Shared dynamics of attentional cost and pattern stability

Effects of attention on phase transitions between bimanual coordination patterns: a behavioral and cost analysis in humans.

The dual-task paradigm has previously been used to investigate the attentional demands associated with postural control. Previous studies have identified both the focus of attention and the difficulty of a postural task as potential factors influencing dual-task performance. The aim of this study was to examine how the instructed focus of attention influences dual-task performance during quiet standing tasks of various levels of difficulty. Thirteen young adults participated in two testing sessions consisting of standing as still as possible on a force platform in different postural conditions, while simultaneously performing a simple reaction time (RT) task. Postural task difficulty was manipulated by various combinations of three bases of support (feet together, tandem and single leg) and two visual conditions (eyes opened and closed). Participants were instructed to focus on either their balance or their RT performance, depending on the testing session. When comparing postural control with respect to session focus, anterior-posterior sway velocity decreased with the addition of the simple RT task when the focus was on balance, but only during the more difficult dual-task conditions. In contrast, sway area and medial-lateral sway velocity did not change between the two instructed focus sessions. Participants responded faster in all dual-task conditions when focusing on RT performance than on balance. The modified attention allocation index indicated that participants' ability to modulate their allocation of attentional resources to respond positively to instruction was more pronounced in the most challenging postural condition. The present findings could have important implications for the interpretation of dual-task performance in both clinical and research settings.

The study investigated the consequences of age-related decline in inhibition processes on intentional switching between bimanual coordination patterns. Fifteen young (24±2.8 years) and 20 older adults (69±5.3 years) performed Stroop tasks and bimanual coordination tasks. Stroop tasks included neutral, congruent, and incongruent conditions. Response time and error rate were measured. Bimanual coordination tasks consisted of performing in-phase (IP) and anti-phase (AP) patterns. Participants were requested to switch as quickly as possible from one pattern to the other, resulting in two different switching directions (AP to IP; IP to AP). Mean and standard deviation (SD) of the continuous relative phase (CRP) were calculated pre- and post-switching for each participant. Total switching time (TST) was measured. The switching phase was also decomposed into reaction time (RT) and reversal time (REvT). Pearson correlation analyses were performed to test for correlations between: (i) SD of CRP and response time in Stroop tasks, and (ii) switching times (TST, RT, RevT) and response time in Stroop task, respectively. In addition, parallel mediation analyses were conducted. Results showed that: (i) the AP pattern was less stable than the IP pattern in both young and older adults, (ii) coordination patterns were less stable in older adults, (iii) response times in Stroop task were longer in the incongruent condition, and (iv) RespTs were longer in older than in young participants, whatever the condition. In the bimanual coordination task, RT, RevT, and TST increased with age. The stability of the IP pattern was correlated with the response times observed in neutral and congruent conditions, while the stability of the AP pattern was correlated with response time observed in the incongruent condition. Correlation and mediation analyses showed that, in the AP to IP switching direction, RT and RevT were both significantly correlated with response times observed in the incongruent condition of Stroop task. These findings suggest that inhibition processes are involved in switching between bimanual coordination patterns, at least to trigger the early phase of switching. They also support the hypothesis that inhibition processes are more involved in maintaining the AP pattern and switching to the IP pattern. Finally, age-related changes in switching times seem to be prominently mediated by alterations of inhibition processes.

BackgroundThe aim of the study was to assess the attentional requirements of steady state treadmill walking in human subjects using a dual task paradigm. The extent of decrement of a secondary (cognitive) RT task provides a measure of the attentional resources required to maintain performance of the primary (locomotor) task. Varying the level of difficulty of the reaction time (RT) task is used to verify the priority of allocation of attentional resources.Methods11 healthy adult subjects were required to walk while simultaneously performing a RT task. Participants were instructed to bite a pressure transducer placed in the mouth as quickly as possible in response to an unpredictable electrical stimulation applied on the back of the neck. Each subject was tested under five different experimental conditions: simple RT task alone and while walking, recognition RT task alone and while walking, walking alone. A foot switch system composed of a pressure sensitive sensor was placed under the heel and forefoot of each foot to determine the gait cycle duration.ResultsGait cycle duration was unchanged (p > 0.05) by the addition of the RT task. Regardless of the level of difficulty of the RT task, the RTs were longer during treadmill walking than in sitting conditions (p < 0.01) indicating that an increased amount of resources are required for the maintainance of walking performance on a treadmill at a steady state. No interaction (p > 0.05) was found between the attentional demand of the walking task and the decrement of performance found in the RT task under varying levels of difficulty. This finding suggests that the healthy subjects prioritized the control of walking at the expense of cognitive performance.ConclusionWe conclude that treadmill walking in young adults is not a purely automatic task. The methodology and outcome measures used in this study provide an assessment of the attentional resources required by walking on the treadmill at a steady state.

The goal of this study was to investigate the effect of predictability on dual-task performance in a continuous tracking task. Participants practiced either informed (explicit group) or uninformed (implicit group) about a repeated segment in the curves they had to track. In Experiment 1 participants practices the tracking task only, dual-task performance was assessed after by combining the tracking task with an auditory reaction time task. Results showed both groups learned equally well and tracking performance on a predictable segment in the dual-task condition was better than on random segments. However, reaction times did not benefit from a predictable tracking segment. To investigate the effect of learning under dual-task situation participants in Experiment 2 practiced the tracking task while simultaneously performing the auditory reaction time task. No learning of the repeated segment could be demonstrated for either group during the training blocks, in contrast to the test-block and retention test, where participants performed better on the repeated segment in both dual-task and single-task conditions. Only the explicit group improved from test-block to retention test. As in Experiment 1, reaction times while tracking a predictable segment were no better than reaction times while tracking a random segment. We concluded that predictability has a positive effect only on the predictable task itself possibly because of a task-shielding mechanism. For dual-task training there seems to be an initial negative effect of explicit instructions, possibly because of fatigue, but the advantage of explicit instructions was demonstrated in a retention test. This might be due to the explicit memory system informing or aiding the implicit memory system.

A longitudinal study of reaction time performance in long-evans rats

Event-related potential evidence of semantic mismatch in a ‘same-different’ reaction time task

ABSTRACTThe primary purpose of this study was to examine the covariation of cardiac output and forearm blood flow during reaction time, mental arithmetic, and cold pressor tasks. Cardiac output was indexed using impedance cardiography, whereas impedance venous occlusion plethysmography was used lo index forearm blood flow. Cardiac output increased significantly over resting values in all three tasks, hut the pattern of these increases differed. Large heart rate increases during mental arithmetic and cold pressor tasks more than offset stroke volume decreases; the increases in the reaction time task were due to relatively smaller heart rate increases with stroke volume augmentation. For forearm blood flow, all task levels were higher than resting levels, but only mental arithmetic levels were statistically higher. The correlation between cardiac output and forearm blood flow change was significant for the reaction time task, but not for the mental arithmetic or cold pressor tasks.

ABSTRACTThis study used both beta‐adrenergic and cholinergic pharmacological blockade to investigate differences in autonomic mediation of heart rate responses during reaction time and sustained handgrip tasks. Forty‐five healthy young men received a venous infusion of saline and then performed each task for the first time. Then, each subject received a second infusion consisting of either saline, propranolol hydrochloride, or atropine sulfate, and repeated each task. For each infusion, the 15 subjects in each group were unaware of which of the three substances they were receiving. The results indicate that heart rate increases during the reaction time task were mediated by increased beta‐adrenergic activity, whereas heart rate increases during handgrip were mediated by a combination of increased beta‐adrenergic activity and vagal withdrawal. These results support the hypothesis that neural mechanisms mediating cardiac adjustments during some types of psychological stress differ qualitatively from mechanisms mediating similar‐appearing adjustments during some types of physical exertion.

Intra-striatal haloperidol and scopolamine injections: effects on choice reaction time performance in rats

Evaluation of Static and Dynamic Balance Tests in Single and Dual Task Conditions in Participants With Nonspecific Chronic Low Back Pain

PURPOSE: Young adults have the capacity to manage dual task conditions with minimal impairment to either the cognitive or the motor task; however, this ability decreases with age. Previous research on dual tasking has primarily examined over ground walking and minimal information is available on dual tasking on a treadmill. The purpose of this study was to examine the effect of dual tasking using a treadmill desk on changes in cognitive performance and gait parameters in young adults (YA) and middle-aged adults (MA). METHODS: YA (n=24; mean age 21.1±1.6 yrs) and MA (n=25; mean age 53.0±5.3 yrs) were recruited to participate in this study. Participants completed five cognitive tests (Stroop Word Color Test, phoneme monitoring, typing test, Sternberg working memory test, and serial 7 subtractions) in a single task (ST) and dual task (DT) condition in a randomized and counterbalanced order. Participants were seated at a desk for ST and walked on a treadmill desk at self-selected speed (mean speed YA=1.5±0.4 mph; MA=1.4±0.5 mph) during DT. An OptoGait system recorded gait parameters of step length, stride length, and coefficient of variation. RESULTS: There were no significant differences in gait parameters or test scores in YA when comparing DT and ST conditions (p>0.05). MA performed worse on word recall score (89.7±11.3 vs 96.6±7.5%, p=0.03), typing speed (44.9±11.2 vs 49.9±13.3 wpm, p=0.00), and Sternberg reaction time (1.5±2.0 vs 1.0±1.9 s, p=0.00) during the DT compared to the ST condition. MA stride length decreased during DT in the Sternberg test (37.7±5.9 vs 36.5±5.3 in, p=0.01) and serial 7 subtractions (37.2±5.7 vs 36.5±5.3 in, p=0.00). MA showed detriments in reaction times on the Stroop test (0.8±1.2 vs 0.6±0.9 s, p=0.00) and Sternberg test (1.5±2.0 vs 0.9±1.5 s, p=0.02) and decreased word recall score (89.7±11.3 vs 97.5±7.0%, p=0.04) compared to YA during the DT condition. CONCLUSION: The impairments in gait and cognitive test scores in MA but not YA suggest that the ability to simultaneously process cognitive demands and treadmill walking requirements decreases with age. Using a treadmill desk might affect work-related performance or gait parameters in middle-aged adults.

Objective:To determine the impact of cognitive interference on foot pedal reaction time among stroke survivors with right- (RH) or left-hemiplegia (LH).Design:Cross-sectional comparison without randomization.Subjects/patients:10 patients post-stroke with RH, 10 with LH; 10 age-matched controls.Methods:Foot pedal response times were measured using three different reaction time (RT) paradigms: simple RT, dual-task RT (counting backward by serial 3 seconds), and choice RT (correct response contingent on stimuli to eliminate pre-programing). RH and LH used the non-paretic leg for all trials. Three 3 (RT task) × 3 (group) mixed-model factorial ANOVAs were used to compare RT, movement time (MT), total response time (TRT).Results:Overall controls demonstrated faster RT than RH (332 ± 73 versus 474 ± 144 ms, P < 0.001) or LH (402 ± 127 ms, P < 0.05); LH group demonstrated faster RT than those with RH (P < 0.05). Control subjects demonstrated significantly faster RT than RH for all RT conditions (P < 0.05 for all). In contrast, controls achieved significantly faster RT than LH for the choice RT condition only (P < 0.05), but not for the simple (P = 0.12) or dual-task RT conditions (P = 0.25).Conclusions:Compared to controls, response time was significantly impaired among LH and RH when the response could not be pre-programmed. While current simple RT testing commonly employed by driver rehab specialists may be sufficient for detecting RT deficits in patients with RH, simple or dual-task RT tests alone may fail to detect RT deficiencies among LH, even when testing the non-paretic limb. Choice RT should be added to post-stroke driver fitness assessment, particularly for patients with LH.

Autonomic activity in relation to symptom ratings and reaction time in unmedicated patients with schizophrenia

Numerous previous studies using the dual-task methodology have indicated that the effect of attentional direction on the performance of motor skill differs as a function of skill levels. Whereas previous studies relied mostly on inter-individual comparisons, this study focused on how the effects of different attentional conditions change within individuals with practice. Participants were instructed to learn a short and a long keying sequence (three versus six keys) and then practiced under two block-wise alternating dual-task conditions. In each trial, a tone, either low- or high-pitched, was presented at one of the three/six keys and participants had to indicate either the pitch of the tone (extraneous dual task) or the key with which the tone was presented (skill-focused dual task) after finishing the execution of the keying sequence. Motor task performance was assessed by reaction time (RT) and movement duration (MD), and the concurrent cognitive task performance was assessed by the error rate. RT was faster in the skill-focused dual-task condition at the beginning of practice, whereas a generally shorter MD was found in the extraneous dual-task condition. The error rate in the extraneous dual task decreased with practice, whereas in the skill-focused dual task, it increased with practice. These results show that the effects of attentional direction differ not only as a function of the amount of practice but also as a function of the stage of information processing. Furthermore, our results indicate that the direction of attention alone does not explain the different patterns of performance at different skill levels seen across dual-task studies; rather, the skill levels, the nature of cognitive demands, the difficulty level of dual tasks, and the complexity of the motor skill could all drive performance differences.