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  • 1
    Electronic Resource
    Electronic Resource
    Influences of object weight and instruction on grip force adjustments (1991)
    Springer
    Experimental brain research 87 (1991), S. 465-469 
    Details
    ISSN: 1432-1106
    Keywords: Precision grip ; Human hand ; Motor control ; Motor programs ; EMG ; Somatosensory input
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary This study investigated the influence of object weight and instructions on grip force responses in humans. Using a precision grip, subjects lifted a small instrumented test object to a predetermined height. Prior to each set of 40 trials, subjects were verbally instructed to either “hold” or “let go” of the object in response to any change in weight. Unpredictably on some trials (〈 20%), a sudden sustained increase (load) or decrease (unload) in vertical load was applied to the object. Grip responses to these induced weight changes were evaluated by measuring grip force, object position, and associated electromyographic (EMG) activity. Grip force changes for a load were over three times greater than those for an unload. Such asymmetry may reflect everyday grasp and manipulation in a gravity-influenced world. Grip force adjustments to loads following “hold” instructions were on the average somewhat larger than those following “let go” instructions, but there was no influence of instructions on responses to unloads. These findings contrast with more robust influences of verbal instruction on automatic postural and proximal upper limb responses and also may suggest that grip force adjustments are influenced to a greater extent by intrinsic task variables than by extrinsic volitional intent. Such organization appears tailored to functional task requirements in natural environmental contexts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231864
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Central patterning of speech movements (1988)
    Springer
    Experimental brain research 71 (1988), S. 515-526 
    Details
    ISSN: 1432-1106
    Keywords: Coordination ; Timing ; Speech movements ; Central patterning ; Sensorimotor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Previous speech kinematic studies have demonstrated systematic timing relations among the upper lip, lower lip, and jaw suggesting the operation of a central pattern generator (CPG). The present study evaluated the consistency of these timing relations following unanticipated perturbation of the lower lip. Using this approach, it was also possible to evaluate the influence of sensory information on the timing of motor output and subsequent coordination of the multiple speech movements. Perturbations were applied to the lower lip during the closing movement associated with the first “p” in “sapapple”. Muscle activity and movements of the upper lip, lower lip, and jaw were obtained. Changes in movement displacement, velocity and duration, the timing and sequencing of peak velocities, EMG area, and EMG rise time were analyzed for the control and load conditions. Similar to previous perturbation results, significant magnitude compensations from the muscles and movements of the upper lip, lower lip, and jaw were observed. In contrast, movement durations and the sequencing of peak velocities were relatively unaffected by the lower lip load. The timing of peak EMG amplitude and consequently the timing of peak closing velocity for all structures (UL, LL, and J) occurred earlier relative to the preceding opening movement. These results are consistent with the interaction of phasic sensory input with centrally-driven commands resulting in a phase-advanced motor output. Further, as the timing of one structure is modified so were all the functionally-linked components thereby maintaining the necessary coordination. As in other rhythmic motor behaviors such as locomotion and chewing, there appears to be a centrally patterned framework for speech movement coordination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248744
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Kinematic variability of grasp movements as a function of practice and movement speed (1988)
    Springer
    Experimental brain research 73 (1988), S. 225-235 
    Details
    ISSN: 1432-1106
    Keywords: Grasp ; Kinematics ; Variability ; Hand ; Motor control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Grasp movements were studied in six female subjects to determine the effects of practice and movement speed on kinematics and movement variability. Subjects performed four-joint pinch movements of the index finger and thumb, with 200 repetitions at each of three durations (100, 200, and 400 ms). As observed previously, movements of high velocity were performed with bell-shaped, single-peaked velocity profiles. In contrast, slower movements (∼200, 400 ms) were performed as a series of two to four submovements with multiple peaks in the associated joint angular velocity profiles. With practice, only the slowest movements (400 ms duration) showed significant reductions in variability of joint end-positions. Surprisingly, variability of finger and thumb joint end-positions did not increase with increasing movement speed as has been observed for arm pointing movements. This was apparently due to reductions in positional variability during deceleration of the movement which offset increases in positional variability during acceleration. Neither practice nor movement speed affected variability of the location of fingertip contact on the thumb, which always occurred on the thumb distal pulpar surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248215
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Sensorimotor characteristics of speech motor sequences (1989)
    Springer
    Experimental brain research 75 (1989), S. 586-598 
    Details
    ISSN: 1432-1106
    Keywords: Sensorimotor ; Speech movements ; Motor control ; Motor programming
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The present experiment focused on the characteristics of sequential speech movements. Subjects generated two successive lip and jaw closing movements associated with the two ‘p's’ in ‘sapapple’. By selectively manipulating the lower lip perturbation it was possible to discern the role of somatic sensory interactions with the presumed sequential movement programming. Lower lip perturbation duration was manipulated to yield two different load conditions. In the Load On (LN) condition, the perturbation remained on for both closing movements. In the Load On/Off (LNF) condition, the perturbation was removed at variable times prior to the second closing movement. Analyses focused on comparing the EMG and resulting kinematic changes for the second “p” closure across the two load conditions relative to the normal control (no load) condition. The second “p” closure was differentially affected by the load conditions resulting in changes in the upper and lower lip compensations. Upper lip changes reflected consistent load duration differences; however, the magnitude of the lower lip EMG and kinematic adjustments did not mirror those of the upper lip. In contrast to the differential upper lip/ lower lip changes observed for the magnitude adjustments, timing adjustments were similar for both upper lip and lower lip suggesting a separation between the specification of magnitude and timing of speech movements. Differential load effects were also observed for the timing of the second closing movements. For the LN condition, the onset of muscle activity and subsequent movement occurred earlier (re: control); for the LNF condition, load removal delayed the onset of muscle activity and the subsequent movement (re: control). Further, the opening movement preceding the second closing movement was modified for both load conditions suggesting that all movements in the sequence, not just closing movements, can be modified. The present results suggest that the programming of speech movement sequences is a dynamic process involving scaling and timing of motor commands relying on various degrees of sensory interaction. The apparent separation in the magnitude and timing specification of the movement sequences suggests the parallel influences of different neural systems. The consequence of this control scheme is that specification of movement parameters for sequential motor acts is a flexible real-time sensorimotor process interacting with less-flexible well-established central motor relations. Further, motor programs for speech may reflect certain generalized movement actions (e.g., oral opening, oral closing) rather than individual words, syllables, or other linguistic categories programmed on a movement-to-movement basis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00249910
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Autogenic and nonautogenic sensorimotor actions in the control of multiarticulate hand movements (1984)
    Springer
    Experimental brain research 56 (1984), S. 582-585 
    Details
    ISSN: 1432-1106
    Keywords: Hand ; Load compensation ; Motor control ; Reflex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Human subjects were trained to generate rapid movements of the thumb and index finger and produce a controlled pinch contact force. When unanticipated loads were applied to oppose thumb flexion movements, the desired pinch contact force was achieved by compensatory adjustments of both the thumb and the index finger flexor muscles. The nonautogenic finger muscle responses were (1) at latencies of 60 to 90 ms, (2) manifest the first time a load was introduced, and (3) absent for thumb loads introduced during a task not requiring coordination of thumb-finger actions. These intermovement sensorimotor mechanisms may reflect a general task-dependent process contributing to coordination of multiarticulate movements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238001
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Variant and invariant characteristics of speech movements (1986)
    Springer
    Experimental brain research 65 (1986), S. 156-166 
    Details
    ISSN: 1432-1106
    Keywords: Speech movements ; Motor planning ; Motor equivalence ; Timing ; Coordination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Upper lip, lower lip, and jaw kinematics during select speech behaviors were studied in an attempt to identify potential invariant characteristics associated with this highly skilled motor behavior. Data indicated that speech motor actions are executed and planned presumably in terms of relatively invariant combined multimovement gestures. In contrast, the individual upper lip, lower lip, and jaw movements and their moment-to-moment coordination were executed in a variable manner, demonstrating substantial motor equivalence. Based on the trial-to-trial variability in the movement amplitudes, absolute positions, and velocities of the upper lip, lower lip, and jaw, it appears that speech motor planning is not formulated in terms of spatial coordinates. Seemingly, object-level planning for speech may be encoded in relation to the acoustic consequences of the movements and ultimately with regard to listener's auditory perceptions. In addition, certain temporal parameters among the three movements (relative times of movement onsets and velocity peaks) were related stereotypically, reflecting invariances characteristic of more automatic motor behaviors such as chewing and locomotion. These data thus appear to provide some additional insights into the hierarchy of multimovement control. At the top of the motor control hierarchy, the overall plan appears to be generated with explicit specification of certain temporal parameters. Subsequently, based upon the plan and within that stereotypic temporal framework, covariable adjustments among the individual movements are implemented. Given the results of previous perturbation studies, it is hypothesized that these covariable velocity and amplitude adjustments reflect the action of sensorimptor mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00243838
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Mechanoreceptive afferent activity in the infraorbital nerve in man during speech and chewing movements (1988)
    Springer
    Experimental brain research 72 (1988), S. 209-214 
    Details
    ISSN: 1432-1106
    Keywords: Mechanoreceptors ; Man ; Infraorbital nerve ; Microneurography ; Trigeminal nerve ; Speech gestures ; Mandibular movements ; Chewing ; Tactile sensibility ; Cutaneous sensibility ; Oral mucosa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The method of microneurography was used to record activity in trigeminal cutaneous and mucosal mechanoreceptive afferents during natural orofacial behaviors such as speech gestures, chewing, licking and swallowing. Multi-unit activity and impulses in single nerve fibers were recorded from the infraorbital nerve. It appeared that these mechanoreceptors respond to contact between the lips, air pressures generated for speech sounds, and to the deformation/strain changes of the facial skin and mucosa associated with various phases of voluntary lip and jaw movements. The relatively vigorous discharge of cutaneous and mucosal afferents during natural movements of the face are consistent with the claim that mechanoreceptors found within the facial skin provide proprioceptive information on facial movements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248519
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    Paper (German National Licenses)
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