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PubMed1990

Neurons in the inferior colliculus of cats sensitive to sound-source elevation.

The sensitivity to variations in sound-source elevation was studied in 48 units, previously examined as to their azimuthal sensitivity, of the inferior colliculi of cats. Of these units, 36 were directionally-sensitive (firing rate varied by more than 50% across the range of positions studied) to both azimuthal and elevational changes. Elevation sensitivity was common to noise stimuli (19/25 units) and pure tones in excess of 6 kHz (17/17 units). Not one of the 8 azimuth-sensitive units with CFs below 6 kHz was directionally-sensitive to the elevation of CF stimuli. The 4 units omnidirectional to azimuthal variation were similarly insensitive to elevation. The shapes of functions relating sound-source elevation to spike count (elevation functions) varied across an apparent continuum, with some very sharply-peaked functions being observed. Peak spike counts almost invariably occurred at stimulus elevations above the horizontal plane. Comparisons of the widths of elevation and azimuth functions at the same sound pressure level were made for 36 units. The relative sharpness of elevation and azimuthal tuning varied across the population. The common association of sensitivity to both azimuth and elevation suggests that elevation sensitivity may be mediated partly by binaural comparisons.

Acoustic Stimulation↗
PubMed1992

Effects of neural transplantation on seizures in the immature genetically epilepsy-prone rat.

To study the hypothesis that neural transplantations can alter seizure susceptibility in a genetic animal model of epilepsy, 93 pubescent genetically epilepsy-prone rats with stage 9 seizures received either bilateral inferior colliculi (N = 21) or lateral ventricle (N = 42) transplants or sham transplants (N = 30). The grafts consisted of embryonic locus ceruleus, neocortical, or cerebellar tissue. Starting 2 days after the transplantation the rats were subjected to audiogenic stimulations every other day for 61 days. Latency to the running and tonic phase, seizure severity score, and duration of the tonic and clonic phase were compared in the neural transplant and sham-operated controls. Rats that received transplants had a longer latency to the tonic phase and a shorter duration of the clonic phase than the controls. At age 110 days the rats had electrodes implanted bilaterally into the angular bundle and were kindled. No difference in kindling rate was found between the rats that received neural grafts and the sham-operated controls. Cerebrospinal fluid concentration of norepinephrine was not altered by the transplants. This study demonstrates that the anticonvulsant effects of neural transplants, using the genetically epilepsy-prone model of epilepsy, are mild.

Acoustic Stimulation↗
PubMed2003

The relevance of neuronal substrates of defense in the midbrain tectum to anxiety and stress: empirical and conceptual considerations.

The medial hypothalamus, amygdala, and dorsal periaqueductal gray constitute the main neural substrates for the integration of aversive states in the brain. More recently, some regions of the mesencephalon, such as the superior and inferior colliculi have also been proposed as part of this system. In fact, fear-like behaviors often result when these sites are electrically or chemically stimulated. Both the behavioral and autonomic consequences of electrical stimulation of the mesencephalic tectum have been shown to be attenuated by minor tranquilizers, probably through enhancement of gamma-aminobutyric acid (GABA)-mediated neurotransmission, which exerts a tonic inhibitory control on the neural circuits responsible for the so-called defense behavior repertoire. Besides GABA, also 5-hydroxy tryptamine serotonin (5-HT), opioids, neuropeptides, histaminergic and excitatory amino acids have all been implicated in the regulation of anxiety-related behaviors induced by stimulation of midbrain tectum. Efforts have been made to characterize how these neurotransmitters interact with each other in the organization of these reactions to aversive stimulation. In this review, we summarize the evidence linking the brain's defense response systems to the concept of fear-anxiety. Furthermore, a case is made for the consideration of the relevance of this body of data to the search for the physiological underpinnings of depression and its consequences.

Animals↗
PubMed1978

Changes in latency and duration of neural responding following developmental auditory deprivation.

The initial latency of spikes evoked by click stimulation and the duration over which spiking occurred were observed in the inferior colliculi of rats. One ear of these animals had been deprived of early auditory stimulation by ligation of the external meatus. Clicks presented to the normally experienced ears evoked spikes in the opposite colliculus with latencies that depended on the characteristic frequency of the unit. Low-frequency (less than 5 kHz) units had latencies from 6-10 msec. Latencies declined to 3-4 msec for high frequency (greater than 20 kHz) units. After an ear had been deprived of sound from 10 days after birth, response latencies of units in the opposite colliculus with characteristic frequencies below about 10 kHz were comparable to controls, but most units above 10 kHz had latencies 2-3 times control latencies. Spike activity evoked in these units did not continue as long as that for most comparable control units. Ears sound deprived for an equal period from 60 days after birth also had changes in latencies and response durations, but these were much less than in the developmentally deprived. Latencies of gross potentials at the auditory nerve were not affected by early deprivation, indicating a central origin for the latency changes.

Acoustic Stimulation↗
PubMed1975

Serotonin-sensitive adenylate cyclase activity of immature rat brain.

Cell-free preparations from superior and inferior colliculi of very young rats (1-3 days old) contained adenylate cyclase systems which were highly responsive to serotonin. The response to serotonin declined markedly during early development and was very low at maturity. Adenylate cyclase activity in the 10,000 times g particulate fraction from colliculi of newborn rats was significantly stimulated by 0.05 muM serotonin. Half-maximal activation was produced with less than 1 muM serotonin. Maximal stimulation of collicular adenylate cyclase was about 80% above basal enzyme activity and occurred with approximately 50 muM serotonin. Tryptamine and several derivatives of serotonin produced responses which were comparable to that obtained with serotonin; 5-methoxytryptamine was uniformly the most active compound tested. Norepinephrine or dopamine produced much smaller increases in adenylate cyclase activity. Stimulation of collicular adenylate cyclase by serotonin was significantly but incompletely blocked by serotonin antagonists, including d-lysergic acid diethylamide (d-LSD), 2-bromo-d-lysergic acid diethylamide, methysergide, 1-methyl-8 beta-carbobenzyloxy-aminomethyl-10 alpha-ergoline and cyproheptadine. Chlorpromazine also produced partial blockade. In contrast, l-lysergic acid diethylamide, haloperidol, propranolol, phenoxybenzamine and morphine were ineffective as serotonin blocking agents. Of the compounds which produced a partial blockage of serotonin action, d-LSD, cyproheptadine and chlorpromazine were themselves capable of stimulating adenylate cyclase activity. These results are consisent with the existence of multiple receptors in rat brain which are capable of interacting with indoleamines.

5-Hydroxytryptophan↗
PubMed2005

Intercollicular commissural projections modulate neuronal responses in the inferior colliculus.

The right and left inferior colliculi (ICs) in the auditory midbrain are connected to one another by a bundle of fibres, the commissure of the IC. Previous studies show that this commissural projection connects corresponding frequency regions in the two sides and originates mainly from excitatory neurons, although some studies suggest a smaller number of GABAergic inhibitory neurons may also project via the commissure. Although the commissure of the IC is a major pathway connecting the most important nuclei of the auditory tectum, little is known about its functional significance. To investigate its role in auditory processing in the rat, we recorded sound-evoked responses of single neurons in one IC while injecting kynurenic acid into a corresponding region of the opposite IC. This procedure enabled us to block reversibly excitation of commissural projections to the recorded IC. The changes in the neural responses when input from the opposite IC was blocked are consistent with the commissural projection exerting both an excitatory and an inhibitory influence. The inhibition could be accounted for by monosynaptic or disynaptic connections. The responses to both monaural and binaural stimulation were affected, and the effects were proportionately greater at near-threshold sound levels. The results suggest that one function of the commissure of the IC may be to modulate the response gain of IC neurons to acoustic stimulation.

Acoustic Stimulation↗
PubMed1999

Input-output relationships of the dorsal nucleus of the lateral lemniscus: possible substrate for the processing of dynamic spatial cues.

One organizing principle of the auditory system is the progressive representation of best tuning frequency. Superimposed on this tonotopy are nucleotopic organizations, some of which are related to the processing of different spatial cues. In the present study, we correlated asymmetries in the outputs of the dorsal nucleus of the lateral lemniscus (DNLL) to the two inferior colliculi (ICs), with asymmetries in the inputs to DNLL from the two lateral superior olives (LSOs). The positions of DNLL neurons with crossed and uncrossed projections were plotted from cases with unilateral injections of retrograde tracers in the IC. We found an orderly dorsal-to-ventral progression to the output that recapitulated the tonotopy of DNLL. In addition, we found a nucleotopic organization in the ventral (high-frequency) part of DNLL. Neurons with projections to the ventromedial (high-frequency) part of the contralateral IC were preferentially located ventrolaterally in DNLL; those with projections to the ventromedial part of the ipsilateral IC were preferentially located ventromedially in DNLL. This partial segregation of outputs corresponded with a partial segregation of inputs from the two LSOs in cases which received closely matched bilateral injections of anterograde tracers in LSO. The ventral part of DNLL received a heavy projection medially from the opposite LSO and a heavy projection laterally from the ipsilateral LSO. The findings suggest a direct relationship in the ventral part of the DNLL between inputs from the two LSOs and outputs to the two ICs. Possible roles for this segregation of pathways in DNLL are discussed in relation to the processing of static and dynamic spatial cues.

Animals↗
PubMedDate not supplied

Superposition of binaural influences on single neuron activity in the medial superior olive elicited by electrical stimulation of the osseous spiral laminae.

The single unit response of medial superior olive (accessory nucleus) neurons was investigated, when elicited by electrical stimulation of nervous processes in the osseous spiral laminae in both cochleae and also by antidromic stimulation from the inferior colliculi. The osseous spiral laminae were stimulated at the first, second or third turns with grounding of one of the unstimulated turns. Time of signal arrival differences (delta tau) at the two cochleae and also intensity differences (deltai) were varied. (2) It is concluded that (A) binaural interaction in the MSO is not based on totally excitatory or inhibitory influences from either ear, but on cycles of excitation and inhibition; (B) these influences approximately obey the laws of superposition, i.e., the influences add linearly to determine discharge. (3) It is demonstrated that: (a) electrical stimulation, unlike acoustical stimulation, elicits a regular neural response; (b) the neural response functions elicited by changes in delta tau are deltai exhibit maxima and minima and are not smooth functions; (c) fine latency changes in the neural response are correlated with changes in delta tau and deltai; (d) the stimulation of different turns of the osseous spiral laminae (producing different current flows) elicits a different neural response depending on the turn stimulated, an effect reflecting the anatomical tonotopic arrangement of the medial superior olive; (e) changes in the stimulus differences delta tau and deltai are correlated with the ratio of the spike count in a short period following the stimulus, to the spike count in a longer total period; (f) changes in the stimulus differences delta tau and deltai elicit a neural response which varies according to the turn stimulated.

Animals↗
PubMed2003

The commissure of the inferior colliculus shapes frequency response areas in rat: an in vivo study using reversible blockade with microinjection of kynurenic acid.

The commissure of the inferior colliculus (CoIC) interconnects corresponding frequency-band laminae in the two inferior colliculi (ICs). Although the CoIC has been studied neurophysiologically in vitro, the effect of the CoIC on the responses of IC neurons to physiological stimuli has not been addressed. In this study, we injected the glutamate receptor blocker kynurenic acid into one IC while recording the frequency response areas (FRAs) of neurons in the other, to test the hypothesis that frequency response properties of IC neurons are influenced by commissural inputs from the contralateral IC. Following blockade of the commissure, 10 of 12 neurons tested exhibited an increase or a decrease in their FRAs. In most neurons (9/12) the response area changed in the same direction, irrespective of whether the neuron was stimulated monaurally (at the ear contralateral to the recorded IC) or binaurally. In one neuron, blockade of the CoIC resulted in an expansion of the response area under binaural stimulation and a contraction under monaural stimulation. In the remaining two units, no effect was observed. Changes in response areas that exceeded the criterion ranged between 17 and 80% of control values with monaural stimulation, and 35 and 77% with binaural stimulation. Area changes could also be accompanied by changes in spike rate and monotonicity. From our observation that FRAs contract following commissure block, we infer that the commissure contains excitatory fibres. The expansion of response areas in other cases, however, suggests that the commissure also contains inhibitory fibres, or that its effects are mediated by disynaptic as well as monosynaptic circuits. The small sample size precludes a definitive conclusion as to which effect predominates. We conclude that inputs from the contralateral IC projecting via the CoIC influence the spectral selectivity and response gain of neurons in the IC.

Acoustic Stimulation↗
PubMed1987

Distribution of somatostatinlike immunoreactivity in the brain of the little brown bat (Myotis lucifugus).

The distribution of somatostatinlike immunoreactive (SLI) perikarya, axons, and terminals was mapped in subcortical areas of the brain of the little brown bat, Myotis lucifugus, using light microscopic immunocytochemistry. A preponderance of immunoreactivity was localized in reticular, limbic, and hypothalamic areas including: 1) in the forebrain: the bed nucleus of the stria terminalis; lateral preoptic, dorsal, anterior, lateral and posterior hypothalamic areas; amygdaloid, periventricular, arcuate, supraoptic, suprachiasmatic, ventromedial, dorsomedial, paraventricular, lateral and medial mammillary, and lateral septal nuclei; the nucleus of the diagonal band of Broca and nucleus accumbens septi; 2) in the midbrain: the periaqueductal gray, interpeduncular, dorsal and ventral tegmental, pretectal, and Edinger-Westphal nuclei; and 3) in the hindbrain: the superior central and parabrachial nuclei, nucleus incertus, locus coeruleus, and nucleus reticularis gigantocellularis. Other areas containing SLI included the striatum (caudate nucleus and putamen), zona incerta, infundibulum, supramammillary and premammillary nuclei, medial and dorsal lateral geniculate nuclei, entopeduncular nucleus, lateral habenular nucleus, central medial thalamic nucleus, central tegmental field, linear and dorsal raphe nuclei, nucleus of Darkschewitsch, superior and inferior colliculi, nucleus ruber, substantia nigra, mesencephalic nucleus of V, inferior olivary nucleus, inferior central nucleus, nucleus prepositus, and deep cerebellar nuclei. While these results were similar in some respects to those previously reported in rodents, they also provided interesting contrasts.

Animals↗
PubMed1986

Autoradiographic localization of calcitonin gene-related peptide binding sites in human and rat brains.

125I-calcitonin gene-related peptide (CGRP) binding sites were mapped in the human brain and rat brains by in vitro macroautoradiography, and compared to each other. Binding experiments were made to characterize 125I-CGRP binding on the human and rat brains. Scatchard analysis of saturation experiments from slide-mounted sections of the human and rat cerebellum displayed 125I-CGRP binding sites with a dissociation constant (Kd) of 0.17 nM and 0.11 nM, respectively, and a maximal number of binding sites (Bmax) of 96.8 fmol/mg and 23.0 fmol/mg protein. 125I-CGRP binding was time-dependent, reversible and saturable with high affinity in the brains. Autoradiograms showed a discrete distribution of 125I-CGRP binding sites throughout the brains of human and rat with patterns similar to each other. In the human brain, the highest binding was seen in the cerebellum, inferior olivary nuclear complex, certain parts of the central gray matter, arcuate nuclei of the medulla oblongata and dorsal motor nucleus of the vagus, and densities of CGRP-binding sites were high in the nucleus accumbens, amygdala, tail of the nucleus caudatus, substantia nigra, ventral tegmental area, medial portion of the inferior colliculus, medial pontine nuclei, locus coeruleus, inferior vestibular nucleus, substantia gelatinosa of the spinal trigeminal nucleus, nucleus of the solitary tract and nucleus cuneatus lateralis. In the rat, high densities were found in the hippocampus pars anterior, nucleus accumbens, ventral and caudal portions of the nucleus caudatus-putamen, central and basolateral nuclei of the amygdala, caudal portion of the insular cortex, medial geniculate body, superior and inferior colliculi, certain portions of the central gray matter, locus coeruleus, inferior olivary nuclei, vagal complex, nucleus cuneatus lateralis and cerebellum. In contrast, in both species, most of the cortical areas including the hippocampus, most of the thalamus, and hypothalamus exhibited few binding sites. In addition, high quantities of the binding sites were seen on the pia mater and on walls of blood vessels in the brain and subarachnoidea. These results revealed essentially homologous locations of CGRP binding sites in the human and rat central nervous systems and well corresponding distributions of binding sites and endogenous CGRP-like immunoreactivity.

Aged↗
PubMed2004

Anticonvulsant effects of carbenoxolone in genetically epilepsy prone rats (GEPRs).

Carbenoxolone (CBX), the succinyl ester of glycyrrhetinic acid, is an inhibitor of gap junctional intercellular communication. Systemic administration of CBX was able to decrease the seizure severity score and to increase the latency time of seizure onset in genetically epilepsy prone rats (GEPRs). In particular, intravenous or intraperitoneal administration of carbenoxolone (5-30 mg/kg) produced a dose-dependent and significant reduction in the clonic and tonic phases of the audiogenic seizures in GEPRs. The anticonvulsant doses were not associated with an impairment of motor coordination. The bilateral microinjection of CBX (0.001-0.50 microg/0.5 microl) into the inferior colliculi, the substantia nigra (pars reticulata or compacta) and the inferior olivary complex was able to reduce the seizure severity score in a dose-dependent manner. The anticonvulsant effects were longer lasting after focal microinjection than after systemic administration. No anticonvulsant effects were observed following focal bilateral microinjections of glycyrrhizin into the same brain areas where CBX was shown to be effective.

Animals↗
PubMed1993

Central angiotensin IV binding sites: distribution and specificity in guinea pig brain.

Our laboratory has reported previously that a unique binding site specific for the hexapeptide angiotensin (A)II(3-8), now referred to as AIV, is present in a number of tissues including bovine adrenal gland, rabbit and guinea pig heart and guinea pig kidney, liver, lung, uterus and brain. The present results extend previous findings in the guinea pig brain and identify binding sites for AIV in the neocortex, paleocortex, hippocampus, medial habenula, superior and inferior colliculi, caudate putamen, thalamus, dorsal tegmentum, central gray, red nucleus, inferior olivary, oculomotor and hypoglossal nuclei and cerebellum. Binding of [125I]AIV in selected regions was shown to be of high affinity (Kd = 0.60-1.47 nM), saturable (maximal number of binding sites = 181-449 fmol/mg of protein) and specific. This binding site was shown to be distinct from the AT1 and AT2 sites with Ki values > 10(-4) M for DuP 753, CGP42112A and PD123177. Changes at the N-terminal of the peptide, either by removal of the valine or by extension of the peptide, resulted in a large decrease in binding affinity. In contrast, C-terminal extensions resulted in little change in affinity for the binding site. Guanosine 5'-0-(3-thiotriphosphate) was shown to have no effect on binding, suggesting that the guinea pig brain binding site is not G-protein-linked. Potential functions associated with this newly discovered A binding site are discussed.

Amino Acid Sequence↗
PubMed1994

Distribution of calbindin D-28k-immunoreactivity in the cat brainstem.

We studied the distribution of calbindin-immunoreactive fibers and cell bodies in the cat brainstem. The densest clusters of immunoreactive perikarya were found in the inferior and superior colliculi, the inferior olive, the periaqueductal gray, the central tegmental field and the substantia nigra, whereas the central linear nucleus, the locus coeruleus, the nucleus incertus, the dorsal and ventral nuclei of the lateral lemniscus, the cuneiform nucleus, the pontine gray, the Kölliker-Fuse nucleus, the dorsal motor nucleus of the vagus and the medial nucleus of the solitary tract had the lowest density. In the lateral tegmental field, the marginal nucleus of the brachium conjunctivum, the superior central nucleus, the nucleus sagulum, the dorsal nucleus of the raphe, the interpeduncular nucleus and the retrorubral nucleus the density of immunoreactive cell bodies was moderate. A high density of immunoreactive fibers was observed in the substantia nigra, the nucleus ruber, the superior and inferior colliculi, the periaqueductal gray, the interpeduncular nucleus, the central, magnocellular and lateral tegmental fields, the marginal nucleus of the brachium conjunctivum, the postpyramidal nucleus of the raphe, the inferior olive, the internal division of the lateral reticular nucleus and the medial and lateral nuclei of the superior olive. A moderate density of calbindin-immunoreactive fibers was found in the retrorubral nucleus, the central linear nucleus, the locus coeruleus, the nucleus sagulum, the dorsal nucleus of the raphe, the cuneiform nucleus, the ventral and dorsal nuclei of the lateral lemniscus, the medial nucleus of the solitary tract, the dorsal motor nucleus of the vagus, and the cuneate nucleus. Other brainstem regions such as the area postrema, the external division of the lateral reticular nucleus, the nucleus ambiguus, the nucleus intercalatus, the nucleus incertus, the pyramidal tract and the trapezoid body had the lowest density of immunoreactive fibers.

Animals↗
PubMed1981

On the localization and mediation of the centrally induced hyperactive urinary bladder response to L-dopa in the rat.

The hyperactive bladder response observed after central adrenergic stimulation with L-dopa, following enzymatic blockade of its peripheral metabolism, was studied in the rat. The bladder response was recorded by a cystometric procedure. The hyperactive bladder action thus produced was noted after transection of the CNS at the level of the superior colliculi but not when the transection was made caudal to the inferior colliculi. No effect was seen after transection of the cauda equina at L6, i.e. parasympathetic decentralisation of the bladder. It is concluded that the hyperactive bladder reaction seen after central adrenergic stimulation is produced in the mesencephalic-pontine region and mediated to the bladder via a central coupling to parasympathetic pathways.

Animals↗
PubMed1976

[Linear dimensions of the lamina of the tectum mesencephali during human ontogenesis].

The dynamics of the establishment of linear dimensions of the lamina of tectum mesencephali in ontogenesis was studied in 145 preparations of human brain. The investigation was performed with by the M. M. Sauliak-Savitskaja apparatus (1953). The obtained data were processed by the method of mathematical analysis. The relief of the superior colliculi was found to be formed earlier than that of the inferior colliculi. The linear dimensions of both colliculi are practically equal to those of adult men during the third year of life. No correlative relationship between the sex of the objects under study and the linear dimensions of the lamina of tectum mesencephali was found as well as between thr right and left parts of the lamina tecti. The linear dimensions of it in all age groups are very variable.

Adolescent↗
PubMed2002

Fos expression in GABAergic cells and cells immunopositive for NMDA receptors in the inferior and superior colliculi following audiogenic seizures in rats.

Given the evidence that the inferior colliculus (IC) and superior colliculus (SC) seem to play key roles in connecting auditory pathways and seizure output pathways in the neuronal network for audiogenic seizures (AS) in rats, we examined Fos activation in GABAergic cells and cells immunopositive for glutamate N-methyl-D-aspartate (NMDA) receptors in the IC and SC following AS using the double-labeling procedure. Generalized tonic-clonic seizures (GTCS), which developed as an advanced form of AS in some of the susceptible rats, induced an increase in Fos expression in three IC substructures-the dorsal cortex of IC (DCIC), central nucleus of IC (CIC), and external cortex of IC (ECIC)-and in one SC substructure, the deep gray layer of SC (DpG). Compared with the rats showing GTCS, rats exhibiting wild running (WR) without proceeding to GTCS showed a different pattern of AS-induced Fos expression. The DpG in the WR animals showed no significant increase in the levels of Fos-like immunoreactivity. The degrees of Fos activation that occurred in GABAergic cells and cells immunopositive for NMDA receptors were similar in the DCIC, CIC, ECIC, and DpG following AS. These results suggest that Fos activation in the DpG is involved in the development from WR to GTCS in AS-susceptible rats. They also provide some evidence that some GABAergic neurons in the IC and SC and glutamatergic afferents (via NMDA receptors) to these structures are activated by AS.

Acoustic Stimulation↗
PubMed1994

Tectal plate gliomas. Part I: Microsurgery of the tectal plate gliomas.

A series of 12 patients with tectal plate gliomas, is presented treated by direct surgery. Mean age was 19 years. All patients presented with signs of raised intracranial pressure and supratentorial hydrocephalus on CT scan. Diplopia was the most common local sign. CT scan and MR imaging showed 4 intrinsic, 6 exophytic, and 2 ventrally infiltrating tectal tumours. The histological diagnosis was low-grade astrocytoma in 7, high-grade astrocytoma in 2, oligodendroglioma in one, oligo-astrocytoma in one, and ependymoma in one case. The suboccipital supra- and transtentorial approach was used in every cases. Tumour resection was generous at the level of the superior colliculi, but on the contrary, resection was limited at the level of inferior colliculi due to the auditory risk. Tumour removal was total (macroscopically) in 9 cases and partial in 3 cases. There were 4 surgical complications and one death related to surgery. Parinaud's syndrome was the most-common postoperative sequelae. Auditory hallucinations and the acoustic neglect syndrome were seen once. In three cases additional radiotherapy and chemotherapy were given once with severe sequelae. The treatment of tectal plate gliomas is controversial. The role of different therapeutic options remains open. We consider the tectal plate as a relatively safer territory for surgery than the ventral part of the midbrain. The brain stem auditory evoked potentials (BAEPs) and middle latency potentials (MLPs) monitoring can help to determine the appropriate limit of surgery.

Adolescent↗