Temporal and spatial control following bilateral versus unilateral training

Principles of motor control and learning such as bilateral coordination and task-specificity, are increasingly incorporated in the design of upper extremity rehabilitation protocols for stroke survivors. Yet most studies investigating the efficacy of new protocols report composite scores of standardized tests, such as the Fugl-Meyer Upper Extremity test (FM) and the Wolf Motor Arm Test, rather than determining how the motor control and coordination of arm movements has changed. Here we present a sub-study of a larger randomized controlled trial comparing a bilateral and unilateral training protocol where participants were assessed on bilateral and unilateral arm reaching. Eligible participants for the arm reaching analysis were 9 (FM=37) and 9 (FM=34) in Bilateral Arm Training with Rhythmic Auditory Cueing (BATRAC) and Dose Matched Therapeutic Exercises (DMTE), respectively. Participants undertook 18 sessions of training for 6 weeks with 20min of active training per session. For bilateral arm reaching, participants after BATRAC were faster, with increased peak acceleration, fewer movement units, and smoother hand paths for each arm. The BATRAC training group showed greater improvements with training than the DMTE group during bilateral reaching for parameters of movement units and smoothness of hand path. For unilateral arm reaching, participants were faster after DMTE for paretic arm reaching; however, this group did not improve to a greater extent than the BATRAC training group. Within group functional gains were seen after BATRAC on FM, Wolf Motor Arm Test (time and weight) and after DMTE on FM and Wolf Weight. There was a positive correlation between movement units and the time component of the Wolf Motor Arm Test. The reaching analysis demonstrates task-specificity in training since BATRAC improves performance in bilateral reaching and DMTE improves performance in unilateral reaching. Temporal/spatial control outcomes in studies of post-stroke interventions can identify functionally relevant motor control changes that are not captured by traditional standardized tests.     

Social and emotional functioning following bilateral and unilateral neurosurgical prefrontal cortex lesions

Alterations in emotional and social functioning such as impaired ability to recognize emotions in others, a lack of empathy and poor insight have commonly been reported following prefrontal cortex damage. This study sought to investigate the subtleties of such difficulties in 34 individuals with discrete unilateral and bilateral neurosurgical lesions encroaching on the orbitofrontal, medial, and dorsolateral regions of the prefrontal cortex. A specifically devised self‐ and informant report measure, the social‐emotional questionnaire was used to examine five factors of functioning: emotion recognition; empathy; social conformity; antisocial behaviour; and sociability. There were some specific significant differences between the clinical and control groups' informant‐ratings in certain domains of social and emotional functioning. Individuals with damage involving the orbitofrontal region were reported to display elevated levels of antisocial behaviour. Individuals with bilateral orbitofrontal lesions were rated as showing significantly reduced social and emotional functioning in comparison with individuals with unilateral lesions and controls. In addition, individuals with bilateral lesions had significantly less insight overall regarding their social‐emotional abilities. The right unilateral lesion group showed significantly less insight into their abilities to recognize emotion in others in comparison with the left unilateral group. In conclusion, these results suggest that specific social‐emotional and insight deficits may form separate constellations of impairment. The findings also indicate that marked changes in social and emotional functioning are more likely following bilateral damage, and unilateral lesions do not inevitably lead to impairments.     

Immediate and delayed recognition of sequentially presented random shapes.

Two experiments tested whether short-term memory accounts for the recency effect observed with rapid sequential presentation of nonverbal stimuli. Four random shapes were presented sequentially (with no interstimulus interval) on each trial at rates of 150 msec, 250 msec, 500 msec, and 1,000 msec per stimulus. Subsequent recognition varied positively with exposure duration, ranging from 57% at 150 msec to 77% at 1,000 msec. Two serial position effects were observed: a slight decrease in recognition accuracy for the first stimulus in each sequence and a large increase in recognition for the last stimulus in each sequence. The recency effect was not altered by an intervening 30-sec delay, an intervening 30-sec copying task, or an intervening 30-sec copying and counting task. Since neither visual nor verbal distractors altered recognition accuracy, it was suggested that all shapes were processed directly into long-term memory storage. It also was hypothesized that long-term storage of a nonverbal stimulus requires identification of a distinctive feature of the stimulus and that this process may continue for a brief period after actual stimulus offset.     

Effect of practice in bilateral and unilateral reaction-time tasks

The effects of practice on bilateral and unilateral reaction times (RTs) for thumb flexion tasks were investigated. Four female and 23 male students were divided into 4 groups who practiced a task under a single condition: unilateral (with either the right or left hand), bilateral, or control. Unilateral and bilateral groups practiced 20 trials 3 days a week for 6 weeks. For the left hand, the RT shortened following practice in the Unilateral-left and Bilateral groups; however, the interaction of the practice group by task was not significant. For the right hand, the RT shortened following practice, but neither the interactions of the practice group by task nor the practice group by measurement time were significant. The changes in the bilateral RTs with practice were significantly correlated with the change of the unilateral-left RT but were not significantly correlated with the change of the unilateral-right RT. As a result, no significant change in bilateral deficit was found. There was no lateral specificity in the effect of practice on RT.     

Mental rotation of laterally presented random shapes in males and females

Eighteen right-handed subjects (9 males, 9 female) were to decide if laterally presented random shapes were identical or a mirror image of a centrally presented standard shape. The lateral shapes were rotated over 0 degrees, 60 degrees, 120 degrees, 180 degrees, 240 degrees, or 300 degrees. For unrotated (0 degrees) mirror image stimuli, females showed a significant right visual-field advantage, whereas males showed no significant hemifield effect. The rate of rotation was equivalent for both sexes. Field of presentation did not affect the rotation rate either. The present results support a growing number of findings that indicate that the interpretation of mental rotation as a typical right-hemispheric spatial-processing task is questionable.     

Leg stiffness: Comparison between unilateral and bilateral hopping tasks

Leg stiffness is a predictor of athletic performance and injury and typically evaluated during bilateral hopping. The contribution of each limb to bilateral leg stiffness, however, is not well understood. This study investigated leg stiffness during unilateral and bilateral hopping to address the following research questions: (1) does the magnitude and variability of leg stiffness differ between dominant and non-dominant legs? (2) Does unilateral leg stiffness differ from bilateral leg stiffness? and (3) Is bilateral leg stiffness determined by unilateral leg stiffness? Thirty-two physically active males performed repeated hopping tests on a force platform for each of the three conditions: bilateral hopping, unilateral hopping on the dominant leg, and unilateral hopping on the non-dominant leg. Leg stiffness was estimated as the ratio of the peak vertical force and the maximum displacement using a simple 1-D mass-spring model. Neither the magnitude nor variability of leg stiffness differed between dominant and non-dominant limbs. Unilateral leg stiffness was 24% lower than bilateral stiffness and showed less variability between consecutive hops and subjects. Unilateral leg stiffness explained 76% of the variance in bilateral leg stiffness. We conclude that leg stiffness estimates during unilateral hopping are preferable for intervention studies because of their low variability.     

Task difficulty and visual similarity increase a distractor's effects on random shapes

Recognition of random shapes followed by a visual distractor is altered by the type of distractor and whether the distractor needs to be attended. Three experiments tested which characteristics modify a visual distractor's effect on random target shapes presented for 75 to 150 msec. Exp. 1 showed that increasing the number of digits to be remembered (1, 3, or 8) increased the effectiveness of digits as distractors. Exeir effect as visual distractors for random target shapes. Random shapes were highly effective as distractors, while pictures of faces or comples colored pictures had a relatively small effect. In Exp. 3 decreasing the presentation time for novel visual distractors decreased recognition of the distractors but not of random target shapes. However, adding a three-digit distractor after the novel visual distractor did decrease recognition of target shapes. Exps. 2 and 3 showed that the order of the recognition tests of the target and distracting stimuli altered target recognition if and only if subjects did know which was to be reported first. These experiments indicate that the effect of a visual distractor depends on both the extent to which it is allotted attention and its visual similarity to the target stimulus.     

Verbal coding and redintegrative memory for shapes.

Four experiments examined the effect of label training on redintegrative memory for novel shapes (remembering the whole shape when only a part is presented). Redintegrative memory was markedly better when subjects were trained with names as compared to unnamed control conditions. The first two experiments demonstrated that the effect of labeling was even stronger when subjects were required to use the labels during the transfer test. This result suggests that the naming effect is not due to attentional differences during training. The last two experiments explored the quality of the assigned labels and the relationship of the label to the visual stimulus. There was a slightly greater effect of relevant meaningful labels on redintegrative memory, but in general all types of names (relevant, irrelevant, and paralog) were facilitative. The experiments suggest that a verbal code can exert a strong influence in tasks that require the integration and retrieval of visual information.     

Vocal and manual response latencies to bilateral and unilateral tachistoscopic letter displays

Bilateral rows of eight letters and unilateral rows of four letters were presented in randomized sequences for 100 ms. Subjects were required to recall all letters in a trial (Experiment I); recall letters from one hemifield cued at exposure (Experiment II); recognize a single letter, making a vocal response (Experiment III); recognize a single letter, making a manual response (Experiment IV). In Experiments I, II and III, identification errors were fewer and vocal response latencies were faster for RVF stimuli, except in the bilateral condition on Experiment I; in Experiment IV manual response latencies were the same, for left and right, bilateral and unilateral conditions. Collectively, the results could not be satisfactorily accounted for by any one hypothesis: report-order, trace-scanning, or cerebral dominance. The relative contribution of each process to the laterality effect was discussed.     

Melodic and harmonic discrimination following unilateral cerebral excision

Seventy-seven subjects who had undergone unilateral temporal, frontal, or frontotemporal lobectomy for the relief of focal epilepsy as well as a group of 20 normal control subjects were tested in two discrimination tasks, requiring the detection of a single-note change in a pattern of three notes played either successively or simultaneously. Patients with right temporal and right frontotemporal excisions demonstrated a significant deficit in melodic discrimination in comparison to the normal control subjects. Further analysis showed that left-temporal lobectomy including excision of Heschl's gyri (the primary auditory receiving area) led to a significant impairment as well, whereas anterior left temporal-lobe damage did not result in a significant deficit. The results suggest that melodic discrimination depends largely but not exclusively on the right temporal lobe, and that the left Heschl's gyri also seem to be necessary to succeed in this task. In the harmonic task, the differences between the groups did not reach significance, although the two tasks were highly correlated.     

Visual search for simple volumetric shapes.

Five experiments measured reaction time (RT) to detect the presence or absence of a simple volumetric shape (target) dependent on the number of display items (distractors) and their depicted three-dimensional (3-D) orientation. Experiments 1-4 examined every pairwise combination of two different simple volumetric shapes in two 3-D orientations. Conditions exhibiting "pop-out" could be predicted by differences in their two-dimensional (2-D) features. Conditions in which search was slower support previously found search asymmetries for particular 2-D features. When the distractors were a mixture of the other shapes in the same 3-D orientation, search was serial, except when the target had a curved principal axis (Experiment 5). The results suggest that these simple volumetric shapes are not processed preattentively.     

Rorschach changes following brief and short-term therapy.

Two groups of 35 patients each, one treated with brief therapy, averaging 14.2 sessions on a once per week basis, and the other group, treated with a short-term type of therapy, averaging 47 sessions on a once per week basis were administered the Rorschach and the Katz Adjustment Scales-Form S three times. The first administration took place before entering therapy. The brief therapy group was tested a second time at termination of treatment and again 8 to 12 months following termination. The short-term therapy group was tested the second time at therapy termination and the third time 10 to 12 months after termination. Each group reported substantially fewer symptoms at termination and continued to report about the same level of symptom reduction at the second retest. The Rorschach data seem to provide an ample basis from which to argue that considerable improvement occurred in the psychological organization and/or operations of both groups, and this appears to have some confirmation in the self-report data.