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Antizipative Anpassung von Griffkräften während des Hebens von Alltagsgegenständen bei Gesunden und nach unilateraler Hirnschädigung
Antizipative Anpassung von Griffkräften während des Hebens von Alltagsgegenständen bei Gesunden und nach unilateraler Hirnschädigung
The aim of this dissertation was to investigate anticipatory grip force scaling when lifting everyday objects. Previous studies were mostly restricted to lifting and grasping of neutral objects. In this study participants lifted everyday objects when grip force was registered. Our routine of everyday life is dominated by object manipulation. The ability to estimate objects properties and anticipate the grip force to grasp and lift the object promotes smooth and efficient object manipulation. We investigated anticipatory grip force scaling when lifting everyday objects in two different samples: healthy subjects (study 1) and patients with unilateral brain damage after stroke (study 2). While the first study reveals basic principles of grip force scaling in healthy Young adults, the second study evaluates the effects of brain damage. For this purpose, different objects of everyday life with a wide range of weight were handled. In study 1 eleven healthy subjects lifted 12 objects under two different conditions. In the first trial, the objects were wrapped with paper to obscure the identity of the objects. Grip force was measured by force sensors taped on the fingertips. In addition, load force was measured by the means of a scale. Data from the first lift under the unwrapped condition confirmed that participants anticipated an object’s weight and scaled their grip force correspondingly. The maximum grip force rate at the force increase phase was identified as the most reliable measure to verify that object weight was predicted. Other force measures like maximum load force rate were not as reliable, they were scaled to object weight also when object identity was not known. Variability and linearity of the relationship between grip force and weight improved during the lifting, assumably with the help of sensory information. A second and third trial with the same object in a separate block did not refine the accuracy of the grip force scaling. The aim of study 2 was to investigate whether left brain damage impairs anticipatory force scaling when lifting everyday objects. Therefore, we examined 26 patients with unilateral brain damage (16 with left brain damage, ten with right brain damage) and 21 healthy control subjects. Different tests, like pantomime of familiar tool-use and imitation of meaningless hand postures, assessed 27 limb apraxia. The objects were equal to the first study, once again grip force was measured with the help of sensors taped on the fingertips. Again, the maximum grip force rate thought to be the most reliable parameter for anticipatory grip force scaling was determined. Regression analysis showed a clear deficit of anticipatory grip force scaling for the group with left- hemisphere stroke. The group with stroke of the right hemisphere yielded non impaired force scaling compared with the control group. Lesion-analyses indicate that stroke in the left inferior frontal gyrus (IFG) and the premotor cortex (PMC) causes the described deficits. Interestingly, these are the same structures which are associated with object manipulation. Further, significant correlations of impaired anticipation with limb apraxia scores were found. However, also dissociations between the tests of limb apraxia und impaired grip force anticipation emerged, which implicates independent processes. Summarized, our findings implicate that the underlying neural substrate is not restricted to a single region; rather it may rely on the intact left hemisphere network. Overlapping is presumably explained as the left hemisphere dominantes tool use either.
Not available
Hörmann, Sandra
2019
German
Universitätsbibliothek der Ludwig-Maximilians-Universität München
Hörmann, Sandra (2019): Antizipative Anpassung von Griffkräften während des Hebens von Alltagsgegenständen bei Gesunden und nach unilateraler Hirnschädigung. Dissertation, LMU München: Faculty of Medicine
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Abstract

The aim of this dissertation was to investigate anticipatory grip force scaling when lifting everyday objects. Previous studies were mostly restricted to lifting and grasping of neutral objects. In this study participants lifted everyday objects when grip force was registered. Our routine of everyday life is dominated by object manipulation. The ability to estimate objects properties and anticipate the grip force to grasp and lift the object promotes smooth and efficient object manipulation. We investigated anticipatory grip force scaling when lifting everyday objects in two different samples: healthy subjects (study 1) and patients with unilateral brain damage after stroke (study 2). While the first study reveals basic principles of grip force scaling in healthy Young adults, the second study evaluates the effects of brain damage. For this purpose, different objects of everyday life with a wide range of weight were handled. In study 1 eleven healthy subjects lifted 12 objects under two different conditions. In the first trial, the objects were wrapped with paper to obscure the identity of the objects. Grip force was measured by force sensors taped on the fingertips. In addition, load force was measured by the means of a scale. Data from the first lift under the unwrapped condition confirmed that participants anticipated an object’s weight and scaled their grip force correspondingly. The maximum grip force rate at the force increase phase was identified as the most reliable measure to verify that object weight was predicted. Other force measures like maximum load force rate were not as reliable, they were scaled to object weight also when object identity was not known. Variability and linearity of the relationship between grip force and weight improved during the lifting, assumably with the help of sensory information. A second and third trial with the same object in a separate block did not refine the accuracy of the grip force scaling. The aim of study 2 was to investigate whether left brain damage impairs anticipatory force scaling when lifting everyday objects. Therefore, we examined 26 patients with unilateral brain damage (16 with left brain damage, ten with right brain damage) and 21 healthy control subjects. Different tests, like pantomime of familiar tool-use and imitation of meaningless hand postures, assessed 27 limb apraxia. The objects were equal to the first study, once again grip force was measured with the help of sensors taped on the fingertips. Again, the maximum grip force rate thought to be the most reliable parameter for anticipatory grip force scaling was determined. Regression analysis showed a clear deficit of anticipatory grip force scaling for the group with left- hemisphere stroke. The group with stroke of the right hemisphere yielded non impaired force scaling compared with the control group. Lesion-analyses indicate that stroke in the left inferior frontal gyrus (IFG) and the premotor cortex (PMC) causes the described deficits. Interestingly, these are the same structures which are associated with object manipulation. Further, significant correlations of impaired anticipation with limb apraxia scores were found. However, also dissociations between the tests of limb apraxia und impaired grip force anticipation emerged, which implicates independent processes. Summarized, our findings implicate that the underlying neural substrate is not restricted to a single region; rather it may rely on the intact left hemisphere network. Overlapping is presumably explained as the left hemisphere dominantes tool use either.