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  • 1
    Electronic Resource
    Electronic Resource
    The integration of haptically acquired size information in the programming of precision grip (1991)
    Springer
    Experimental brain research 83 (1991), S. 483-488 
    Details
    ISSN: 1432-1106
    Keywords: Precision grip ; Motor programming ; Size-weight illusion ; Force production ; Haptic manual exploration ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Recent evidence for the use of visual cues in the programming of the precision grip has been given by Gordon et al. (1991). Visually invoked size-related information influenced the physical forces used to produce a lift, even when it was not consistent with other sensory information. In the present study, blind-folded subjects were required to feel the size of an object by haptic exploration prior to lifting it. Two boxes of equal weight and unequal size were used for the lift objects and were attached to an instrumented (grip) handle. Grip force and load force, their rates, and the vertical move ment of the object were measured. Most subjects report that the small box was heavier, which is consistent with size-weight illusion predictions. However, peak grip force, grip force rate, peak load force, and load force rate were greater for the large box when the boxes were randomly presented, but not when the same boxes were lifted consecutively. If subjects did not feel the box prior to a lift, these parameters were scaled in between those normally employed for the large and small box. Most subjects apparently programmed the parallel increase of the grip and load force during the loading phase as one force rate pulse. This represented a “target strategy” in which an internal neural representation of the objects weight determined the actual target parameter (i.e. just enough force required to overcome gravity). The other subjects exhibited a slower stepwise increase in grip and load force rate. The subjects choosing this “probing strategy” did not scale the force parameters differently for the two boxes. Furthermore, they did not perceive any difference between the objects' weight. Together, these results suggest that haptic exploration may be used to convey size information and further support the hypoth esis that size-related information may be combined with other sensory information in the programming of the precision grip.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229825
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  • 2
    Electronic Resource
    Electronic Resource
    Integration of sensory information during the programming of precision grip: comments on the contributions of size cues (1991)
    Springer
    Experimental brain research 85 (1991), S. 226-229 
    Details
    ISSN: 1432-1106
    Keywords: Precision grip ; Motor control ; Motor programming ; Vision ; Size-weight ; Illusion ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Evidence has recently been given by Gordon et al. (1991a, b) for the use of visually and haptically acquired information in the programming of lifts with the precision grip. The size-related information influences the development of manipulative forces prior to the lift-off, and the force output for larger objects is adjusted for a heavier weight even if the weight of the objects is kept the same. However, the size influences on the force output were small compared to the relative effects of the expected weight in previous trials (Johansson and Westling 1988). In the present study, both the size and weight of objects were changed between consecutive lifts to more fully determine the strength of visual size cues. During most trials, the size and weight covaried (i.e. the weight was proportional to the volume). However, in some trials, only the size was switched while the weight was kept the same to create a mismatch between the size and weight. The forces were still appropriately scaled towards an expected weight proportional to the volume of the object. It was concluded that visual size cues are highly purposeful. The effects were much larger than previously reported and were similar in magnitude to the effects based upon the expected weight. Thus, the small effects reported in the previous experiments may have been a result of conflicting “size-weight” information.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230004
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  • 3
    Electronic Resource
    Electronic Resource
    Development of human precision grip (1992)
    Springer
    Experimental brain research 90 (1992), S. 399-403 
    Details
    ISSN: 1432-1106
    Keywords: Precision grip ; Motor development ; Motor programming ; Vision ; Size-weight illusion ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Recent evidence has shown that visual and haptical size information can be used by adults to estimate the weight of the object, forming the basis of the force programming during precision grip (Gordon et al. 1991a, b,). The present study examined the development of the capacity to use visual size information. In the first experiment, 30 children (age 1–7 years) and 10 adults performed a series of lifts with two boxes presented in an unpredictable order. The boxes were equal in weight but unequal in size and were attached to an instrumented grip handle which measured the employed grip force, load force, position and their corresponding time derivatives. The isometric force development was not influenced by the box size before the age of 3. However, the children aged 3 years and older demonstrated greater visual influences on the force programming than adults. To determine more precisely when children began to use visual size information, a second experiment in which the size and weight covaried was performed on 15 children. Children still did not use the size information during the force programming until the later half of the third year. It is concluded that this ability, probably involving associative transformations between the size and weight of objects, emerges around one year after anticipatory control based on somatosensory information pertaining to the weight of the object.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227254
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  • 4
    Electronic Resource
    Electronic Resource
    Representation of braille characters in human nerve fibres (1990)
    Springer
    Experimental brain research 81 (1990), S. 589-592 
    Details
    ISSN: 1432-1106
    Keywords: Braille ; Mechanoreceptors ; Microneurography ; Somatosensory ; Tactile ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have used microneurographic techniques in human subjects to record mechanoreceptive afferent responses to standard Braille characters scanned across the finger pads. Responses from all four mechanoreceptor classes (FA I, FA II, SA I and SA II) have been reconstructed to form two-dimensional Spatial Event Plots (raster plots) of the Braille alphabet. Both the SA I and FA I responses resolve the dot patterns of Braille characters with sufficient fidelity that the representations of the individual characters can be recognized visually. Responses from SA II and FA II afferents do not resolve the Braille characters. We believe that the Spatial Event Plots derived from SA I and FA I responses closely approximate the images that are transmitted within a human nerve during Braille reading.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02423508
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  • 5
    Electronic Resource
    Electronic Resource
    Visual size cues in the programming of manipulative forces during precision grip (1991)
    Springer
    Experimental brain research 83 (1991), S. 477-482 
    Details
    ISSN: 1432-1106
    Keywords: Precision grip ; Motor control ; Motorprogramming ; Vision ; Size-weight illusion ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A size-weight illusion was used to examine the role of visual cues in the programming of manipulative forces during the lifting of test objects utilizing the preci sion grip. Three different boxes of equal weight and unequal size were lifted. These were equipped with an instrumented grip handle to measure the employed grip force, load force (vertical lifting force), force rates and vertical movement. All fifteen subjects participating in the study reported that the smallest box was the heaviest which is consistent with size-weight illusion predictions. However, the rate of increase of the isometric grip and load forces initially during the lift, the peaks of the grip and load force and the vertical acceleration were all found to increase with the box size. Thus, despite the conscious perception indicating a heavier weight for the small object, the motor program was scaled for a lighter weight. Yet, no differences were found in grip force during the static phase of the lift, where weight related information was apparently available via sensory feed back. Previous studies have reported that the program ming of the precision grip is based on somatosensory information gained during previous lifts (Johansson and Westling 1984, 1988a, b). The present study suggests that visual cues are integrated in the programming of manipu lative forces during precision grip.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00229824
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  • 6
    Electronic Resource
    Electronic Resource
    Mechanoreceptor activity from the human face and oral mucosa (1988)
    Springer
    Experimental brain research 72 (1988), S. 204-208 
    Details
    ISSN: 1432-1106
    Keywords: Mechanoreceptors ; Man ; Face ; Infraorbital nerve ; Microneurography ; Trigeminal nerve ; Tactile sensibility ; Cutaneous sensibility ; Oral mucosa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The feasibility of adopting the microneurography technique (Vallbo and Hagbarth 1968) as a tool to investigate the mechanoreceptive innervation of peri- and intra-oral tissues was explored. Multi-unit activity and impulses in single nerve fibers were recorded from the infraorbital nerve in healthy volunteers. The innervation territories of individual nerve fascicles were mapped. These varied considerably but most fascicle fields comprised the corner of the mouth. Twenty-four single mechanoreceptive units were recorded. Eighteen innervated the skin of the face, and six innervated the mucous membranes of the lips or cheeks. A majority of the mechanoreceptive afferent units were slowly adapting with small and well defined receptive fields. It is suggested that the various slowly adapting responses may originate from two different types of afferent units. No afferents showed response properties similar to typical Pacinian-corpuscle afferents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00248518
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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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  • 8
    Electronic Resource
    Electronic Resource
    Development of human precision grip (1992)
    Springer
    Experimental brain research 90 (1992), S. 393-398 
    Details
    ISSN: 1432-1106
    Keywords: Precision grip ; Motor programming ; Motor development ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The development of anticipatory control during lifts with the precision grip was examined in 100 children aged 1 to 15 years and in 15 adults. The children were instructed to lift an instrumented test object by using the precision grip between the thumb and index finger. The employed grip force, load force (vertical lifting force), vertical position and their corresponding time derivatives (i.e., grip and load force rates and acceleration) were recorded. The weight of the object was varied between trials to access the influence of the object's weight in the previous trial on the isometric force output. Already by the second year, children began to use information pertaining to the object's weight in the previous lift, i.e., they began to use an anticipatory control strategy. This occurred concomitant to the development of mainly bell shaped force rate profiles (Forssberg et al. 1991). The succeeding development of a more mature anticipatory control was gradual and adult-like capacity was not reached until 8–11 years of age.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227253
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  • 9
    Electronic Resource
    Electronic Resource
    Development of human precision grip (1995)
    Springer
    Experimental brain research 104 (1995), S. 323-330 
    Details
    ISSN: 1432-1106
    Keywords: Motorcontrol ; Friction ; Precision grip ; Motor development ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The adaptation of the grip forces to the frictional condition between the digits and an object relies on feedforward sensorimotor mechanisms that use tactile afferent input to intermittently update a sensorimotor memory that controls the force coordination, i.e., the ratio between grip force (normal to the grip surface) and load force (tangential to the grip surface). The present study addressed the development of these mechanisms. Eighty-nine children and 15 adults lifted an instrumented object with exchangeable grip surfaces measuring the grip and load forces. Particularly in trials with high friction (sandpaper), the youngest children used a high grip force to load force ratio. Although this large safety margin against slips indicated an immature capacity to adapt to the frictional condition, higher grip forces were produced for more slippery material (silk versus sandpaper). The safety margin decreased during the first 5 years of age, in parallel with a lower variability in the grip force and a better adaptation to the current frictional condition. The youngest children (18 months) could adapt the grip force to load force ratio to the frictional condition in a series of lifts when the same surface structure was presented in blocks of trials, but failed when the surface structure was unpredictably changed between subsequent lifts. The need for repetitive presentation suggests a poor capacity to form a sensorimotor memory representation of the friction or an immature capacity to control the employed ratio from this representation. The memory effects, reflected by the influences of the frictional condition in the previous trial, gradually increased with age. Older children required a few lifts and adults only one lift to update their force coordination to a new friction. Hence, the present finding suggests that young children use excessive grip force, a strategy to avoid frictional slips, to compensate for an immature tactile control of the precision grip.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00242017
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