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Even though impaired visuospatial abilities can negatively affect daily functioning, there are very few training programs that attempt to improve visuospatial abilities. The purpose of this study was to examine if a single training session with a computerized version of the Corsi Block Tapping Task could improve mental rotation skills. Fifty-three young adults were assigned to one of two groups: (1) control group (mean age = 21.4; 10 females), who had 20 min of rest after their baseline assessment, or (2) training group (mean age = 21.5; 17 females), who had 20 min of training on the Corsi Block Tapping Task after their baseline assessment. The primary outcome was reaction time on a computer-based mental rotation task, and it was assessed both before and after the rest or training. There was a significant interaction between time (pre vs. post) and group (control vs. training) on mental rotation performance (p = 0.04), with the training group performing on average 124 ms faster on accurate trials than the control group at post-test. This preliminary study suggested that improving mental rotation may be feasible through targeted cognitive training. Future studies will consider multiple sessions of Corsi Block Tapping Task training to maximize training benefits (i.e., dose–response), as well as longer term retention in cognitively intact and impaired individuals. [ABSTRACT FROM AUTHOR]

Various behavioural tasks measure response inhibition encompassing the ability to cancel unwanted actions, evaluated via stop signal reaction time (SSRT). It is unclear whether SSRT is an unchangeable inherent measure of inhibitory network integrity or whether it can improve with repetition. The current study explored if and how SSRT changed over two sessions for the Anticipatory Response Inhibition Task (ARIT), and how this compared with the Stop Signal Task (SST). Forty-four participants repeated the ARIT and SST over two sessions. SSRT and its constituent measures (Go trial reaction time, stop signal delay) were calculated. SSRT reflecting non-selective response inhibition was consistent between sessions in the ARIT and SST (both p > 0.293). Reaction time and stop signal delay also remained stable across sessions in the ARIT (all p > 0.063), whereas in the SST, reaction time (p = 0.013) and stop signal delay (p = 0.009) increased. SSRT reflecting behaviourally selective stopping on the ARIT improved (p < 0.001) over two sessions, which was underpinned by changes to reaction time (p < 0.001) and stop signal delay (p < 0.001). Overall, the maximal efficiency of non-selective inhibition remained stable across two sessions in the ARIT. Results of the SST confirmed that non-selective inhibition can, however, be affected by more than inhibitory network integrity. Behaviourally selective stopping on the ARIT changed across sessions, suggesting the sequential neural process captured by the SSRT occurred more quickly in session two. These findings have implications for future studies that necessitate behavioural measures over multiple sessions. [ABSTRACT FROM AUTHOR]

The grating orientation discrimination task (GOT) is a sensitive and reliable measure of tactile spatial resolution, or acuity. We used the GOT in three experiments to investigate the effects of hand posture and hand visibility on spatial acuity. Participant sex and experimental design were also manipulated. Healthy adult participants received brief touches to their index fingertips of grated, domed objects. Their task was to decide whether the gratings ran 'along' or 'across' their finger. Measures of the smallest grating width for which participants could reliably discriminate between orientations were recorded as threshold. Experiment 1 evaluated the effect of two- versus one-interval discrimination, hand used and participant sex. Experiments 2 and 3 evaluated the effects of hand visibility (visible or covered) and hand posture (in front or to the side). Females were better than males; the two-interval task resulted in lower thresholds than the one-interval task; and left and right hand thresholds were not significantly different. Most importantly, while hand visibility did not have a significant effect on the task, thresholds were affected by hand posture—worse when the hand was oriented to the side of the body than in front. These results replicate previously reported effects of sex (or finger size), but failed to replicate the so-called 'visual enhancement of touch' (VET) effect. We also report a meta-analysis of 27 VET studies, finding a significant effect of 'non-informative' vision on tactile perception. Our novel finding is that hand posture affects tactile acuity. [ABSTRACT FROM AUTHOR]

The perceptual feature of a task such as how a task goal is perceived influences performance and coordination of bimanual actions in neurotypical adults. To assess how bimanual task goal modifies paretic and non-paretic arm performance and bimanual coordination in individuals with stroke affecting left and right hemispheres, 30 participants with hemispheric stroke (15 right-hemisphere damage—RHD); 15 left-hemisphere damage—LHD) and 10 age-matched controls performed reach-to-grasp and pick-up actions under bimanual common-goal (i.e., two physically coupled dowels), bimanual independent-goal (two physically uncoupled dowels), and unimanual conditions. Reach-to-grasp time and peak grasp aperture indexed motor performance, while time lags between peak reach velocities, peak grasp apertures, and peak pick-up velocities of the two hands characterized reach, grasp, and pick-up coordination, respectively. Compared to unimanual actions, bimanual actions significantly slowed non-paretic arm speed to match paretic arm speed, thus affording no benefit to paretic arm performance. Detriments in non-paretic arm performance during bimanual actions was more pronounced in the RHD group. Under common-goal conditions, movements were faster with smaller peak grasp apertures compared to independent-goal conditions for all groups. Compared to controls, individuals with stroke demonstrated poor grasp and pick-up coordination. Of the patient groups, patients with LHD showed more pronounced deficits in grasp coordination between hands. Finally, grasp coordination deficits related to paretic arm motor deficits (upper extremity Fugl–Meyer score) for LHD group, and to Trail-Making Test performance for RHD group. Findings suggest that task goal and distinct clinical deficits influence bimanual performance and coordination in patients with left- and right-hemispheric stroke. [ABSTRACT FROM AUTHOR]

Unilateral spatial neglect (USN) is a common neurological syndrome that develops after a right hemisphere lesion. By examining the performance of the modified Posner task added to the vertical dimensions of the left and right visual fields, we studied whether the lower left area had different neglect symptoms than the other locations. 41 patients with right hemisphere damage were classified into those with mild USN (USN+ ; n = 20) and without USN (USN− ; n = 21). Twenty older participants made up the healthy control (HC; n = 20) group. All participants recorded deficits in the paper-and-pencil tests established for neglect and reaction times in the modified Posner task. In the paper-and-pencil tests, there was no difference in deficit between the upper and lower left visual fields in any of the groups. According to the modified Posner task, the USN+ group exhibited delays in reaction time in the lower left visual field rather than the upper left visual field. Importantly, reaction times were delayed, and USN symptoms persisted, particularly for the lower left quadrant. Our findings imply that the modified Posner task can accurately uncover neglect symptoms in the case of mild USN. [ABSTRACT FROM AUTHOR]

The capacity to plan movement following stroke is diminished when reaching from a standing position. Two mechanisms have been proposed: increased task complexity compared to simpler tasks and inhibition between the pathways controlling whole-body posture and upper extremity reaching. The objective of this study was to determine if task complexity alone can alter planning and release (or involuntary execution) capacity when whole-body postural adjustment is not required. Data were collected from 10 stroke survivors and 8 age-matched controls. Ballistic elbow extension movements were performed with and without voluntary shoulder abduction, adding complexity by anti-gravity arm support that enhanced the expression of abnormal muscle synergies linking elbow and shoulder after stroke. Our primary finding was in support of our hypothesis that startReact (involuntary release of planned movement by a startling stimulus) would be intact but that the increased task complexity would decrease the capacity to plan and release movement. StartReact was intact for both tasks with and without shoulder abduction. Despite the intact startReact response across both conditions following stroke, the incidence of startReact was decreased during the shoulder abduction task similar to prior studies showing a decrease during tasks of higher complexity. Our results suggest that individuals with stroke have a diminished capacity to plan and release movement as task complexity increases. This study highlights the unique potential for startReact to be used as a clinical tool to probe the capacity to plan and release movement following stroke and how that capacity is affected by the complexity of the task being performed. Such a tool may be useful for assessing functional impairments and tracking changes during the rehabilitation process. [ABSTRACT FROM AUTHOR]

The retrieval of phonological, lexical, semantic, or syntactic language information from long-term memory plays an important role in language processing. However, it remains unclear whether variability analysis of brain signals obtained using functional near-infrared spectroscopy (fNIRS) is able to separate language-related task conditions. This study employed multifractal detrended fluctuation (MFDF) analysis focusing on the width of the multifractal spectrum to elucidate whether high complexity tasks increase the fractal dynamics of brain activation signals compared to low complexity tasks. Nine Japanese college students participated in a long-term memory retrieval experiment using low (n ± 1) and high (n ± 2) complexity tasks. Our results showed that high complexity tasks induced a significantly larger multifractal spectral width in the posterior medial temporal gyri bilaterally, due to higher cognitive demands. These findings suggest that in addition to conventional techniques based on mean amplitude analysis and general linear modelling of fNIRS data, the use of MFDF analysis offers a powerful alternative methodology to gain a deeper understanding of long-term memory retrieval in language memory processing. [ABSTRACT FROM AUTHOR]

Elderly individuals may be at increased risk of falls than their peers. Early identification of balance disorders and their appropriate intervention are crucial for patients with dementia. The aim of this study was to identify postural instability in patients from mild to moderate dementia while performing transitional locomotor tasks under different conditions. Fifty-four patients with dementia and 30 healthy controls voluntarily participated in the study. The transitional locomotor task was performed on two force platforms under four conditions: unimpeded transition, obstacle clearance, step-up and step-down trials. The recording of center of foot pressure displacements was divided into three distinct phases: 1st phase—quiet standing before the transitional locomotor task, 2nd phase—forward stepping, 3rd phase—quiet standing after the transitional locomotor task. Patients with dementia were characterized by a longer transitional locomotor task time than the control group under all conditions (P < 0.03). Significant differences in quiet standing before the transitional locomotor task were observed between patients with dementia and the control group, but only in unimpeded transition and obstacle clearance trials (P < 0.02). No significant differences in quiet standing after step transition were observed between patients with dementia and the control group (P > 0.05). Postural control research in patients with dementia should focus on the functional motor task rather than on a simple motor task (quiet standing). Because even patients with mild dementia have impaired dynamic balance, the assessment of transitional locomotor tasks performed by patients with dementia might provide an indicator of an early diagnosis of dementia and might lead to better individualized physiotherapy. [ABSTRACT FROM AUTHOR]

Tasks measuring the sense of agency often manipulate the predictability of action outcomes by introducing spatial deviation. However, the extent to which spatial predictability of an outcome influences the sense of agency when spatial deviation is controlled for remains untested. We used a novel task to investigate the effect of several factors (action–outcome contingency, spatial deviation, and spatial predictability when controlling for spatial deviation of action outcomes) on the sense of agency. We also investigated trait predictors of metacognition of agency—the degree to which participants' confidence in their agency judgements corresponds to the accuracy of those judgements. Initial and replication samples completed contingency, deviation, and predictability versions of the task. Across samples, participants' sense of agency was impacted by action–outcome contingency and spatial deviation of action outcomes. Manipulation of the spatial predictability of action outcomes did not reliably impact the sense of agency. Metacognition of agency was related to alexithymic traits—higher alexithymia scores were associated with reduced metacognition of agency. [ABSTRACT FROM AUTHOR]

Self-motion perception refers to the ability to perceive how the body is moving through the environment. Perception of self-motion has been shown to depend upon the locomotor action patterns used to move the body through the environment. Two separate lines of enquiry have led to the establishment of two distinct theories regarding this effect. One theory has proposed that distances travelled during locomotion are perceived via higher order perceptual variables detected by the haptic perceptual system. This theory proposes that two higher order haptic perceptual variables exist, and that the implication of one of these variables depends upon the type of gait pattern that is used. A second theory proposes that self-motion is perceived via a higher order perceptual variable termed multimodally specified energy expenditure (MSEE). This theory proposes that the effect of locomotor actions patterns upon self-motion perception is related to changes in the metabolic cost of locomotion per unit of perceptually specified traversed distance. Here, we test the hypothesis that the development of these distinct theories is the result of different choices in methodology. The theory of gait type has been developed based largely on the results of homing tasks, whereas the effect of MSEE has been developed based on the results of distance matching tasks. Here we test the hypothesis that the seemly innocuous change in experimental design from using a homing task to using a distance matching task changes the type of perceptual variables implicated in self-motion perception. To test this hypothesis, we closely replicated a recent study of the effect of gait type in all details bar one—we investigated a distance matching task rather than a homing task. As hypothesized, this change yielded results consistent with the predictions of MSEE, and distinct from gait type. We further show that, unlike the effect of gait type, the effect of MSEE is unaffected by the availability of vision. In sum, our findings support the existence of two distinct types of higher order perceptual variables in self-motion perception. We discuss the roles of these two types of perceptual variables in supporting effective human wayfinding. [ABSTRACT FROM AUTHOR]

To gain insight into how human observers select items in the visual field we pitted two attentional biases against one another in a single free choice design. The first bias is the nasal-temporal asymmetry during free choice tasks, where observers tend to choose targets that appear in their temporal hemifield over targets appearing in their nasal hemifield. The second is the choice bias found in studies of attentional priming. When observers have to select between a stimulus that shares features with a preceding target and a stimulus sharing features with previous distractors, they have a strong tendency to choose the preceding search target and this bias increases the more often the same search is repeated. Our results show that both biases affect saccadic choice, but they also show that the nasal-temporal bias can modulate the strength of the priming effects, but not vice versa. The priming effect was stronger for stimuli appearing in the temporal than in the nasal hemifield, but the nasal-temporal bias was similar for primed and unprimed targets. Additionally, our findings are the first to show how search repetition leads to faster saccades. The observed difference between the effects of the NTA and priming biases may reflect the difference in neural mechanisms thought to be behind these biases and that biases at lower levels may outrank higher-level biases, at least in their effect on visual attention. [ABSTRACT FROM AUTHOR]

The present study aimed to separate the neural activities between response inhibition and memory updating processes in the Count/Nocount task. Memory load was manipulated to investigate the memory updating process. Within each trial, participants were asked to count/withhold counting the number of O/X letters in the Count/Nocount task. The participants were asked to silently add 1 if a Count letter was presented in the low load condition, and add 2 in the high load condition. Data from 28 healthy participants showed that: (1) in both high load and low load conditions, the latencies of P2 and N2 components were shorter for the Nocount than Count trials, indicating faster attentional orienting and conflict monitoring processes for the Nocount stimuli (i.e., inhibition processes triggered by the Nocount stimuli against those response execution processes triggered by Count stimuli); (2) more positive frontal P3 amplitudes were evoked for the Nocount relative to the Count stimuli, indicating a more intensive response inhibition process for the Nocount trials; (3) a more positive parietal P3 component was evoked for the low load relative to high load condition, indicating a more intensive working memory updating process for the high load condition. This load effect was absent for the frontal P3 component, suggesting that the frontal P3 might not be associated with the memory updating process. In sum, both the cognitive inhibition process (reflected by the frontal P3 component) and working memory updating process (reflected by the parietal P3 component) appear to be involved in the Count/Nocount task. [ABSTRACT FROM AUTHOR]

Recent evidences suggest that binaural vestibular stimulation affects tactile temporal processing. However, it remains difficult to determine the physiological mechanisms supporting the vestibular–somatosensory interactions observed during a TOJ task. Controlling the activation of the right or left vestibular system separately could allow to better understand the physiological bases of these findings and reconcile previous studies. The objective of the present study was to examine tactile temporal processing using a temporal order judgment task following selective stimulation of the right and left vestibular system with bi-thermal caloric vestibular stimulation (CVS). A total of 24 right-handed participants received bi-thermal CVS either in the right ear (n = 12) or the left ear (n = 12). Participants held vibrators in both hands which delivered a signal temporally separated by a variable asynchrony. Participants had to report the hand where the vibration was perceived first. The task was performed in three different CVS conditions: (1) baseline, (2) warm CVS, and (3) cold CVS. Analysis of the logistics curve parameters—just noticeable difference (JND) and point of subjective simultaneity (PSS)—for each participant in each CVS conditions revealed an increase in JND greater following warm CVS. A significant increase in JND following warm CVS was measured bilaterally. However, cold CVS increased JND only when CVS was applied in the left ear, but not in the right ear. Finally, no influence of CVS on PSS was observed. [ABSTRACT FROM AUTHOR]

We explored the organization of motor units recorded in the flexor digitorum superficialis into stable groups (MU-modes) and force-stabilizing synergies in spaces of MU-modes. Young, healthy participants performed one-finger and three-finger accurate cyclical force production tasks. Two wireless sensor arrays (Trigno Galileo, Delsys, Inc.) were placed over the proximal and distal portions of the muscle for surface recording and identification of motor unit action potentials. Principal component analysis with Varimax rotation and factor extraction was used to identify MU-modes. The framework of the uncontrolled manifold hypothesis was used to analyze inter-cycle variance in the space of MU-modes and compute the index of force-stabilizing synergy. Multiple linear regression between the first MU-mode in the three-finger task and the first MU-modes in the three single-finger tasks showed no differences between the data recorded by the two electrodes suggesting that MU-modes were unlikely to be synonymous with muscle compartments. Multi-MU-mode synergies stabilizing task force were documented across all tasks. In contrast, there were no force-stabilizing synergies in the three-finger task analyzed in the space of individual finger forces. Our results confirm the synergic organization of motor units in single-finger tasks and, for the first time, expand this result to multi-finger tasks. We offer an interpretation of the findings within the theoretical scheme of control with spatial referent coordinates expanded to the analysis of individual motor units. The results confirm trade-offs between synergies at different hierarchical levels and expand this notion to intra-muscle synergies. [ABSTRACT FROM AUTHOR]

Sensorimotor adaptation can involve multiple learning processes with different time courses, and these processes may have different patterns of transfer. In this study, we tested how slow learning and fast learning transfer across tasks, and the specificity of transfer. We tested two natural goal-directed tasks: pointing and walking toward a visible target. We also tested a novel "hand locomotion" task in which subjects used pointing movements to cause simulated self-motion in virtual reality. The hand locomotion task used the same physical movement as pointing, but performed the same function as stepping. During an experimental block, subjects performed alternating training trials with perturbed visual feedback and test trials with no feedback. The test trials were either the same task to measure adaptation, or a different task to measure transfer. Perturbations on adaptation trials varied over time as a sum of sinusoids with different frequencies. Fast learning would be expected to produce equal responses to fast and slow perturbations, while slower learning would dampen responses to higher frequency perturbations. Subjects were generally not aware of the smoothly varying perturbations, but showed detectable adaptation for all three tasks. Only pointing produced significantly different responses to high- and low-frequency perturbations, consistent with slow learning. Adaptation of pointing produced more transfer to the hand locomotion task, which shared the same effector and motor actions, than to the stepping task. The other tasks showed fast learning but little or no slow learning, and equal transfer to tasks with different effector or function. Our results suggest that the slower components of sensorimotor adaptation are more movement specific, while faster learning is more generalizable. [ABSTRACT FROM AUTHOR]

Visually guided reaching precision and accuracy depend on the level of coupling between movements of the eyes and hand. In the present study, participants performed central fixations and either saccadic or smooth pursuit eye movements during fast and accurate reaching tasks involving eye–hand coupling and decoupling to better understand type of eye movement influence over upper limb control. Some eye–hand coupling and decoupling tasks also included hand reversals, where the hand moves away from the target to direct a cursor toward the target to account for various levels of hand–cursor and eye–cursor coupling. Regardless of eye-movement type, eye–hand–cursor coupling produced an endpoint accuracy advantage over decoupling. Use of hand reversal decreased peak speed and increased response time of the hand, whether considering fixation or a given eye movement. Use of smooth pursuit slowed hand movements relative to saccades, yet improved endpoint accuracy. Compared to central fixations, using smooth pursuit also slowed hand movements, while using saccades decreased, thus improved, hand reaction times. Data suggest an advantage, when using smooth pursuit to track the hand movement for the greatest endpoint accuracy, an advantage when using saccades for the fastest movements, and an eye–hand coupling advantage when using saccades for the shortest reactions. Researchers should provide clear eye-movement instructions for participants and/or monitor the eyes when assessing similar upper limb control to account for possible differences in eye movements used. Moreover, the type of eye movement chosen for participants should correspond to the primary goal of the task. [ABSTRACT FROM AUTHOR]

This study investigated the effects of mental fatigue (MF) induced by a 90-min AX-continuous performance test (AX-CPT) on balance control by addressing the issue of the heterogeneity of individuals' responses. Twenty healthy young active participants were recruited. They had to carry out two balance tasks (sway as little as possible on a stable support with the eyes open and closed) when standing on a force platform before and after performing a 90-min AX-CPT. The NASA-TLX test was used to assess the subjective manifestations of MF. Objective cognitive performance was measured using results from the AX-CPT. Inter-individual differences in behavioral deterioration due to MF were analyzed with a hierarchical cluster analysis, which categorizes participants' behaviors into subgroups with similar characteristics. The cluster analysis revealed that the achievement of the AX-CPT induced various levels of MF and balance impairments within the whole sample. A significant relationship between the level of MF and the degree of balance disturbance was observed only when participants stood with the eyes open, thus suggesting that inter-individual differences in vulnerability to MF could stem from differences between subjects in the level of engagement of visual attention and/or from differences in field dependency for balance control. These findings show that the completion of the same prolonged demanding cognitive task induces a strong heterogeneity in subjects' responses, with marked individual differences in MF vulnerability that affect balance control differently according to the sensory context. [ABSTRACT FROM AUTHOR]

The visual, vestibular, and haptic perceptual systems are each able to detect self-motion. Such information can be integrated during locomotion to perceive traversed distances. The process of distance integration is referred to as odometry. Visual odometry relies on information in optic flow patterns. For haptic odometry, such information is associated with leg movement patterns. Recently, it has been shown that haptic odometry is differently calibrated for different types of gaits. Here, we use this fact to examine the relative contributions of the perceptual systems to odometry. We studied a simple homing task in which participants travelled set distances away from an initial starting location (outbound phase), before turning and attempting to walk back to that location (inbound phase). We manipulated whether outbound gait was a walk or a gallop-walk. We also manipulated the outbound availability of optic flow. Inbound reports were performed via walking with eyes closed. Consistent with previous studies of haptic odometry, inbound reports were shorter when the outbound gait was a gallop-walk. We showed that the availability of optic flow decreased this effect. In contrast, the availability of optic flow did not have an observable effect when the outbound gait was walking. We interpreted this to suggest that visual odometry and haptic odometry via walking are similarly calibrated. By measuring the decrease in shortening in the gallop-walk condition, and scaling it relative to the walk condition, we estimated a relative contribution of optic flow to odometry of 41%. Our results present a proof of concept for a new, potentially more generalizable, method for examining the contributions of different perceptual systems to odometry, and by extension, path integration. We discuss implications for understanding human wayfinding. [ABSTRACT FROM AUTHOR]

Motor adaptation plays an important role in the acquisition of new motor skills. It has been reported that cognitive tasks can promote motor adaptation; however, which cognitive tasks effectively promote motor adaptation remains unknown. This study aimed to examine what factors of cognitive tasks contribute to promoting motor adaptation. Forty-two healthy young adults were randomly assigned to one of three groups: incongruent Stroop task group (iSTG), congruent Stroop task group (cSTG), and control group (CG). All participants underwent 20 blocks of a mouse-tracking task on the 1st and 2nd days. Before the mouse tracking task on the 1st day, the iSTG and cSTG completed the incongruent and congruent Stroop tasks, respectively. Participants in the CG did not perform any cognitive tasks. On the 28th day, all participants underwent 3 blocks of the mouse tracking task to evaluate their retention of motor adaptation. As a result, on the 1st day, the mouse tracking task performance improved equally for both groups. However, on the 2nd and 28th days, the mouse tracking task performance in the iSTG showed greater improvements for all blocks compared to those in the CG. These results suggest that the incongruent Stroop task promotes motor adaptation, but the congruent Stroop task does not. In addition, it is suggested that factors, which are primarily involved in the incongruent Stroop task, might promote motor adaptation. [ABSTRACT FROM AUTHOR]

Gait stability and secondary task performance are affected by the need to share attention when dual-tasking. Further decrements may result from the need to switch attention between multiple secondary tasks. The aim of the current study was to determine the effects of attention switching upon gait stability and task performance in healthy younger and older adults. Ten healthy younger and ten healthy older adults walked on a treadmill at their preferred speed during three trials including: (1) baseline walking; (2) non-switching task walking, requiring response to an auditory-spatial or visual-spatial cue presented in an expected order; and (3) switching task walking, which required response to an auditory-spatial or visual-spatial cue presented in an unexpected order. Response time and accuracy, the margin of stability in the frontal (MoSML) and sagittal planes (MoSA: anterior, MoSP: posterior), step width and step length were calculated for non-switching and switching tasks. The MoSML, MoSA, MoSP, step width and step length during non-switching and switching tasks were normalized to baseline walking. Older adults took significantly longer to respond to cues and made more errors during the switching task compared to younger adults. Younger adults took narrower steps (p < 0.01) and displayed a reduction in MoSML (p < 0.01) during the switching task compared with the non-switching task. Conversely, older adults displayed no differences in MoSML between tasks. These findings suggest that attention switching results in different task prioritization strategies in younger and older adults during walking. [ABSTRACT FROM AUTHOR]

Several tests of mental rotation ability have been used to investigate its development and the origins of sex differences. One of the most used tests is the mental rotation test (MRT) by Vandenberg and Kuse. A limitation of the MRT is that it is a pen-and-paper test with 2D images of 3D objects. This is a challenge to the ecological validity of the MRT because mental rotation typically involves physical 3D objects that are also physically manipulated. The purpose of the present study was to compare mental rotation ability as evaluated by the MRT to three new tasks with physical objects (toy bricks) that were physically manipulated. The different tasks allowed us to vary the processing demands on mental rotation while standardizing other aspects of the tasks. Fifty-nine females and twenty-eight males completed the LMR and HMR conditions (low- and high-mental rotation demands, respectively) of the brick building task (BBT), a visual search task, and the MRT. As demands on mental rotation for the BBT increased, performance decreased and a sex difference, with males outperforming females, increased. There were correlations between all tasks, but they were larger between the versions of the BBT with the MRT. The results suggest that spatial skill is an assembly of interrelated subskills and that the sex difference is sensitive to the demands on mental rotation and dimensionality crossing. The benefits of the BBT are that it is ecologically valid, avoids dimensionality crossing, and the demands on mental rotation can be manipulated. [ABSTRACT FROM AUTHOR]

We explored how reward and value of effort shapes performance in a sustained vigilance, reaction time (RT) task. It was posited that reward and value would hasten RTs and increase cognitive effort by boosting activation in the sensorimotor cortex and inhibition in the frontal cortex, similar to the horse-race model of motor actions. Participants performed a series of speeded responses while expecting differing monetary rewards (0 pence (p), 1 p, and 10 p) if they responded faster than their median RT. Amplitudes of cortical alpha, beta, and theta oscillations were analysed using the event-related desynchronization method. In experiment 1 (N = 29, with 12 females), reward was consistent within block, while in experiment 2 (N = 17, with 12 females), reward amount was displayed before each trial. Each experiment evaluated the baseline amplitude of cortical oscillations differently. The value of effort was evaluated using a cognitive effort discounting task (COGED). In both experiments, RTs decreased significantly with higher rewards. Reward level sharpened the increased amplitudes of beta oscillations during fast responses in experiment 1. In experiment 2, reward decreased the amplitudes of beta oscillations in the ipsilateral sensorimotor cortex. Individual effort values did not significantly correlate with oscillatory changes in either experiment. Results suggest that reward level and response speed interacted with the task- and baseline-dependent patterns of cortical inhibition in the frontal cortex and with activation in the sensorimotor cortex during the period of motor preparation in a sustained vigilance task. However, neither the shortening of RT with increasing reward nor the value of effort correlated with oscillatory changes. This implies that amplitudes of cortical oscillations may shape upcoming motor responses but do not translate higher-order motivational factors into motor performance. [ABSTRACT FROM AUTHOR]

Motor flexibility, the ability to employ multiple motor strategies to meet task demands, may facilitate ambulation in complex environments that constrain movements; loss of motor flexibility may impair mobility. The purpose of this study was to determine the effects of obesity (a specific model of mobility impairment) and advanced age on motor flexibility during a task that constrained foot placement while walking. Twenty-one community-dwelling obese (OB) and 25 normal weight (NW) older adults (46 total older adults—OA) and 10 younger adults (YA) walked normally on a treadmill (baseline) then walked while stepping on lighted cues projected onto the treadmill at locations corresponding to average foot placement during normal walking (cued). The uncontrolled manifold (UCM) analysis was used to partition total variance in a set of seven lower-limb segment angles into components that did ("bad" variance) and did not ("good" variance) affect step-to-step variance in the trajectory of the swing foot. Motor flexibility was operationalized as an increase (baseline to cued) in total variance with an increase in good variance that exceeded the change in bad variance. There was no significant group × walking task interaction for total and good variance for OB vs NW, but there was a strong and significant interaction effect for OA vs YA (p < 0.01; Cohen's d > 1.0). Whereas YA reduced both good and bad variance, OA increased good variance beyond the change in bad variance. In OA, these changes were associated with several functional measures of mobility. Cued walking may place greater demands on OA requiring greater reliance on motor flexibility, although otherwise healthy older obese adults may be able to compensate for functional and cognitive declines associated with obesity by increasing motor flexibility under such tasks. The extent to which motor flexibility is employed during novel or constrained tasks may be a biomarker of healthy aging and a target for (re)habilitation. [ABSTRACT FROM AUTHOR]

StartReact elicits faster, larger, and more appropriate muscle activation in stroke survivors but has been only cursorily studied to date during multi-jointed reaching. Our objective was to evaluate StartReact on unrestricted, two-dimensional point-to-point reaching tasks post-stroke. Data from 23 individuals with stroke were collected during point-to-point reaching. Voluntary and StartReact trials were compared between mild, severe/moderate, and the unimpaired arm. StartReact showed an increase in probability of muscle activity, larger muscle activity amplitude, and faster muscle activity onset. Despite changes in muscle activity, metrics of movement (distance, final error, linear deviation) were not different between StartReact and Voluntary trials except in severe/moderate stroke who had larger reaching distances during StartReact. While StartReact impacted many metrics of muscle activity, the most profound effect was on the probability of muscle activity increasing 34% compared to voluntary which allowed severe/moderate subjects to increase reaching distance but did not translate to decrease in final error suggesting that the additional movement was not always directed towards the appropriate target. These results indicate that SR has the capacity to activate paralyzed muscle in severe/moderate patients, but future studies are needed to explore the possible use of SR in the rehabilitation. [ABSTRACT FROM AUTHOR]

High-status individuals have been found to be less attuned to the behaviour of others in the social environment, at least in the absence of any specific instructions to pay attention to them. Previous work using neural measures has shown that socioeconomic status (SES) influences the degree to which people are attuned to the actions of others. In particular, individuals from low-SES backgrounds were found to exhibit more mu-suppression, which has been suggested to reflect greater levels of sensorimotor resonance, compared to their high-SES counterparts. However, it is unclear whether such effects on brain activity translate into behaviour. Here, we examined differences in automatic imitation between high-SES and low-SES individuals. The automatic imitation task involves participants making actions in response to a numerical cue, while simultaneously being exposed to an action that is incongruent or congruent with the cued response. Patterns of interference effect reveal the extent to which the congruence of the observed action affects performance of the cued response. Interference thus indexes self–other processing, where high levels of interference suggest an increased susceptibility to the actions of others. Our results show that individuals from low-SES backgrounds exhibit more interference than individuals from high-SES backgrounds. Regression analyses revealed a negative relationship between SES and the degree of interference. Overall, our findings suggest that differences in SES are linked to differences in self–other processing, which could be relevant for broader behavioural tendencies exhibited by individuals at varying levels of a social structure. [ABSTRACT FROM AUTHOR]

The aim of the present study was to evaluate the effects of mental fatigue (MF) induced by a 90-min continuous demanding cognitive task on balance control. Twenty healthy young participants were recruited. They had to perform three postural tasks (on a stable support with eyes open, with eyes closed and on a wobble board) while standing on a force platform before and after watching a documentary in a control condition or carrying out a prolonged continuous demanding cognitive task (AX-continuous performance test—AX-CPT) in a MF condition. Results showed that performing the AX-CPT generated MF since participants felt a higher subjective workload from the NASA Task Load Index after the AX-CPT than after viewing the documentary. Both the AX-CPT and the viewing of the documentary impaired balance control, mainly by affecting postural regulatory mechanisms which evolved towards a less automatic and less complex regulation mode with an increased participation of cognitive resources. MF generated by the AX-CPT affected balance control by compromising the attentional processing, while the deleterious influence of watching a documentary on postural control could stem from an adverse effect of prolonged sitting on balance control during subsequent standing. [ABSTRACT FROM AUTHOR]

The motor-cognitive model holds that motor imagery relies on executive resources to a much greater extent than do overt actions. According to this view, engaging executive resources with an interference task during motor imagery or overt actions will lead to a greater lengthening of the time required to imagine a movement than to execute it physically. This model is in contrast to a currently popular view, the functional equivalence model, which holds that motor imagery and overt action use identical mental processes, and thus should be equally affected by task manipulations. The two competing frameworks were tested in three experiments that varied the amount and type of executive resources needed to perform an interference task concurrent with either an overt or imagined version of a grasping and placing action. In Experiment 1, performing a concurrent calculation task led to a greater lengthening of the time required to execute motor imagery than overt action relative to a control condition involving no interference task. Further, an increase in the number of responses used to index performance affected the timing of motor imagery but not overt actions. In Experiment 2, a low-load repetition task interfered with the timing of motor imagery, but less so than a high load calculation task; both tasks had much smaller effects on overt actions. In Experiment 3, a word generation task also interfered with motor imagery much more than with overt actions. The results of these experiments provide broad support for the motor-cognitive model over the functional equivalence model in showing that interfering with executive functions had a much greater impact on the timing of motor imagery than on overt actions. The possible roles of different executive processes in motor imagery are discussed. [ABSTRACT FROM AUTHOR]

Fitts' Law is a well-studied principle in psychology which holds that movement time (MT) varies with the size and distance of a target across a wide range of tasks. In a recent study, the authors demonstrated that performance on a current trial in a Fitts' Law paradigm is affected by what happens during the previous trial (Tang et al. in Psychon Bull Rev 25(5):1833–1839, 2018). The aim of the present study was to explore how long this trial-to-trial transfer might last and whether or not the transfer would occur between the left and right hands. A series of experiments was carried out using discrete trials, a paradigm in which the current authors and others have previously established that Fitts' Law operates (Fitts and Peterson in J Exp Psychol 67(2):103–112, 1964; Tang et al. 2018). Three inter-trial intervals (3 s, 4 s, and 5 s) were used in separate testing sessions, the order of which was counterbalanced across participants. In addition, trial-to-trial transfer was tested within a single hand and between hands. The results demonstrate that transfer from one trial to the next could bridge 4 s when either the right or the left hand was used and would disappear by 5 s. Moreover, the effect transferred between the two hands. The endpoint accuracy of the current trial was not affected by the previous trial. These findings suggest that the trial-to-trial effect reduces over time and that the transfer of sensorimotor memory or the task set is independent of the particular hand used. [ABSTRACT FROM AUTHOR]

Previous research utilising a between-subjects design has indicated that the use of noise-dampening ear protectors might enhance interoceptive accuracy (IAcc). In the present study, we further examined this effect using a repeated-measures, within-participants design, and investigated potential mechanisms that might explain the effect. 50 participants completed the heartbeat tracking task (HTT) with and without the use of industrial ear protectors, in a counter-balanced order. Participants were asked to count the number of heartbeats occurring in five discrete time intervals of 25, 35, 45, 55 and 95 s, without feeling for a manual pulse. HTT scores were significantly higher when ear protectors were worn, and the improvement in performance was greatest for participants with lower baseline IAcc. The ear protectors were associated with significantly increased self-reported heartbeat audibility, task-related confidence and concentration, and decreased levels of distractibility. Heartbeat audibility was also correlated with HTT performance when the ear protectors were worn. Because the use of industrial ear defenders resulted in increased heartbeat audibility, this manipulation should not be used to assess causal hypotheses related to changes in IAcc. However, it may serve as a simple, non-invasive manipulation to assess the effects of 'externalised' interoceptive signals. [ABSTRACT FROM AUTHOR]

Musical expertise promotes both the perception and the processing of music. The aim of the present study was to analyze if musicians compared to non-musicians already have auditory processing advantages at the neural level. 50 musicians and 50 non-musicians worked on a task to determine the individual auditory difference threshold (individual JND threshold). A passive oddball paradigm followed while the EEG activity was recorded. Frequent standard sounds (528 hertz [Hz]) and rare deviant sounds (individual JND threshold, 535 Hz, and 558 Hz) were presented in the oddball paradigm. The mismatch negativity (MMN) and the P3a were used as indicators of auditory discrimination skills for frequency differences. Musicians had significantly smaller individual JND thresholds than non-musicians, but musicians were not faster than non-musicians. Musicians and non-musicians showed both the MMN and the P3a at the 535 Hz and 558 Hz condition. In the individual JND threshold condition, non-musicians, whose individual JND threshold was at 539.8 Hz (and therefore even above the deviant sound of 535 Hz), predictably showed the MMN and the P3a. Musicians, whose individual JND threshold was at 531.1 Hz (and thus close to the standard sound of 528 Hz), showed no MMN and P3a—although they were behaviorally able to differentiate frequencies individually within their JND threshold range. This may indicate a key role of attention in triggering the MMN during the detection of frequency differences in the individual JND threshold range (see Tervaniemi et al. in Exp Brain 161:1–10, 2005). [ABSTRACT FROM AUTHOR]

To evaluate the effect of dual tasking that combines walking with a mental tracking task on spatiotemporal gait parameters in younger and older adults. After completing the International Physical Activity Questionnaire (IPAQ), participants performed single tasks: preferred paced walk (PPW); fast paced walk (FPW); single-leg stance (SLS); spelling backwards cognitive task (CT). Thereafter, dual tasks: PPW + CT; FPW + CT; SLS + CT. Spatiotemporal gait parameters and the durations of SLS and SLS + CT were measured. Twenty younger and 20 older adults participated. The IPAQ scores were similar in both groups. Compared to the single task, stride length was shorter, stride time was longer, and stride length and time variability were higher during the PPW and FPW dual tasks in both groups. Older age was associated with shorter stride length during PPW and FPW, and longer stride time during FPW dual compared to single tasks. The older group exhibited shorter times during SLS and SLS + CT compared to younger group. Despite similar self-reported fitness, older age is associated with shorter stride length and longer stride time during FPW dual tasks as well as short times during SLS + CT, which may indicate diminished balance and posture stability. [ABSTRACT FROM AUTHOR]

In sequential, repetitive tasks, we often partially reuse former motor plans. This causes a persistence of an earlier adopted posture (termed motor hysteresis). The cost-optimization hypothesis states that a partial reuse reduces the cognitive cost of a movement, while the persistence in a former posture increases its mechanical cost. An optimal fraction of reuse, which depends on the relative cognitive and mechanical cost, minimizes the total movement cost. Several studies postulate differences in mechanical or cognitive cost as a result of hemispheric lateralization. In the current study, we asked whether these differences would result in different fractions of motor plan reuse. To this end, left- and right-handed dominant participants executed a sequential motor task (opening a column of drawers) with their dominant and non-dominant hand. The size of the motor hysteresis effect was measured as a proxy for the fraction of plan reuse. Participants used similar postures and exhibited a similar hysteresis effect, irrespective of hand and handedness. This finding indicates that either the cognitive and mechanical costs of a motor task are unaffected by hemispheric differences or that their effect on motor planning is negligible. [ABSTRACT FROM AUTHOR]

Experimental pain inhibits primary motor cortex (M1) excitability. Attenuating pain-related inhibition of M1 excitability may be useful during rehabilitation in individuals with pain. One strategy to attenuate M1 excitability is to influence prefrontal and premotor cortex activity. Working memory tasks, e.g. the two-back task (TBT), engage prefrontal and premotor cortices and may influence M1 excitability. We hypothesized that performing the TBT during pain would influence pain-related changes in M1 excitability. Participants (n = 28) received rigorous training in the TBT before baseline testing. Experimental pain was induced by injecting hypertonic saline into the first dorsal interosseous (FDI) muscle. Participants rated pain intensity on a 0–10 numerical rating scale (NRS) every second min until pain-resolved (PR) during the performance of the TBT (n = 14) or during REST (n = 14). In the TBT, letters were presented pseudo-randomly, and accuracy and reaction time to identified letters corresponding to letters shown two times back were recorded. M1 excitability was assessed using transcranial magnetic stimulation. Motor-evoked potentials (MEPs) were recorded at baseline, and at PR, PR + 10, PR + 20, and PR + 30 min. Four minutes after hypertonic saline injection, the pain NRS scores were higher in the TBT group than the REST group (p = 0.009). No time × group interaction was found for MEPs (p = 0.73), but a main effect of time (p < 0.0005) revealed a reduction of MEPs at PR up until PR + 30 (p < 0.008). The TBT accuracy improved at PR + 30 in both groups (p = 0.019). In conclusion, the pain-induced reduction in corticomotor excitability was unaffected by performing a working memory task, despite greater pain in the TBT group. [ABSTRACT FROM AUTHOR]

Humans normally adapt earlier segments of multistep motor actions in such a way that the execution of later segments is facilitated. For example, the kinematics of grasping movements are adapted to the requirements of the intended subsequent object manipulations. Here we studied which factors foster adaptation of earlier action segments to later ones in a novel task for which no prior experience existed. Participants executed a two-step isometric force production task, in which the force produced in the first segment determined the difficulty of the second segment. Adaptation of the first segment to the second one benefited from explicit knowledge of the dependency between both segments but not from extensive prior experience with the second segment. These observations show that adaptation of motor actions to subsequent actions demands the construction of a task representation that allows to plan the first action segment with respect to its successor. How specifically the first segment is tailored to the second one does not depend on prior experience with the second segment but depends on experience from performing the interdependent two-step action sequence. [ABSTRACT FROM AUTHOR]

How do we decide which object to pick up when faced with two alternatives? Imagine one object is near, but needs to be carried a long distance, and the other object is far, but needs to be carried a short distance. You might predict that participants would favour the far object that needs to be carried a short distance. In other words, they would procrastinate and delay picking up an object to minimise physical effort. In actuality, participants prefer to carry the near object a long distance, which is called pre-crastination. Pre-crastination may be preferred to procrastination because picking up the first object hastens completion of the first goal of the task and, subsequently, decreases cognitive load. The goal of the current study was to further investigate the mechanisms of the pre-crastination effect. This was done by converting the primarily walking task used in the first study on pre-crastination to a reach-to-grasp task. This change enabled the measurement of the duration of information processing (i.e., reaction time) when participants decided which object to move. Surprisingly, participants exhibited a range of behaviours: about 40% pre-crastinated, 40% procrastinated, and 20% neither pre-crastinated nor procrastinated. We suggest that scaling the task down from a walking task to a reach-to-grasp task altered the physical effort, cognitive load, and the interaction between these task demands. This enabled some participants to pre-crastinate and others to procrastinate. There was an intriguing relationship between the duration of information processing and the behaviour of participants: participants with the shortest reaction time had the strongest tendency to pre-crastinate, and participants with the longest reaction time had the strongest tendency to procrastinate. These findings fit with the automatic pre-crastination response hypothesis; that the "decision" to pre-crastinate is automatic. This automaticity caused the short durations of information processing for participants who pre-crastinated. Participants who procrastinated had to, first, inhibit the automatic response to pre-crastinate, which caused long durations of information processing. [ABSTRACT FROM AUTHOR]

In our earlier research, kinematic and kinetic parameters of grasping differed significantly when participants grasped the same object once in a traditional laboratory paradigm, and once as part of a captivating computer game. We attributed this finding to the fact that grasping movements in the laboratory were repetitive and meaningless, while those in the computer game were embedded in complex behavior and served a meaningful purpose. In that work, we argued that grasping in the computer game is more characteristic of everyday life behavior; however, this conclusion has been criticized on the grounds that a computer game is not a typical everyday activity. The present study therefore compares grasping in a traditional laboratory paradigm to that in an indisputably everyday context: grocery shopping. Thirty-three young adults executed externally triggered arm movements to grasp nondescript objects (laboratory task, L) and place them on a tablet, or they walked through a fictitious grocery store towards a shelf to grasp grocery products and placed them into a shopping basket (everyday-like task, E). Size, shape, weight and location of to-be-grasped objects were identical in both tasks. We found that of the analyzed 16 kinematic parameters, 13 differed significantly between tasks. Specifically, grip apertures were larger, movements were slower and grip–transport coupling was more variable in E compared to L. We conclude that kinematic differences between both persist even if task is more realistic than in our earlier research. Our findings are compatible with the notion that movement planning is less stringent in E than in L. [ABSTRACT FROM AUTHOR]

The presence of motor redundancy means that movement variability can be split into a 'task-space' component that affects task performance, and a 'null space' component which has no effect on task performance. While the control of task-space variability during learning is essential, because it is directly linked to performance, how the nervous system controls null space variability during learning has not been well understood. One factor that has been hypothesized to govern the change in null space variability with learning is task difficulty, but this has not been directly tested. Here, we examined how task difficulty influences the change in null space variability with learning. Healthy, college-aged participants (N = 36) performed a bimanual steering task, where they steered a cursor through a smooth W-shaped track of a certain width as quickly as possible while attempting to keep the cursor within the track. Task difficulty was altered by changing the track width and participants were split into one of the three groups based on the track width that they practiced on—wide, narrow, or progressive (where the width of the track progressively changed from wide to narrow over practice). The redundancy in this task arose from the fact that the position of the cursor was defined as the average position of the two hands. Results showed that movement time depended on task difficulty, but all groups were able to decrease their movement time with practice. Learning was associated with a reduction in null space variability in all groups, but critically, there was no effect of task difficulty. Further analyses showed that while the task-space variability showed an expected speed-accuracy tradeoff with movement time, the null space variability showed a qualitatively different pattern. These results suggest differential control of task and null space variability in response to changes in task difficulty with learning, and may reflect a strong preference to minimize overall movement variability during learning. [ABSTRACT FROM AUTHOR]

Transfer, in which capability acquired in one situation influences performance in another is considered, along with retention, as demonstrative of effectual learning. In this regard, interlimb transfer of functional capacity has commanded particular attention as a means of gauging the generalisation of acquired capability. Both theoretical treatments and prior empirical studies suggest that the successful accomplishment of a physical training regime is required to bring about generalised changes that extend to the untrained limb. In the present study, we pose the following question: Does interlimb transfer occur if and only if the training movements are executed? We report findings from JG—an individual recruited to a larger scale trial, who presented with (unilateral) deficits of motor control. We examined whether changes in the performance of the untrained right limb arose following practice undertaken by the impaired left limb, wherein the majority of JG's attempts to execute the training task were unsuccessful. Comparison was made with a group of "control" participants drawn from the main trial, who did not practice the task. For JG, substantial gains in the performance of the untrained limb (registered 3 days, 10 days and 1 year following training) indicated that effective learning had occurred. Learning was, however, expressed principally when the unimpaired (i.e. untrained) limb was utilised to perform the task. When the impaired limb was used, marked deficiencies in movement execution remained prominent throughout. [ABSTRACT FROM AUTHOR]

Individuals are often required to complete two tasks simultaneously, such as walking while talking. Although the influence of performing a cognitive task during upright standing has been studied, less is known regarding how individuals prioritize the performance of multiple goal-directed tasks. The purpose of this study was to examine how young adults prioritize the performance of two goal-directed tasks while standing: generating speech (communicating) while performing a postural-manual task. Fifteen young adult female participants completed four conditions of the postural-manual task, quietly and while talking; a control condition of speech while standing was also completed. Task accuracy was defined as holding a block within an opening without hitting the perimeter and speaking clearly. Participants generally prioritized accurate communication over accurate completion of the postural-manual task, as evidenced by modifying their manual and postural strategies and decreasing manual accuracy. [ABSTRACT FROM AUTHOR]

Functional behaviour affords that we form goals to integrate sensory information about the world around us with suitable motor actions, such as when we plan to grab an object with a hand. However, much research has tested grasping in static scenarios where goals are pursued with repetitive movements, whereas dynamic contexts require goals to be pursued even when changes in the environment require a change in the actions to attain them. To study grasp goals in dynamic environments here, we employed a task where the goal remained the same but the execution of the movement changed; we primed participants to grasp objects either with their right or left hand, and occasionally they had to switch to grasping with both. Switch costs should be minimal if grasp goal representations were used continuously, for example, within the left dominant hemisphere. But remapped or re-computed goal representations should delay movements. We found that switching from right-hand grasping to bimanual grasping delayed reaction times but switching from left-hand grasping to bimanual grasping did not. Further, control experiments showed that the lateralized switch costs were not caused by asymmetric inhibition between hemispheres or switches between usual and unusual tasks. Our results show that the left hemisphere does not serve a general role of sensorimotor grasp goal representation. Instead, sensorimotor grasp goals appear to be represented at intermediate levels of abstraction, downstream from cognitive task representations, yet upstream from the control of the grasping effectors. [ABSTRACT FROM AUTHOR]

Peripersonal space (PPS) is created by a multisensory interaction between different sensory modalities and can be modified by experience. In this article, we investigated whether an auditory training, inside the peripersonal space area, can modify the PPS around the head in sighted participants. The auditory training was based on echolocation. We measured the participant's reaction times to a tactile stimulation on the neck, while task-irrelevant looming auditory stimuli were presented. Sounds more strongly affect tactile processing when located within a limited distance from the body. We measured spatially dependent audio-tactile interaction as a proxy of PPS representation before and after an echolocation training. We found a significant speeding effect on tactile RTs after echolocation, specifically when sounds where around the location where the echolocation task was performed. This effect could not be attributed to a task repetition effect nor to a shift of spatial attention, as no changes of PPS were found in two control groups of participants, who performed the PPS task after either a break or a temporal auditory task (with stimuli located at the same position of echolocation task). These findings show that echolocation affects multisensory processing inside PPS representation, likely to better represent the space where external stimuli, have to be localized. [ABSTRACT FROM AUTHOR]

Injury to the cervical spinal cord results in deficits in bimanual control, reducing functional independence and quality of life. Despite this, little research has investigated the control strategies which underpin bimanual arm/hand movements following cervical spinal cord injury (cSCI). Using kinematics and surface electromyography this study explored how task symmetry affects bimanual control, in patients with an acute cSCI (< 6 m post injury), as they performed naturalistic bimanual reach-to-grasp actions (to objects at 50% and 70% of their maximal reach distance), and how this differs compared to uninjured age-matched controls. Twelve adults with a cSCI (mean age 69.25 years), with lesions at C3-C8, categorized by the American Spinal Injury Impairment Scale (AIS) at C or D and 12 uninjured age-matched controls (AMC) (mean age 69.29 years) were recruited. Participants with a cSCI produced reach-to-grasp actions which took longer, were slower, less smooth and had longer deceleration phases than AMC (p < 0.05). Participants with a cSCI were less synchronous than AMC at peak velocity and just prior to object pick up (p < 0.05), but both groups ended the movement in a synchronous fashion. Peak muscle activity occurred just prior to object pick up for both groups. While there seems to be a greater reliance on the deceleration phase of the movement, we observed minimal disruption of the more impaired limb on the less impaired limb and no additional effects of task symmetry on bimanual control. Further research is needed to determine how to take advantage of this retained bimanual control in therapy. [ABSTRACT FROM AUTHOR]

In many activities, we need to predict the arrival of an occluded object. This action is called prediction motion or motion extrapolation. Previous researchers have found that both eye tracking and the internal clocking model are involved in the prediction motion task. Additionally, it is reported that concurrent hand movement facilitates the eye tracking of an externally generated target in a tracking task, even if the target is occluded. The present study examined the effect of concurrent hand movement on the estimated time to contact in a prediction motion task. We found different (accurate/inaccurate) concurrent hand movements had the opposite effect on the eye tracking accuracy and estimated TTC in the prediction motion task. That is, the accurate concurrent hand tracking enhanced eye tracking accuracy and had the trend to increase the precision of estimated TTC, but the inaccurate concurrent hand tracking decreased eye tracking accuracy and disrupted estimated TTC. However, eye tracking accuracy does not determine the precision of estimated TTC. [ABSTRACT FROM AUTHOR]

The current study investigated the role of automatic encoding and maintenance of remembered, past, and present visual distractors for reach movement planning. The previous research on eye movements showed that saccades curve away from locations actively kept in working memory and also from task-irrelevant perceptually present visual distractors, but not from task-irrelevant past distractors. Curvature away has been associated with an inhibitory mechanism resolving the competition between multiple active movement plans. Here, we examined whether reach movements underlie a similar inhibitory mechanism and thus show systematic modulation of reach trajectories when the location of a previously presented distractor has to be (a) maintained in working memory or (b) ignored, or (c) when the distractor is perceptually present. Participants performed vertical reach movements on a computer monitor from a home to a target location. Distractors appeared laterally and near or far from the target (equidistant from central fixation). We found that reaches curved away from the distractors located close to the target when the distractor location had to be memorized and when it was perceptually present, but not when the past distractor had to be ignored. Our findings suggest that automatically encoding present distractors and actively maintaining the location of past distractors in working memory evoke a similar response competition resolved by inhibition, as has been previously shown for saccadic eye movements. [ABSTRACT FROM AUTHOR]

Many actions involve multiple action steps, which raises the question how far ahead people plan when they perform such actions. Here, we examined higher-order planning for action sequences and whether people planned similarly or differently when acting individually or together with an action partner. For individual performances, participants picked up an object with one hand and passed it to their other hand before placing it onto a target location. For joint performances, they picked up the object and handed it to their action partner, who placed it onto the target location. Each object could be grasped at only two possible grasping positions, implying that the first selected grasp on the object determined the postures for the rest of the action sequence. By varying the height of the target shelf, we tested whether people planned ahead and modulated their grasp choices to avoid uncomfortable end postures. Our results indicated that participants engaged in higher-order planning, but needed task experience before demonstrating such planning during both individual and joint performances. The rate of learning was similar in the two conditions, and participants transferred experience from individual to joint performance. Our results indicate similarity in mechanisms underlying individual and joint action sequence planning. [ABSTRACT FROM AUTHOR]

Prior research has concluded that the correlations of isometric finger forces represent the extent to which the fingers are controlled as a single unit. If this is the case, finger force correlations should be consistent with estimates of the controlled (dynamical) degrees of freedom in finger forces. The present study examined the finger force correlations and the dynamical degrees of freedom in four isometric force tasks. The tasks were to produce a preferred level of force with the (a) Index, (b) Ring, (c) Both fingers and also to (d) Rest the fingers on the load cells. Dynamical degrees of freedom in finger forces were lowest in the Both finger force task and progressively higher in the Ring, Index and Resting finger force tasks. The finger force correlations were highest in the Resting and lowest in the Index and Ring finger tasks. The results for the dynamical degrees of freedom in finger forces were consistent with a reduction in degrees of freedom in response to the degrees of freedom problem and the task constraints. The results for the finger force correlations were inconsistent with a reduction in the dynamical degrees of freedom. These findings indicate that finger force correlations do not necessarily reflect the coupling of finger forces. The findings also highlight the value of time-domain analyses to reveal the organization of control in isometric finger forces. [ABSTRACT FROM AUTHOR]

In a choice reaction time (RT) paradigm, providing partial advance information (a precue) about the upcoming response has been shown to decrease RT, presumably due to preprogramming of the precued parameters. When advance information about a particular aspect of a movement is provided (precued), several different strategies might be used to prepare the motor system during the foreperiod. For example, in studies where response preparation time was manipulated, precues were provided specifying the required arm and direction but movement amplitude was left uncertain. In this case it was shown that a default movement was preprogrammed whose amplitude was intermediate between the alternatives (Favilla et al. in Exp Brain Res 75(2):280-294, , Exp Brain Res 79(3):530-538, ; Ghez et al. in Exp Brain Res 115(2):217-233, ). However, this strategy did not appear to be used in a RT task since there was an absence of online adjustments to movement. Therefore, it appeared movements were not initiated until all parameters had been correctly specified and programmed by the nervous system (Bock and Arnold in Exp Brain Res 90:(1):209-216, ). The present study reinvestigated the notion of a default movement preparation strategy in a choice RT paradigm, employing the triggering effect of a startling acoustic stimulus. On control trials (80 dB imperative stimulus), the movements were initiated toward the correct targets. Providing a startle stimulus (124 dB) resulted in the early initiation of a 'default' movement whose amplitude fell in between the potential response alternatives. Thus, the current experiment found behavioral evidence of default intermediate-amplitude movement preparation as a strategy under conditions of response amplitude uncertainty. [ABSTRACT FROM AUTHOR]

We used two methods, analytical inverse optimization (ANIO) and uncontrolled manifold (UCM) analysis of synergies, to explore age-related changes in finger coordination during accurate force and moment of force production tasks. The two methods address two aspects of the control of redundant systems: Finding an optimal solution (an optimal sharing pattern) and using variable solutions across trials (covarying finger forces) that are equally able to solve the task. Young and elderly subjects produced accurate combinations of total force and moment by pressing with the four fingers of the dominant hand on individual force sensors. In session-1, single trials covered a broad range of force-moment combinations. Principal component (PC) analysis showed that the first two PCs explained about 90% and 75% of finger force variance for the young and elderly groups, respectively. The magnitudes of the loading coefficients in the PCs suggested that the young subjects used mechanical advantage to produce moment while elderly subjects did not (confirmed by analysis of moments produced by individual digits). A co-contraction index was computed reflecting the magnitude of moment produced by fingers acting against the required direction of the total moment. This index was significantly higher in the young group. The ANIO approach yielded a quadratic cost function with linear terms. In the elderly group, the contribution of the forces produced by the middle and ring fingers to the cost function value was much smaller than in the young group. The angle between the plane of experimental observations and the plane of optimal solutions (D-angle), was very small (about 1.5°) in the young group and significantly larger (about 5°) in the elderly group. In session-2, four force-moment combinations were used with multiple trials at each. Covariation among finger forces (multifinger synergies) stabilizing total force, total moment, and both was seen in both groups with larger synergy indices in the young group. Multiple regression analysis has shown that, at higher force magnitudes, the synergy indices defined with the UCM method were significantly related to the percent of variance accounted by the first two PCs and to the D-angle computed using the ANIO method. We interpret the results as pointing at a transition with age from synergic control to element-based control (back-to-elements hypothesis). Optimization and analysis of synergies are complementary approaches that focus on two aspects of multidigit coordination, sharing and covariation, respectively. [ABSTRACT FROM AUTHOR]

Previous studies of postural preparation to action/perturbation have primarily focused on anticipatory postural adjustments (APAs), the changes in muscle activation levels resulting in the production of net forces and moments of force. We hypothesized that postural preparation to action consists of two stages: (1) Early postural adjustments (EPAs), seen a few hundred ms prior to an expected external perturbation and (2) APAs seen about 100 ms prior to the perturbation. We also hypothesized that each stage consists of three components, anticipatory synergy adjustments seen as changes in covariation of the magnitudes of commands to muscle groups (M-modes), changes in averaged across trials levels of muscle activation, and mechanical effects such as shifts of the center of pressure. Nine healthy participants were subjected to external perturbations created by a swinging pendulum while standing in a semi-squatting posture. Electrical activity of twelve trunk and leg muscles and displacements of the center of pressure were recorded and analyzed. Principal component analysis was used to identify four M-modes within the space of muscle activations using indices of integrated muscle activation. This analysis was performed twice, over two phases, 400-700 ms prior to the perturbation and over 200 ms just prior to the perturbation. Similar robust results were obtained using the data from both phases. An index of a multi-M-mode synergy stabilizing the center of pressure displacement was computed using the framework of the uncontrolled manifold hypothesis. The results showed high synergy indices during quiet stance. Each of the two stages started with a drop in the synergy index followed by a change in the averaged across trials activation levels in postural muscles. There was a very long electromechanical delay during the early postural adjustments and a much shorter delay during the APAs. Overall, the results support our main hypothesis on the two stages and three components of the postural preparation to action/perturbation. This is the first study to document anticipatory synergy adjustments in whole-body tasks. We interpret the results within the referent configuration hypothesis (an extension of the equilibrium-point hypothesis): The early postural adjustment is based primarily on changes in the coactivation command, while the APAs involve changes in the reciprocal command. The results fit an earlier hypothesis that whole-body movements are controlled by a neuromotor hierarchy where each level involves a few-to-many mappings organized to stabilize its overall output. [ABSTRACT FROM AUTHOR]

How we interact with objects depends on what we intend to do with them. In the current work, we show that priming and the kinematics of grasping depend on the goals of grasping, as well as the context in which tasks are presented. We asked participants to grasp familiar kitchen tools in order to either move them, grasp-to-move (GTM), or to demonstrate their common use, grasp-to-use (GTU). When tasks were blocked separately (Experiment 1), we found that priming was only evident for the GTU task. However, when tasks were presented in the same block of trials (Experiment 2), we observed priming for both tasks. Independent of priming, differences in kinematics and reaction times according to task were evident for both Experiments. Longer reaction times for the GTU task indicate more extensive planning, and differences in grasping reflect the characteristics of subsequent actions. Priming of real grasping is determined by task goals as well as task setting, both of which are likely to modulate how object features (affordances) are perceived and influence the planning of future actions. [ABSTRACT FROM AUTHOR]