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Biomedical subjects

H Bantli

Publications and source records attributed to H Bantli.

At least 19 recordsLinked to original sources
PubMed1980

Effects of cerebellar stimulation on unitary activity within a chronic epileptic focus in a primate.

Experiments were performed in unanesthetized awake monkeys to determine the effects of cerebellar stimulation on the activity of single cells within a chronic alumina cream seizure focus in the motor cortex. Six indices were used to characterize the epileptic and non-epileptic activity of the neurons within the focus. Cerebellar stimulation did not produce any statistically significant effect on these indices. This was partly due to large fluctuations in these parameters which occurred independent of the stimulus. Therefore it was concluded that these negative results were due to the intrinsic variability in these parameters and that an evaluation of cerebellar stimulation based on these indices was not adequate. Therefore, cross-correlation analysis was used to examine the effects of cerebellar stimulation on the excitability of neurons within the focus. This technique demonstrated that cerebellar stimulation modulated neuronal activity in the focus with 3 different profiles. These alterations in excitability were similar during the occurrence of either epileptic or non-epileptic activity in a single neuron. These results show that cerebellar stimulation can increase and decrease the excitability of neurons in an experimental seizure focus during both epileptic and non-epileptic activity.

Action Potentials↗
PubMed1979

An HRP and autoradiographic study of cerebellar corticonuclear-nucleocortical reciprocity in the monkey.

Combined injections of 3H-leucine and HRP were made into the monkey cerebellar cortex in order to identify any reciprocal connections between the corticonuclear and the nucleocortical pathways. These combined intraaxonal labeling experiments have demonstrated a considerable overlap of orthogradely labeled Purkinje cell axons and terminals with retrogradely labeled HRP-positive neurons in the ventrolateral region of the dentate nucleus following combined injections into the lateral hemisphere, and in the dorsal area of the dentate following combined injections into medial cortical areas of the anterior lobe. There were also areas within the deep cerebellar nuclei where orthogradely labeled corticonuclear terminals did not overlap with retrogradely labeled nucleocortical neurons.

Animals↗
PubMed1978

Organizational features of the cat and monkey cerebellar nucleocortical projection.

The organization of the cerebellar nucleocortical projection in the cat and the monkey has been studied using orthograde and retrograde neuroanatomical tracing techniques. Injections of tritiated leucine in the cat cerebellar nuclei orthogradely labeled nucleocortical fibers throughout their course to the cerebellar cortex. Their branch points in the corpus medullare, in the folial white matter, and in the granular layer were evident from the dense, continuous distribution of silver grains overlying these labeled axons. The results from the cat showed that the cerebellar nucleocortical projection is organized principally into three rostrocaudally oriented longitudinal cortical zones. Fastigial nucleocortical fibers were directed principally to the medial 1.5-2.5 mm of the ipsilateral vermis, with a lighter projection to the lateral vermis ipsilaterally and to the medial area of the vermis contralaterally. The interposed nuclei projected mainly to the paravermis-medial hemispheric zone of the cerebellar cortex. Nucleocortical fibers from the posterior interposed nucleus projected principally to the paramedian lobule, to the medial hemispheric area of Crus I and the lobus simplex, and to the flocculus and paraflocculus. Nucleocortical projections from the anterior interposed nucleus coursed to the anterior lobe paravermis and to the ventral folia of the paramedian lobule. A lighter projection from the interposed nuceli was found to the lateral edge of the vermis and into intermediate areas of the hemisphere. Dentatocortical fibers were directed into the lateral folia of Crus I and Crus II of the lateral hemispheric zone, with a ligher projection to intermediate areas of the hemisphere of the posterior lobe and along the lateral edge of the anterior lobe hemisphere. Along the periphery of each cortical zone, the nucleocortical projection from adjacent deep nuclei overlapped slightly. The retrograde transport of horseradish peroxidase (HRP) from injection sites in the lateral hemisphere, in the medial hemisphere--paravermis, and in the vermis labeled neurons localized mainly within the dentate, interposed, and fastigial nuclei, respectively. Retrograde labeling experiments carried out in monkeys indicated that the organization of the nucleocortical projection in this species is different than that of the cat. In the primate, the nucleocortical projection to the lateral hemisphere, to the medial hemisphere--paravermis, and to the vermis appeared to arise principally from the dentate nucleus. There was a secondary input to the paravermis and vermis arising from the interposed and fastigial nuclei, respectively. This evidence suggests that the cerebellar nucleocortical system undergoes a significant phylogenetic change in its organization between the cat and primate. These organization differences are discussed in light of possible functional implications.

Animals↗
PubMed1978

Multiple branching of cerebellar efferent projections in cats.

The retrograde labeling of neurons in the deep cerebellar nuclei with horseradish peroxidase was used to compare the morphological characteristics of neurons in the dentate and interposed nuclei projecting in the cerebellothalamic, cerebello-olivary, and cerebellar nucleocortical pathways. The results from these studies demonstrated that cerebellothalamic and nucleocortical projections from the dentate and interposed nuclei originate from similar populations of spindle- and multipolar-shaped neurons with somal diameters throughout the range of cells present in the deep nuclei. However, only spindle-shaped neurons with somal diameters of 9--15 microns project in the cerebello-olivary pathway. From these anatomical studies, it was concluded that some of the neurons in the dentate and interposed nuclei which project to the thalamus, inferior olive, and cerebellar cortex have similar morphological characteristics. Electrophysiological experiments were carried out to investigate whether or not some of these neurons project to all three sites viaaxon collaterals. From stimulus sites in the thalamus, inferior olive, and cerebellar cortex, numerous neurons were antidromically activated in the cerebellar nuclei. Collision experiments between these antidromic responses confirmed that single neurons projected to all three of these sites. These studies therefore demonstrate that the axons of some neurons in the dentate and interposed nuclei have collateral branches in both the ascending and descending limbs of the brachium conjunctivum as well as in the cerebellar nucleocortical pathway. Functional implications of the collateral branching of cerebellar efferent projections are discussed.

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PubMed1977

The intracerebellar nucleocortical projection in a primate.

Experiments were performed to determine if a nucleocortical system, a projection from the cerebellar nuclei to the cerebellar cortex, was present in primates. Both electrophysiological and neuroanatomical techniques were employed to investigate this question. It was shown that neurons within the dentate and interposed nuclei were antidromically activated by stimuli applied to the cerebellar cortex. In addition, cells in these nuclei were retrogradely labelled following injections of small amounts of horseradish peroxidase in the cerebellar cortex. The injection of tritiated leucine in the deep nuclei resulted in the labelling of fibers projecting from these structures to the cerebellar cortex which appeared to terminate within the granular layer. Additional electrophysiological studies showed that neurons projecting to the cerebellar cortex could also be antidromically activated from the ventrolateral thalamic nucleus, indicating that the nucleocortical projection in the primate arises at least in part as collaterals from neurons in the deep cerebellar nuclei which also project to extracerebellar structures, as was shown in the cat.

Action Potentials↗
PubMed1976

Characteristics of the output from the dentate nucleus to spinal neurons via pathways which do not involve the primary sensorimotor cortex.

Experiments were performed to determine the action of the dentate output on neurons in the spinal cord mediated by pathways which do not involve the primary sensorimotor and premotor cortices. The dentate nucleus was electrically stimulated by stereotaxically placed electrodes in Rhesus monkeys whose contralateral sensorimotor and premotor cortices were ablated. The resultant changes in excitability of lumbar alpha motorneurons activated by Ia afferents from nerves innervating femoral, hamstring, gastrocnemius-soleus and peroneal muscles were measured by intracellular recordings and by determining the percent change in the amplitude of the monosynaptic reflex recorded from ventral roots. The effect of stimulation of the dentate nucleus on proprioceptive reflexes was determined by recording the changes in postsynaptic potentials evoked by selective stimulation of Ia and Ib afferent fibers. The results demonstrated that dentate nucleus exerts a significant action on the excitability of spinal neurons via pathways which do not include the sensorimotor and premotor cortices. Whether the dentate stimulus produced an increase or decrease in the excitability of these neurons was dependent upon the site within the dentate nucleus at which the stimulus was applied, demonstrating that, in the decorticate preparation, the output from this nucleus is quite heterogeneous. In addition, stimulation of the dentate nucleus in these monkeys did not affect the Ia reflex pathway but significantly changed the amplitude of the inhibitory postsynaptic potential evoked by Ib afferents in lumbar alpha motorneurons.

Animals↗
PubMed1976

Anatomical and physiological evidence for a cerebellar nucleo-cortical projection in the cat.

Combined neuroanatomical and electrophysiological experiments were performed to test the hypothesis that axon collaterals of neurons in the cerebellar nuclei project to the cerebellar cortex in cats. The anatomical studies demonstrated that (a) following the injection of tritiated leucine into the deep cerebellar nuclei, labeled fibers could be traced into the granular layer of the cerebellar cortex, and (b) following the injection of horseradish peroxidase into the cerebellar cortex, retrogradely labeled horseradish peroxidase-positive neurons were identified in the deep nuclei. The electrophysiological experiments confirmed the anatomical findings. Neurons in the dentate and interposed nuclei, identified by their antidromic activation from the brachium conjunctivum, could also be activated antidromically from the cerebellar surface. Collision experiments demonstrated that projections from the deep cerebellar nuclei to the cerebellar cortex are in part collaterals of efferent neurons projecting through the brachium conjunctivum. Care was taken to ensure that all recordings were obtained from the region of cell somata in order to minimize the likelihood of recording from neuronal elements passing through the cerebellar nuclei. These combined neuroanatomical and electrophysiological studies provide strong evidence supporting the existence of a collateral system from cerebellar output neurons to the cerebellar cortex. The existence of this collateral system emphasizes that the cerebellar cortex and cerebellar nuclei may comprise a functional unit in which these collaterals may serve as a substrate for feedback control of the cerebellar cortex by the cerebellar output.

Action Potentials↗
PubMed1976

Activation of neurons in the cerebellar nuclei and ascending reticular formation by stimulation of the cerebellar surface.

Electrical stimulation of the cerebellar surface has been used therapeutically for the control of certain epileptic seizure and motor disorders. Recent hypotheses suggest that the therapeutic results in the treatment of epilepsy might be a consequence of the activation of Purkinje cells which subsequently inhibit the epileptic activity in the cerebrocellular loop. These experiments establish that an anatomical substrate exists whereby the effects of stimulating the cerebellar surface might be mediated by the ascending reticular formation and the non-specific thalamic nuclei. Specifically, the stimulation of the cerebellar surface activates not only Purkinje cells but also cerebellar afferent systems, climbing fibers and mossy fibers, and neurons in the cerebellar nuclei and reticular formation. In addition, recordings from neurons in the ascending reticular formation suggest that stimulation of the cerebellar surface can affect processing of ascending sensory information, thus influencing neural integration of non-specific sensory system.

Afferent Pathways↗
PubMed1975

Monosynaptic activation of a direct reticulo-spinal pathway by the dentate nucleus.

Experiments were performed to test the hypothesis that the output of the dentate nucleus can affect the excitability of spinal neurons via the reticular formation. In the first group of studies, the response of neurons in the medial reticular formation to stimulation of the dentate nucleus was investigated. In the second set of experiments, stimuli were applied in the same region of the medial reticular formation in order to determine whether neurons in the dentate nucleus could be antidromically activated from this part of the brainstem. The results indicate that the output from the dentate nucleus monosynaptically activates medial reticular neurons which project to the spinal cord. This finding, together with the observation that stimulation of the medial reticular formation can antidromically activate neurons in the dentate nucleus, demonstrates that there is an anatomical substrate by which the dentate nucleus can affect the excitability of spinal neurons via a rapidly conducting reticulospinal pathway.

Animals↗
PubMed1975

Effect of delayed local cooling on experimental spinal cord injury.

The authors report studies indicating that delayed local cooling is effective in minimizing the neurological deficits of experimental spinal cord injury in cats. Cortical evoked responses were useful in predicting the neurological outcome; untreated animals whose evoked response disappeared for 6 hours failed to recover whereas all treated animals in the same group recovered dramatically. Decompression by laminectomy alone proved ineffective. Possible explanations for the therapeutic effects of cooling and the significance of the delay are briefly discussed.

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