Experimental Brain Research

Holländer, Horstmar

doi: 10.1007/BF00235047pmid: 5441443

221 10 10 3 3 Horstmar Holländer Max-Planck-Institut für Psychiatrie Munich Germany Summary Small lesions were made in the visual cortex of 15 adult cats both uni-and bilaterally. Using thermocoagulation it was possible to make lesions restricted to particular cortical cytoarchitectonic areas. The degeneration in the lateral geniculate body (LGB) was studied with silver impregnation methods of Nauta and Laidlaw and Pink and Heimer. The distribution of terminal degeneration was mapped by means of a new 3-dimensional reconstruction technique. The man results are as follows: 1. Most of the fibres projecting from the visual cortex to the LGB come from area 18. They terminate in laminae A and A 1 and in the central interlaminar nucleus. Rostral portions of area 18 project to rostral parts of the LGB and caudal portions to caudal parts. The medial portion of area 18 projects more medially in the LGB and the lateral portion projects more laterally. 2. Area 17 does not project to any part of the LGB. A projection from the most caudal part of area 17 to the tail of the LGB cannot, however, be entirely excluded. 3. Area 19 and possibly also the suprasylvian gyrus project to the medial interlaminar nucleus and to the ventral nucleus. One of these cortical areas or both send fibres to laminae A and A 1 , and to the central interlaminar nucleus. 4. The nucleus lateralis posterior of the thalamus receives fibres from area 17, area 18, and possibly also from area 19 and the suprasylvian gyrus.

Dieckmann, G.; Sasaki, K.

doi: 10.1007/BF00235048pmid: 4315064

221 10 10 3 3 G. Dieckmann K. Sasaki Neuroanatomische Abteilung Max-Planck-Institut für Hirnforschung Frankfurt/Main West-Germany Neurochirurgische Universitätsklinik D - 665 Homburg-Saar Dept. of Physiology Kyoto University Yoshida Sakyo-Ku Kyoto Japan Summary 1. Field potentials in the cerebral cortex elicited by low frequency (6–10/sec) repetitive stimulation of the putamen (Put) and pallidum (Pal) were recorded by glass microelectrodes inserted at various depths in the cortex and analysed together with those evoked by stimulation of different thalamic nuclei. Surface cortical potentials recorded by a gross electrode and intracellular potential changes in cortical neurones were also provided to complement field potential analysis. 2. Stimulation of putamen or pallidum produced characteristic laminar field potentials which were similar to those elicited by stimulation of the centrum medianum (CM) nucleus in the thalamus. Superficial slow negative and deep positive potentials showed much the same time course as in a mirror image and the polarity change at 0.10–0.25 mm depth in the cortex. These profiles of field potentials indicate that putamen- and pallidum-induced potentials are pure recruiting responses in every respect. Latency of Put-induced responses was always longer than that of Pal- and CM-induced responses, the latter two being comparable. Duration was wider in the responses evoked by CM stimulation than those by Put and Pal. The optimal frequency for Put- and Pal-induced recruiting responses was 7–9/sec and the same as that for CM-induced responses in every experiment. 3. Current spread of Put and Pal stimulation to surrounding structures such as the internal capsule was outruled, since entirely different responses (augmenting responses) could be evoked in the cortex by stimulation of the internal capsule delivered through the same electrode after withdrawal of the electrodes by 1–2 mm from Put and Pal to the internal capsule. 4. The cortical area in which Put- and Pal-evoked recruiting responses were recorded was more restricted than the area for CM-induced recruiting responses and was mainly in area 6 a β. 5. The results lead us to refer to and discuss a hypothesis for the pathways of CM-induced recruiting responses that has been made on previous anatomical findings.

Harrington, Thomas; Merzenich, Michael

doi: 10.1007/BF00235049pmid: 4985999

221 10 10 3 3 Dr. Thomas Harrington Dr. Michael M. Merzenich Department of Physiology The Johns Hopkins University, School of Medicine Baltimore Maryland USA Laboratory of Neurophysiology 283 Medical Sciences Building University of Wisconsin 53706 Madison Wisconsin USA Department of Psychology University of Nevada Reno Nevada USA Summary The human capacity to scale the intensity of brief mechanical indentations of the hairy skin was measured by the method of subjective magnitude estimation. The afferent discharges evoked by nearly identical stimuli delivered to comparable locations on the hairy skin in monkeys were recorded in a number of types of first-order mechanoreceptive afferents. It was shown that of these only those which adapt slowly to mechanical stimuli possess sufficient dynamic range of response to account for the range of human pressure sensation. Two such afferents innervating the hairy skin, previously identified by others as the Type I and Type II afferents, were studied in detail as regards their responses to brief mechanical stimuli of different intensities. The relation of the human subject's estimate of intensity to stimulus magnitude is described by a power function with an exponent of about 0.4. Using impulse frequency in the “early steady state” as a measure, the responses of both types of slowly adapting mechanoreceptive afferents are related to stimulus magnitudes by power functions with exponents averaging about 0.5. On the assumption that the stimuli used elicit similar patterns of discharge in the first-order afferents innervating the hairy skin of men and monkeys, the results support the general proposition, now shown to hold for a number of senses, that the intensity of human sensation is determined by the functional properties of the first-order sensory fibers, and that the final behavioral output in the form of a subjective estimate of magnitude is a linear function of the frequency of discharge in those first-order fibers.

Sans, A.; Raymond, J.; Marty, R.

doi: 10.1007/BF00235050pmid: 5441444

221 10 10 3 3 A. Sans J. Raymond R. Marty Faculté des Sciences Laboratoire de Neurophysiologie Montpellier France Summary Electric stimulation of the vestibular nerve was carried out on 69 cats under pentobarbital or chloralose anaesthetic. The responses were recorded in the thalamus and on the cerebral cortex with a permanent check of the stimulation threshold in the vestibular nuclei. The exploration of the cerebral cortex by means of macro-electrodes revealed the existence of two centres of responses: the first situated in the rostral section of the anterior suprasylvian sulcus, the second in the upper part of the posterior sigmoid gyrus, at the level of the postcruciate dimple. As revealed by micro-electrodes, two centres of responses also exist in the thalamus —one in the dorso-median part of the VPL, the other in the middle section of the VL. On the basis of these results it seems likely that the impulses emanating from the vestibular nuclei arrive at the cerebral cortex by two distinct paths —one direct vestibulo-thalamic path (VPL) terminating at the level of the two cortical centres already mentioned and one indirect vestibulo-cerebello-thalamic (VL). In the latter case confirmation is needed that this path terminates at the level of the motory cortex. Taking into account published data on the paths and the termination of the proprioceptive impulses in the cortex it is possible to propose the elements of a coherent systematisation of the regulation of the posture at the level of the cortex.

Koizumi, J.; Shiraishi, H.

doi: 10.1007/BF00235051pmid: 5441445

221 10 10 3 3 J. Koizumi H. Shiraishi Department of Neuropsychiatry School of Medicine, Chiba University Chiba Japan Summary The tuber cinereum of hypothalamus, cerebral cortex, cerebellar cortex and caudate nucleus of rabbits were examined under the electron microscope following intramuscular administration of chlorpromazine with special consideration of ultrastructural changes in amount and distribution of glycogen granules in their hypothalamus. In these regions, normal astrocytes and their processes contain glycogen granules diffusely scattered in the cytoplasm. In the neurons of the normal hypothalamus and cerebellar cortex, glycogen granules are seen in some presynaptic endings and distal parts of dendrites but not in the perikaryal cytoplasm. In the tuber cinereum of the hypothalamus, after chlorpromazine administration, abundant glycogen granules accumulate at the postsynaptic sites, especially in peripheric parts of dendrites, and clusters of glycogen granules appear in the perikaryal cytoplasm of the nerve cells. These findings are interpreted as an increase of glycogen in these cellular regions and the suggestion is made that chlorpromazine inhibits the glycolytic metabolism in the distal parts of dendrites, particularly at postsynaptic sites and in the perikarya of nerve cells of the hypothalamus.

Malcolm, Lynne; Bruce, I.; Burke, W.

doi: 10.1007/BF00235052pmid: 4315065

221 10 10 3 3 Lynne J. Malcolm I. S. C. Bruce W. Burke Department of Physiology University of Sydney Sydney Australia Summary 1. Cats with chronically implanted electrodes have been used to study the excitability of the lateral geniculate nucleus (LGN) during alertness, non-alertness and sleep. Excitability has been assessed by the amplitude of the field response in the LGN to electrical stimulation of the optic tract and by the amplitude of the antidromic response in the optic tract evoked by stimulating the LGN. 2. Changes in responsiveness associated with eye movements in the awake animal have been avoided. The change from the alert state to the non-alert state is accompanied by a decrease in the excitability of both the LGN cells and the optic tract nerve endings. 3. Postsynaptic excitability decreases further in slow-wave (SW) sleep but during low-voltage-fast-activity (LVF) sleep it returns to a level that is intermediate between that of alertness and non-alertness. During the ponto-geniculooccipital (PGO) waves of LVF sleep excitability is phasically enhanced to above the alert level. 4. Presynaptic excitability during SW sleep and LVF sleep in the intervals between the PGO waves is less than during non-alertness, but during the waves it returns to the alert level. 5. Our findings indicate that the optic tract endings are tonically depolarized in the alert animal and that the depolarization is reduced in non-alertness and reduced further in sleep. Depolarization is phasically enhanced during the PGO waves. 6. It is suggested that the LGN may be the first site on the visual pathway at which information is modified according to the animal's state of consciousness.

Rolls, E.; Cowey, A.

doi: 10.1007/BF00235053pmid: 4986000

221 10 10 3 3 E. T. Rolls A. Cowey Institute of Experimental Psychology University of Oxford England Summary Density of cones and ganglion cells was studied in horizontal sections of retina in the rhesus monkey ( Macaca, mulatta) and the squirrel monkey ( Saimiri s ciureus). The lower angular density of cones in the fovea of Saimiri correlates with its visual acuity, which is poorer than that of Macaca (0.74 and 0.65 min of arc respectively). Cone density falls more steeply with angular eccentricity from the fovea in Saimiri , in accordance with its relatively poorer peripheral acuity. Comparable results were obtained with retinal ganglion cells, but the comparisons at the fovea itself are more difficult because of the lateral displacement of these elements in the foveal region. The cortical magnification of the visual field (that is, the number of mm of cortex per degree of visual field) is lower for both the foveal and parafoveal representations at the striate cortex in Saimiri. This was correlated with its poorer foveal and parafoveal acuity. It was shown that with increasing eccentricity from the fovea, the fall in the magnification of the visual field at the striate cortex is approximately proportional to the decrease in ganglion cell density at the retina. The results of this study, in which acuity and topography of the visual system are compared in two species of monkey, are consistent with the view that both retinal topography, and the cortical magnification of the visual field, are closely related to visual acuity.

Singer, W.; Creutzfeldt, O.

doi: 10.1007/BF00235054pmid: 4315066

221 10 10 3 3 W. Singer O. D. Creutzfeldt Department of Neurophysiology Max-Planck-Institute of Psychiatry 23 Munich W.-Germany Summary In the lateral geniculate body (LGB), intra- and quasi-intracellular records were done. With small light stimuli shone into different parts of the receptive field, EPSPs and IPSPs could be elicited. Stimulation of the exact center of an on-center cell produced a pure excitatory response, that of an off-center neurone pure inhibition. This response lasted throughout the stimulus. At light off, inhibition was elicited in on-center cells and excitation in off-center cells. A stimulus in the field periphery produced a mixed response with a small and short excitation followed by large inhibition in on-center cells, and a short inhibition followed by postsynaptic depolarization in off-center cells. At light off, on-center cells showed depolarization after a short polarizing phase, and off-center cells a broad polarization which interrupted the initial small excitation. The latencies of both the excitatory and inhibitory center responses at light on and off characteristic for the two types of neurones, were 20–30 msec shorter than the reversed responses elicited by stimulation of the receptive field surround. The findings are compatible with a model in which each geniculate on-center cell gets its major excitatory input from one optic tract on-center fibre and inhibitory input from several off-center fibres with nearby receptive fields. An off-center LGB-cell receives its main excitation essentially from one offcenter fibre and inhibition from several on-center cells. The responses to moving stimuli also agreed with this model. The presence of recurrent inhibition within the LGB could be confirmed by electrical stimulation. But it could not be decided whether the reciprocal inhibition of on- and off-center cells was due to forward or backward inhibition. The spontaneous activity of on- and off-center cells which were simultaneously recorded with one electrode, showed a mutual inhibition 6–8 msec after one cell had fired. Anatomical data relevant to the model are discussed and some functional implications are suggested.