Post-stroke deficits in the anticipatory control and bimanual coordination during naturalistic cooperative bimanual action.

BACKGROUND: Unilateral stroke leads to asymmetric deficits in movement performance; yet its effects on naturalistic bimanual actions, a key aspect of everyday functions, are understudied. Particularly, how naturalistic bimanual actions that require the two hands to cooperatively interact with each other while manipulating a single common object are planned, executed, and coordinated after stroke is not known. In the present study, we compared the anticipatory planning, execution, and coordination of force between individuals with left and right hemisphere stroke and neurotypical controls in a naturalistic bimanual common-goal task, lifting a box. METHOD: Thirty-three individuals with chronic stroke (15 LCVA, 18 RCVA) and 8 neurotypical age-matched controls used both hands to lift a box fitted with force transducers under unweighted and weighted conditions. Primary dependent variables included measures of anticipation (peak grip and load force rate), execution (peak grip force, load force), and measures of within-hand (grip-load force coordination) and between-hand coordination (force rate cross-correlations). Primary analyses were performed using linear mixed effects modeling. Exploratory backward stepwise regression examined predictors of individual variability within participants with stroke. RESULTS: Participants with stroke, particularly the RCVA group, showed impaired scaling of grip and load force rates with the addition of weight, indicating deficits in anticipatory control. While there were no group differences in peak grip force, participants with stroke showed significant impairments in peak load force and in grip-load force coordination with specific deficits in the evolution of load force prior to object lift-off. Finally, there were differences in spatial coordination of load force rates for participants with stroke, and especially the RCVA group, as compared to controls. Unimanual motor performance of the paretic arm and hemisphere of lesion (right hemisphere) were the key predictors of impairments in anticipatory planning of grip force and bimanual coordination among participants with stroke. CONCLUSIONS: These results suggest that individuals with stroke, particularly those with right hemisphere damage, have impairments in anticipatory planning and interlimb coordination of symmetric cooperative bimanual tasks.

Non-contingent affective outcomes influence judgments of control.

Our main goal in these experiments was to examine whether affective valence plays a role in judgments of control (JoC) in intentional action. To test this, we asked participants to completevariationsofasimple aiming task in which words appeared in place of clicked targets. The affective content of the words was manipulated during the experiments but was not contingent on participants' performance. Throughout the task, participants were periodically asked to judge their JoC.Thus, JoC judgments in this task included contributions of a well-established cue to judgments of control, task performance, and a source of affect that was not related to task performance. We found thatmetacognitions of controlvaried consistentlyacross levels of affect, with stronger judgments of being in control for conditions with positive outcome words (e.g., 'puppy') and the weaker judgments of being in control for conditions with negative outcome words (e.g.,'killer').These results suggestaffective outcomes can influence JoC, even though the outcomes are not related to performance.

What am I doing? It depends: agency and action identification.

Actions can be identified at a range of levels, from higher level, outcome-related descriptions to lower level, movement-related descriptions. But how do these levels of identification influence the experience of control (agency) over a task? We addressed the relation between the level of action identification and agency using a hierarchical task modeled from typing. Participants memorized letter sequences and reported them by moving a cursor to targets that contained letters. To manipulate lower level (aiming) difficulty, the targets were either large or small. To manipulate higher level (memory) difficulty, the letter sequences were either constant or random within a block. We found effects of higher and lower level difficulty on agency and action identification. Moreover, we found interactive effects of higher and lower level difficulty on performance. We discuss these findings in terms of contributions to the study of agency, and some differences from the results of previous studies of action identification.

Does attention solve the "apples-and-oranges" problems of judging task difficulty and task order?

How do we compare the difficulty of different kinds of tasks, and how we do sequence tasks of different kinds when the basis for the ordering is the tasks' difficulty levels? The ability to do these things requires a common currency, but the identity of that currency, if it exists, is unknown. We hypothesized that people may believe that the time that attention is paid to tasks enables people to compare and sequence tasks of different kinds. To evaluate this hypothesis, we tested three groups of participants. One group estimated the proportion of time that performance of a task requires attention-what we called attention time proportions or ATPs. We obtained ATPs for tasks that were "more intellectual" (counting) and others that were "more physical" (locomotion). Two additional groups made 2-alternative-forced-choice decisions about the relative ease and preferred sequencing of all possible pairs of tasks for which ATPs were independently obtained. We found that ATPs predicted judgments of task difficulty and preferred task order.

Control used and control felt: Two sides of the agency coin.

Agency has been defined as the sense of ownership and control of our actions, and the metacognition of agency has now been examined in a number of studies. Here we examined the relations between task demands, the feeling of being in control, and the feeling of using control. As task demands increase, we might feel as if we use a lot of control while feeling little control over the task. It therefore seems possible that the amount of control one feels they have used and how much in control one feels are separable components of the metacognition of control. In two experiments, we manipulated task demands and assessed these two aspects of metacognition. The source of task demand differed for the two experiments. In Experiment 1, we manipulated task demands by varying the sizes of targets in an aiming task. As predicted, we found that reports of control used increased, while reports of control felt decreased, for more difficult aiming conditions. In Experiment 2, we found a similar relation using a different source of demand: response conflict. We connect these reports of control to previous investigations of task demand and agency, as well as prominent conceptions of cognitive control.