Experimental Brain Research

Rustioni, A.; Kaufman, A.

doi: 10.1007/BF00234821pmid: 64365

221 27 27 1 1 A. Rustioni A. B. Kaufman Departments of Anatomy and Physiology, Division of Health Affairs School of Medicine, Medical Research Wing, Room 359, University of North Carolina at Chapel Hill 27514 Chapel Hill NC USA Summary In order to identify cells of origin in the spinal cord of non-primary afferents to the dorsal column nuclei (DCN), the retrograde transport of horseradish peroxidase (HRP) has been utilized in adult cats. 10 to 30% HRP was injected bilaterally (0.6 μl per side) in the dorsal medulla of nine cats. In most instances the spread of the injected enzyme extended a few millimeters rostrocaudally and infiltrated the DCN as well as other nuclei and fiber tracts. Labelled cells in these cases are numerous in the upper cervical, brachial and lumbosacral cord but are sparse in thoracic segments below T 1 . At upper cervical levels (C 1 -C 4 ) HRP-positive neurons are distributed throughout the grey matter but are especially concentrated in the medial part of lamina VI. Cells projecting to the dorsal medulla are mainly localized in lamina IV and, more ventrally, along the medial border of the dorsal horn in the brachial and lumbosacral cord. Labelled cells at these levels are also scattered within lamina I and laminae VI through VIII in cases in which the focus of the injection involved extensive portions of the medulla. From cases in which bilateral HRP injections were preceded by spinal tractotomy, it appears that the axons of at least the majority of labelled cells in lamina IV ascend in the ipsilateral dorsal quadrant of the spinal cord. In another group of adult cats, 0.1 to 0.25 μl of 30 to 50% HRP was injected unilaterally in the dorsal medulla at the level of, or rostral to, the obex. With these volumes of exogenous enzyme, an intense reaction product is largely confined within the limits of the DCN. Labelled cells in these cases are found almost exclusively in the medial part of lamina VI at upper cervical levels and, at brachial and lumbosacral levels, throughout lamina IV and medially in lamina V on the side of the cord ipsilateral to the injection. The results are discussed in relation to the organization of the dorsal horn and ascending pathways with special reference to cells of origin of the spinocervical tract.

Menétrey, D.; Giesler, G.; Besson, J.

doi: 10.1007/BF00234822pmid: 832686

221 27 27 1 1 D. Menétrey G. J. Giesler Jr. J. M. Besson I.N.S.E.R.M. - U. 161 Unìtè de recherche de Neurophysiologie Pharmacologique 2, rue d'Alésia 75014 Paris France Department of Psychology University of California 90024 Los Angeles California USA Laboratoire de Physiologie des Centres Nerveux, Université Pierre et Marie Curie 4, avenue Gordon-Bennett F - 75016 Paris France Summary Electrophysiological properties of neurones in the spinal cord dorsal horn were studied in decerebrated, immobilized spinal rats. Extracellular recordings were performed at the thoraco-lumbar junction level. Each track was systematically located by extracellular injection of pontamine sky blue. According to their responses to mechanical peripheral stimuli, cells were classified in four classes: Class 1 cells: Cells activated only by nonnoxious stimuli. They were divided into — 1A: hair movement and/or touch and 1B: hair movement and/or touch and pressure or pressure only. Class 2 cells: Cells driven by both nonnoxious and noxious stimuli, divided into — 2A: hair movement and/or touch, pressure, pinch and/or pin-prick, and 2B: pressure, pinch and/or pin-prick. Class 3 cells: Cells only activated by noxious stimuli (pinch and/or pin-prick). Class 4 cells: Cells responding to joint movement or pressure on deep tissues. Peripheral transcutaneous or sural nerve stimulation clearly showed that class 1 cells were activated only by A fiber input while 68% of classes 2 and 3 cells received A and C input. Histological examination indicated that cells driven only by noxious input were located either in the deepest part or in the marginal zone (lamina I) of the dorsal horn. Nevertheless, some lamina I cells were also driven by both nonnoxious and noxious stimuli. In addition, there is a great deal of overlap between class 1 and class 2 cells. This fact was confirmed by considering the wide distribution in the dorsal horn of cells receiving A and C input. However, spinal organization of the different classes of cells consists of a preferential distribution rather than a strict lamination. This study indicates that properties of dorsal horn interneurones in the rat have a high degree of similarity with those previously described in other species (cat and monkey).

Virsu, V.; Lee, B.; Creutzfeldt, O.

doi: 10.1007/BF00234823pmid: 832687

221 27 27 1 1 V. Virsu B. B. Lee O. D. Creutzfeldt Department of Neurobiology Max-Planck Institute for Biophysical Chemistry Am Fassberg D - 3400 Göttingen-Nikolausberg Federal Republic of Germany Department of General Psychology University of Helsinki SF00170 Helsinki 17 Finland Summary The receptive fields of LGN cells were investigated with stationary light and dark spot and annulus stimuli. Stimulus size and background intensity were varied while stimulus/background contrast was kept constant. The speed of dark adaptation varied considerably from cell to cell. Dark adaptation made responses more sustained in all neurones and eliminated the oscillatory on-responses evoked under some conditions in the light-adapted cells. Dark adaptation led also to a disappearance of early phasic inhibition in on-responses, and increased response rise time and latency. The power of surround responses to inhibit centre responses decreased slightly at low levels of light adaptation in LGN cells but much less than in retinal ganglion cells. Some other traces of changing retinal surround effects also appeared in the LGN on dark adaptation. For example, the functional size of receptive fields increased at low levels of illuminance as has been observed in retinal ganglion cells and the receptive fields as estimated from response peaks were larger than those estimated from sustained components.

Lee, B.; Virsu, V.; Creutzfeldt, O.

doi: 10.1007/BF00234824pmid: 832688

221 27 27 1 1 B. B. Lee V. Virsu O. D. Creutzfeldt Department of Neurobiology Max-Planck-Institute for Biophysical Chemistry Am Fassberg D - 3400 Göttingen-Nikolausberg Federal Republic of Germany Department of General Psychology University of Helsinki SF-00170 Helsinki 17 Finland Summary The responses of neurones in laminae A and A1 of the cat lateral geniculate nucleus to moving stimuli were investigated at different background luminances. Moving bright slits, dark bars and edges were employed; the contrast of stimuli against the background was held constant. Background intensities varied from 10 −3 to 10 2 td. Responses as stimuli passed across the centres of LGN receptive fields became stronger with increasing levels of light adaptation up to 10 −1 –10 1 td and then remained constant. Responses as stimuli passed through surround regions altered qualitatively with adaptation level, generally increasing in strength and complexity with background luminance. As a bright slit for on-centre cells or dark bar for off-centre cells left the surround, in almost all units a strong secondary peak could be elicited by an appropriate selection of the adaptation conditions. Many features of the responses to moving stimuli could not be predicted from the responses to stationary stimuli under different adaptation conditions described in the previous paper.

Gary-Bobo, E.; Bonvallet, M.

doi: 10.1007/BF00234825pmid: 832689

221 27 27 1 1 E. Gary-Bobo M. Bonvallet Laboratoire de Neurophysiologie Collège de France 11 place Marcelin Berthelot F- 75231 Paris Cedex 05 France Laboratoire de Physiologie, U.E.R. St Antoine 27 rue Chaligny F- 75571 Paris Cedex 12 France Summary Single shock stimulations have been applied stereotaxically and bilaterally in the region of the caudo-thalamic groove of the cat. These stimulations elicit diphasic potentials in the amygdala. Using combined methods of stimulation and lesion, it has been demonstrated that these electrical responses are due to the excitation of fibers projecting rostrally in the lateral border of the contralateral fimbria and caudally in the homologous part of the homolateral fimbria. A commissural path has been identified in the rostral part of the fimbria-fornix. Analysis of the experimental data has shown that the projection system consists of a discrete bundle of fibers which probably reaches the amygdala directly, in the dorsal part of the basal nucleus. The length of the explored portion of this pathway has been measured. The calculated conduction velocity of this amygdalopetal commissural component of the fimbria is 4.5 m/sec.

Rose, D.; Horn, G.

doi: 10.1007/BF00234826pmid: 832690

221 27 27 1 1 D. Rose G. Horn Department of Anatomy, The Medical School University of Bristol BS8 1TD Bristol England Summary The effects of intravenous doses (200 μg) of LSD on the activity of single neurones in the primary visual cortex have been studied in cats anaesthetized with urethane. Cells were stimulated with a bright bar of light moved over the receptive field, and orientation tuning was assessed quantitatively before and after administration of the drug. Changes in neuronal activity were compared with those observed in a control sample of cells recorded when the cats were given no drug. LSD increased the responsiveness of some cells to visual stimuli and decreased that of others, but some cells were not affected. The changes in responsiveness were dose dependent; the larger doses of the drug (expressed in μg/kg body weight) tended to depress the responses and the smaller doses to enhance them. The effects appeared earlier in complex cells than in simple cells. Changes in spontaneous activity, direction selectivity and orientational properties were found in some cells.

Allen, G.; Gilbert, P.; Marini, R.; Schultz, W.; Yin, T.

doi: 10.1007/BF00234827pmid: 401741

221 27 27 1 1 G. I. Allen P. F. C. Gilbert R. Marini W. Schultz T. C. T. Yin Istituto di Fisiologia Umana Universita Cattolica S. Cuore via della Pineta Sacchetti 644 I - 00168 Rome Italy Karolinska Institutet, Histologiska Avdelningen Tomtebodavägen 8 S - 10401 Stockholm 60 Sweden Department of Physiology The Johns Hopkins University, School of Medicine 725 N. Wolfe 21205 Baltimore Maryland USA Department of Physiology School of Medicine, State University of New York 14214 Buffalo New York USA Summary The patterns of convergence of cerebral and peripheral nerve inputs onto interpositus neurons were studied in cebus monkeys. The strongest inputs to interpositus neurons are from motor and somatosensory cortex, with weaker inputs from peripheral nerves and cerebral area 6. The neurons in the anterior portion of interpositus receive cerebral and peripheral inputs primarily representing the hindlimb, while inputs to neurons in the posterior division represent forelimb or mixed forelimb and hindlimb. The hindlimb neurons integrate signals principally from motor cortex, somatosensory cortex, nerves, supplementary motor and medial premotor areas, while forelimb neurons receive inputs from motor, somatosensory, lateral premotor cortical areas and nerves. The results from this study are compared with those from studies of interpositus and dentate neurons in cat and monkey in order to determine the role of n. interpositus in movement. It is suggested that the inputs integrated by interpositus neurons are consistent with a role in up-dating skilled movements.

Schwarz, D.; Tomlinson, R.

doi: 10.1007/BF00234828pmid: 832685

221 27 27 1 1 D. W. F. Schwarz R. D. Tomlinson Laboratory of Otoneurology, Depts. of Otolaryngology and Physiology University of Toronto Toronto Ontario Canada Summary Extraocular proprioceptive input to cerebellar vermis, lobule VI, was investigated in cats under N 2 O analgesia by recording neuronal responses to eye muscle stretch. Both optic tracts were transected and the periorbital skin and conjunctiva were locally anaesthetized. Eye rotation within the physiological range was achieved by applying a pull of predetermined length and tension to each of the eight musculi recti at their insertion to the globe. Within lobule VI, only small patches of cortex receive stretch receptor afferents. The information made available by these afferents corresponds to a change of eye position. Minimal responses were dependent upon angular deflections of a few degrees. Maximal response amplitudes were obtained within the physiological range of angular deflections and angular velocities for the units tested. Most cells responded to stretch of more than one muscle. Three types of convergence were found: (1) neurons responding according to a certain direction of a conjugated movement of both eyes, (2) neurons responding to movements in either direction of one plane, (3) more complicated response patterns.