Parkinsonian Patients Reduce Their Stroke Size with Increased Processing Demands

Parkinson's disease (PD) patients often show reductions in writing size (micrographia) as the length of the text they produce increases. The cause for these reductions in stroke size are not well understood. Reductions in stroke size could be associated with either concurrent processing demands that result from the coordination and control of fingers, wrist, and arm during writing and the processing of future words or increased extension of the wrist joint as the execution of the writing progresses to the right across the page, resulting in increased stiffness in the pen-limb system. Parkinson's patients and elderly controls wrote phrases of different lengths with target patterns in various serial positions. When the number of words to be written increased, PD patients reduced their stroke size of the initial target pattern, while the elderly controls did not reduce their stroke size. There was no systematic change in stroke size of the second pattern as function of serial position. This result suggests that PD patients reduce the size of their handwriting strokes when concurrent processing load increases.     

A RAFT THAT FLOATS: EXPERIENCE,TRADITION, AND SCIENCES IN GUSTAFSON'S THEOCENTRIC ETHICS

Abstract. Although James Gustafson's use of the Christian Bible and tradition is not fully displayed in the essays published here, Bible and tradition are a crucial part of a composite rationale, which includes experience and the sciences, for his theocentric ethics. Gustafson's theocentric ethics employs the sciences to back, inform, and correct the Christian tradition and offers grounds for respecting the natural piety and morality of “nonreligious” persons while explaining and justifying why Christians draw on major themes and metaphors from their tradition that should penetrate their piety and morality. His proposal should reorient the thinking of theological ethics more than it has thus far.     

Detection of stimulus change: The hypothetical roles of visual transient responses

Two random-dot patterns (D1 and D2) were displayed briefly in close temporal succession, separated by an interstimulus interval (ISI). The two patterns were identical except that D2 could contain one more element (addition) or one less element (subtraction) than D1. Observers were required to detect the addition or subtraction using a two-alternative forced-choice method. Three experiments were designed to examine Phillips and Singer’s (1974) suggestion that detection of additions and subtractions can be explained in terms of neural ON and OFF responses. Experiment 1 replicated Phillips and Singer’s finding that performance is progressively impaired as the ISI is increased. In Experiment 2, sudden shifts in luminance between D1 and D2 were combined with several durations of ISI to produce transient responses in a novel manner. Experiment 3 explored the roles of transient neural responses and of configurational changes as determinants of performance. Most predictions based on Phillips and Singer’s model were confirmed by the experimental outcomes. Some discrepancies between theory and data are noted, and directions for further research are suggested.     

On the psychological reality of a natural rule of syllable structure

If natural rules in phonology, such as the rule which deletes a word final consonant before a consonant, are frequently found in unrelated languages, it must be because they tap universal features of production and/or perception. The present experiment employed a learning task to see whether naive subjects have a predisposition for the natural rule as opposed to its converse (consonant deletion before a vowel). The Ss first learned four novel words (nouns) - two beginning with a consonant, two with a vowel - as paired associates to English ‘translations’. Then three novel adjectives were combined with each of the four nouns, following the natural rule for one group of Ss, the unnatural rule for the other. The twelve phrases were cued by their English translations and the S had to respond to each with the phonologically correct sequence of adjective and noun; confirmation followed each response. The Ss learning the unnatural corpus had a strong tendency to give natural responses, whereas the converse was not true. Consequently they made many more errors en route to mastery than their natural counterparts, even when the operative rule was displayed on the first trial by presenting in turn each adjective with its four following nouns. It appears that our Ss had implicit knowledge of the natural rule, even though it does not operate to any significant extent in English.     

Sensory and motor impairment in the nerve compression block

Recently nerve compression block as a method of investigating movement control without kinaesthetic feedback has been questioned on the grounds that motor impairment (as measured by nerve conduction parameters) is a confounding factor. In order to clarify the relationship between sensory and motor function, behavioural data was obtained on both at systematic time intervals throughout the duration of the block. The findings indicated that significant decrements in tapping measures occurred somewhat earlier in the time course of the block than decreases in kinaesthetic discrimination. Also, contrary to assumption, the majority of subjects ceased to perform prior to total kinaesthetic loss. The data suggest that motor impairment is a “crucial” issue (Laszlo, 1966) in the use of this technique, and provide further behavioural support for the neurological findings of Kelso, Stelmach and Wanamaker (1974).     

Preprogramming, programming and reprogramming of aimed hand movements as a function of age

The present experiments were conducted to investigate the relationship between age and the response programming operations underlying the execution of a ballistic motor act. In an initial experiment, two separate age groups of female subjects (mean ages of 21.9 and 69.1 years) performed aimed-movements of the right hand and arm in one of two movement directions (left or right), under preprogramming, programming, and reprogramming conditions. These operations were examined by providing advance information about the direction of an impending movement and manipulating the degree of correspondence between the advance information and a subsequent reaction signal. The results indicated that subjects in the older age group reacted and moved more slowly than subjects in the younger age group, however, there was no interaction between age and the three response programming conditions. Such findings indicated that the basic operational characteristics of these processes remain unaffected with advancing chronological age. Also, irrespective of age and response programming condition, responses to the right were initiated faster than responses to the left. This difference was especially accentuated for reprogramming. A second experiment, using a new stimulus-response mapping, replicated the left-right difference in initiation time; this difference was reversed when the left hand was used to execute the designated movement, indicating that this finding is indeed a response programming phenomenon. Further discussion focused on the possible operations underlying reprogramming.     

Trunk-assisted prehension: specification of body segments with imposed temporal constraints

The authors used a trunk-assisted prehension task to examine intersegment coordination. Participants (N = 7) reached to grasp an object placed beyond full arm extension, thus requiring trunk flexion to achieve the target object, under 4 varying temporal constraints. Kinematic analyses were performed in which the motions of the arm, the trunk, and the endpoint were characterized. The spatial trajectories and the segments' peak velocity data revealed that under high temporal constraints the arm was more responsible for endpoint motion than the trunk, whereas in the unconstrained condition the trunk was more involved. In addition, the arm exhibited a decline in spatial variability toward the end of the movement in all conditions, whereas the trunk did not. The present study is the first to show that when temporal demand is increased for a trunk-assisted prehensile task, the arm plays a larger role than the trunk in the transport of the hand to the object. The data also suggest that the arm participates in the fine accuracy control of the reach, whereas the trunk does not.     

Developmental features of rapid aiming arm movements across the lifespan

Using a lifespan approach, the authors investigated developmental features of the control of ballistic aiming arm movements by manipulating movement complexity, response uncertainty, and the use of precues. Four different age groups of participants (6- and 9-year-old boys and girls and 24- and 73-year-old men and women, 20 participants in each age group) performed 7 types of rapid aiming arm movements on the surface of a digitizer. Their movement characteristics such as movement velocity, normalized jerk, relative timing, movement linearity, and intersegment intervals were profiled. Analyses of variance with repeated measures were conducted on age and task effects in varying movement complexity (Study 1), response uncertainty (Study 2), and precue use (Study 3) conditions. Young children and senior adults had slower, more variant, less smooth, and less linear arm movements than older children and young adults. Increasing the number of movement segments resulted in slower and more variant responses. Movement accuracy demands or response uncertainty interacted with age so that the 6- and 74-year-old participants had poorer performances but responded similarly to the varying treatments. Even though older children and young adults had better performances than young children and senior adults, their arm movement performance declined when response uncertainty increased. The analyses suggested that young children's and senior adults' performances are poorer because less of their movement is under central control, and they therefore use on-line adjustments. In addition, older children and young adults use a valid precue more effectively to prepare for subsequent movements than do young children and senior adults, suggesting that older children and young adults are more capable of organizing motor responses than are young children and senior adults.     

Viewing behavior: Ocular and attentional disengagement

In five experiments, we examined the role of the ocular and attentional systems in determining saccadic latencies. Prior to making a saccade to a target stimulus, subjects were required to direct their attention to a foveal stimulus or to an eccentric stimulus. Either stimulus could be extinguished before the onset of the target. Saccadic latencies were shortest when the foveal stimulus was extinguished, regardless of whether it was attended or not. Control experiments showed that subjects were able to attend properly and that warning, arising from turning off a stimulus before target onset, could not completely account for the results. The results were discussed in terms of ocular disengagement, attentional disengagement, and joint ocular-attentional disengagement. It was concluded that an explanation emphasizing ocular disengagement provided the best account of the data.     

Age differences in the maintenance and restructuring of movement preparation

In 2 experiments, elderly and young subjects performed simple reaction time, choice reaction time, and movement plan restructuring tasks, using a stimulus precuing paradigm. In Experiment 1, the precue display (200 ms) and preparation interval (250, 500, 750, or 1,000 ms) were experimentally determined. In Experiment 2, the precue display interval was subject determined. For the restructuring task, the precue specified the response on 75% of the trials, enabling movement plan preparation with respect to movement parameters of arm and direction. On remaining trials, the precue incorrectly specified the response, requiring movement plan restructuring. Elderly, but not young, subjects restructured a movement plan for direction more quickly than for arm or for both parameters. These findings indicate that elderly individuals have poorer movement plan maintenance for direction than for arm and thus exhibit functional change in movement preparation processes relative to young individuals.