brainstem auditory-evoked potentials significantly altered; however, the latency of peak V is slightly (but significantly) shortened in comparison to that of patients with the same degree of hearing loss but no tinnitus. In this study the hypothesis that the extralemniscal auditory system is involved in the generation of tinnitus is tested. We made use of the fact that neurons of the extralemniscal auditory system also receive input from the somatosensory system, and that stimulation of the somatosensory system can influence the processing of auditory information in the extralemniscal system. In 4 of 26 patients with mild-to-severe tinnitus whose median nerve was stimulated electrically, the tinnitus increased noticeably during stimulation, in 6 the intensity of the tinnitus decreased noticeably, and in the remaining 16 there was no noticeable change in the tinnitus. In some of the patients the character of the tinnitus changed in a complex way. There were no significant differences in hearing thresholds in these three groups of patients. Electrical stimulation of the median nerve in 12 individuals with normal hearing who did not have tinnitus either had no effect on the loudness of sounds or it caused a slight increase in the loudness.

Auditory Pathways↗
PubMed2002

Aminergic projections to cochlear nucleus via descending auditory pathways.

The cochlear nucleus (CN) receives descending input from a variety of auditory nuclei. Descending inputs from the superior olive in particular have been well described, especially those of olivocochlear neurons, which terminate ultimately in the cochlea. It has been demonstrated that olivocochlear neurons receive serotonergic and noradrenergic inputs and thus form a route by which the aminergic system may modulate cochlear mechanisms. Since olivocochlear neurons send collaterals into the CN, it is possible that they also from a route by which the aminergic systems modulate CN processes. The goal of the current study was to determine if neurons in the superior olive that projected to the CN received serotonergic or noradrenergic inputs. The retrograde tracer WGAapoHRP-Au was injected into the CN of cats. The brainstems were silver-enhanced to visualize the tracer and then immunohistochemically processed with antibodies raised against serotonin or dopamine-beta-hydroxylase (DBH) to label serotonergic or noradrenergic fibers, respectively. The sections were viewed with high power light microscopy to determine if the retrogradely labeled neurons were contacted by serotonin- or DBH-immunoreactive varicosities. Retrogradely labeled cells were observed in auditory brainstem nuclei known to project to the CN including the superior olivary complex and inferior colliculus bilaterally and the opposite CN. In these regions, retrogradely labeled neurons were closely associated with serotonin- and/or DBH-immunoreactive varicosities. Assuming a synaptic relationship between the projection neurons and varicosities, these results indicate that the serotonergic and noradrenergic systems innervate the descending pathways to the CN. Since the serotonergic and noradrenergic systems modulate their targets based on level of arousal, these results support the theory that descending systems are involved in selective attention.

Animals↗
PubMed2002

Early cochlear implantation in children allows normal development of central auditory pathways.

The goal of this study was to determine whether there is a sensitive period during early development when a cochlear implantation can occur into a minimally degenerate and/or highly plastic central auditory system. Our measure of central auditory deprivation was latency of the P1 auditory evoked potential, whose generators include auditory thalamocortical areas. Auditory evoked potentials were recorded in 18 congenitally deaf children who were fitted with cochlear implants by 3.5 years of age. The P1 latencies of the children with implants were compared with the P1 latencies of their age-matched peers with normal hearing. There was no significant difference between the P1 latencies of the children with implants and the children with normal hearing. The present results suggest that early implantation occurs in a central auditory system that is minimally degenerate and/or highly plastic. Studies are ongoing to assess the consequences to the developing central auditory system of initiating electrical stimulation at later ages.

Age Factors↗