Associations between adolescent-mother and adolescent-best friend interactions

The present study examined associations between adolescent-mother and adolescent-best friend interactions during conflict resolution tasks. Adolescents (N = 39) were videotaped while discussing unresolved problems with their mothers and then with their best friends. Mothers' behavior with adolescents and adolescents' behavior with mothers and with best friends were coded for conflict, withdrawal, communication skills, support-validation, and problem-solving. Mothers' communication and support-validation with adolescents was positively associated with adolescents' communication and support-validation with best friends, respectively. However, their behavior was not identical. Mothers were more communicative and supportive with adolescents than adolescents were with their best friends. Second, adolescents' withdrawal and support-validation with mothers was positively associated with their withdrawal and support-validation with best friends, respectively. However, they exhibited less withdrawal with their mothers than with their best friends. Possible explanations for these findings, as well as directions for future research, are discussed.     

Visual aiming movements in Alzheimer's disease

This study examined whether AD affects the control of pointing movements. Sixteen older adults with probable AD and 10 age-matched healthy adults pointed at targets varying in size (3 and 7 mm in diameter) and located at three positions (at the midline and 33 degrees to the left and right). Results revealed the patients exhibited longer movement time, lower peak velocity and more time in deceleration, although they exhibited effects of target size and location comparable to the healthy controls. AD, then, would appear to slow down movement without affecting the motor system's ability to respond to task demands.     

Patterns of limb apraxia in primary progressive aphasia

Primary progressive aphasia (PPA) is a syndrome characterized by a progressive language deficit without other dementia features for at least two years (). Other deficits that are likely to co-exist with aphasia, such as apraxia, have only been investigated in a few case studies and only at a rudimentary level for the most part. In this study we investigate the frequency and severity of apraxic deficits in PPA patients. Ten PPA patients and twelve aged-matched healthy adults performed eight transitive gestures to pantomime and to imitation. Gesture performance was measured along five movement dimensions and a composite score based on the arithmetic mean of the five dimensions was calculated. Overall, PPA patients performed worse than controls with both pantomime and imitation. Furthermore, individual comparisons revealed that out of the three apraxia patterns described by (pantomime alone, imitation alone, or apraxia in both conditions), the most frequent pattern in PPA patients was apraxia in both conditions. This result corresponds with previous findings in populations of stroke and Alzheimer's patients. Considering the occurrence of apraxia in this population, this study supports the idea that a comprehensive apraxia assessment should be administered in cases of PPA.     

Prism aftereffects disrupt interlimb rhythmic coordination

The authors examined effects of prism-induced proprioceptive aftereffects on coordination of 95 participants and compared interlimb rhythmic coordination performed before versus after exposure to prisms of varying optical displacements. The observed steady states of relative phase for postprism exposure coordination were shifted by a small but significant amount, but not across all prism conditions. Phase-shift direction was not specific to the direction of optical displacement and was not, across all conditions, proportional to the magnitude of optical displacement. Prism exposure was associated with increased relative phase variability for all prism conditions. A no-prism control group showed no changes in interlimb rhythmic coordination. The results suggest that prism-induced proprioceptive aftereffects have general, disruptive effects on interlimb rhythmic coordination.     

Long-term motor programming improvements occur via concatenation of movement sequences during random but not during blocked practice

According to S. T. Klapp (1995, 1996), extensive practice serves to induce the concatenation of multiple-element responses. One benefit of the chunking process, argued Klapp, is more efficient execution of motor programming. The authors conducted the present study with 30 participants to investigate that proposition. The chunking process was found to be very transient following some practice regimes. Specifically, compared with exposure to random practice, extensive blocked practice resulted in only temporary movement sequence consolidation. The present results provide support for the claim that random practice not only leads to improvements in the completion of intratrial movement planning processes but also affects the structure of the memory developed during practice. Both components are important contributors to long-term improvements in movement preparation associated with a high contextual-interference practice condition.     

Consistent and variable practice conditions: effects on relative and absolute timing

The authors conducted the present experiments to resolve the discrepancy between studies in which relative-timing learning has been found to be enhanced by consistent practice conditions and contextual interference experiments in which relative-timing learning has been found to be enhanced more by random practice than by blocked practice. There were 40 participants in Experiment 1 and 48 in Experiment 2. The results of Experiment 1 extended previous findings: The learning of the relative-timing pattern was systematically enhanced by the degree to which the practice conditions promoted movement consistency (constant > blocked > serial > random). Experiment 2 provided evidence that the discrepancy between the relative-timing effects in the 2 groups of studies was a product of the way in which relative-timing goals and feedback were presented. When the feedback was presented as segment times, random practice resulted in generally more stable relative-timing patterns during acquisition than blocked practice did. Thus, in both experiments, the learning of the relative-timing pattern was enhanced by more stable relative-timing conditions during acquisition. Absolute-timing learning, as indexed by the transfer tests, was enhanced by serial or random practice as compared with constant or blocked practice, and was relatively unaffected by feedback conditions directed at the relative-timing pattern. In terms of motor programming theory, those findings are taken as additional evidence for the disassociation of memories supporting generalized motor program (GMP) performance, as indexed by relative timing, and parameter performance, as indexed by absolute timing.     

Transitive gesture production in apraxia: visual and nonvisual sensory contributions

The production of transitive limb gestures is optimized when the appropriate tool can be physically manipulated. Little research has addressed the independent contributions of visual and nonvisual sources of sensory information to this phenomenon. In this study, 12 control, 37 LHD, and 50 RHD stroke patients performed transitive limb gestures to pantomime (to verbal command with the object visible) and object manipulation. Performance was more accurate in the object manipulation condition, suggesting that haptic and kinesthetic cues are important for transitive gesture production. Various patterns of performance were observed in the stroke groups, indicating that selective damage to the haptic/kinesthetic processing system is possible and common following unilateral stroke.