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  • 1
    Electronic Resource
    Electronic Resource
    Neurons of the pretectal area convey spinal input to the motor thalamus of the cat (1991)
    Springer
    Experimental brain research 84 (1991), S. 12-24 
    Details
    ISSN: 1432-1106
    Keywords: Pretectum ; Thalamus ; Dorsal columns ; Spinal cord ; Sensorimotor functions ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The aim of this study was to corroborate lesioning work (Mackel and Noda 1989), suggesting the pretectal area of the rostral midbrain acts as a relay between the spinal cord and the ventrolateral (VL) nucleus of the thalamus. For this purpose, extracellular recordings were made from neurons in the pretectal area which were antidromically activated by stimulation in the rostral thalamus, particularly in VL. The neurons were tested for input from the dorsal columns of the spinal cord, the dorsal column nuclei, and the ventral quadrant of the spinal cord. Latencies of the antidromic responses ranged between 0.6 and 3.0 ms (median 1.0 ms): no differences in latencies were associated with either location of the neurons in the pretectal area or with the site of their thalamic projection. Orthodromic responses to stimulation of ascending pathways were seen in the majority of neurons throughout the pretectal area sampled. Latencies of orthodromic responses varied considerably, with ranges of 0.9–9 ms, 6–20 ms, and 2.5–20 ms upon stimulating the dorsal column nuclei, dorsal columns, and ventrolateral quadrant, respectively. The shortest-latency responses to stimulation of the dorsal column nuclei or of the ventral quadrant were likely to be monosynaptic. Temporal and spatial facilitation of the responses to ascending input were common. The data show that neurons of the pretectal area are capable of relaying somatosensory input ascending from the spinal cord to the rostral thalamus. It is suggested that the pretectofugal output to VL converges with cerebellar input in VL neurons and becomes incorporated in cerebello-cerebral interactions and, ultimately, the control of movement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231758
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  • 2
    Electronic Resource
    Electronic Resource
    Morphological and physiological identification of neurons in the cat motor cortex which receive direct input from the somatic sensory cortex (1990)
    Springer
    Experimental brain research 80 (1990), S. 209-212 
    Details
    ISSN: 1432-1106
    Keywords: Pyramidal cells ; Nonpyramidal cells ; Cortico cortical fibers ; Sensory-motor ; Intracellular recording ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The population of neurons in the cat motor cortex which receives monosynaptic input from a specific functional region of the somatic sensory cortex was identified with the techniques of intracellular recording and staining with HRP. Both pyramidal and nonpyramidal cells located in the superficial layers of the pericruciate cortex responded to stimulation of the sensory cortex with short latency, excitatory postsynaptic potentials. More than half of the labeled cells were classified as pyramidal cells and the remainder as sparsely spinous or aspinous nonpyramidal cells. The characteristics of the EPSP's of the 2 groups of cells, ie. latency, time from beginning to peak and amplitude were found to vary only slightly. The results suggest that input from the sensory cortex impinges upon neurons which may in turn have an excitatory or inhibitory effect on corticofugal neurons in the motor cortex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228864
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  • 3
    Electronic Resource
    Electronic Resource
    Minimal stimulus parameters and the effects of hyperpolarization on the induction of long-term potentiation in the cat motor cortex (1991)
    Springer
    Experimental brain research 87 (1991), S. 295-302 
    Details
    ISSN: 1432-1106
    Keywords: Plasticity ; Corticocortical ; Sensorimotor integration ; Motor learning and memory ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The aim of the research program of which the present work is a part is to understand the neural mechanisms involved in motor learning and memory. One of the mechanisms postulated to be involved in this process is the induction of long-term potentiation (LTP) in the motor cortex. LTP can be induced in motor cortical neurons by tetanic stimulation of their afferents from the somatosensory cortex. In the present study, the effects of different stimulating parameters on the induction of LTP were examined, using in-vivo, intracellular recordings from anesthetized cats. The expression of LTP was documented by measuring the amplitude and rise-time of excitatory postsynaptic potentials (EPSPs) before and after tetanic stimulation. The minimal tetanic stimulation capable of systematically inducing LTP was found to consist of a train of stimuli at 50 Hz, 5 s. Shorter trains of stimulation produced only a short-lasting, transient potentiation. In different cells, identical stimulation parameters resulted in different degrees of potentiation of synaptic responses. Following all the stimulation trains examined, EPSP amplitudes were transiently depressed before reaching potentiated levels. The duration of this depression was directly correlated with the duration and the frequency of the tetanic stimulation. In all the cells in which LTP was induced, the variability in the amplitudes of potentiated EPSP was significantly greater than that of control EPSP amplitudes. Hyperpolarization of the postsynaptic cell, during the delivery of the tetanic stimulation, inhibited the induction of LTP. These phenomena are discussed in relation to the postulated mechanisms of LTP induction in the cortex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231846
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  • 4
    Electronic Resource
    Electronic Resource
    Corticocortical connections to the motor cortex from the posterior parietal lobe (areas 5a, 5b, 7) in the cat demonstrated by the retrograde axonal transport of horseradish peroxidase (1984)
    Springer
    Experimental brain research 54 (1984), S. 476-484 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00235473
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  • 5
    Electronic Resource
    Electronic Resource
    Formation of new synapses in the cat motor cortex following lesions of the deep cerebellar nuclei (1990)
    Springer
    Experimental brain research 80 (1990), S. 23-33 
    Details
    ISSN: 1432-1106
    Keywords: Synaptic plasticity ; Sprouting ; Corticocortical synapses ; Functional recovery ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effects of unilateral lesions of the deep cerebellar nuclei on the corticocortical (CC) projection from the somatosensory to the motor cortex were studied in adult cats, utilizing electrophysiological and electron microscopical methods. Axon terminals in the motor cortex belonging to CC afferents were labeled by degeneration induced by lesions of the somatosensory cortex; neurons in the motor cortex were labeled by the Golgi/EM method. In each cat, data from the motor cortex (MCx) contralateral (experimental) and ipsilateral (control) to the cerebellar lesion were compared. Cerebellar lesions produced marked motor deficits, which receded gradually and disappeared after 30 to 40 days. Subsequent lesions of the somatosensory cortex (area 2) contralateral to the cerebellar lesions resulted in the reappearance of the cerebellar symptoms. The number of CC synapses per unit area in experimental MCx was significantly higher than in control MCx. The increase in the number of CC synapses was apparent throughout layers II–V of the MCx, but was most prominent in layers II/III. The increase in the number of CC synapses in experimental MCx was due mainly to an increase of axon terminals synapsing with dendritic spines belonging to pyramidal neurons. In comparison, the numbers and spatial distribution of CC synapses with aspinous, nonpyramidal neurons from both experimental and control MCx were similar. Field potentials in the experimental MCx, evoked by stimulation of area 2, were altered following cerebellar lesions. In experimental MCx, the polarity of the early component of the field potentials reversed at cortical depths corresponding to layers II–III, whereas this reversal was not observed in control MCx. These findings suggest that lesions of the cerebellar nuclei induced sprouting of axon terminals in the MCx to establish a new function. The results provide the first anatomical evidence for the generation of new synapses in the adult CNS which is not induced by elimination of existing synapses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00228843
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