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Biomedical subjects

B Nienhuis

Publications and source records attributed to B Nienhuis.

24 records · Page 2Linked to original sources
PubMed1992

Postural organization in patients with hereditary motor and sensory neuropathy.

The postural organization in patients with hereditary motor and sensory neuropathy (HMSN) type I or II was studied clinically by means of a force platform. Balance was registered in 14 barefooted HMSN patients and healthy matched control subjects during quiet stance. The effect of visual deprivation was tested to determine the degree of visual dependency. The effect of the simultaneous performance of a concurrent attention-demanding task (Stroop task) was tested to estimate the level of balance automaticity. In comparison with control subjects, the HMSN patients showed a basically decreased efficiency of postural control (p less than .01) as well as an increased visual control of posture (p less than .05) in both directions of sway. No loss of balance automaticity was found, which suggested an on-line central adaptation to the slowly developing peripheral impairments. The results provide a starting point for understanding the balance problems and gross motor disabilities in HMSN patients.

Adult↗
PubMed1991

Dual-task assessment of reorganization of postural control in persons with lower limb amputation.

Postural control in persons with lower limb amputation was studied using a cognitive approach to motor learning. The aim of this study was to show that an important characteristic of the central reorganization process after a lower limb amputation is the gradually decreasing need of attentional resources to perform a motor task. A dual-task procedure was developed to estimate the level of automaticity of a quiet, upright standing task. The effect of a concurrent attention-demanding task (Stroop task) on the efficiency of balance control was determined using force-platform measurements at the start and the end of the rehabilitation process. In contrast with a control group, the amputation group showed interference effects on body sway caused by the concurrent task both at the start (p less than .05) and, less severe, at the end of rehabilitation (p less than .05). Improvement of balance control was significant only for the dual-task condition (p less than .05). The results corroborated the hypothesis that dual tasks give information about the restoration of automaticity of postural control as an essential characteristic of the central reorganization process in persons with lower limb amputation. The role of dual-task procedures as a useful approach to skill assessment is discussed.

Adult↗
PubMed1988

Contrast discrimination: invariant to spatial parameters.

Contrast discrimination thresholds were measured for 2-dimensional difference-of-Gaussian stimuli using a spatial 2-alternative forced-choice method. The stimulus diameter was varied from 0.4 to 3 deg and the distance between the centres of stimuli from 1 to 12 deg. When the two stimuli were presented on opposite sides of the fixation point on the horizontal meridian the discrimination thresholds were invariant to stimulus size and distance. When the stimulus configuration was vertical and moved to the temporal visual field, the discrimination thresholds were found to depend slightly on the inter-stimulus distance. A high-contrast bar placed between the stimuli did not influence the discrimination sensitivity.

Contrast Sensitivity↗
PubMed1988

The visual assessment of the spatial location of a bright bar.

Vernier acuity, three-line interval bisection and line-width discrimination experiments were performed for a target bar stimulus with an asymmetrical orthoaxial contrast profile. This was done in an attempt to identify the nature of the spatial primitives that are involved in the visual coding of spatial location. We conclude that both the zero-crossings and the centroid or extremum of the zero-bounded region of the neural activity distribution that is elicited by the presentation of the target bar, are in principle available to perception. It probably depends on the spatial characteristics of the applied stimulus pattern and the adopted strategy which features are actually used in different localization tasks.

Adult↗