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PubMed1974

Septal tryptophan-5-hydroxylase: divergent response to raphe lesions and parachlorophenylalanine.

A soluble form of tryptophan-5-hydroxylase activity was found to be present in areas rich in serotonergic terminals (colliculi, hippocampus, septal area, and remaining telencephalon) as well as in brainstem, an area rich in cell bodies. The enzymatic activity in all brain regions, except the septal area, was inhibited to varying degrees following administration of parachlorophenylalanine. Destruction of the raphe nuclei in the midbrain led to a large and comparable decrease in both serotonin content and tryptophan hydroxylase activity of the hippocampus. In contrast, these lesions did not significantly affect the enzymatic activity of the septal area although the serotonin content was decreased by 72 percent. These findings suggest that the major portion of the tryptophan hydroxylase activity of the septal area is uniquely different from that found in other telencephalic areas in that it is not localized in serotonergic nerve terminals nor is it inhibited by parachlorophenylalanine.

Animals↗
PubMed1976

[Characteristics of the reactions of neurons of successive links in the auditory pathway to changes in the timing of acoustic signals].

Afferent impulsation was compared for different levels of the auditory system: the cochlear nuclei, posterior colliculi, and the auditory cortex. While moving from the cochlear nuclei over to the posterior colliculi and the auditory cortex, the number of neurons describing the temporal structure of the amplitude-modulated signal's envelope in the impulse activity pattern, becomes sharply reduced; the number of neurons selectively responding to certain phases of the envelope increases; the firing rate of neurons of the auditory pathway's higher levels decreases; the repetition rates becomes narrow due to limitation from both the high- and the low-frequency sides. Selectivity of responses to combination of such signal parameters as the frequency of the carrier and the rhythm of the amplitude modulation, increases. Specificity of the neuronal responses increases on certain combinations of such parameters of the frequency-modulated sounds as the frequency range in the signal, the direction and speed of the frequency modulation. The data obtained revealed some general tendencies of the impulsation transformation in successive levels of the auditory pathway.

Animals↗
PubMed1977

Anoxic-ischemic encephalopathy in the human neonatal period. The significance of brain stem involvement.

Although the human brain stem is considered relatively invulnerable to ischemic anoxia, evaluation of 16 cases of a single acute asphyxial episode either at or following birth indicates that such involvement is a frequent and characteristic aspect of anoxic encephalopathy in the infant. Ischemic cell change, neuronal loss, and nuclear or reticular formation gliosis were present in the brain stem of all but one infant. At least two topographic patterns of anoxic encephalopathy exist: (1) a rostrocaudal pattern of decreasing vulnerability, with the cerebral cortex being most sensitive and the brain stem least sensitive, and (2) a pattern of brain stem and thalamic damage. Of the two, the latter pattern appears to follow most acute asphyxial episodes in the human neonate and infant.

Adolescent↗
PubMed1979

Brain stem auditory evoked responses: studies of waveform variations in 50 normal human subjects.

Brain stem auditory evoked responses (BAERs) were recorded in 50 normal adult subjects at various click rates. Attention was paid to absolute latencies, interwave latencies, interear interwave latencies, absolute amplitudes, and various amplitude ratios. The variability of waves VI and VII suggests that the clinical utility of these waves is restricted-their absence is not necessarily due to a CNS lesion. The wave IV-V complex appears with six different patterns. These variations must therefore be considered normal; none should be misconstrued as indicative of disease of the CNS. Repeated studies over a period of two to nine months showed no statistically significant changes in amplitude or latency measurements with the passage of time. Knowledge of these normal values and their variations, as a precondition for establishing criteria for abnormality, is essential to the interpretation of BAERs in clinical situations.

Acoustic Stimulation↗
PubMed2001

Measurement of the midbrain diameter on routine magnetic resonance imaging: a simple and accurate method of differentiating between Parkinson disease and progressive supranuclear palsy.

Anteroposterior diameters of the suprapontine midbrain, the pons, and the collicular plate were measured in 50 patients with various parkinsonian syndromes (Parkinson disease [PD] [n = 20], progressive supranuclear palsy [PSP] [n = 16], and multiple-system atrophy of striatonigral type [n = 14]) and 12 age-matched healthy control subjects by means of axial T2-weighted magnetic resonance images. While no differences in midbrain diameter were found between patients with PD (mean, 18.5 mm) and control subjects (mean, 18.2 mm), patients with PSP had significantly lower midbrain diameters (mean, 13.4 mm) than patients with PD and control subjects (P<.001), without any overlap between these 2 groups. However, midbrain diameters of patients with multiple-system atrophy were also significantly lower than those of control subjects and patients with PD, with individual values showing overlap with the PSP, PD, and control groups. Pontine and collicular plate diameters did not contribute additional information. We therefore conclude that measurement of anteroposterior diameter of the midbrain on axial T2-weighted magnetic resonance images is a reliable means to differentiate patients with PSP from those with PD and should be incorporated into the diagnostic criteria for PSP.

Aged↗
PubMed1981

Binaural interaction components. Their possible origins in guinea pig auditory brainstem response.

A two-step ablation technique under visual control was used to clarify the possible sites of origin of the binaural interaction component (BIC) of the auditory brainstem-evoked response (ABR). The BIC is obtained by summing ABRs elicited by monaural clicks to each ear and subtracting this sum from the ABR elicited by binaural clicks. Among the results were the following: first, the ABR and the BIC remained virtually unchanged after collicular aspiration; second, after midsagittal section of the brainstem, both wave III in the ABR and the BIC were abolished. These results suggest that although the inferior colliculus is a powerful integrative center for the processing of binaural signals, the neural structures in the guinea pig necessary for the primary generation of the BIC must be located caudal to the colliculus, yet rostral to the medial nucleus of the trapezoid body.

Animals↗
PubMed1975

Echolalic speech in childhood autism. Consideration of possible underlying loci of brain damage.

The speech of echolalic autistic children is (1) specifically lacking in appropriate use of expressive-intonational features, but (2) the echolalic child's clear articulation of words and phrases indicates that discrimination of phonemic features is intact. The impairment in aphasic disorders is just the reverse. Failure to attend to auditory stimuli and the characteristic language disorder are among the most consistent findings in autistic children; they could be related. Discrimination of differential stress emphasis is the way the normal young child extracts major morphemic word stems and syntactic features from environmental speech; this may be a primitive perceptual function of brain stem auditory centers. The brain stem auditory system is especially vulnerable to perinatal injury. Damage to this system is an example of the kind of lesion that might lead to behavioral handicaps without neurological signs.

Animals↗
PubMed1996

Common patterns of increased and decreased fos expression in midbrain and pons evoked by noxious deep somatic and noxious visceral manipulations in the rat.

Immunohistochemical detection of the protein product (Fos) of the c-fos immediate early gene was used to study neuronal activation in the rostral pons and midbrain of halothane-anesthetised rats following noxious deep somatic or noxious visceral stimulation. In animals exposed only to halothane anesthesia, Fos-like immunoreactive (IR) neurons were located in the midbrain periaqueductal gray matter, tectum, and parabrachial nucleus. Following noxious stimulation of hindlimb muscle, knee joint, vagal cardiopulmonary, or peritoneal nociceptors, there was, compared to halothane-only animals, a significant increase in the numbers of Fos-like (IR) cells in the caudal ventrolateral periaqueductal gray and the intermediate gray lamina of the superior colliculus. Given the general agreement that increased Fos expression is a consequence of increased neuronal activity, the finding that a range of noxious deep somatic and noxious visceral stimuli evoked increased neuronal activity in a discrete, caudal ventrolateral periaqueductal gray region is consistent with previous suggestions that this region is an integrator of deep noxious evoked reactions. The noxious deep somatic and noxious visceral manipulations also evoked, compared to halothane-only animals, reductions in the numbers of Fos-like IR cells in the stratum opticum of the superior colliculus and the unlaminated portion of the external subnucleus of the inferior colliculus. To our knowledge this is the first report of reductions in Fos-expression in the tectum evoked by noxious stimulation. In separate experiments, the effects of noxious deep somatic and noxious visceral manipulations on arterial pressure and heart rate were measured. The noxious visceral manipulations evoked substantial and sustained falls in arterial pressure (15-45 mmHg), and heart rate (75-100 bpm), whereas the depressor and bradycardiac effects of the noxious deep somatic manipulations were weaker, not as sustained, or entirely absent. As similar distributions and numbers of both increased and decreased Fos-like IR cells were observed after each of the deep noxious manipulations, it follows that the deep noxious evoked increases and decreases in Fos expression were not secondary to the evoked depressor or bradycardiac effects.

Animals↗
PubMed1996

Distribution of the calcium-binding proteins parvalbumin and calretinin in the auditory brainstem of adult and developing rats.

Parvalbumin (PV), calretinin (CR), and calbindin (CB) are calcium-binding proteins which are presumably involved in the regulation of the intracellular calcium concentration. Within the rat auditory system, CB is transiently expressed in several nuclei during the period of synapse refinement, indicating a specific function of CB during development, yet little is known in this regard about PV and CR. In order to gather more information about calcium-binding proteins during development, we analyzed the spatiotemporal distribution of PV and CR in the rat auditory brainstem using immunocytochemistry. In the adult, PV was heavily present in somata and neuropil of all nuclei and in fibers of all tracts. CR was found in somata of the cochlear nucleus and peripheral aspects of the inferior colliculus as well as in fibers extending into the superior olivary complex and the nuclei of the lateral lemniscus. The developmental expression of PV was characterized by a relatively late appearance in somata (at postnatal day 8), followed by a rapid increase to adult levels. In contrast, CR immunoreactivity was already strong two days before birth, yet the number and intensity of labeled neurons subsequently decreased and CR disappeared almost completely in the superior olivary complex, nuclei of the lateral lemniscus, and central aspects of the inferior colliculus. These data, together with those on CB, show that CR, CB, and PV are sequentially expressed during auditory brainstem development. They also suggest that the presence of the three proteins can be correlated with definite developmental stages.

Aging↗
PubMed1996

Transient retinal ganglion cells in the developing rat are characterized by specific morphological properties.

To determine whether dendritic development of mammalian retinal ganglion cells (RGCs) is affected by axonal target specificity, the morphology of three populations of maturing RGCs was examined. These included RGCs that exhibited either a transient, topographically incorrect, projection to the caudal superior colliculus (SC), or a transient projection to the caudal inferior colliculus (IC), in addition to a control group that exhibited a topographically correct projection to the caudal SC. Projection populations were identified by retrograde transport of rhodamine labeled latex microspheres injected into target nuclei. Labeled RGCs were then injected in vitro with Lucifer yellow to reveal the details of their dendritic morphology. Retinal ganglion cells making target errors, most of which ultimately die, were found to undergo a remarkable degree of morphological differentiation and could be categorized according to the adult type I, II, or III criteria. However, the relative proportions of these cell types were different among RGCs making transient connections versus those whose projections were preserved. Approximately half of the RGCs making topographically incorrect projections to the SC belonged to type III, in contrast to 6% that made a topographically correct projection. In addition, the population of cells sending axons to caudal IC did not include type III RGCs, but consisted of small type II neurons. The development of the basic dendritic form of each RGC type was only modestly influenced by its projection pattern; dendritic trees of cells making transient projections were essentially normal with only a slight, but statistically significant, reduction in dimensions. Moreover, dendritic remodeling was evident during maturation of neurons making either transient or normal projections. Together, these findings indicate that target specificity plays a relatively minor role on dendritic development of retinal ganglion cells.

Animals↗
PubMed1996

Distribution of GABAA, GABAB, and glycine receptors in the central auditory system of the big brown bat, Eptesicus fuscus.

Quantitative autoradiographic techniques were used to compare the distribution of GABAA, GABAB, and glycine receptors in the subcortical auditory pathway of the big brown bat, Eptesicus fuscus. For GABAA receptors, the ligand used was 35S-t-butylbicyclophosphorothionate (TBPS) for GABAB receptors, 3H-GABA was used as a ligand in the presence of isoguvacine to block binding to GABAA sites; for glycine, the ligand used was 3H-strychnine. In the subcortical auditory nuclei there appears to be at least a partial complementarity in the distribution of GABAA receptors labeled with 35S-TBPS and glycine receptors labeled with 3H-strychnine, GABAA receptors were concentrated mainly in the inferior colliculus (IC) and medial geniculate nucleus, whereas glycine receptors were concentrated mainly in nuclei below the level of the IC. Within the IC, there was a graded spatial distribution of 35S-TBPS binding; the most dense labeling was in the dorsomedial region, but very sparse labeling was observed in the ventrolateral region. There was also a graded spatial distribution of 3H-strychnine binding. The most dense labeling was in the ventral and lateral regions and the weakest labeling was in the dorsomedial region. Thus, in the IC, the distribution of 35S-TBPS was complementary to that of 3H-strychnine. GABAB receptors were distributed at a low level throughout the subcortical auditory nuclei, but were most prominent in the dorsomedial part of the IC.

Animals↗