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The thalamus, with its reciprocal connections to and from cortical, subcortical, and cerebellar regions, is a central active participant in multiple functional brain networks. Structural MRI studies measuring the entire thalamus without respect to its regional or nuclear divisions report volume shrinkage in diseases including HIV infection, alcohol use disorder (AUD), and their comorbidity (HIV+AUD). Here, we examined relations between thalamic subregions (anterior, ventral, medial, and posterior) and neuropsychological functions (attention/working memory, executive functioning, episodic memory, and motor skills). Volumes of thalamic subregions were derived from automatic segmentations of standard T1 weighted MRIs of 65 individuals with HIV, 189 with AUD, 80 with HIV+AUD comorbidity, and 141 healthy controls (CTRL). Total thalamic volume was smaller and cognitive and motor composite scores were lower in the three diagnostic groups relative to the CTRL group. The AUD and HIV+AUD groups had significantly smaller thalamic subregional volumes than the CTRL group. The HIV+AUD group had smaller anterior thalamic volume than the HIV-only group and smaller ventral thalamic volume than the AUD-only group. In the HIV+AUD group, memory scores correlated with anterior thalamic volumes, attention/working memory scores correlated with posterior and medial thalamic volumes, and motor skill scores correlated with posterior thalamic volumes. Exploratory analyses focused on the HIV+AUD group indicated that within the posterior thalamic region, the pulvinar and medial geniculate nuclei were related to attention/working memory scores, and the pulvinar was related to motor skills scores. This study is novel in locating volume deficits in specific thalamic subregions, in addition to the thalamus as a whole, in HIV, AUD, and their comorbidity and in identifying functional ramifications of these deficits. Taken together, this study highlights the relevance of thalamic subregional volume deficits to dissociable cognitive and motor processes.

Whether the direction of a hand motion that is congruent or incongruent with a concurrent target motion can influence representational momentum for that target was examined. Participants viewed a leftward or rightward moving target while moving their hand rightward, leftward, or not moving their hand. Prior studies of mental rotation found that congruency or incongruency of the direction of mental rotation and the direction of a concurrent physical rotation of a stimulus influenced mental rotation. As mental rotation and representational momentum each involve extrapolation of target motion, it could be predicted that congruency of the direction of hand motion and the direction of target motion might influence representational momentum of the target. Robust representational momentum occurred in all conditions, but there was no effect of congruency of hand motion and target motion, nor of the presence or absence of hand motion, on representational momentum. The results are consistent with a hypothesis that the generation of representational momentum involves sensory processes rather than motor processes. [ABSTRACT FROM AUTHOR]

Individuals often need to make quick decisions based on incomplete or "noisy" information. This requires the coordination of attentional, perceptual, cognitive, and behavioral mechanisms. This poses a challenge for isolating the unique effects of each subprocess from behavioral data, which reflect the summation of all subprocesses combined. Sequential sampling models offer a more detailed examination of behavioral data, enabling us to separate decisional and non-decisional processes at play in a task. Participants were required to identify briefly presented shapes while perceptual (duration, size, location) and response features (location-congruent/-incongruent/-neutral) of the task were manipulated. The diffusion model (Ratcliff, 1978) was used to dissociate decisional and executive processes in the task. In Experiment 1, stimuli were presented for either 20 or 80 ms to the left or right of a central fixation while response keys were positioned horizontally. In Experiment 2, stimulus size was manipulated rather than duration. In Experiment 3, response keys were positioned vertically. Results showed a duration x response mapping interaction. Participants displayed stimulus–response (S–R) congruency biases only on short-duration trials. This effect was observed for both horizontal and vertical response key mappings. Stimulus size affected participant response speed, but did not elicit S–R congruency biases. The present findings show that when perceptual quality of evidence is poor, individuals rely more heavily on spatial-motor mechanisms when making speeded choice decisions. Furthermore, positioning response keys vertically is insufficient to eliminate S–R congruency effects. Diffusion model parameters are presented and implications of the model are discussed. [ABSTRACT FROM AUTHOR]

Gilles de la Tourette syndrome (GTS) is a neuropsychiatric disorder. Because motor signs are the defining feature of GTS, addressing the neurophysiology of motor processes is central to understanding GTS. The integration of voluntary motor processes is subject to so-called "binding problems", i.e., how different aspects of an action are integrated. This was conceptualized in the theory of event coding, in which 'action files' accomplish the integration of motor features. We examined the functional neuroanatomical architecture of EEG theta band activity related to action file processing in GTS patients and healthy controls. Whereas, in keeping with previous data, behavioral performance during action file processing did not differ between GTS and controls, underlying patterns of neural activity were profoundly different. Superior parietal regions (BA7) were predominantly engaged in healthy controls, but superior frontal regions (BA9, BA10) in GTS indicated that the processing of different motor feature codes was central for action file processing in healthy controls, whereas episodic processing was more relevant in GTS. The data suggests a cascade of cognitive branching in fronto-polar areas followed by episodic processing in superior frontal regions in GTS. Patients with GTS accomplish the integration of motor plans via qualitatively different neurophysiological processes. [ABSTRACT FROM AUTHOR]

The thalamus, with its reciprocal connections to and from cortical, subcortical, and cerebellar regions, is a central active participant in multiple functional brain networks. Structural MRI studies measuring the entire thalamus without respect to its regional or nuclear divisions report volume shrinkage in diseases including HIV infection, alcohol use disorder (AUD), and their comorbidity (HIV+AUD). Here, we examined relations between thalamic subregions (anterior, ventral, medial, and posterior) and neuropsychological functions (attention/working memory, executive functioning, episodic memory, and motor skills). Volumes of thalamic subregions were derived from automatic segmentations of standard T1 weighted MRIs of 65 individuals with HIV, 189 with AUD, 80 with HIV+AUD comorbidity, and 141 healthy controls (CTRL). Total thalamic volume was smaller and cognitive and motor composite scores were lower in the three diagnostic groups relative to the CTRL group. The AUD and HIV+AUD groups had significantly smaller thalamic subregional volumes than the CTRL group. The HIV+AUD group had smaller anterior thalamic volume than the HIV-only group and smaller ventral thalamic volume than the AUD-only group. In the HIV+AUD group, memory scores correlated with anterior thalamic volumes, attention/working memory scores correlated with posterior and medial thalamic volumes, and motor skill scores correlated with posterior thalamic volumes. Exploratory analyses focused on the HIV+AUD group indicated that within the posterior thalamic region, the pulvinar and medial geniculate nuclei were related to attention/working memory scores, and the pulvinar was related to motor skills scores. This study is novel in locating volume deficits in specific thalamic subregions, in addition to the thalamus as a whole, in HIV, AUD, and their comorbidity and in identifying functional ramifications of these deficits. Taken together, this study highlights the relevance of thalamic subregional volume deficits to dissociable cognitive and motor processes. • Alcohol use disorder (AUD) and HIV+AUD had regional thalamic volume deficits. • HIV+AUD had smaller anterior thalamic volumes than HIV. • Only the HIV+AUD showed functional deficits related to regional thalamic volumes. • Lower memory scores correlated with smaller anterior thalamic volumes. • Attention/working memory scores correlated with posterior and medial volumes. [ABSTRACT FROM AUTHOR]

The development of the ability to adapt one's motor performance to the constraints of a movement task was examined in a longitudinal study involving 7 to-9-year-old children who were asked to perform a preparatory handwriting task. The capacity for sensorimotor synchronization was captured by the standard deviation of the relative phase between pacing signals and writing movements and the capacity to adjust wrist-finger coordination while performing repetitive movements was analyzed by autocorrelations of the vertical pen-tip displacements. While the capacity for synchronization improved with age, the autocorrelations were positive at short time lags only and hardly changed with age. A measure of "the long-term memory" of time series (Hurst exponent) confirmed that the findings were systematic rather than noise. Collectively, the results indicate that flexible movement strategies emerge early on in the first 3 years of formal handwriting education. Implications for educational and clinical practice are considered. [ABSTRACT FROM AUTHOR]

It is widely believed that predicted tactile action outcomes are perceptually attenuated. The present experiments determined whether predictive mechanisms necessarily generate attenuation or, instead, can enhance perception—as typically observed in sensory cognition domains outside of action. We manipulated probabilistic expectations in a paradigm often used to demonstrate tactile attenuation. Adult participants produced actions and subsequently rated the intensity of forces on a static finger. Experiment 1 confirmed previous findings that action outcomes are perceived less intensely than passive stimulation but demonstrated more intense perception when active finger stimulation was removed. Experiments 2 and 3 manipulated prediction explicitly and found that expected touch during action is perceived more intensely than unexpected touch. Computational modeling suggested that expectations increase the gain afforded to expected tactile signals. These findings challenge a central tenet of prominent motor control theories and demonstrate that sensorimotor predictions do not exhibit a qualitatively distinct influence on tactile perception. [ABSTRACT FROM AUTHOR]

Gilles de la Tourette syndrome (GTS) is a neuropsychiatric disorder. Because motor signs are the defining feature of GTS, addressing the neurophysiology of motor processes is central to understanding GTS. The integration of voluntary motor processes is subject to so-called “binding problems”, i.e., how different aspects of an action are integrated. This was conceptualized in the theory of event coding, in which ‘action files’ accomplish the integration of motor features. We examined the functional neuroanatomical architecture of EEG theta band activity related to action file processing in GTS patients and healthy controls. Whereas, in keeping with previous data, behavioral performance during action file processing did not differ between GTS and controls, underlying patterns of neural activity were profoundly different. Superior parietal regions (BA7) were predominantly engaged in healthy controls, but superior frontal regions (BA9, BA10) in GTS indicated that the processing of different motor feature codes was central for action file processing in healthy controls, whereas episodic processing was more relevant in GTS. The data suggests a cascade of cognitive branching in fronto-polar areas followed by episodic processing in superior frontal regions in GTS. Patients with GTS accomplish the integration of motor plans via qualitatively different neurophysiological processes.

What are the affordances of artifacts? One view is that the affordances of artifacts, just as the affordances of natural objects, pertain to possible ways in which they can be manipulated (e.g., a computer keyboard affords grasping). Another view maintains that, given that artifacts are sociocultural objects, their affordances pertain primarily to their culturally-derived function (e.g., a computer keyboard affords typing). Whereas some have tried to provide a unifying notion of affordance to capture both aspects, here I argue that they should be kept separate. In this paper, I introduce a distinction between standard affordances, which concern the function of artifacts, and ad-hoc affordances, which refer to how artifacts are manipulated. I then argue for the neuropsychological plausibility of such a distinction, linking it to the dissociation between function knowledge and manipulation knowledge. Finally, I defend the equal status of these forms of knowledge and, hence, of standard and ad-hoc affordances, and I show that this has some implications for the debate on the role of motor processes in the conceptual knowledge of artifacts. [ABSTRACT FROM AUTHOR]

Attentional manipulations have been shown to influence subsequent evaluations of objects and images. For example, images used as distractors in a visual search task are subsequently rated more negatively than are target images. One powerful manipulation of attention occurs when we plan and execute movements toward objects in our environment. Here, in two experiments, we show that selective attention to real-world objects subsequently improves emotional appraisal of those objects—an effect we term "target appreciation." Participants were presented with abstract images on three-dimensional objects, and were cued to either reach and grasp one of the two objects, or to respond to the cued object with a keyboard. Images presented on target objects were appraised more positively when compared with novel images. In contrast, images associated with obstacles or distractor objects were not appraised differently than novel images, despite the attentional suppression thought to be required to successfully avoid or ignore these objects. We speculate that this automatic appreciation of the objects of selective attention may be adaptive for organisms acting in complex environments. [ABSTRACT FROM AUTHOR]

This study sought to explore the type of fundamental movement skills (FMS) performed during Active Video Game (AVG) play, as well as the frequency with which these FMS are performed. In addition, this study aimed to determine the relationship between FMS performance and energy expenditure during 15 min of AVG play across two Microsoft Xbox Kinect AVGs. Fundamental movement skills were observed via video by two raters and energy expenditure derived using Actiheart monitors in children aged 10–15 years. Six different FMS were observed during AVG play with differences in the number of FMS performed between the two AVGs. The overall energy expended (Joules/kg/minute), however, was similar between the AVGs, suggesting the frequency of FMS did not influence overall energy expended during play. The movements observed during AVG play that possibly accounted for the energy expenditure, were not of a quality that could be classified as FMS. This research demonstrates that children playing these two games have the opportunity to repeatedly perform mostly two FMS, namely jumping and dodging. The goal of the AVGs, however, could be achieved with generalized movements that did not always meet the criteria to be classified as a FMS. [ABSTRACT FROM AUTHOR]

The involvement of motor processes in mental rotation is experience-dependent: different levels of expertise in sensorimotor interactions lead to different strategies in mental rotation. In the present study, wrestlers, gymnasts, and nonathletes physically rotated objects that were either light (wooden) or heavy (lead) but otherwise having the same sizes and shapes. They then performed a mental rotation task using photographs of these objects in which the material and therefore the weight was visible. I hypothesized that wrestlers would rely more heavily on experience-based sensorimotor strategies in performing mental rotation because during their athletic practice they not only manipulate external "objects" (i.e., their opponent) but also have to plan future actions taking into account past experience of these "objects" (for example their weight). All participants reported that lead objects were harder to physically rotate than wooden ones. However, only wrestlers mentally rotated lead objects more slowly than wooden ones—as they would if they were physically rotating them—suggesting the involvement of motor processes. These findings show that the involvement of motor processes in mental rotation depends on specific rather than mere sensorimotor experience. [ABSTRACT FROM AUTHOR]

Both eye and hand movements have been shown to selectively interfere with visual working memory. We investigated working memory in the context of simultaneous eye-hand movements to approach the question whether the eye and the hand movement systems independently interact with visual working memory. Participants memorized several locations and performed eye, hand, or simultaneous eye-hand movements during the maintenance interval. Subsequently, we tested spatial working memory at the eye or the hand motor goal, and at action-irrelevant locations. We found that for single eye and single hand movements, memory at the eye or hand target was significantly improved compared to action-irrelevant locations. Remarkably, when an eye and a hand movement were prepared in parallel, but to distinct locations, memory at both motor targets was enhanced—with no tradeoff between the two separate action goals. This suggests that eye and hand movements independently enhance visual working memory at their goal locations, resulting in an overall working memory performance that is higher than that expected when recruiting only one effector.

Both eye and hand movements have been shown to selectively interfere with visual working memory. We investigated working memory in the context of simultaneous eye-hand movements to approach the question whether the eye and the hand movement systems independently interact with visual working memory. Participants memorized several locations and performed eye, hand, or simultaneous eye-hand movements during the maintenance interval. Subsequently, we tested spatial working memory at the eye or the hand motor goal, and at action-irrelevant locations. We found that for single eye and single hand movements, memory at the eye or hand target was significantly improved compared to action-irrelevant locations. Remarkably, when an eye and a hand movement were prepared in parallel, but to distinct locations, memory at both motor targets was enhanced—with no tradeoff between the two separate action goals. This suggests that eye and hand movements independently enhance visual working memory at their goal locations, resulting in an overall working memory performance that is higher than that expected when recruiting only one effector. [ABSTRACT FROM AUTHOR]

Motor-based theories of facial expression recognition propose that the visual perception of facial expression is aided by sensorimotor processes that are also used for the production of the same expression. Accordingly, sensorimotor and visual processes should provide congruent emotional information about a facial expression. Here, we report evidence that challenges this view. Specifically, the repeated execution of facial expressions has the opposite effect on the recognition of a subsequent facial expression than the repeated viewing of facial expressions. Moreover, the findings of the motor condition, but not of the visual condition, were correlated with a nonsensory condition in which participants imagined an emotional situation. These results can be well accounted for by the idea that facial expression recognition is not always mediated by motor processes but can also be recognized on visual information alone. [ABSTRACT FROM AUTHOR]

The Structured Interview for Psychosis-Risk Syndromes (SIPS) contains criteria for the Attenuated Positive Symptom Syndrome (APSS), a period of subthreshold positive symptoms that predates full-blown psychosis. Motor abnormalities are often associated with these symptoms but have not been adequately studied. We assessed a diverse sample of 192 APSS participants (27.1% female; 47.9% white; mean age = 20.03 years) for motor dysfunction (SIPS G.3. score) at baseline and conversion to psychosis every 3 months for up to 2 years. Fifty-nine (30.7%) participants converted to psychosis. Baseline G.3. score was significantly higher among converters than nonconverters (mean difference = 0.66; t[95.929] = 2.579, p < 0.05). No significant differences in baseline G.3. were found between demographic groups or those with differential medication use. These results point to the use of G.3. as a potential predictor of psychosis among APSS individuals and potentially implicate the shared biological underpinnings of motor dysfunction in the APSS and full-blown psychotic illnesses. [ABSTRACT FROM AUTHOR]

Background: Previous meta-analytical research examining cocaine and methamphetamine separately suggests potentially different neuropsychological profiles associated with each drug. In addition, neuroimaging studies point to distinct structural changes that might underlie differences in neuropsychological functioning.Objectives: This meta-analysis compared the effect sizes identified in cocaine versus methamphetamine studies across 15 neuropsychological domains.Method: Investigators searched and coded the literature examining the neuropsychological deficits associated with a history of either cocaine or methamphetamine use. A total of 54 cocaine and 41 methamphetamine studies were selected, yielding sample sizes of 1,718 and 1,297, respectively. Moderator analyses were conducted to compare the two drugs across each cognitive domain.Results: Data revealed significant differences between the two drugs. Specifically, studies of cocaine showed significantly larger effect-size estimates (i.e., poorer performance) in verbal working memory when compared to methamphetamine. Further, when compared to cocaine, methamphetamine studies demonstrated significantly larger effect sizes in delayed contextual verbal memory and delayed visual memory.Conclusion: Overall, cocaine and methamphetamine users share similar neuropsychological profiles. However, cocaine appears to be more associated with working memory impairments, which are typically frontally mediated, while methamphetamine appears to be more associated with memory impairments that are linked with temporal and parietal lobe dysfunction. [ABSTRACT FROM AUTHOR]

Carrying weight while walking is a common activity associated with increased musculoskeletal loading, but not all individuals accommodate to the weight in the same way. Different accommodation strategies could lead to different skeletal forces, stimuli for bone adaptation and ultimately bone competence. The purpose of the study was to explore the relationships between calcaneal bone competence and biomechanical accommodation variables measured during weighted walking. Twenty healthy men and women (10 each; age 27.8 ± 6.8 years) walked on a treadmill at 1.34 m/s while carrying 0, 44.5 and 89 N weights with two hands in front of the body. Peak vertical ground reaction force and sagittal plane angular displacements of the trunk and left lower extremity during weight acceptance were measured and used to quantify accommodation. Calcaneal bone stiffness index T-score (BST) was measured using quantitative ultrasound. Correlation and stepwise multiple regression were used to predict calcaneal BST from the accommodation variables. Accommodations of the foot and ankle explained 29 and 54% (p ≤ .015) of the variance in calcaneal BST in different regression models. Statistical resampling using 1000 replications confirmed the strength and consistency of relationships, with the best model explaining 94% of the variance in calcaneal BST. Individuals who change foot and ankle function when carrying heavier weight likely alter the control of gravitational and muscular forces, thereby affecting calcaneal loading, bone adaptation and bone competence. These novel findings illustrate the importance of gait accommodation strategies and highlight a potential clinical consequence that requires further investigation. [ABSTRACT FROM AUTHOR]

Past research has shown that the movement times of imagined aiming movements were more similar to actual movement times after the individual has experienced executing the movements. The purpose of the present study was to determine if experience with a set of movements altered the imagination of movements that were not experienced. Participants imagined a series of reciprocal aiming movements in different movement difficulty contexts (created by altering target width and movement amplitude) before and after actually executing a series of aiming movements. The range of difficulties of the imagined movements included difficulty contexts that were within (Experiment 1) or outside (Experiment 2) the range of difficulty experienced during execution. It was found that imagined movement times of movements within the range of movement difficulties experienced were more consistent with Fitts' Law after movement experience, whereas imagination of more difficult movements was not altered by experience. It is suggested that execution did not enhance imagination of more difficult movements because the relative contributions of motor planning and control to the more difficult movements were different from those in the experienced movements. Thus, the enhancement of imagination through experience might only occur when mechanisms underlying the executed and imagined movements are similar. [ABSTRACT FROM AUTHOR]

The vertical ground reaction force (VGRF) during rear-foot striking running typically exhibits peaks referred to as the impact peak and the active peak; their timings and magnitudes have been implicated in injury. Identifying the structure of time-series can provide insight into associated control processes. The purpose here was to detect long-range correlations associated with the time from first contact to impact peak (TIP) and active peak (TAP); and the magnitudes of impact (IPM) and active peaks (APM) using a Detrended Fluctuation Analysis, and Auto-Regressive Fractionally Integrated Moving Average models. Twelve subjects performed an 8min trial at their preferred running speed on an instrumented treadmill. TIP, TAP; IPM, and APM were identified from the VGRF profile for each footfall. TIP and TAP time-series did not demonstrate long-range correlations, conversely IPM and APM time-series did. Short range correlations appeared as well as or instead of long range correlations for IPM. Conversely pure powerlaw behaviour was demonstrated in 11 of the 24 time series for APM, and long range dependencies along with short range correlations were present in a further 9 time series. It has been hypothesised that control mechanisms for IPM and APM are different, these results support this hypothesis. [ABSTRACT FROM AUTHOR]

Perceptual-motor calibration has been described as a mapping between perception and action, which is relevant to distinguish possible from impossible opportunities for action. To avoid movement errors, it is relevant to rapidly calibrate to immediate changes in capabilities and therefore this study sought to explain in what conditions calibration is most efficient. A systematic search of seven databases was conducted to identify literature concerning changes in calibration in response to changes in action capabilities. Twenty-three papers satisfied the inclusion criteria. Data revealed that calibration occurs rapidly if there is a good match between the task that requires calibration and the sources of perceptual-motor information available for exploration (e.g. when exploring maximal braking capabilities by experiencing braking). Calibration can take more time when the perceptual-motor information that is available is less relevant. The current study identified a number of limitations in the field of perceptual-motor research. Most notably, the mean participant age in the included studies was between 18 and 33years of age, limiting the generalizability of the results to other age groups. Also, due to inconsistent terminology used in the field of perceptual-motor research, we argue that investigating calibration in older cohorts should be a focus of future research because of the possible implications of impaired calibration in an aging society. [ABSTRACT FROM AUTHOR]

Mental rotation of visual images of body parts and abstract shapes can be influenced by simultaneous motor activity. Children in particular seem to have a strong coupling between motor and cognitive processes. We investigated the influence of a rotational hand movement performed by rotating a knob on mental rotation performance in primary school-age children (N= 83; Age range: 7.0-8.3 and 9.0-10.11 years). In addition, we assessed the role of motor ability in this relationship. Boys in the 7-8-year-old group were faster when mentally and manually rotating in the same direction than in the opposite direction. For girls and older children this effect was not found. A positive relationship was found between motor ability and accuracy on the mental rotation task: stronger motor ability related to improved mental rotation performance. In both age groups, children with more advanced motor abilities were more likely to adopt motor processes to solve mental rotation tasks if the mental rotation task was primed by a motor task. Our evidence supports the idea that an overlap between motor and visual cognitive processes in children is influenced by motor ability.

In this study we investigated the intricate interplay between central linguistic processing and peripheral motor processes during typewriting. Participants had to typewrite two-constituent (noun-noun) Finnish compounds in response to picture presentation while their typing behavior was registered. As dependent measures we used writing onset time to assess what processes were completed before writing and inter-key intervals to assess what processes were going on during writing. It was found that writing onset time was determined by whole word frequency rather than constituent frequencies, indicating that compound words are retrieved as whole orthographic units before writing is initiated. In addition, we found that the length of the first syllable also affects writing onset time, indicating that the first syllable is fully prepared before writing commences. The inter-key interval results showed that linguistic planning is not fully ready before writing, but cascades into the motor execution phase. More specifically, inter-key intervals were largest at syllable and morpheme boundaries, supporting the view that additional linguistic planning takes place at these boundaries. Bigram and trigram frequency also affected inter-key intervals with shorter intervals corresponding to higher frequencies. This can be explained by stronger memory traces for frequently co-occurring letter sequences in the motor memory for typewriting. These frequency effects were even larger in the second than in the first constituent, indicating that low-level motor memory starts to become more important during the course of writing compound words. We discuss our results in the light of current models of morphological processing and written word production.

Although knee motions have been observed at loss of balance, the ankle and hip strategies have remained the focus of past research. The present study aimed to investigate whether knee motions contribute to feet-in-place balance recovery. This was achieved by experimentally monitoring knee motions during recovery from forward falling, and by simulating balance recovery movements with and without knee joint as the main focus of the study. Twelve participants initially held a straight body configuration and were released from different forward leaning positions. Considerable knee motions were observed especially at greater leaning angles. Simulations were performed using 3-segment (feet, shanks+thighs, and head+arms+trunk) and 4-segment (with separate shanks and thighs segments) planar models. Movements were driven by joint torque generators depending on joint angle, angular velocity, and activation level. Optimal joint motions moved the mass center projection to be within the base of support without excessive joint motion. The 3-segment model (without knee motions) generated greater backward linear momentum and had better balance performance, which confirmed the advantage of having only ankle/hip strategies. Knee motions were accompanied with less body angular momentum and a lower body posture, which could be beneficial for posture control and reducing falling impact, respectively. [ABSTRACT FROM AUTHOR]

Two four-choice reaction time (RT) experiments used the lateralized readiness potential (LRP) and the limb selection potential (LSP) to assess the effects of spatial S-R compatibility on motor processes. Individual stimuli were presented at one corner of a square centered at fixation, and each response was made with the left or right hand or foot. In Experiment 1, the correct response was determined by stimulus location, whereas in Experiment 2 it was determined by stimulus identity. Horizontal and vertical compatibility affected both RT and response accuracy, but the LRP and LSP results suggested that compatibility had little or no direct effect on the duration of motor processes. In addition, the results suggest that the relatively new LSP measure is a useful index of motor activation processes. Its insensitivity to horizontal stimulus artifacts makes it especially useful for studying the effects of horizontal spatial compatibility. [ABSTRACT FROM AUTHOR]

The main objectives of this pilot study were to: (1) investigate stance time variability (STV) during stair stepping in older adults with osteoarthritis (OA) before and after total knee arthroplasty (TKA), and compare to an age- and sex-matched group of healthy controls with native knees and (2) evaluate the relationship between quadriceps strength and STV during stair stepping before and after TKA. A prospective, observational, pilot study was carried out on 13 individuals (15% male, mean age 62.71±6.84years) before and after TKA using an instrumented stairway, patient-reported outcomes, timed stair stepping test, and quadriceps strength measures. At 6-months post-operatively, STV during stair descent was significantly greater in the TKA-GROUP compared to the CONTROL-GROUP, but was not significantly different at 12-months compared to controls. There were no significant differences in STV for stair ascent between the pre- and post-operative visits, or compared to controls. There was a trend toward significance for the relationship between quadriceps strength and STV during stair ascent (P=0.059) and descent (P=0.073). Variability during stair stepping may provide an important, short-term rehabilitation target for individuals following TKA and may represent another parameter to predict declines in functional mobility. [ABSTRACT FROM AUTHOR]

Purpose: The present study sought to determine if adults with ADHD demonstrate reduced graphomotor learning relative to controls.Method: Twenty-eight control adults (n=14) and adults with ADHD (n=14) were recruited and wrote a novel grapheme on a digitizing tablet 30 times. Participants with ADHD were counterbalanced on and off stimulant medication.Results: Control participants, F(1,13)=13.786, p=.003, ω(2)partial=.460, and participants with ADHD on medication, F(1,13)=10.462, p=.007, ω(2)partial=.387, demonstrated significant improvement in graphomotor fluency with equivalent practice whereas participants with ADHD off medication did not, F(1,12)=0.166, NS.Conclusions: Results indicate that graphomotor program learning in adults with ADHD may occur more slowly than typically developing peers. Findings have implications for providing accommodations to adults with ADHD, potential benefits of stimulant medication, and using digitizing technology as a neuropsychological assessment instrument. [ABSTRACT FROM AUTHOR]

A paucity of objective outcome measures exists for assessing movement disorders, including degenerative lumbar spinal stenosis (LSS). Fitts's Law provides a novel approach to clinical outcome measurement since performance is resistant to learning, and task difficulty can be altered. The objective of the present study was to compare, using a Fitts's task, movement performance of individuals with and without LSS to determine if motor difficulties that arise with LSS impede the planning, initiation, or execution of deliberate lower limb movements. Twelve pre-surgical LSS patients and twelve control participants from the community performed a Fitts's Law (foot reaching) task, while LSS participants also completed pain and disability questionnaires. Fitts's Law was evident for both groups, however the LSS group's movements were more adversely impacted as task difficulty increased. Specifically, the LSS group's movement time and time to peak velocity (ttPV) increased as task index of difficulty increased, while peak velocity decreased. Correlations between ttPV and leg pain, and with stenosis impairment severity respectively, provided evidence that less support leg pain and less stenosis impairment severity yield faster ttPV in the moving leg at the highest index of difficulty. Therefore a lower extremity Fitts's Law task captured differences in the planning and execution of leg movements between healthy and LSS populations. [ABSTRACT FROM AUTHOR]

Two experiments examined the dynamic interaction between cognitive resources in short-term memory and bimanual object manipulation by extending recent research by Logan and Fischman (2011). In Experiment 1, 16 participants completed a bimanual end-state comfort task and a memory task requiring serial recall of 12 words or pictures. The end-state comfort task involved moving two glasses between two shelves. Participants viewed the items, performed the end-state comfort task, and then serially recalled the items. Recall was evaluated by the presence or absence of primacy and recency effects. The end-state comfort effect (ESCE) was assessed by the percentage of initial hand positions that allowed the hands to end comfortably. The main findings indicated that the ESCE was disrupted; the primacy effect remained intact; and the recency effect disappeared regardless of the type of memory item recalled. In Experiment 2, 16 participants viewed six items, performed an end-state comfort task, viewed another six items, and then serially recalled all 12 items. Results were essentially the same as in Experiment 1. Findings suggest that executing a bimanual end-state comfort task, regardless of when it is completed during a memory task, diminishes the recency effect irrespective of the type of memory item. [ABSTRACT FROM AUTHOR]

Weighted walking is a functional activity common in daily life and can influence risks for musculoskeletal loading, injury and falling. Much information exists about weighted walking during military, occupational and recreational tasks, but less is known about strategies used to accommodate to weight carriage typical in daily life. The purposes of the study were to examine the effects of weight carriage on kinematics and peak ground reaction force (GRF) during walking, and explore relationships between these variables. Twenty subjects walked on a treadmill while carrying 0, 44.5 and 89 N weights in front of the body. Peak GRF, sagittal plane joint/segment angular kinematics, stride length and center of mass (COM) vertical displacement were measured. Changes in peak GRF and displacement variables between weight conditions represented accommodation. Effects of weight carriage were tested using analysis of variance. Relationships between peak GRF and kinematic accommodation variables were examined using correlation and regression. Subjects were classified into sub-groups based on peak GRF responses and the correlation analysis was repeated. Weight carriage increased peak GRF by an amount greater than the weight carried, decreased stride length, increased vertical COM displacement, and resulted in a more extended and upright posture, with less hip and trunk displacement during weight acceptance. A GRF increase was associated with decreases in hip extension (|r|=.53, p=.020) and thigh anterior rotation (|r|=.57, p=.009) displacements, and an increase in foot anterior rotation displacement (|r|=.58, p=.008). Sub-group analysis revealed that greater GRF increases were associated with changes at multiple sites, while lesser GRF increases were associated with changes in foot and trunk displacement. Weight carriage affected walking kinematics and revealed different accommodation strategies that could have implications for loading and stability. [ABSTRACT FROM AUTHOR]