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Biomedical subjects

Y Shinoda

Publications and source records attributed to Y Shinoda.

At least 109 records · Page 6Linked to original sources
PubMed1980

Evidence for a primary cortical origin of a middle latency auditory evoked potential in cats.

The origin of the scalp-recorded auditory evoked potential, Pa, was examined in cats anesthetized with chloralose-urethane and immobilized with gallamine triethiodide. This potential is a prominent positive wave which peaks approximately 12--15 msec following click stimuli. Mapping revealed that Pa is distributed on the scalp in the region overlying cortical area AI, contralateral to the stimulated ear. The cortical potential recorded from AI was a surface-positive wave, restricted to the anterior portion of AI. Laminar analysis of the cortical evoked potentials demonstrated the existence of a dipole generator at that area. The onset of this potential coincided with the onset of the scalp-recorded Pa. Comparison of the scalp and the cortex-recorded potentials showed that both the amplitude-intensity function and the amplitude-rate function for the scalp-recorded potential closely paralleled those recorded from AI. Acute and chronic lesion studies showed that extirpation of AI (particularly the anterior part) almost completely abolished the Pa response. This evidence indicates that the scalp-recorded Pa of cats is generated almost entirely from the anterior part of the contralateral AI.

Animals↗
PubMed1979

Spinal branching of pyramidal tract neurons in the monkey.

The branching pattern of individual pyramidal tract (PT) neurons of the monkey motor cortex was studied by activating these neurons antidromically from within the cervical motor nuclei and also from other regions of the spinal cord. 1. Fifty-four neurons were activated from motor nuclei in the cervical cord. Twenty-eight of these were activated from one segment and six (11%) were activated from motor nuclei of different segments. The remaining 20 neurons were activated from motor nuclei and also from unspecified region(s) of the gray matter. 2. Another 156 neurons were activated from unspecified regions(s) of cervical gray matter which could have been motor nuclei or outside the nuclei, and 64 of these were activated from more than one segment. 3. The branching patterns of PT neurons sending axons directly to motor nuclei innervating distal forelimb muscles suggested that they branch less than the rest of PT neurons.

Animals↗
PubMed1978

Projection from area 3a to the motor cortex by neurons activated from group I muscle afferents.

Two receiving areas in the pericruciate cortex are known for inputs from group I muscle afferents of forelimb nerves. One focus is near the postcruciate dimple of area 3a, and the other in the lateral sigmoid gyrus of the motor cortex (area 4gamma). The cortico-cortical projection of area 3a to 4gamma, and the relay by this projection of group I muscle afferent input to the motor cortex were investigated in cats. The following results were obtained. 1. Seventy-four neurons within area 3a were antidromically activated by intracortical microstimulation of the motor cortex. 2. Although excitation evoked by stimulation of group I muscle afferents could be demonstrated for only a few (8 of 48) cortico-cortical neurons in extracellular recordings, due to the methodological limitations discussed, this input evoked EPSPs in 8 of 9 cortico-cortical neurons recorded intracellularly. Therefore, it is likely that the majority of neurons projecting from area 3a to the motor cortex have an excitatory synaptic input from group I afferents. 3. Neurons projecting from area 3a to the motor cortex were most commonly found in cortical layer III, although some were found in layer V. 4. Five of nine pyramidal tract neurons of area 3a had a strong excitatory synaptic input from group I muscle afferents. 5. A new type of pyramidal tract neuron was found which has cortico-cortical axon collaterals connecting the two cytoarchitectonic regions. These various neurons may be part of a feedback system from muscle afferents to the motor cortex.

Afferent Pathways↗
PubMed1978

Spinal mechanisms of the functional stretch reflex.

A sudden and rapid angular displacement of the limb evokes, in human and monkey subjects, a segmented pattern of electromyographic activity in muscles which are stretched. While the first segment is acknowledged to represent a tendon jerk, it has been proposed that the second segment, occurring with a shorter latency than a reaction time, is mediated by a transcortical loop. The present experiments were conducted in cats to determine the properties of muscle responses to torque perturbations analogous to those used in the monkey, and to determine if the integrity of supraspinal pathways is required for the individual response segments to occur. Torque perturbations which flexed the forearm evoked a segmented response in the electromyogram of the cat triceps muscle. This response typically consisted of three early segments with latencies of 10, 30 and 60 msec which were similar to the M1, M2, and M3 segments described in the monkey. The M3 and occasionally M2 components were depressed when the cat followed rather than resisted the perturbation. A torque pulse of 10 msec duration was sufficient to elicit a near maximal M1 response while torque pulses in excess of 20 msec were required to evoke the M2 response. To determine if any of these components required mediation by the cerebral cortex, experiments were conducted in decerebrate and spinal cats. Similar torque perturbations produced segmented electromyographic responses in the triceps muscles which were indistinguishable in their timing from those observed in intact cats. The torque required to produce the segmented responses was comparable as well. All three segments were dependent upon the activation of receptors in the homonymous muscle and did not require cutaneous input. These observations show that receptor properties and/or spinal mechanisms involved in the stretch reflex are sufficient to produce a segmented response similar to that observed in intact animals.

Animals↗
PubMed1978

Pattern of projections of individual pyramidal tract neurons to the spinal cord of the monkey.

The results suggest : (1) that PT neurons sending axons to motor nuclei innervating distal forelimb muscles branch less than other PT neurons; (2) that a group of PT neurons located close together may influence various species of motoneurons, but that this influence is the strongest on motoneurons of one species; (3) that individual PT neurons terminate only on a small fraction of a given motoneuron group.

Efferent Pathways↗
PubMed1978

The intraspinal branching patterns of fast and slow pyramidal tract neurons in the cat.

Antidromic activation of single pyramidal tract neurons (PTNS) was obtained in cats by stimulating either the dorso-lateral funiculus with ball-electrodes, or the spinal gray matter with microelectrodes. The results indicate that the distribution area of single PTNS is much wider than the area of a single motor nucleus, suggesting that single PTNS may influence different motor nuclei.

Animals↗
PubMed1977

Spinal branching of rubrospinal axons in the cat.

The branching patterns of rubrospinal (RS) axons projecting to the cervical spinal cord between C3 and C8 were studied in the cat. RS neurons were identified by their antidromic responses to microstimulation of local axon branches within the cervical gray matter. Twenty-six of 58 RS neurons projecting to the cervical gray matter also sent axon branches to the thoracic spinal cord. Two out of 40 of these RS neurons also sent axon branches to the lumbar spinal cord. Using a collision technique, it was demonstrated that stem axons of rubrospinal neurons commonly sent multiple collaterals to different cervical segments. Neurons projecting to the cervical spinal cord alone were located in the dorsal quadrants of the red nucleus. Those projecting to cervical, as well as to more caudal segments, were intermingled with the former, and in slightly more ventral portions of the red nucleus. The presence of RS neurons projecting to widely separate levels of the spinal cord suggests that individual RS neurons may be capable of ultimately influencing two or more different motoneuron pools.

Animals↗
PubMed1976

Spinal branching of corticospinal axons in the cat.

Branching patterns of single corticospinal (CS) neurons were studied in the cat by activating these neurons antidromically from various regions of the spinal cord. 1. One hundred and ninety-three neurons were activated antidromically by microstimulation in the gray substance of the cervical cord and the majority of them were found in the forelimb area of the pericruciate cortex. 2. Branches to the lower levels of the spinal cord were found for 30% of the neurons projecting to the cervical gray matter. 3. The remaining 70% sent axons only to the cervical gray matter and some of them sent multiple branches to several segments in the cervical cord. 4. Only a few CS neurons located outside of the forelimb area could be activated from the cervical cord, but all of them also sent branches to the lower levels of the spinal cord. Neurons projecting to both the cervical cord and the lower levels were intermingled in the cortex with those projecting only to the cervical cord. 5. CS neurons activated from a given area of the cervical cord were often clustered together in a small area of the cortex, although some of these CS neurons sent their other branches to other parts of the spinal cord and neurons projecting to other parts were also intermingled among them. 6. The functional significance of multiple axonal branching of CS neurons is discussed in relation to cortical motor functions.

Animals↗
PubMed1975

Neural pathways from the vestibular labyrinths to the flocculus in the cat.

In decerebrate, unanesthetized cats, responses in the flocculus were evoked by electric stimulation of the vestibular nerves and by natural stimulation of horizontal head angular acceleration. Field potentials in the flocculus and intracellular recording from Purkinje cells following vestibular nerve stimulation indicated that the responses were produced by mossy fiber inputs. Field potentials evoked from the contralateral labyrinth were as large as those from the ipsilateral one. There was considerable convergence of bilateral labyrinthine mossy fiber inputs to a Purkinje cell. In view of the effects of incision at the midline of the cerebellum and the brain stem, inputs from the contralateral labyrinth were mainly conveyed through the midline of the brain stem and partly through the midline of the cerebellum. Primary vestibular afferents were involved in the transcerebellar crossed pathway. Fibers of the secondary vestibular neurons projecting to the contralateral flocculus were implicated in the brain stem-mediated pathway and, in part, presumably in the transcerebellar crossed pathway. About one-third of the axon spikes examined in the flocculus responded to horizontal head angular acceleration. Commissural inhibition was observed in more than half of the axon spikes in the flocculus which were presumed to be mono- or polysynaptically activated from the vestibular nerve.

Animals↗
PubMed1975

Experimental rheumatoid arthritis-like features induced by prolonged sensitization with focal antigens.

Prolonged sensitization with emulsion of an autologous or isologous subcutaneous abscess of Arthus type induced by injection of hen egg-white was performed in 34 rabbits which were divided into (high responder and intermediate responder groups (H- and M-groups) according to individual difference of immune responses. The development of a rheumatoid factor-like substance (RFLS) was demonstrated after 30 experimental days and subsequently observed in 21 out of 33 rabbits. There was no significant difference in the incidence of RFLS between both groups. As to the relation between the development of RFLS and types of focal antigens, the group of the autologous W-substance showed a higher incidence of RFLS than the N-substance. Acute and/or chronic synovitis was demonstrated in 13 of 33 rabbits and inflammatory changes were more intensive and extensive in the later period of experiment. Presence of RFLS in the affected synovial tissues, chiefly in the cytoplasm of plasma cells and mononuclear cells, occasionally in a free state was revealed by immunofluorescent study, and depositions positive for IgG and beta 1C were observed in the wall of blood vessels and fibrinous thrombi in the affected synovial tissues.

Animals↗