The connections of the primate subthalamic nucleus: indirect pathways and the open-interconnected scheme of basal ganglia-thalamocortical circuitry

The current view of basal ganglia organization holds that functionally corresponding subregions of the frontal cortex, basal ganglia and thalamus form several parallel segregated basal ganglia-thalamocortical circuits. In addition, this view states that striatal output reaches the basal ganglia output nuclei (the substantia nigra pars reticulata (SNR) and the internal segment of the globus pallidus (GPi)) via a 'direct' pathway, and via an 'indirect pathway' which traverses the external segment of the globus pallidus (GPe) and the subthalamic nucleus (STN). However, the topographical relationships of GPe and STN, and their topographical relationships with the basal ganglia-thalamocortical circuits are still unclear. The present work reviewed primate data on the topographical organization of STN afferents from GPe, and STN efferents to the pallidum, striatum and SNR, and examined these data with respect to a tripartite (motor, associative and limbic) functional subdivision of the striatum and pallidum. This examination indicated the following. (1) On the basis of its efferent connections, the STN may be divided into a motor and an associative territories, as well as a smaller limbic territory, each projecting to corresponding areas in the pallidum and striatum. (2) Efferents from GPe are in a position to contact subthalamic cells projecting to GPi/SNR, thus providing anatomical support for the existence of indirect pathways. (3) Moreover, given the tripartite division of the striatum, pallidum, and STN, the available data indicate the existence of indirect pathways connecting functionally corresponding subregions of the striatum, pallidum, and STN, as well as indirect pathways connecting functionally non-corresponding subregions. On the basis of the above we suggested that there may be two types of indirect pathways, one which terminates in the same subregion in GPi/SNR as the direct pathway arising from the same striatal subregion, and another which terminates in a different GPi/SNR subregion than the direct pathway arising from the same striatal subregion. We termed the former a 'closed indirect pathway' and the latter an 'open indirect pathway'. The application of these concepts to the surveyed data suggested the existence of three closed indirect pathways, each connecting the corresponding functional (motor, associative, and limbic) regions of the striatum, pallidum, STN, and SNR, as well as of two open indirect pathways, one connecting the associative striatum to the motor subregions of the basal ganglia, and the other connecting the associative striatum to the limbic subregions of the basal ganglia. While the organization of the closed indirect pathways fits the closed segregated arrangement of basal ganglia-thalamocortical circuitry, the organization of the open indirect pathways fits the recently suggested open interconnected scheme of basal ganglia thalamocortical circuitry. The clinical implications of this scheme for Huntington's disease are discussed.     

A New Test of Image Theory

This paper investigates two hypotheses of the screening phases of two-staged multiattribute choice procedures: the editing phase in which dominated choice alternatives are eliminated and the compatibility test of image theory. As the importance weights and rejection thresholds of the compatibility test are recalcitrant to elicitation, we develop a new method to examine the compatibility phase treating importance weights and rejection thresholds as latent parameters. Our method allows a checkup of the application of a compatibility test without any knowledge of subjects' importance weights and rejection thresholds. Our experimental findings show that the compatibility test enjoys consistency rates of some 70% as compared to consistency rates of about 15% for the editing hypothesis of the elimination of dominated choice alternatives. This result is supported by applying Selten's measure of predictive success. Copyright 1998 Academic Press.     

Vestibular nucleus projections to nucleus tractus solitarius and the dorsal motor nucleus of the vagus nerve: potential substrates for vestibulo-autonomic interactions

Autonomic effects of vestibular stimulation are important components of phenomena as diverse as acute vestibular dysfunction and motion sickness. However, the organization of neural circuits mediating these responses is poorly understood. This study presents evidence for direct vestibular nucleus projections to brain stem regions that mediate autonomic function. One group of albino rabbits received injections of Phaseolus vulgaris leucoagglutinin into the vestibular nuclei. The tracer was visualized immunocytochemically with standard techniques. Anterogradely labeled axons from the caudal medial vestibular nucleus (cMVN) and inferior vestibular nucleus (IVN) could be traced bilaterally to nucleus tractus solitarius (NTS). Fewer axons ended near the somata of neurons in the dorsal motor nucleus of the vagus nerve (DMX). A second group of rabbits received pressure or iontophoretic injections of cholera toxin B-HRP or Fluoro-Gold into a region including NTS and DMX. Retrogradely labeled neurons were observed bilaterally in the caudal half of cMVN and ipsilaterally in IVN. The labeled somata were small and they tended to occupy the center of cMVN in transverse sections. These previously unreported vestibular nucleus projections to NTS and DMX are a potential substrate for vestibular influences on autonomic function. In particular, they may contribute to both cardiovascular control during head movements (e.g., orthostatic reflexes) and autonomic manifestions of vestibular dysfunction, motion sickness and exposure to altered gravitational environments.     

新型镍矿捕收剂浮选试验研究

针对某镍矿矿石日趋贫细杂化,应用传统捕收剂浮选回收率下降的特点,进行新型镍矿捕收剂CH12的浮选试验研究.结果表明,CH12是一种有效的镍矿捕收剂,可以在磨矿细度为-0.074 mm粒级占76%的条件下.使镍矿的粗选浮选回收率达到90%以上;同时应用抑制剂CMC,强烈抑制脉石矿物,可以使镍精矿品位提高到6.85%,Mg的含量降低到5.30%,达到了工业熔炼的要求.     

New growth of axons in the cochlear nucleus of adult chinchillas after acoustic trauma

This study determined the effect of acoustic overstimulation of the adult cochlea on axons in the cochlear nucleus. Chinchillas were exposed to an octave-band noise centered at 4 kHz at 108 dB sound pressure level for 1.75 h. One chinchilla was never exposed to the noise, and several others had one ear protected by an ear plug or prior removal of the malleus and incus. Exposure of unprotected ears caused loss of inner and outer hair cells and myelinated nerve fibers, mostly in the basal half of the cochlea. Cochlear nerve fiber degeneration, ipsilateral to the exposed ears, was traced to regions of the cochlear nucleus representing the damaged parts of the cochlea. In silver impregnations of a deafferented zone in the posteroventral cochlear nucleus, the concentration of axons decreased by 43% after 1 month and by 54% after 2 months. However, by 8 months, the concentration of thinner axons, with diameters of less than 0.46 microm, increased by 46-90% over that at 2 months. The concentration of axons with larger diameters did not change. Between 2 and 8 months small axonal endings appeared next to neuronal cell bodies. This later increase of thinner axons and endings is consistent with a reactive growth of new axons of relatively small diameter. The emergence of small perisomatic boutons suggests that the new axons formed synaptic endings, which might contribute to an abnormal reorganization of the central auditory system and to the pathological changes that accompany acoustic overstimulation.