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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 115 (1997), S. 1-5 
    ISSN: 1432-1106
    Keywords: Key words Procedural learning ; Basal ganglia ; Caudate ; Putamen ; Muscimol ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  To study the role of the basal ganglia in learning of sequential movements, we trained two monkeys to perform a sequential button-press task (2×5 task). This task enabled us to examine the process of learning new sequences as well as the execution of well-learned sequences repeatedly. We injected muscimol (a GABA agonist) into different parts of the striatum to inactivate the local neural activity reversibly. The learning of new sequences became deficient after injections in the anterior caudate and putamen, but not the middle-posterior putamen. The execution of well-learned sequences was disrupted after injections in the middle-posterior putamen and, less severely, after injections in the anterior caudate/putamen. These results suggest that the anterior and posterior portions of the striatum participate in different aspects of learning of sequential movements.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 115 (1997), S. 137-146 
    ISSN: 1432-1106
    Keywords: Key words Arm aiming movements ; Fitts’ law ; Context dependency ; Sequential action ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Arm movements in the horizontal plane consisting of two segments were examined to determine whether the difficulty of the second segment influenced the kinematic characteristics of the first segment. The direction of the first segment was an elbow extension movement away from the trunk and remained constant throughout the experiment. The direction of the second segment varied between forearm extension and flexion movements. Based on Fitts’ law, two different indexes of difficulty (ID) of the second segment were utilized by changing target size and movement amplitude. The effects of changing ID were examined for two different movement amplitudes. All movements were single-joint movements employing elbow flexion/extension and were recorded by an x-y digitizer. Variations in the ID of the second segment produced context-dependent kinematic changes in the performance of the initial segment. Movement duration increased when the ID was increased by reducing target size for both extension-extension sequence and extension-flexion sequences. Peak velocity also decreased for higher ID targets in the extension-flexion sequence. However, there was an interaction between the ID and movement amplitude in the extension-flexion sequence. In this sequence the duration of movement for the high ID/large movement amplitude condition increased substantially compared with the low ID/small movement amplitude condition. In addition, changing ID of the second segment influenced the time between the two segments (intersegment interval) in the extension-flexion sequence. Collectively, these data suggest that the planning of complex movements is based in part on the accuracy demands of multiple segments of the sequence.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1106
    Keywords: Key words Cerebellum ; Locomotion ; Perturbation ; Adaptive process ; Cerebellar patients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  This study examined the responses of cerebellar patients and a group of age- and sex-matched control subjects to repeated changes in treadmill speed in order to test whether cerebellar patients can adapt their gait to this type of perturbation and, if so, whether their responses are comparable to those of controls. While the subject walked on the treadmill, a perturbation consisting of a sudden slowing of the treadmill followed by a sudden increase back to the original speed was applied repeatedly at a specific time during the step cycle. Both the control subjects and cerebellar patients were able to compensate for the perturbations by minimizing their postural sway and changing step length. However, the nature of the compensatory changes in step length differed between these subject groups. Control subjects compensated for the perturbation by consistently using the same leg to initiate the response to the perturbation and by adapting a pattern of stepping such that the EMG characterizing the response occurred in a manner that was entrained to the timing of the normal locomotor cycle. In contrast, the patients, although undergoing modifications in step length, employed a much less consistent motor pattern from trial to trial than that of the normal subjects. An inconsistent pattern among their responses was apparent in both the analysis of stepping and in the EMG activity of the gastrocnemius and anterior tibial muscles. These results suggest that, although the cerebellar patients can adapt their behavior in response to locomotor perturbations, they do not establish a motor pattern comparable to that employed by normal subjects.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 118 (1998), S. 293-297 
    ISSN: 1432-1106
    Keywords: Key words Procedural memory ; Sequential movements ; Memory transfer ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The purpose of this study was to characterize the nature and structure of procedural memory. We have previously studied the process of learning sequential behavioral procedures using monkeys. The monkey’s task was to press five consecutive pairs of buttons (indicated by illumination) in the correct order for every pair, which he had to find by trial-and-error in a block of trials. The whole sequence was called a “hyperset”; each pair was called a “set”. We first examined whether monkeys learned to perform a hyperset as a single sequence or learned the order of button-presses individually for each set. To answer this question, we generated hypersets that were the same as the hypersets that had been extensively learned except that the order of the sets was reversed. The performance of these “reversed hypersets” was much worse than the performance of the original learned hypersets and was similar to the performance of new hypersets, as regards both the number of errors and the performance time. The result suggests that monkeys learned a hyperset as a sequence. To examine whether the learned performance was specific to the hand used for practice, we had monkeys use the same hand throughout the long-term practice of each hyperset, and then tested the opposite hand. The performance using the opposite hand was worse than the performance using the trained hand, but was better than the performance for new hypersets. This indicates that the memory for the sequential procedure is only partially accessible to the hand that was not used for the practice.
    Type of Medium: Electronic Resource
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