Cory Potts - Academia.edu (original) (raw)

Papers by Cory Potts

Journal of Neuroengineering and Rehabilitation, Nov 9, 2023

Background Unilateral stroke leads to asymmetric deficits in movement performance; yet its effect... more 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.

Daily life requires use of the arms for a variety of tasks under competing cognitive demands, suc... more Daily life requires use of the arms for a variety of tasks under competing cognitive demands, such as reaching for objects in a visually-cluttered kitchen cabinet while holding a conversation. Prior studies have suggested that such demands may impact motor performance, including selection of the most efficient arm to use to reach to a target in a given location. The research conducted here expands upon prior studies by 1) examining the role of cognitive load in arm choice efficiency using a novel virtual reality paradigm designed to mimic the demands of real-life visual search, object selection, and reaching to targets, and 2) examining the impact of such demands on motor performance in individuals with stroke. To manipulate cognitive demand, we varied the semantic similarity of objects in the reaching space and the presence or absence of a secondary task. We hypothesized that cognitive load would modulate efficiency of arm choice and performance in both neurotypicals and individuals with stroke. The results showed reduced efficiency of arm choice for the stroke and neurotypical control groups under increased demand. Under cognitive load, participants with stroke also showed slower reach initiation, slower movements, increased reach curvature, and increased performance differences between the paretic and non-paretic arms. These data indicate that cognitive factors influence arm choice efficiency in naturalistic reaching tasks in neurotypical individuals, and both arm choice efficiency and motor performance in stroke. Efficiency and performance decrements under cognitive load may in turn influence reduced use of the paretic arm during daily activities.

Psychological Research-psychologische Forschung, Jan 3, 2021

How do we compare the difficulty of different kinds of tasks, and how we do sequence tasks of dif... more 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.

Acta Psychologica, Oct 1, 2017

There is no generally accepted method for measuring manual position control. We developed a metho... more There is no generally accepted method for measuring manual position control. We developed a method for doing so. We asked university students to hold a handle that had one rotational degree of freedom. The angular position of the handle depended on the degree of pronation-supination of the forearm. The subjects' task was to hold the handle as steadily as possible to keep a needle positioned in a pie-shaped target zone on a computer screen. If the needle remained in the zone for 0.5 s, the gain of the feedback loop increased; otherwise the gain decreased or remained at the starting value of 1. Through this adaptive procedure, we estimated the maximum gain that could be achieved at each of the four pronation-supination angles we tested (thumb up, thumb down, thumb in, and thumb out) for each hand. Consistent with previous research on manual control, and so validating our measure, we found that our participants, all of whom were right-handed, were better able to maintain the needle in the target zone when they used the right hand than when they used the left hand and when they used midrange wrist postures (thumb up or in) rather than extreme wrist postures (thumb down or out). The method provides a valid test of manual position control and holds promise for addressing basic-research and practical questions.

Experimental Brain Research, Jul 12, 2018

Although reaching and walking are commonly coordinated, their coordination has been little studie... more Although reaching and walking are commonly coordinated, their coordination has been little studied. We investigated decision-making related to reaching and walking in connection with a recently discovered phenomenon called pre-crastination-the tendency to expend extra effort in the service of hastening goal or sub-goal completion. In the earlier studies where pre-crastination was discovered, participants decided which of two buckets to carry to the end of a walkway, picking the bucket they thought was easier. Surprisingly, the majority of participants chose to carry the bucket that was closer to the start position, which meant that the bucket they chose had to be carried farther than the bucket they did not choose. Here we inquired into participants' sensitivity to reaching effort and walking effort by varying how far participants had to reach to pick up a bucket, how heavy the bucket was, and how far participants had to walk with the bucket they chose. We found that participants were willing to lean and reach far to pick up an empty bucket that was a shorter walk from the start position. However, as reaching costs and carrying costs increased, participants prioritized shorter reaches over shorter walking distances. The results show that although pre-crastination is a robust tendency, there are limits to the kinds of costs people are willing to incur to complete sub-goals as soon as possible.

Psychological Research-psychologische Forschung, Apr 11, 2021

Actions can be identified at a range of levels, from higher level, outcome-related descriptions t... more 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.

Attention, perception & psychophysics, Nov 7, 2017

Tasks that require less physical effort are generally preferred over more physically demanding al... more Tasks that require less physical effort are generally preferred over more physically demanding alternatives. Similarly, tasks that require less mental effort are generally preferred over more mentally demanding alternatives. But what happens when one must choose between tasks that entail different kinds of effort, one mainly physical (e.g., carrying buckets) and the other mainly mental (e.g., counting)? We asked participants to choose between a bucket-carrying task and a counting task. Our participants were less likely to choose the bucket task when it required a long reach rather than a short reach, and our participants were also less likely to choose the bucket task the smaller the final count value. We tested the hypothesis that subjective task durations provided a common currency for comparing the difficulties of the two kinds of tasks. We found that this hypothesis provided a better account of the task choice data than did an account that relied on objective task durations. Our study opens the door to a new problem in the study of attention, perception, and psychophysics-judging the difficulty of different kinds of tasks. The approach we took to this problem, which relies on two-alternative forced choice along with modeling the basis for the choice, may prove useful in future investigations.

Social Science Research Network, 2023

Attention, perception & psychophysics, Jun 4, 2019

Agency has been defined as the sense of ownership and control of our actions, and the metacogniti... more 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.

Psychological Science, 2014

In this article, we describe a phenomenon we discovered while conducting experiments on walking a... more In this article, we describe a phenomenon we discovered while conducting experiments on walking and reaching. We asked university students to pick up either of two buckets, one to the left of an alley and one to the right, and to carry the selected bucket to the alley’s end. In most trials, one of the buckets was closer to the end point. We emphasized choosing the easier task, expecting participants to prefer the bucket that would be carried a shorter distance. Contrary to our expectation, participants chose the bucket that was closer to the start position, carrying it farther than the other bucket. On the basis of results from nine experiments and participants’ reports, we concluded that this seemingly irrational choice reflected a tendency to pre-crastinate, a term we introduce to refer to the hastening of subgoal completion, even at the expense of extra physical effort. Other tasks also reveal this preference, which we ascribe to the desire to reduce working memory loads.