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Biomedical subjects

H L Teulings

Publications and source records attributed to H L Teulings.

8 recordsLinked to original sources
PubMed1997

Parkinsonism reduces coordination of fingers, wrist, and arm in fine motor control.

This experiment investigates movement coordination in Parkinson's disease (PD) subjects. Seventeen PD patients and 12 elderly control subjects performed several handwriting-like tasks on a digitizing writing tablet resting on top of a table in front of the subject. The writing patterns, in increasing order of coordination complexity, were repetitive back-and-forth movements in various orientations, circles and loops in clockwise and counterclockwise directions, and a complex writing pattern. The patterns were analyzed in terms of jerk normalized for duration and size per stroke. In the PD subjects, back-and-forth strokes, involving coordination of fingers and wrist, showed larger normalized jerk than strokes performed using either the wrist or the fingers alone. In the PD patients, wrist flexion (plus radial deviation) showed greater normalized jerk in comparison to wrist extension (plus ulnar deviation). The elderly control subjects showed no such effects as a function of coordination complexity. For both PD and elderly control subjects, looping patterns consisting of circles with a left-to-right forearm movement, did not show a systematic increase of normalized jerk. The same handwriting patterns were then simulated using a biologically inspired neural network model of the basal ganglia thalamocortical relations for a control and a mild PD subject. The network simulation was consistent with the observed experimental results, providing additional support that a reduced capability to coordinate wrist and finger movements may be caused by suboptimal functioning of the basal ganglia in PD. The results suggest that in PD patients fine motor control problems may be caused by a reduced capability to coordinate the fingers and wrist and by reduced control of wrist flexion.

Adult↗
PubMed1995

Micrographia in Parkinson's disease.

A computational neural model of movement production in normal and Parkinson's disease (PD) is used to provide a neural account for the source of micrographia in PD handwriting. It is hypothesized that smaller than normal pallido-thalamic signals, due to dopamine depletion, are responsible for the observed overall smallness, slowness and variability in PD handwriting. Experimental data from PD patients that show micrographia support this hypothesis and imply the functional segregation of basal ganglia neural populations.

Adult↗
PubMed1993

Invariant properties between stroke features in handwriting.

A handwriting pattern is considered as a sequence of ballistic strokes. Replications of a pattern may be generated from a single, higher-level memory representation, acting as a motor program. Therefore, those stroke features which show the most invariant pattern are probably related to the parameters of the higher-level representation, whereas the more noisy features are probably related to the parameters derived at the lower levels (top-down hierarchy). This hierarchy of invariances can be revealed by the signal-to-noise ratio (SNR), the between-parameter correlations, and the between-condition correlations. Similarly, at the higher level a sequence of strokes may act as a unit from which individual strokes are derived (sequence hierarchy). This hierarchy of invariances can be revealed by the between-stroke correlation, which forms a weaker criterion than rescalability, which has been rejected mostly. Previous research showed that vertical stroke size has higher SNRs and higher between-condition correlations than stroke duration or peak force, whereas the latter two features were also negatively correlated. This suggested that vertical stroke size is a higher-level parameter than the other two. The present research largely confirmed this top-down hierarchy and even for upstrokes and downstrokes separately. Downstrokes were more invariant than upstrokes in terms of vertical stroke size. However, contrary to the vertical stroke size, the horizontal stroke size was not invariant. Both vertical and horizontal sizes showed substantial between-stroke correlations. In contrast, the stroke durations did not show any between-stroke correlations. This suggests that stroke segmentation is reliable in spite of the discrete sampling of the handwriting movements.

Adult↗
PubMed1990

The independence of horizontal and vertical dimensions in handwriting with and without vision.

The purpose of this study was to investigate the relationship between horizontal and vertical components of handwriting production when subjects were instructed to vary the size of these components separately or together. The effect of vision on these instructed size transformations also was examined. Eight female adults participated in the experiment. The basic task was to write the words 'poppy' and 'wood' cursively five times, the first time in their normal size and then with four size transformations. These transformations--one-fourth, one-half, double, and four-times their normal size--were made under three different sets of instructions (width only, height only, both) and in two visual conditions (normal, blindfolded), for a total of six sets of five repetitions. The individual slopes (changes in actual values across the transformation values) for width and height under instructions to change both parameters were almost identical to the width and height slopes under instructions to change only the single parameter, supporting the notion of the independence of the horizontal and vertical components. Further, an analysis of these individual slopes indicated that the size transformations were significantly greater (p less than 0.05) (and closer to the instructed values) with vision than without vision.

Adult↗
PubMed1987

Temporal and spatial characteristics in repetitive movement.

The question addressed is whether temporal or spatial characteristics of a movement sequence are represented in a motor program. Subjects executed one to five straight-line strokes as fast as possible on a digitizing tablet. The duration and length of each stroke were computed and intercorrelated. Nineteen out of 20 possible correlations were significant for length per stroke data while only one of the 20 correlations was significant for duration. Further, performance data on the five stroke patterns were sorted to examine whether the first stroke determined the overall temporal/spatial pattern of the subsequent strokes executed. It was found that only sorting by length of the first stroke produced different subsets of movement patterns. These results are argued to be in support of the hypothesis that the spatial microstructure is controlled in a prepared movement sequence.

Female↗