| 1. |
- Andrew, Churchill, et al.
(författare)
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Vision of the hand and environmental context in human prehension
- 2000
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Ingår i: Experimental Brain Research. - : Springer Science and Business Media LLC. - 0014-4819 .- 1432-1106. ; 134:1, s. 81-89
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Tidskriftsartikel (refereegranskat)abstract
- Previous findings on the role of visual contact with the hand in the control of reaching and grasping have been contradictory. Some studies have shown that such contact is largely irrelevant, while more recent ones have emphasised its importance. In contrast, information arising from the surrounding environment has received relatively little attention in the study of prehensile actions. In order to identify the roles of both sources of information, we made kinematic comparisons between three conditions. In the first, reaching was performed in a dimly lit room and compared with a second condition in which reaches in the dark, but with the thumb and first finger illuminated, were made to a luminous object. This contrast allows the effects of environmental context to be identified. A comparison between the second and a third condition, in which both vision of the hand and the environment was removed, but the object was still visually available, enabled the assessment of how and when vision of the hand plays a role. Removing environmental cues had effects both early and late in the reach, while vision of the hand was only crucial in the period after peak deceleration. In addition, removal of both sources of information resulted in larger grip apertures. Differences and similarities between our findings and those of other studies are discussed, as is the ongoing debate about the relative importance of visual feedback of the hand in the control and co-ordination of prehensile actions. We conclude with suggestions for further research based on the set-up used in the present study.
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| 2. |
- Domellöf, Erik, 1970-, et al.
(författare)
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Functional asymmetries in the stepping response of the human newborn : a kinematic approach
- 2007
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Ingår i: Experimental Brain Research. - : Springer Berlin/Heidelberg. - 0014-4819 .- 1432-1106. ; 177:3, s. 324-335
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Tidskriftsartikel (refereegranskat)abstract
- In order to investigate subtle expressions of functional asymmetries in newborn leg movements, kinematic registrations were made on a sample of 40 healthy fullterm newborn infants during performance of the stepping response. Time–position data were collected from markers attached to the hip, knee and ankle joints of the left and right leg, and movements of both legs recorded simultaneously. Findings included evident side differences in terms of smoother trajectories of the right leg as a consequence of less movement segmentation compared to the left leg. Additionally, analyses of intralimb coordination revealed side differences with regard to stronger ankle–knee couplings and smaller phase shifts in the right leg. The findings suggest that asymmetries in newborn stepping responses are present in terms of spatio-temporal parameters and intralimb coordination. No evidence of a lateral preference in terms of frequency of the first foot moved was found. The present study adds new understanding to the lateralized attributes of the stepping response in the human newborn and as such points to new directions of research on the nature of laterality in the future.
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| 3. |
- Rönnqvist, Louise, et al.
(författare)
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Motor asymmetries in the human newborn are state dependent but independent of position in space
- 2000
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Ingår i: Experimental Brain Research. - : Springer Science and Business Media LLC. - 0014-4819 .- 1432-1106. ; 134:3, s. 378-384
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Tidskriftsartikel (refereegranskat)abstract
- Human newborns have a preference for turning and maintaining the head to one side of the body. Most studies confirm a right-sided preference in supine. Few have addressed the state dependency of this lateral bias, and even fewer have examined whether it is also expressed in the semi-upright position. We investigated whether it varies as a function of behavioural state and position in space. Kinematic recordings of head movements were made with the newborn secured on a platform in the supine or semi-upright position, which alleviated biomechanical and postural constraints imposed by gravity. Newborns differed as to whether they had a vertex, Caesarean or breech delivery. The majority of infants maintained a right-sided preference in both positions, but it was strongly mediated by state. Delivery type did not account for any lateral bias. These findings provide convincing evidence that a lateral bias in movement and positioning of the head are reflections of active neural processes rooted in the regulation of state.
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