Greater Task Difficulty Research Articles

Development and Validation of Quadri Condition Dichotic Double Word Test in Kannada

Introduction: Dichotic listening (DL) is a test where auditory stimuli are presented simultaneously to each ear. DL has clinical applications in assessing APD, schizophrenia, and brain injury. It is sensitive to hemisphere differences and has been used to study language lateralization. The study aimed to develop, validate, and establish norms for a Quadri condition Dichotic Double Word Test (free recall, forced right, forced left, and switch attention) in the Kannada language (DDWT-K). Methods: This study was carried out in two phases. Phase 1 aimed to develop and validate the DDWT-K and phase 2 involved data collection. The developed novel dichotic test was administered on 100 normal-hearing adults in four conditions – free recall, forced right, forced left, and switch attention. Results: The results showed significant ear differences in free recall condition indicating right ear advantage. The switch attention condition showed slightly poorer performance when compared to both the forced attention condition indicating greater task difficulty. The test-retest reliability was above 0.7 for all the conditions indicating good reliability. Conclusions: The findings demonstrated the best preservation of the original dichotic effects and hence ready for clinical use.

CAREGIVER WELL-BEING OUTCOMES IN A STROKE TRANSITIONS TRIAL: THE EFFECTS OF CAREGIVER BURDEN AND PREPARATION

Abstract The Michigan Stroke Transitions Trial (MISTT) was an open, pragmatic randomized trial which tested the effectiveness of a 60-day in-home social work case management for patients and caregivers transitioning home after hospitalization for a stroke. This secondary analysis explores the effect of caregiver burden and preparation on caregiver outcomes. The analytic sample is the 169 caregivers who participated in MISTT. Dependent variables are the Bakas Caregiver Outcomes Scale (BCOS) and the Patient Health Questionnaire-9 (PHQ9) at 90 days after discharge home. Key predictors include the Preparedness for Caregiving Scale and the Oberst Caregiving Burden Scale which measures caregivers’ perception of burden in relation to the both the time and difficulty of caregiving tasks. Analyses that controlled for outcomes at 7 days post discharge as well as caregiver age, marital status, and education were conducted using Stata v.16. Results indicate that caregivers who perceived caregiving tasks as more difficult had worse outcomes as measured by the BCOS. In addition, there was a significant interaction between task difficulty and age such that the effect of task difficulty on BCOS declined with age. In addition, depression was associated with greater task difficulty and less preparation. This study contributes to a growing body of work related to the complexity of transitions of care and has implications for how we support caregivers as their care recipient moves from inpatient to outpatient care.

Greater task difficulty during unilateral motor tasks changes intracortical inhibition and facilitation in the ipsilateral primary motor cortex in young men

This study aimed to clarify the changes in short-interval intracortical inhibition (SICI) and facilitation (ICF) in the ipsilateral primary motor cortex (iM1) when the task difficulty during unilateral force-matching tasks was manipulated. Twelve young male adults matched their left index finger abduction force to a displayed target force. Task difficulty was manipulated by varying the acceptable force range of the mean target force (5% MVC). Briefly, unilateral force-matching tasks with lesser and greater task difficulty (EASY and DIFF, respectively) were assigned acceptable force ranges of ± 7% and ± 0% of the target force, respectively. To evaluate SICI and ICF in iM1, paired-pulse transcranial magnetic stimulation with 2-ms and 10-ms interstimulus intervals was applied to correct motor-evoked potentials (MEPs) from the first dorsal interosseous muscle during each task. Test stimulus intensity to evoke the MEP with a peak-to-peak amplitude of approximately 0.5–1.5 mV for each task was lower in DIFF than in EASY (P = 0.001), indicating that DIFF increased corticospinal excitability of the ipsilateral hemisphere compared with EASY. The MEPs in SICI and ICF were significantly larger in DIFF than in EASY (P < 0.050). These results suggest that greater corticospinal excitability in the ipsilateral hemisphere during DIFF is associated with reduced SICI and increased ICF.

Brain functional connectivity dynamics at rest in the aftermath of affective and cognitive challenges.

Carry‐over effects on brain states have been reported following emotional and cognitive events, persisting even during subsequent rest. Here, we investigated such effects by identifying recurring co‐activation patterns (CAPs) in neural networks at rest with functional magnetic resonance imaging (fMRI). We compared carry‐over effects on brain‐wide CAPs at rest and their modulation after both affective and cognitive challenges. Healthy participants underwent fMRI scanning during emotional induction with negative valence and performed cognitive control tasks, each followed by resting periods. Several CAPs, overlapping with the default‐mode (DMN), salience, dorsal attention, and social cognition networks were impacted by both the preceding events (movie or task) and the emotional valence of the experimental contexts (neutral or negative), with differential dynamic fluctuations over time. Temporal metrics of DMN‐related CAPs were altered after exposure to negative emotional content (compared to neutral) and predicted changes in subjective affect on self‐reported scores. In parallel, duration rates of another attention‐related CAP increased with greater task difficulty during the preceding cognitive control condition, specifically in the negative context. These findings provide new insights on the anatomical organization and temporal inertia of functional brain networks, whose expression is differentially shaped by emotional states, presumably mediating adaptive homeostatic processes subsequent to behaviorally challenging events.

Learner-Controlled Practice Difficulty and Task Exploration in an Active-Learning Gaming Environment

Background. With the use of computer-based simulations and games becoming increasingly common in education and organizational contexts for delivering training and instruction, learners are being granted unprecedented control over their learning. This increase in learner control leaves large differences in how learners challenge themselves and explore their learning environments. Learners can benefit from task difficulty, an aspect of challenge, when they are neither overwhelmed nor underwhelmed. The purpose of the present lab study was to test a model of how encouraging learners to challenge themselves with greater task difficulty when practicing a video game could be a “double-edged sword” in terms of their skill-based learning. Method. Using a first-person shooter computer game as the criterion task, 120 undergraduate males were randomly assigned to one of two groups. Half of the participants were encouraged to practice at a difficulty level that matched their skill level, while the other half were encouraged to practice at a difficulty that greatly exceeded their skill. Exploratory behavior was reflected in the variety of weapons used. Results. Findings supported a model of inconsistent mediation predicting that difficulty encouragement instructions would lead to higher selected practice difficulty, which in turn would have positive direct effects on skill transfer yet negative indirect effects through exploratory behavior. Discussion. The present study demonstrated that encouraging learners to practice at high levels of task difficulty is a “double-edged sword.” Although high levels of task difficulty can help in the preparation for future difficulties, it can also undermine exploratory behavior which is an important aspect of the learning process. This research speaks to the potential of encouraging learners to practice under difficult conditions without undermining their learning.

Unintended activity in homologous muscle during intended unilateral contractions increases with greater task difficulty.

The present study aimed to examine (1) the effect of task difficulty on unintended muscle activation (UIMA) levels in contralateral homologous muscle, (2) the difference between young and old adults in degree of UIMA with respect to task difficulty, and (3) temporal correlations between intended and contralateral unintended muscle activity at low frequency during unilateral intended force-matching tasks. Twelve young (21.8±2.4years) and twelve old (69.9±5.3years) adult men performed steady isometric abductions with the left index finger at 20-80% of maximal voluntary contraction force. Two task difficulties were set by adjusting the spacing between two bars centered about the target force used for visual feedback on a monitor. The amplitude of surface electromyogram (aEMG) for both hands was calculated and normalized with respect to the maximal value. To determine if oscillations between intended and unintended muscle activities were correlated, cross-correlation function (CCF) of rectified EMG for both hands at low frequency was calculated for samples deemed adequate. The unintended aEMG (right hand) had significant main effects in task difficulty, age, and target force (all P<0.05) without any interactions. Distinct significant peaks in CCF (0.38 on average, P<0.05) with small time lags were present between rectified EMGs of intended and unintended muscles in 14 of the 17 samples. The current results indicate that UIMA increases with greater task difficulty regardless of age, and temporal correlations exist between intended and contralateral unintended muscle activities at low frequency.

Modulation of microsaccade rate by task difficulty revealed through between- and within-trial comparisons

Microsaccades (MSs) are small eye movements that occur during attempted visual fixation. While most studies concerning MSs focus on their roles in visual processing, some also suggest that the MS rate can be modulated by the amount of mental exertion involved in nonvisual processing. The current study focused on the effects of task difficulty on MS rate in a nonvisual mental arithmetic task. Experiment 1 revealed a general inverse relationship between MS rate and subjective task difficulty. During Experiment 2, three task phases with different requirements were identified: during calculation (between stimulus presentation and response), postcalculation (after reporting an answer), and a control condition (undergoing a matching sequence of events without the need to make a calculation). MS rate was observed to approximately double from the during-calculation phase to the postcalculation phase, and was significantly higher in the control condition compared to postcalculation. Only during calculation was the MS rate generally decreased with greater task difficulty. Our results suggest that the nonvisual cognitive processing can suppress MS rate, and that the extent of such suppression is related to the task difficulty.

Reduction of Influence of Task Difficulty on Perceptual Decision Making by STN Deep Brain Stimulation

Neurocomputational models of optimal decision making ascribe a crucial role-the computation of conflict between choice alternatives-to the subthalamic nucleus (STN). Specifically, these models predict that deep brain stimulation (DBS) of the STN will diminish the influence of decision conflict on decision making. In this work, patients with Parkinson's disease judged the direction of motion in random dot stimuli while ON and OFF DBS. To induce decision conflict, we varied the task difficulty (motion coherence), leading to increased reaction time (RT) in trials with greater task difficulty in healthy subjects. Results indicate that DBS significantly influences performance for perceptual decisions under high decision conflict. RT increased substantially OFF DBS as the task became more difficult, and a diffusion model best accounted for behavioral data. In contrast, ON DBS, the influence of task difficulty on RT was significantly reduced and a race model best accounted for the observed data. Individual data fits of evidence accumulation models demonstrate different information processing under distinct DBS states. Furthermore, ON DBS, speed-accuracy tradeoffs affected the magnitude of decision criterion adjustment significantly less compared to OFF DBS. Together, these findings suggest a crucial role for the STN in adjusting decision making during high-conflict trials in perceptual decision making.

Dual Task Performance in Normal Aging: A Comparison of Choice Reaction Time Tasks

This study examined dual task performance in 28 younger (18–30 years) and 28 older (>60 years) adults using two sets of choice reaction time (RT) tasks paired with digit tasks. Set one paired simple choice RT with digit forward; set two paired complex choice RT with digit backward. Each task within each set had easy and hard conditions. For the simple choice RT, participants viewed single letters and pressed a specified keyboard key if the letter was X or Z or a different key for other letters (easy). For the hard condition, there were 4 target letters (X, Z, O, Y). Digit forward consisted of 4 (easy) or 5 (hard) digits. For the complex choice RT, participants viewed 4×4 matrices of Xs and Os, and indicated whether four Xs (easy) or four Xs or four Os (hard) appeared in a row. Digit backward consisted of 3 (easy) or 4 (hard) digits. Within each set, participants performed every possible combination of tasks. We found that in the simple choice RT tasks older adults were significantly slower than, but as accurate as younger adults. In the complex choice RT tasks, older adults were significantly less accurate, but as fast as younger adults. For both age groups and both dual task sets, RT decreased and error rates increased with greater task difficulty. Older adults had greater dual task costs for error rates in the simple choice RT, whereas in the complex choice RT, it was the younger group that had greater dual task costs. Findings suggest that younger and older adults may adopt differential behavioral strategies depending on complexity and difficulty of dual tasks.

Smoking withdrawal shifts the spatiotemporal dynamics of neurocognition

Smoking withdrawal is associated with significant deficits in the ability to initiate and maintain attention for extended periods of time (i.e. sustained attention; SA). However, the effects of smoking abstinence on the temporal dynamics of neurocognition during SA have not been evaluated. Twenty adult smokers underwent functional magnetic resonance imaging scans following smoking as usual and after 24-hours abstinence. During scanning they completed a SA task with two levels of task difficulty, designed to measure both sustained (i.e. over the duration of the task) and transient (i.e. event-related) activation. Smoking abstinence significantly decreased task accuracy regardless of task difficulty. Compared to smoking as usual, abstinence resulted in decreased sustained activation in right inferior and middle frontal gyri but increased transient activation across dispersed cortical areas including precuneus and right superior frontal gyrus. Greater task difficulty was associated with even greater transient activation during abstinence in mostly right hemisphere regions including right inferior frontal gyrus. These findings suggest smoking withdrawal shifts the temporal and spatial dynamics of neurocognition from sustained, right prefrontal activation reflecting proactive cognitive control (Braver, Gray & Burgess 2009) to more dispersed and transient activation reflecting reactive control.

The effects of a motor and a cognitive concurrent task on walking in children with developmental coordination disorder

The effects of type (cognitive vs. motor) and difficulty level (easy vs. hard) of a concurrent task on walking were examined in 10 boys and 4 girls (age 4–6 years) with developmental coordination disorder (DCD) and 28 age- and gender-matched unaffected children. Each child performed free walking (single task), walking while carrying an empty tray (dual task, the concurrent task being motor and easy), walking while carrying a tray with 7 marbles (the concurrent task being motor and hard), walking while repeating a series of digits forward (the concurrent task being cognitive and easy), and walking while repeating the digits backward (the concurrent task being cognitive and hard). Walking was affected by the concurrent task (i.e., dual-task cost) in the children with DCD more so than in the comparison children. Greater task difficulty also increased the dual-task cost in the children with DCD more so than in the comparison children. These patterns were only noted for the motor concurrent task. The cognitive concurrent task also affected walking, but the dual-task costs did not differ between difficulty levels, nor between the groups.

Functional Magnetic Resonance Imaging and Working Memory in Adolescents with Gestational Cocaine Exposure

To assess the effect of gestational cocaine exposure on the prefrontal cortex (PFC) with functional magnetic resonance imaging (fMRI). Using an n-back task, we obtained fMRI with a 3T Siemens scanner on 49 adolescents, 25 who were exposed to cocaine and 24 who were not exposed. The primary outcome was PFC activation during task performance. Five functionally derived regions of interest (ROI) were defined; in addition, 2 a priori anatomical ROIs were generated for Brodmann regions 10 and 46. Of the 49 adolescents who underwent imaging, data from 17 who were exposed to cocaine and 17 who were not exposed were in the final analysis. Groups had similar performance on the n-back task (P >/= .4), with both showing a fewer number of correct responses on the 2-back than the 1-back (P < .001), indicating increased demands on working memory with greater task difficulty. In functionally derived ROIs, imaging results showed increased activation for both groups in the 2-back versus the 1-back condition. In anatomical ROIs, both groups showed greater activation in the 2-back versus the 1-back condition, with activation in the non-exposed group proportionally greater for the left prefrontal region (P = .05). In this sample of adolescents, participants who were exposed to cocaine and participants who were not exposed were similar in performance on an executive function task and in fMRI activation patterns during task performance.

Employee Turnover and Organizational Performance: Testing a Hypothesis from Classical Public Administration

Empirical studies of public employee turnover, particularly using turnover as an independent variable, are rare; and most of the literature assumes turnover to have a negative impact on organizations. This study examines a provocative but little supported hypothesis that has recently emerged in the private sector literature that turnover may provide positive benefits to the organization, at least up to a point. Using data from several hundred public organizations over a nine-year period, we test the proposition that moderate levels of turnover may positively affect organizational performance. We find that while turnover is indeed negatively related to performance for the organization's primary goal, it does have the hypothesized nonlinear relationship for a secondary output that is characterized by greater task difficulty.

Functional brain activation during arithmetic processing in females with fragile X Syndrome is related to FMR1 protein expression.

Arithmetic processing deficits in persons with fragile X Syndrome (fraX), the most common heritable cause of mental retardation, are well known. In this study, we characterize the neural underpinnings of these performance deficits using functional MRI. Given that a single gene defect (FMR1) is known to be responsible for this disorder, we also assess whether brain activation in arithmetic processing areas is related to amount of FMR1 protein expression (FMRP). Subjects included 16 females with fraX, and 16 female age-matched controls. Subjects viewed arithmetic equations with two (1 + 3 = 4) or three (2 + 3 - 1 = 5) operands, and were asked to judge whether the results were correct or not. Subjects with fraX showed significant impairment in behavioral performance on the 3-operand but not the 2-operand arithmetic equations. Significant brain activation was observed bilaterally in the prefrontal and parietal cortices for unaffected subjects, and bilateral prefrontal and left angular gyrus for subjects with fraX, for both trial types. Subjects with fraX exhibited less overall activation than did unaffected subjects in both types of trials; and, unlike the unaffected group, did not show increased extent of activation in association with greater task difficulty. During the 3-operand trials, activation in bilateral prefrontal and motor/premotor, and left supramarginal and angular gyri were positively correlated with FMRP, suggesting that decreased FMR1 protein expression underlies deficits in math performance in persons with fraX. More broadly, this investigation demonstrates a unique bridging of cognitive and molecular neuroscience and represents a useful approach for the study of brain development and function.

Assessment of interlimb coordination by gait analysis

The effects of type (cognitive vs. motor) and difficulty level (easy vs. hard) of a concurrent task on walking were examined in 10 boys and 4 girls (age 4–6 years) with developmental coordination disorder (DCD) and 28 age- and gender-matched unaffected children. Each child performed free walking (single task), walking while carrying an empty tray (dual task, the concurrent task being motor and easy), walking while carrying a tray with 7 marbles (the concurrent task being motor and hard), walking while repeating a series of digits forward (the concurrent task being cognitive and easy), and walking while repeating the digits backward (the concurrent task being cognitive and hard). Walking was affected by the concurrent task (i.e., dual-task cost) in the children with DCD more so than in the comparison children. Greater task difficulty also increased the dual-task cost in the children with DCD more so than in the comparison children. These patterns were only noted for the motor concurrent task. The cognitive concurrent task also affected walking, but the dual-task costs did not differ between difficulty levels, nor between the groups.

Tire-Rim Mismatch Explosions: Human Factors Analyses of Case Studies Data

Data from 13 accidents involving mismatches of 16 inch tires and 16.5 inch rims were analyzed. These mismatches resulted in tire bead failures during inflation that caused the assembly to explode leading to serious injuries and deaths. The data indicated a number of consistent findings. In ten of the accidents an “entrapment” situation existed in which the person inflating the tire and subsequently injured was not the person who selected the components and placed the tire on the rim. While there was great variance in training, experience and knowledge of tire busters, virtually all were unaware of this mismatch hazard. Tire busters typically did not look for size information on rims, and such information was either not displayed or displayed poorly. Regarding task feedback, because the outer flange diameter of the 16 inch and 16.5 inch rims are virtually the same, placing the tire on the 16.5 inch rim did not provide feedback that something was wrong due to greater task difficulty. Also, the fact that the tire did not properly seat was not attributed to a size mismatch but rather to other more common seating problems. Efforts to warn about the mismatch hazard on the products have not met warnings design criteria and generally have not been effective.

Greater task difficulty amplifies the facilitatory effect of des-glycinamide arginine vasopressin on appetitively motivated learning.

Rats were trained in a discrete-trial forward autoshaping paradigm to touch an extended lever to earn food pellets. Reinforcement was delivered either simultaneously with or 6 s after lever retraction which occurred either non-contingently after 15 s or when the animal touched the lever. Treatment with des-glycinamide arginine vasopressin (DGAVP; 15 micrograms/kg, sc) 1 hr before sessions increased the rate of acquisition of the extended-lever-touch response and also facilitated development of intertrial (adjunctive) nose poking. Effects of the peptide were more robust in the more difficult, delayed reinforcement task. DGAVP lacks the classical peripheral activity of vasopressin. In both experiments, peptide treatment was terminated before asymptotic levels of performance were attained; the continued facilitation of acquisition in treated groups suggests a specific enhancement of learning and/or enhanced memory retrieval.