Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “HANDWRITING”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,135 records · Page 63Linked to original sources
PubMed1989

Visual control of movement patterns and the grammar of action.

In this experiment adult subjects copied three types of material (letters, reversed letters and geometric shapes) with and without sight of the hand and the writing trace. Without vision the number of movement segments decreased and the sequence and direction of movements were altered. This means that subjects did not use a fixed stored representation to produce items nor did they obey the rules of Goodnow and Levine's (1973) grammar of action. When spatial location is made more difficult by the removal of vision, movement production is simplified to reduce the number of relocations required. The use of consistent directions of movement depends on the ability to use visual control of spatial location.

Form Perception↗
PubMed1993

Neural representations for sensory-motor control, I: Head-centered 3-D target positions from opponent eye commands.

This article describes how corollary discharges from outflow eye movement commands can be transformed by two stages of opponent neural processing into a head-centered representation of 3-D target position. This representation implicitly defines a cyclopean coordinate system whose variables approximate the binocular vergence and spherical horizontal and vertical angles with respect to the observer's head. Various psychophysical data concerning binocular distance perception and reaching behavior are clarified by this representation. The representation provides a foundation for learning head-centered and body-centered invariant representations of both foveated and non-foveated 3-D target positions. It also enables a solution to be developed of the classical motor equivalence problem, whereby many different joint configurations of a redundant manipulator can all be used to realize a desired trajectory in 3-D space.

Brain↗
PubMed1993

On Fitts's and Hooke's laws: simple harmonic movement in upper-limb cyclical aiming.

Can discrete, single-shot movements and continuous, cyclical movements be reduced to a single concept? In the classical, computational approach to human motor behaviour, cyclical aimed movement has generally been considered to derive from discrete primitives through a concatenation mechanism. Much importance, accordingly, has been attached to discrete-movement paradigms and to techniques allowing the segmentation of continuous data. An alternative approach, suggested by the nonlinear dynamical systems theory, views discreteness as a limiting case of cyclicity. Although attempts have been made recently to account for discrete movements in dynamical terms, cyclical paradigms have been favoured. The concatenation interpretation of cyclical aimed movement is criticized on the ground that it implies a complete waste of mechanical energy once in every half-cycle. Some kinematic data from a one-dimensional reciprocal (i.e., cyclical) aiming experiment are reported, suggesting that human subjects do save muscular efforts from one movement to the next in upper-limb cyclical aiming. The experiment demonstrated convergence on simple harmonic motion as aiming tolerance was increased, an outcome interpreted with reference to Hooke's law, in terms of the muscles' capability of storing potential, elastic energy across movement reversals. Not only is the concatenation concept problematic for understanding cyclical aimed movements, but the very reality of discrete movements is questionable too. It is pointed out that discrete motor acts of real life are composed of complete cycles, rather than half-cycles.

Attention↗
PubMed1993

Acquired agraphia caused by focal brain damage.

Motor and linguistic aspects of writing were evaluated in 31 subjects with focal damage in 1 of 3 regions of the left hemisphere: (1) dorsolateral frontal lobe sparing primary motor cortex (group FL), (2) parietal lobe (group PL), or (3) temporal lobe (group TL). A standard procedure was used to evaluate writing for grapheme formation, spatial arrangement, spelling, word selection, grammar, and perseveration. It was predicted that agraphia would be observed in all 3 groups, and that the most severe impairments would be associated with frontal lobe damage, particularly in aspects of writing dependent on sequencing (grapheme formation, spelling, and grammar). It was found that agraphia was common in all groups, particularly in the acute epoch, and that all groups showed considerable recovery of writing by the chronic epoch. Few differences were found between groups. However, the FL group was impaired on spelling and grammar relative to the PL group in the acute epoch and impaired on grammar relative to the TL group in the chronic epoch. The findings are consistent with the notion that writing relies on a distributed neuroanatomical network, which acts in concert to link fragments of visuomotor activity with component linguistic elements.

Adult↗
PubMed1993

Changes in motor planning during the acquisition of movement patterns in a continuous task.

Changes in the planning and execution of movements were studied as a function of practice on a continuous motor task. Twelve subjects learned to move a pen through a cut-out square and maze patterns with their eyes closed. Maze patterns consisted of six, eight, ten, or twelve segments that were connected by intersections. Task performance was studied during six blocks. Although the mazes could be traced continuously in a clockwise direction, selecting a wrong turn at an intersection resulted in coming to a dead end. Performance at intersections was analyzed by determining the number of correct (and incorrect) turns following mechanically forced stops and the number of correctly planned and executed turns without any halt. In addition, movement time and pause duration were analyzed. With practice an increase in the number of correctly executed turns indicated that subjects gradually learned to group segments into chunks of increasing size. It was found that up to eight segments could be organized and executed as a single unit. Finally, with practice a non-linear performance improvement was found, suggesting that the learning process proceeded through qualitatively different learning stages. It is concluded that within five minutes subjects gradually changed their movement strategy from a sequential, trial-and-error mode in which planning and execution occurred segment by segment, to a mode in which concurrent planning was realized, i.e. in which the planning of oncoming segments occurred concurrently with the execution of segments.

Adult↗
PubMed1993

Exploitation of elasticity as a biomechanical property in the production of graphic stroke sequences.

In the present study we report several findings which indicate that subjects exploit elasticity of muscles and tendons as a biomechanical property of the motor system in the execution of graphic stroke sequences. The drawing movements of 15 right-handed subjects were analyzed, who copied a geometrical pattern consisting of four line segments. Three of these segments were connected by an acute and an obtuse angle. A first analysis concerning stroke-direction preferences shows that subjects tended to produce final strokes in preferred movement directions and obeyed an end-state stability constraint. Subsequently, we analyzed the copying movements with respect to (1) pauses at acute and obtuse angles, (2) local deviations in angle size, and (3) size variations of the strokes surrounding the angles. The results reveal a higher incidence of pauses at obtuse than at acute angles. Furthermore, a local sharpening of angles was found which was most pronounced at obtuse angles. Finally, systematic size variations of the strokes surrounding the angles were found. The results are considered to reflect the functional use of elasticity during task performance. It is concluded that biomechanical properties of the motor system significantly influence higher-order preparatory processes involved in multi-trajectory control.

Adult↗
PubMed1993

Analysis of actual and mental movement times in graphic tasks.

This paper reports on a study of movement times and movement time variability of graphic gestures which were executed either physically or mentally. The results revealed that temporal parameters for actual as well as mental graphic movements in the same subject and for the same hand were very similar, irrespective of the writing amplitude. It is suggested that the programming of motor acts, whether they are physically executed or only virtually, share to a considerable extent the same timing mechanism.

Adult↗
PubMed1982

An operant approach to the treatment of writer's cramp.

A theoretical model of writer's cramp is presented. In addition to the original emotional arousal and subsequent conditioned stimuli inherent in a classical conditioning paradigm, this model stresses the role of operant behaviors in the maintenance of the disorder. The immediate consequences of the actual cramp and subsequent escape behaviors are emphasized. An extinction procedure consisting of response-cost and response-prevention measures is tested using an A-B-A-B design. Two patients totally unable to write, were able to increase cramp latency and were gradually retrained to write. Follow-up assessments at 6, 9 and 12 months confirmed the treatment gains.

Adult↗
PubMed1983

Writer's cramp--a habit for reversal?

Four patients with writer's cramp were treated by nurse-therapists who used a combination of habit reversal, in vivo exposure and re-education. All four resumed normal writing activities after an average of four sessions. At follow-up 2-6 yr later, only one had relapsed, and she improved after further sessions. The brevity and simplicity of this method recommend it in the treatment of writer's cramp.

Adult↗