Subcortical Neurons Research Articles

Ultrastructure of neurofibrillary tangles in progressive supranuclear palsy.

Ultrastructure of neurofibrillary tangles was investigated on the subcortical neurons of an autopsy case of progressive supranuclear palsy. The patient was a 64-year-old female and suffered from her illness for 9 years. Two kinds of ultrastructure were observed in the subcortical neurofibrillary tangles, i.e. that 150 A straight tubules and the 220 A twisted tubules. They appeared separately in each neuron and a transition between these two structures could not be remarked. Besides, a few particles with a paracrystalline hexagonal structure were observed in some subcortical neurons.

On the development of non-pyramidal neurons and axons outside the cortical plate: the early marginal zone as a pallial anlage.

The development of non-pyramidal neurons was studied in the pallium of albino rats using autoradiography after thymidine labelling (determination of “birth dates”), Golgi impregnations (differentiation of dendrites and axons) and electron microscopy including 3D-reconstructions (cytoplasmic differentiation and early synaptogenesis). The marginal zone appears between E13 and E14 and contains glial cells, axons and preneurons from the beginning. The latter can be identified by structural criteria (contacts, cytoplasm, nuclei). The first vertically oriented pyramidal neurons (cortical plate) appear within the marginal zone not before E16, separating its contents into a superficial (lamina I) and a deep portion (intermediate and subventricular zone). Since this old neuronal population of lamina I and the subcortical pallial region can be followed until adulthood, it is proposed to call the early marginal zone a “pallial anlage”. It can be demonstrated that during the whole period of neuron production (until E21) non-pyramidal neurons are added to all parts of the “pallial anlage”. The structural differentiation of non-plate neurons is described. Neurons form specific, desmosome-like contacts with axonal growth cones already on E14. Typical synapses (vesicle aggregations) have been observed two days later. In lamina I two types of neurons develop: horizontal neurons (Cajal-Retzius cells) and multipolar neurons (small spiny stellate cells). Subcortical pallial neurons retain mostly their clear horizontal orientation. Only neurons situated very close to the lower border of the cortex show dendritic branches extending into lamina VI. Axons appearing early in the neocortex originate not only from subcortical regions, but also from neurons of the paleopallium, the archicortex, the limbic cortex and the neighbouring neocortex. The tangential growth of the neocortex, as estimated from E14 onwards causes a strong dilution of the elements of the “pallial anlage” until adulthood. The classification of neurons outside the cortical plate and the fate of the total “pallial anlage” are discussed. As a consequence of these observations some modifications of the terminology of the Boulder Committee are proposed.

Long term recording from cortical and subcortical neurons in unrestrained cats

A system for obtaining chronic unit recording from cortical and subcortical neurons in unrestrained cats is described. This system has been used and tested in a population of trained animals for several years, and possesses the following major advantages: the microelectrode may be easily changed in the event that it becomes damaged or if a longer traverse is desired; it has proved feasible to maintain stable records from the same population of cells for as long as 14 days; the electrode can be moved through the brain of the conscious animal, affording the opportunity to map a large number of different cells in the same individual. Details of the construction of reliable glass-insulated platinum-iridium microelectrodes are presented.

Modulation of cortical and pyramidal tract induced motor responses by electrical stimulation of the basal ganglia

Two general mechanisms based on anatomical studies are possible for modulation of motor activity by the caudate nucleus and globus pallidus. These mechanisms are: (1) modulation of the output of cortical neurons that exert motor influences; and (2) modulation of subcortical neurons that exert motor influences. Differentiation between these two mechanisms was accomplished in the present study by two experimental approaches, both of which employed the conditioning-test paradigm. The first approach was an investigation of caudate nucleus or globus pallidus modulation (conditioning stimulus) of flexor responses of the anterior tibialis muscle elicited by electrical stimulation of the sensorimotor cortex (test stimulus) or pyramidal tract (test stimulus). These investigations were carried out in the intact and in decorticate cats. The second approach was an analysis of modulation of cortically induced pyramidal tract responses (direct and indirect, D-I potentials) by conditioning shock trains delivered to various loci within the caudate nucleus or globus pallidus. Both approaches were designed to determine which inhibitory and facilitatory motor influences of the basal ganglia occured at a cortical or subcortical level. Simultaneous stimulation of a locus within the caudate nucleus and the sensorimotor cortex evoked either an enhancement, reduction or no alteration of the cortically induced increase in flexor responses (measured by Ia afferent activity, EMG, myogram). In contrast, no inhibitory influences occurred from caudate nucleus stimulation upon pyramidal tract induced flexor responses in either the intact or decorticate preparation. Inhibitory loci were distributed toward the rostral portion of the caudate nucleus, whereas facilitatory loci were distributed throughout; this distribution was statistally sigificant (X 2; P < 0.01). Only enhancement or no influence upon cortical induced or pyramidal tract induced responses were obtained by conditioning stimuli to the globus pallidus. In the unanesthetized but immobilized cat, trains of shocks delivered to the caudate nucleus enhanced, reduced or had no influence upon the cortically evoked direct (D) and indirect (I) potentials recorded in the bulbar pyramidal tract. The distribution of facilitatory and inhibitory loci was organized in a similar fashion as in the anesthetized preparation. From these observations, a model was proposed in which the output of the caudate nucleus exerts both facilitatory or inhibitory modulation of the tonically active globus pallidus cells. The latter in turn predominantly or exclusively facilitate output of pyramidal tract neurons as well as the output of subcortical structures; both effects facilitate motor responses at the spinal level.

Effect of electrical stimulation on activity of neuron populations of human subcortical brain structures

Tests were carried out on patients with parkinsonism treated by the method of long-stay implanted electrodes. The character of responses of the subcortical neuron populations to stimulation by single pulses was recorded extracellularly during the rapeutic and diagnostic procedures. The thalamic nuclei had the highest level of excitability, followed by the strio-pallidary complex and, finally, by nuclei of the brain stem. Threshold pulses evoked spike activity only in the region of stimulation. Supraliminal pulses evoked a local decrease in unit activity together with simultaneous but varied distant changes in activity in the neuron populations elsewhere in the subcortex.

Excitatory and inhibitory processes acting upon cerebellar Purkinje cells during maturation in the rat; influence of hypothyroidism.

The functional maturation of the cerebellum has been studied in normal rats from 3 days after birth until adulthood and over the same period in animals rendered hypothyroidic through propylthiouracile injections. Evoked field potentials and unitary activities were recorded from the cerebellar nuclei and from the molecular layer and Purkinje cell (P.C.) layer of the cerebellar cortex. The following observations are reported: 1. a few P.C. axons are functional and presumably connected to subcortical neurons as early as 3 days after birth. However the maturation of the bulk of P.C. axons only occurs after the 6th day; 2. climbing fiber responses of the P.C. (C.F.Rs) are also present on day 3, although the dendritic components of the response only appear several days later. C.F.R. maturation is achieved at the end of the first postnatal month and is only slightly disturbed by hypothyroidism; 3. some connections between mossy fibers (M.F.), granule cells and P.C. also seem to exist on days 3 to 4, but the functional maturation of the parallel fibers occurs principally during the 10th to 30th day period. This maturation is delayed to a considerable extent by hypothyroidism: 4. the efficiency of parallel fibers to excite P.C. increases strongly from the 10th to the 20th day; this evolution is also markedly slowed down in hypothyroid rats; 5. some inhibitory action can already be characterized in the cerebellar cortex on day 10, but most inhibitory interneurones and their synapses on P.C. become mature from the 10th to the 15th day. Furthermore, inhibition exerted by these cells on P.C. is more prolonged in the immature rat than in the adult. Hypothyroidism markedly delays the maturation of these inhibitory processes.

The effects of varying doses of Δ9-tetrahydrocannabinol on the human visual and somatosensory evoked response

The present study was designed to determine the effects of varying oral doses of Δ 9-THC on the human visual and somatosensory evoked response. Two groups of 10 subjects were studied. One group reported smoking marijuana at least twice a week (frequent user group) while subjects in the second group reported their marijuana use did not exceed twice per month (occasional user group). Δ 9-THC was extracted from raw marijuana plant material and administered orally on sugar cubes in doses of 0.2, 0.4 and 0.6 mg/kg. All subjects received each dose of Δ 9-THC and a placebo in a randomized sequence. Recording sessions were separated by at least one week. Data are reported for visual and somatosensory evoked responses recorded from frontal, central and occipital scalp 4 h after drug administration. For each response recorded under drug and placebo conditions amplitudes and latencies of consistently identifiable wave components were calculated and analyzed. No consistent evoked response differences were found between the frequent and occasional user groups. The most prominent finding was the consistency with which Δ 9-THC slowed the latency of evoked response waves while producing relatively little change in amplitude. In contrast, most drugs have been found to exert their main effects on evoked response amplitude with only slight alterations of latency. It was thus hypothesized that Δ 9-THC acts to increase the threshold of cortical and subcortical neurons or neural networks involved in producing the evoked response rather than to selectively inhibit brain-stem centers. Δ 9-THC administration produced no evidence of an excitatory action on the central nervous system. In those infrequent instances in which Δ 9-THC did produce a change in evoked response amplitude it was always a decrease. Unlike alcohol, Δ 9-THC did not alter amplitude hemispheric asymmetry.

Fine-structure of bilateral radionecrosis in the dorsal hippocampus.

The data with which this paper deals were obtained from white rats receiving limited head X-irradiation, tested for behavioral changes, and sacrificed for light and electron microscopic evaluation 1 year after the irradiation. No evidence was found for a general loss or change in cortical or subcortical neurons. On the other hand, there was bilateral focal degeneration in the fimbria of the fornix in the dorsal hippocampus. This involved considerable numbers of pyramidal and granule cells, presumably secondary to delayed vascular changes. Widespread hypertrophy of astrocytes was noted throughout the irradiated zone. Within each central necrotic zone invasive collagen, reticulin and fibrin were present. In general, blood vessels showed only occasional evidence of thickening. However, the blood vessels in the areas of frank necrosis in the fimbria and internal capsule exhibited intense thickening leading to hyalinization.

A technique for recording activity of subcortical neurons in moving animals

The technique which has been described allows stereotaxic orientation of micro-electrodes for single unit recording in the intact monkey. The method provides for vertical penetrations and for minimum loss of time between completion of one penetration and reorientation of the electrode for the subsequent penetration.

Relation of pyramidal tract activity to force exerted during voluntary movement.

in a series P of studies of the relation of discharge 01 pyramlda1 tract neurons (PTNs) to voluntary movement. The first of the previous studies (5) showed that PTN activity both at rest and during movement is related to axonal conduction velocity. PTNs with the highest axonal conduction velocities tend to be silent during motor quiescence and to show phasic activity in association with movement. PTNs with lower axonal conduction velocities are for the most part active even in the absence of movement; with movement they show both upward and downward modulation of their resting discharge frequency. A second study (6) was carried out to obtain information as to the point in the interval between stimulus and response at which PTN discharge takes place in association with a conditioned hand movement. It was found that for many PTNs, responses to the conditioned stimulus (the onset of a light) preceded the first peripheral electromyographic correlates of the conditioned response (wrist extension). The fact that these PTN responses preceded the electromyographic response showed that they were not consequent upon feedback resulting from the movement. 1

On the Functional Significance of the Hippocampal θ–Rhythm

Publisher Summary This chapter focuses on the functional significance of the hippocampal θ-rhythm. The appearance of the θ-rhythm in the hippocampogram depends on a moderate level of reticular activation. In this condition the hippocampal output elicits a rhythmic firing of subcortical neurones. Via the anterior thalamic nuclei and the gyrus cinguli a hippocampo-hippocampal circuit is closed, and reactivation of the hippocampus at the same rate is quite possible. This circuit as well as the other thalamo-neocortical circuits of the nuclei lateralis dorsalis and in part medialis dorsalis are not consistently affected by the ascending influences of the activating reticular formation. In conditions of moderate arousal the hippocampal output during the appearance of the θ-rhythm has enough driving power to exert definite control on the bioelectrical activity of subcortical and neocortical structures. It is evident that the preceding considerations cannot be directly extended to higher mammals. The depression or suppression of the hippocampal θ-rhythm does not necessarily mean that the hippocampus has lost or basically changed its functional significance.

Unit analysis of visual input to posterior limbic cortex. I. Photic stimulation.

ArticlesUNIT ANALYSIS OF VISUAL INPUT TO POSTERIOR LIMBIC CORTEX. I. PHOTIC STIMULATIONMichel Cuénod, Kenneth L. Casey, and Paul D. MacLeanMichel Cuénod, Kenneth L. Casey, and Paul D. MacLeanPublished Online:01 Nov 1965https://doi.org/10.1152/jn.1965.28.6.1101MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByFunctional organization of the extrinsic and intrinsic circuitry of the parahippocampal regionProgress in Neurobiology, Vol. 33, No. 3Electrophysiological responses of neurones in the nucleus accumbens to hippocampal stimulation and the attenuation of the excitatory responses by the mesolimbic dopaminergic systemBrain Research, Vol. 324, No. 1An olfactory input to the hippocampus of the cat: Field potential analysisBrain Research, Vol. 182, No. 1Peripheral auditory input to the midbrain limbic area and related structuresBrain Research, Vol. 167, No. 1Visual properties of neurons in the posterior suprasylvian gyrus of the catExperimental Neurology, Vol. 59, No. 1Visual properties of neurons in pulvinar, nucleus lateralis posterior and nucleus suprageniculatus thalami in the cat. I. Qualitative investigationBrain Research, Vol. 44, No. 2Representation of the visual field in striate and adjoining cortex of the owl monkey(Aotus trivirgatus)Brain Research, Vol. 35, No. 1Unit study of exteroceptive inputs to claustrocortex in awake, sitting, squirrel monkeyBrain Research, Vol. 28, No. 1Comparative studies on cortical representation of visionVision Research, Vol. 11Effects of various photoperiods on the temporal distribution of paradoxical sleep in ratsExperimental Neurology, Vol. 27, No. 1Regional activities within the human hippocampus and hippocampal gyrusExperimental Neurology, Vol. 26, No. 2Somatic stimuli, spinal pathways, and size of cutaneous fibers influencing unit activity in the medial medulary reticular formationExperimental Neurology, Vol. 25, No. 1Projections from the cingulate cortex in the ratBrain Research, Vol. 12, No. 2The architecture of the cortical taste nerve areas in squirrel monkey (Saimiri sciureus) and their relationships to insular, sensorimotor and prefrontal regionsBrain Research, Vol. 8, No. 1A technique for recording activity of subcortical neurons in moving animalsElectroencephalography and Clinical Neurophysiology, Vol. 24, No. 1Effects of nitrazepam and phenobarbital on hippocampal and lateral geniculate neurones in the catInternational Journal of Neuropharmacology, Vol. 7, No. 1A chronically fixed stereotaxic device for intracerebral exploration with macro- and micro-electrodesElectroencephalography and Clinical Neurophysiology, Vol. 22, No. 2 More from this issue > Volume 28Issue 6November 1965Pages 1101-1117 https://doi.org/10.1152/jn.1965.28.6.1101PubMed4956845History Published online 1 November 1965 Published in print 1 November 1965 Metrics