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At least 19 recordsLinked to original sources
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↗
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↗
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↗
PubMed1987

[Characteristics of the areas of synchronization of the neuronal responses of the inferior colliculi in greater horseshoe bats to the presentation of amplitude-modulated stimuli].

Response areas of synchronized discharges measured at different values of modulation rates were studied in inferior colliculus of bats (Rhinolophus ferrumequinum). Single neurons showed a variety of synchronized response areas to sinusoidally amplitude-modulated stimuli (thresholds of synchronized discharge plotted versus modulation rates, carrier frequency and modulation depth are constant). All neurons showed best modulation frequency where minimal thresholds could be obtained. Synchronized response areas measured in collicular units were sharply or widely tuned, some showed upper thresholds, tuning curves were symmetrical or asymmetrical. The data suggest that response features of studied units prove to be well suited for processing echoes produced by wing beats of flying insects.

Acoustic Stimulation↗
PubMed1985

[Overall synchronized response of the inferior colliculi to lateralization of complex sounds].

Interaural differences in time, intensity or phase introduced into a different frequency component of complex sounds results in changes of amplitude and form of the frequency following response depending on the frequency and phase ranges of the sounds. This relationship may be due to physical differences in stimulation of both ears, i. e. to differences in the sound wave forms and, consequently, in conditions of the convergence of both monaural afferent inflows.

Animals↗
PubMedDate not supplied

[The role of the temporal areas in conditioned reflex activity following section of the brachia of the inferior colliculi].

The role of the neocortex temporal areas in the closing function was studied in chronic experiments on cats in the norm and after section of the posterior colliculi brachia. The techniques of functional elimination of the temporal neocortex by cold and section of the posterior colliculi brachia were used. Functional elimination of the cortical temporal areas prevents formation of a stable conditioned reflex in the first twenty sessions with cooling. Conditioned reflexes elaborated after section of the posterior colliculi brachia are not manifested in the case of cooling of the temporal areas throughout the period of observation (18 sessions). At the same time the conditioned reflexes elaborated before the section, are restored quite rapidly (five to six sessions). Hence, the neocortex temporal areas are more important for setting up conditioned connections than for their preservation and the use of connections previously elaborated.

Animals↗
PubMed1987

Diurnal variation of cation pump enzyme activity in pineal and seven other rat brain regions.

Adult female Long-Evans rats were maintained on an automatically regulated artificial lighting schedule of light:dark (L:D) 14.5:9.5 for 12 wk. After sacrifice at 0630, 1130, 1600, 1800, 2000, 2200, 0230, or 0400, the pineals were removed, weighed, and assayed for N-acetyltransferase (NAT), melatonin, Mg++-paranitrophenylphosphatase (pNPPase), and K-pNPPase activity. The brains were quickly dissected into the following areas: cerebellum, superior colliculi, inferior colliculi, visual cortex, auditory cortex, sensorimotor cortex, and the hypothalamic area around the suprachiasmatic nucleus. These regions were weighed and 10% sucrose homogenates were prepared for determinations of protein, Mg++-pNPPase, and K+-pNPPase activity. Pineal melatonin rose over six-fold from 144 +/- 70 pg/gland at 1130 to 981 +/- 173 pg/gland at 0230. Similarly, pineal NAT activity rose over 11-fold, from 119 +/- 12 pmol/gland/h to 1315 +/- 232 pmol/gland/h at the same times. K+-pNPPase activity rose by about two-thirds, from 133 +/- 12.8 nmol/gland/h to 224 +/- 22.3 nmol/gland/h from 1600 to 0230. However, when expressed per mg protein, these differences in pNPPase activity were not significant. There were no significant daily rhythms discernible in any of the seven other brain regions across these times. We conclude that cation pump enzyme activity varies only slightly with time in the rat brain and pineal gland, in spite of definite daily rhythms of pineal melatonin and NAT activity.

4-Nitrophenylphosphatase↗
PubMed1988

Differentiation between brain lesions in experimental thiamine deficiency.

Dietary deprivation of thiamine combined with pyrithiamine administration in rats was used for pathophysiological and morphological investigations. The animals passed through three different symptomatic stages, ranging from slight neurological abnormalities to generalized seizures from day 8 up to day 11. Hypothermia was a consistent finding during the second week. Histological examination revealed two types of neuropathological lesions in the rats. Those in the colliculi inferiores and the vestibular nuclei were characterized by a bullous spongiform appearance of the neuropil with severely damaged, pale and oedematous nerve cells. Alterations in the thalamus and inferior olives, however, showed eosinophilic nerve cell necrosis of the ischemic type which resembles the thalamic pathology found in human cases of Wernicke's encephalopathy.

Animals↗
PubMed1991

Superior paraolivary nucleus in the pigmented guinea pig: separate classes of neurons project to the inferior colliculus and the cochlear nucleus.

The superior paraolivary nucleus is a large component of the superior olivary complex in rodents and a major source of input to the inferior colliculi and the cochlear nuclei. In the present study, retrograde transport of the fluorescent tracers Fluoro-Gold, Fluoro-Ruby (tetramethyl rhodamine conjugated to dextran), fluorescein-coated microspheres, and Fast Blue were used to reveal the morphology and collateral projection patterns of cells in the superior paraolivary nucleus. The ascending projections to the inferior colliculus from the superior paraolivary nucleus arise mainly from round, multipolar cells, including large cells that project exclusively to the inferior colliculi and not to the cochlear nuclei. Projections to the ipsilateral and contralateral inferior colliculi arise from cells with similar morphology and, in fact, many of the cells that project contralaterally project ipsilaterally as well. Projections to the ipsilateral and contralateral cochlear nuclei arise primarily from cells that do not have collicular projections. On average, the somas of these cells are significantly smaller and more elongated than those that project to the inferior colliculi. Overlap between these ascending and descending systems is restricted to a small percentage of cells that send collateral projections to both the ipsilateral cochlear nucleus and the ipsilateral inferior colliculus. These cells are small and moderately elongated. Thus the ascending and descending projections examined here arise largely from different cells that belong to different morphological classes.

Animals↗
PubMed1986

Short-latency auditory evoked potentials in the monkey. II. Intracranial generators.

The generators of the short-latency auditory evoked potentials (SLAEPs) in the monkey have been defined by intracranial mapping from cochlea to auditory cortex. SLAEP components other than 1a and the slow negativity (SN) following wave 7 derive from compound action potentials propagated in subcortical auditory pathways. The component generators are complex due to the presence of two bursts of activity in the eighth nerve, to the fact that the ascending auditory fibers both synapse on and bypass specific relay nuclei, and to the differences in orientation of segments of the auditory pathways. Most SLAEP components recorded at the surface reflect the summation of activity from multiple generators. However, much of the activity seen within subcortical structures cannot be traced to the surface of the brain. Component 1a is identified with the cochlear summating potential, while 1b reflects the initial afferent volley in the distal portion of the eighth nerve. Component 2 represents the initial depolarization of the eighth nerve terminals within the ipsilateral cochlear nucleus. Component 3h reflects the second volley of activity in the distal portion of the eighth nerve and the outflow of the cochlear nucleus which decussates in the trapezoid body. Component 3v represents the initial cochlear nucleus outflow volley ascending the lateral lemniscus. Component 4 principally reflects the second volley of activity within the eighth nerve terminals, and outflow from the ipsilateral superior olivary complex ascending in that lateral lemniscus, with a possible contribution from activity in the contralateral CNC. Component 5 represents the outflow of the contralateral superior olivary complex ascending in that lateral lemniscus. Component 6 reflects another volley from the ipsilateral superior olivary complex ascending in that lateral lemniscus, as well as outflow from both inferior colliculi propagating in their brachii. The generators of component 7 are the most complex encountered, representing volleys in both lateral lemnisci, activity of the contralateral inferior colliculus, and activity in both auditory radiations. A component that follows wave 7, seen best in mastoid-to-mastoid recording linkage, represents outflow from both inferior colliculi propagating in their brachia. Components 8 and 9 principally reflect propagated action potentials in the auditory radiations bilaterally, with an additional contribution from activity of both inferior colliculi. The SN mainly represents volume-conducted postsynaptic potentials from both inferior colliculi and cochlear nuclei.

Animals↗
PubMed1992

Organization of the superior olivary complex in the guinea pig: II. Patterns of projection from the periolivary nuclei to the inferior colliculus.

The superior olivary complex is a major source of auditory projections to the inferior colliculus. Although the projections from the medial and lateral superior olivary nuclei have been well characterized, projections from the surrounding periolivary nuclei have received relatively little attention. In the guinea pig, cytoarchitectonic criteria can be used to distinguish 11 periolivary nuclei that can be divided into four groups. These are: 1) a lateral group that comprises the anterolateral and posteroventral periolivary nuclei and the lateral nucleus of the trapezoid body; 2) a dorsal group that comprises the dorsal and dorsolateral periolivary nuclei; 3) a ventral group that comprises the rostral, ventromedial, and anteroventral periolivary nuclei and the ventral nucleus of the trapezoid body; and 4) a medial group that comprises the superior paraolivary nucleus and the medial nucleus of the trapezoid body. In the present study we used horseradish peroxidase and fluorescent tracers to identify olivocollicular cells in each of the periolivary nuclei. The lateral, dorsal, and medial periolivary groups project bilaterally, and the ventral periolivary group projects ipsilaterally. Within groups, individual nuclei contain different numbers of olivocollicular cells. The posteroventral periolivary nucleus is the only periolivary nucleus that does not project to the inferior colliculus. The superior paraolivary nucleus is the only periolivary nucleus that contains significant numbers of individual cells that project to both inferior colliculi. The remaining periolivary nuclei project only ipsilaterally or contain separate populations of cells that project to the two inferior colliculi.

Animals↗
PubMedDate not supplied

MR imaging of the mesencephalic tectum: normal and pathologic variations.

Variations of the quadrigeminal plate (mesencephalic tectum) were determined on midline sagittal MR images of the brain in 93 patients without known mesencephalic abnormalities and in 10 patients with known aqueductal stenosis or obstruction. Measurements of the thicknesses of the superior and inferior colliculi and the length of the tectum were made on the midline sagittal section. Images were obtained with a 0.5 T system with spin-echo pulse sequences using a TE of 30 or 40 msec with a TR of 500-1500 msec. The average thickness of the superior and inferior colliculi was about 5 mm, but the range was from 2-7 mm on the midline sagittal section. Abnormally thin colliculi appeared to have no clinical significance while abnormal thickness was observed in patients with neoplastic disease, sarcoidosis, and mesencephalic "beaking." While most neoplasms have abnormal signal intensity on T2-weighted images, small lesions may be difficult to perceive on transaxial images due to volume averaging or noncontiguous sections. Measurements of the tectum, on the commonly obtained midline sagittal section, may be useful for patients with small infiltrative lesions.

Adolescent↗
PubMedDate not supplied

[Characteristics of borderline modulation frequencies in the differentiation of tonal and amplitude-modulated stimuli following the removal of the inferior colliculus in rats].

Elaboration of differentiation between sound stimuli was carried out in 15 laboratory rats. After bilateral ablations of auditory inferior colliculi the border frequency of stimulus amplitude modulation was determined for all rats when they still could differentiate between tonal and amplitude-modulated stimuli. Decrease in frequency of modulation by 2 Hz and more from the border frequency caused a complete loss of ability to differentiate. In all rats bilateral inferior colliculi ablations completely disturbed differentiation between tonal and amplitude-modulated signals with modulation frequency below 183-191 Hz (the range of border frequencies). The surgery however did not affect differentiation between tonal and amplitude-modulated signals with the modulation frequencies above 183-191 Hz. The data suggest that the functions of completion of coding of amplitude-modulated stimuli in the auditory system is strictly linked with definite structures.

Acoustic Stimulation↗
PubMed1991

Vascular factors in the neurotoxic damage caused by 1,3-dinitrobenzene in the rat.

Using a 3 x 10 mg/kg dose schedule of 1,3-dinitrobenzene (DNB) over two days in Fischer rats, we have found the following changes in vascular function and structure during the early phase of the symmetrical brain stem lesions. 1. Marked increase in cerebral blood flow generally but especially in the inferior colliculi, from 6 h after the final dose of DNB. 2. Increasing incidence of petechial haemorrhages in inferior colliculi, cerebellar roof, vestibular and superior olivary nuclei from 12 h. 3. Focal leakage of horseradish peroxidase and many sleeve-like arteriolar haemorrhages seen in vibratome sections and by scanning electron microscopy (SEM) in these regions from 12 h. 4. Periarteriolar oedema and protein leakage present in step-serial sections in these regions from 12 h, with astrocyte swelling and occasional small infarcts. These changes suggest that the vascular bed may play an important role in the pathogenesis of these lesions, perhaps in parallel with early astroglial damage. They are discussed in relation to (i) the known presence of xanthine oxidase in the vascular bed of the brain and the likelihood of "useless redox cycling' with free radical generation from this enzyme's interaction with nitroheterocyclic compounds, and (ii) the possible role of free radical damage to endothelial cells in this intoxication and in the analogous lesions of natural and experimental Wernicke's encephalopathy.

Animals↗