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  • 1
    ISSN: 1432-1106
    Keywords: Cortico-cortical connections ; Area 4γ ; Cats ; Parietal cortex ; Ansate sulcus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The physiological properties of neurons lying along the posterior bank of the ansate sulcus and the projection of these neurons to area 4γ of the motor cortex of the cat were studied and the following results were obtained: (1) Short latency antidromic responses were recorded from neurons along the medial-lateral bank of the posterior ansate sulcus following intracortical microstimulation (ICMS) delivered to motor cortex, area 4γ. (2) The posterior ansate region projects topographically to the motor cortex. Neurons in the most medial part of the ansate region project to the medial part of 4γ, while neurons in the central and lateral parts of the ansate region project to the more lateral parts of area 4γ. (3) In 33 cases, receptive field information was available for both the antidromically activated ansate neuron and from neurons around the stimulating site in 4γ. In 58% of the cases, both cortical sites received afferent input from within the same part of the periphery. (4) Afferent input to the motor cortex was examined following combined ablations of the primary somatosensory cortex (SI) and third somatosensory cortex (SIII) including all of area 5. We conclude that the integrity of these cortical regions is not necessary for afferent input to reach the motor cortex.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1106
    Keywords: Corticocortical connections ; Motor cortex ; Areas 4, 5a, 5b, 7 ; Posterior parietal lobe ; Retrograde transport of HRP ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Neurons in the parietal region of the cerebral cortex, projecting to the ipsilateral distal forelimb area of the motor cortex (area 4γ) were identified in the cat brain using the horseradish peroxidase (HRP) retrograde tracing method. After making microinjections of HRP into the distal forelimb area of the motor cortex, clusters of HRP-labeled cell bodies were observed in different regions of the ipsilateral parietal cortex. In particular these clusters of labeled cells were found in areas 5a, 5b and 7. The area 5a cluster is formed from closely packed irregularly-shaped cells, the area 5b cluster is made up of dispersed medium-sized pyramidal cells, while area 7 contains a cluster of widely dispersed small pyramidal cells. Typically, labeled cell bodies were found in lamina III of cortex. Labeled cell bodies were neither observed in the contralateral cortex nor in the visual cortex (areas 17, 18 and 19). Since parietal cortex receives projections from primary somatosensory and visual cortex, the projections from parietal to motor cortex may well form the neural substrate for the processing of convergent sensory information used in voluntary movements.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 38 (1980), S. 349-355 
    ISSN: 1432-1106
    Keywords: Motor cortex ; Monkey evoked potential ; Sensory pathway
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have shown (Asanuma et al., 1979c) that the monkey motor cortex receives peripheral somesthetic inputs directly from the thalamus. In the present experiments, we studied the pathways which mediated these inputs by stimulating superficial radial (SR) and deep radial (DR) nerves and recording evoked potentials from the motor and sensory cortices and the following results were obtained: 1. The focus for SR and DR evoked potentials in the sensory cortex was located in a circumscribed small area whereas in the motor cortex, the evoked potentials were distributed in a wide area along the central sulcus including the distal forelimb area. 2. Ablation of the sensory cortex reduced the size, but neither abolished nor changed the latency of the evoked potentials in the motor cortex. 3. Section of dorsal column nearly abolished the evoked potentials in the motor cortex, but only halved their size in the sensory cortex. 4. Section of ventrolateral cervical column including the spinothalamic tract halved the size of evoked potentials in the sensory cortex, but did not change the size in the motor cortex. 5. It is concluded that direct peripheral inputs to the motor cortex are mediated primarily through the dorsal column system whereas the peripheral inputs to the sensory cortex are mediated through both dorsal column and spinothalamic tract.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1106
    Keywords: Postsigmoid gyrus ; Area 4γ ; Motor cortex ; Ansate sulcus ; Cats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The physiological properties of neurons in the postsigmoid gyrus lying along the anterior bank of the ansate sulcus and the pattern of projection of these neurons to the motor cortex, area 4γ, were investigated in the cat and the following results were obtained. (1) Neurons lying along the anterior bank of the ansate sulcus receive somatotopically organized afferent input from the skin and deep structures on the contralateral side of the body. (2) Short latency antidromic responses were recorded from all regions along the bank of the sulcus following intra-cortical microstimulation (ICMS) of area 4γ. (3) The projection of neurons to area 4γ was topographically organized. Neurons in the lateral portions projected to more lateral parts of 4γ, whereas neurons in the medial region of the postsigmoid gyrus sent axons to the more medial regions of the motor cortex. (4) In 50 cases, receptive fields were recorded from both the antidromically identified postsigmoid gyrus neuron and from neurons around the activation site in area 4γ. In 62% of these instances, both cortical sites received afferent input from within the same part of the periphery.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1106
    Keywords: Sensory cortex ; Motor effects ; ICMS ; Area 2 pr.i
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary (1) Intracortical microstimulation (ICMS) delivered to area 2 preinsularis (area 2 pr. i) of the second somatosensory cortex, SII, elicited contralateral distal limb movements with threshold currents as low as 2 μA. (2) The effective sites for a particular movement were located in a small area within the depth of the cortex extending along the direction of the radial fibers. (3) Neurons in an area for a particular movement generally received peripheral input from the skin overlying the muscle to which the area projected. (4) ICMS in area 2 pr.i produced powerful monosynaptic as well as disynaptic activation of pyramidal tract neurons, suggesting that the effect was mediated by the pyramidal tract. (5) Ablation of the motor cortex did not eliminate or otherwise reduce the low threshold responses from area 2 pr.i suggesting that the described effect is independent of the motor cortex.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1106
    Keywords: Parietal cortex ; Ansate sulcus ; Facial muscles ; ICMS ; Cats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The lateral branch of the posterior bank of the ansate sulcus within the parietal cortex, areas 5a and 5b, was mapped using intracortical microstimulation (ICMS). Motor effective sites for contraction of facial muscles were identified using ICMS currents of less than 30 μA. Of the 177 effective sites, 78% were activated with threshold currents of less than 20 μA, and of these, 33% responded to stimulus strengths of less than 10 μA. Since neurons in this portion of the ansate region send projections to the face region of motor cortex, area 4γ, the possibility existed that the motor effects might be mediated through area 4γ. To examine this possibility we ablated both the anterior sigmoid gyrus (ASG) and the second somatosensory cortex, SII, including area 2pri, a region shown to contain a low threshold motor component, and report that the motor effect recorded from the ansate region is independent of both the ASG and area 2pri.
    Type of Medium: Electronic Resource
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