Correction: Data-driven analyses of motor impairments in animal models of neurological disorders.

[This corrects the article DOI: 10.1371/journal.pbio.3000516.].

Well-being of professional older adults' caregivers in Alberta's assisted living and long-term care facilities: a cross-sectional study.

BACKGROUND: For the care need of older adults, long-term care (LTC) and assisted living (AL) facilities are expanding in Alberta, but little is known about the caregivers' well-being. The purpose of the study was to investigate the physical health conditions, mental and emotional health (MEH), health behaviour, stress levels, quality of life (QOL), and turnover and absenteeism (TAA) among professional caregivers in Alberta's LTC and AL facilities. METHODS: This cross-sectional survey involved 933 conveniently selected caregivers working in Alberta's LTC and AL facilities. Standardised questions were selected from the Canadian Community Health Survey, Patient Health Questionnaire-9, and Short Form-36 QOL survey revalidated and administered to the participants. The new questionnaire was used to assess the caregivers' general health condition (GHC), physical health, health behaviour, stress level, QOL, and TAA. Data were analysed using descriptive statistics, Cronbach alpha, Pearson's correlation, one-way analysis of variance, and multiple linear regression. RESULTS: Of 1385 surveys sent to 39 facilities, 933 valid responses were received (response rate = 67.4%). The majority of the caregivers were females (90.8%) who were ≥ 35 years (73.6%), worked between 20 to 40 h weekly (67.3%), and were satisfied with their GHC (68.1%). The Registered Nurses had better GHC (mean difference [MD] = 0.18, p = 0.004) and higher TAA than the Health Care Aides (MD = 0.24, p = 0.005). There were correlations between caregivers' TAA and each of MEH (r = 0.398), QOL (r = 0.308), and stress (r = 0.251); p < 0.001. The most significant predictors of TAA were the propensity to quit a workplace or the profession, illness, job stress, and work-related injury, F (5, 551) = 76.62, p < 0.001, adjusted R2 = 0.998. CONCLUSION: Reducing the caregivers' job stressors such as work overload, inflexible schedule, and poor remuneration, and improving their quality of life, health behaviour, and mental, emotional, and physical health conditions may increase their job satisfaction and reduce turnover and absenteeism.

Perceived strategies for reducing staff-turnover and improving well-being and retention among professional caregivers in Alberta's continuing-care facilities: A qualitative study.

This qualitative study explored potential factors that lead to turnover and absenteeism and how to improve well-being and retention among professional older-adult-caregivers in Alberta's assisted living (AL) and long-term care (LTC) facilities. Four hundred and forty-seven participants aged 45-54 years were interviewed through a five-item, content-validated open-ended questionnaire. The questionnaire was self-administered in the English language and the soft copy of their responses was transferred into NVIVO version 12 software for coding. A thematic narrative analysis grounded in the "happy productive worker" theory was completed. The main themes were caregivers' perception of the factors affecting their well-being, absenteeism, and turnover, and caregivers' suggestions on ways to improve their well-being and retention. Participants reported that their professional well-being was suboptimal. They suggested that their employers should provide them with the needed social, psychological, and professional support, improve wages and hire more staff to ameliorate absenteeism and turnover rates.

Data-driven analyses of motor impairments in animal models of neurological disorders.

Behavior provides important insights into neuronal processes. For example, analysis of reaching movements can give a reliable indication of the degree of impairment in neurological disorders such as stroke, Parkinson disease, or Huntington disease. The analysis of such movement abnormalities is notoriously difficult and requires a trained evaluator. Here, we show that a deep neural network is able to score behavioral impairments with expert accuracy in rodent models of stroke. The same network was also trained to successfully score movements in a variety of other behavioral tasks. The neural network also uncovered novel movement alterations related to stroke, which had higher predictive power of stroke volume than the movement components defined by human experts. Moreover, when the regression network was trained only on categorical information (control = 0; stroke = 1), it generated predictions with intermediate values between 0 and 1 that matched the human expert scores of stroke severity. The network thus offers a new data-driven approach to automatically derive ratings of motor impairments. Altogether, this network can provide a reliable neurological assessment and can assist the design of behavioral indices to diagnose and monitor neurological disorders.

Exploring the role of shift work in the self-reported health and wellbeing of long-term and assisted-living professional caregivers in Alberta, Canada.

BACKGROUND: Numerous studies have found negative outcomes between shift work and physical, emotional, and mental health. Many professional caregivers are required to work shifts outside of the typical 9 am to 5 pm workday. Here, we explore whether shift work affects the health and wellbeing of long-term care (LTC) and assisted-living (AL) professional caregivers. METHOD: The Caring for Professional Caregivers research study was conducted across 39 LTC and AL facilities in Alberta, Canada. Of the 1385 questionnaires distributed, 933 surveys (67.4%) were returned completed. After identifying 49 questions that significantly explained variances in the reported health status of caregivers, we examined whether there was a relationship between these questions and reported health status of caregivers working night shifts. RESULTS: We found significant differences between responses from those working different shifts across six of seven domains, including physical health, health conditions, mental/emotional health, quality of life, and health behaviors. In particular, we found that night shift caregivers were more likely to report incidents of poor heath (i.e., they lacked energy, had regular presences of neck and back pain, regular or infrequent incidents of fatigue or low energy, had difficulty falling asleep, and that they never do exercise) and less likely to report incidents of good health (i.e., did not expect their health to improve, were not satisfied with their health, do not have high self-esteem/were happy, were unhappy with their physical appearance, and do not get a good night's sleep), compared to caregivers working other shifts. CONCLUSIONS: Our study shows that professional caregivers working the night shift experience poor health status, providing further evidence that night shift workers' health is at risk. In particular, caregivers reported negative evaluations of their physical, mental/emotional health, lower ratings of their quality of life, and negative responses to questions concerning whether they engage in healthy behaviors. Our findings can support healthcare stakeholders outline future policies that ensure caregivers are adequately supported so that they provide quality care.

Long- but not short-term tool-use changes hand representation.

Tool-use has been found to change body representation. For example, participants who briefly used a mechanical grabber to pick up objects perceived their forearms to be longer immediately after its use (e.g., Cardinali et al., Curr Biol 19(12):R478-R479, 2009; they incorporated the tool into their perceived arm size). While some studies have investigated the long-term effects of tool-use on body representation, none of these studies have used a tool that encapsulates the entire body part (e.g., a glove). Moreover, the relationship between tool-use and the body model (the representation of the body's spatial characteristics) has yet to be explored. To test this, we recruited 19 elite baseball players (EBP) and 18 age-matched controls to participate in a hand representation task. We included EBP because of their many years (8+) of training with a tool (baseball glove). The task required participants to place their hands underneath a covered glass tabletop (no vision of their hands), and to point to where they believed 10 locations (the tips and bases of each finger) were on their hands (Coelho et al., Psychol Res 81(6):1224-1231, 2017). Each point's XY coordinates was tracked using an Optotrak camera. From these coordinates, we mapped out the participants perceived hand size. The results showed that when compared to the controls, EBP underestimated hand width and finger length of both hands. This indicates that long-term tool use produces changes in the body model for both, the trained and untrained hands. We conducted a follow-up study to examine if 15 min of glove use would change perceived hand size in control participants. Novice baseball players (participants without baseball experience: NBP) were recruited and hand maps were derived before and after 15 min of active catching with a glove. Results showed no significant differences between the pre and post hand maps. When we compared between the two experiments, the EBP showed smaller hand representation for both hand width and finger length, than the NBP. We discuss these results in relation to theories of altered body ownership.

Complexity of movement preparation and the spatiotemporal coupling of bimanual reach-to-grasp movements.

There is a movement preparation cost for bimanual asymmetric reaching movements compared to bimanual symmetric movements. This is likely caused by the complex spatiotemporal coupling of bimanual asymmetric movements. The spatiotemporal coupling of bimanual reach-to-grasp movements has been investigated, but not the potential movement preparation costs. The purpose of the present study was to investigate the relationship between movement preparation costs and spatiotemporal coupling of reach-to-grasp movements. Twenty-four participants made unimanual, bimanual symmetric, and bimanual asymmetric reach-to-grasp movements in four-choice reaction time tasks. There was a movement preparation cost for bimanual symmetric reach-to-grasp movements compared to unimanual movements, which was not previously seen for reaching movements. Coordinating two symmetric grasps probably caused this bimanual symmetric cost, as we have previously shown that there is no bimanual symmetric cost for reaching movements. It was also surprising that the complexity of movement preparation was comparable for bimanual symmetric and asymmetric reach-to-grasp movements. However, the spatial coupling of bimanual asymmetric movements at movement initiation suggested that they were prepared as bimanual symmetric movements. Online control was then used to modify these symmetric reach-to-grasp movements into asymmetric movements. Preparing bimanual symmetric reach-to-grasp movements in advance instead of asymmetric movements likely prevented a bimanual asymmetric cost.

Bimanual joint action: correlated timing or "bimanual" movements accomplished by two people.

A crew of two rowing together in perfect synchrony is an example of a task that requires each performer to maintain meticulous timing when coordinating their movements with the other. At the individual level, temporal coordination of the limbs has been observed in bimanual pointing movements even when made to targets of different distance. Timing of the arms is not independent; rather there is a natural temporal coupling. The aim of this experiment was to investigate whether the temporal characteristics of pointing movements can be observed under joint conditions. Sixteen pairs of participants made short and long, unimanual and bimanual pointing movements. In the unimanual and bimanual solo conditions, participants made the movements alone. In the joint condition, each participant contributed one arm to the joint "bimanual" movements. Absolute temporal coupling at movement initiation and termination was measured by the differences in reaction time and total response time. Relative temporal coupling at movement initiation and termination was measured by correlating reaction time and total response time of the left and right limbs. Pointing movements had synchronous movement termination in the bimanual solo conditions and asynchronous termination in the unimanual solo and bimanual joint conditions. The initiation and termination of the arms were not correlated in the unimanual solo condition (initiation r = 0.01, termination r = 0.03). Small-to-medium correlations (r = 0.19, r = 0.24) were observed in the bimanual joint condition, and they were larger than the unimanual solo condition (p = 0.022, p = 0.063). As expected, there were large correlations in the bimanual solo conditions (r = 0.91, r = 0.81). Our findings suggest that absolute temporal coupling does not occur between individuals, but there is evidence for relative temporal coupling in the bimanual joint condition.

Gaze anchoring guides real but not pantomime reach-to-grasp: support for the action-perception theory.

Reach-to-grasp movements feature the integration of a reach directed by the extrinsic (location) features of a target and a grasp directed by the intrinsic (size, shape) features of a target. The action-perception theory suggests that integration and scaling of a reach-to-grasp movement, including its trajectory and the concurrent digit shaping, are features that depend upon online action pathways of the dorsal visuomotor stream. Scaling is much less accurate for a pantomime reach-to-grasp movement, a pretend reach with the target object absent. Thus, the action-perception theory proposes that pantomime movement is mediated by perceptual pathways of the ventral visuomotor stream. A distinguishing visual feature of a real reach-to-grasp movement is gaze anchoring, in which a participant visually fixates the target throughout the reach and disengages, often by blinking or looking away/averting the head, at about the time that the target is grasped. The present study examined whether gaze anchoring is associated with pantomime reaching. The eye and hand movements of participants were recorded as they reached for a ball of one of three sizes, located on a pedestal at arms' length, or pantomimed the same reach with the ball and pedestal absent. The kinematic measures for real reach-to-grasp movements were coupled to the location and size of the target, whereas the kinematic measures for pantomime reach-to-grasp, although grossly reflecting target features, were significantly altered. Gaze anchoring was also tightly coupled to the target for real reach-to-grasp movements, but there was no systematic focus for gaze, either in relation with the virtual target, the previous location of the target, or the participant's reaching hand, for pantomime reach-to-grasp. The presence of gaze anchoring during real vs. its absence in pantomime reach-to-grasp supports the action-perception theory that real, but not pantomime, reaches are online visuomotor actions and is discussed in relation with the neural control of real and pantomime reach-to-grasp movements.

Sex differences in the response of total PYY and GLP-1 to moderate-intensity continuous and sprint interval cycling exercise.

BACKGROUND: Exercise interventions are often less effective at improving body composition for females than males, potentially due to post-exercise hormonal responses that increase energy intake in females. Recently, sprint interval training was shown to effectively reduce body fat in females despite being relatively low during exercise energy expenditure. PURPOSE: To determine whether any sex difference in total PYY, GLP-1 or perceived hunger exists following moderate-intensity continuous exercise (MICT) and sprint interval exercise (SIT) METHODS: Twenty-one active participants (11 females) participated in three sessions in a randomized crossover design: (1) MICT, 30-min cycling at 65% VO2max; (2) SIT, 6 × 30 s "all-out" sprints with 4-min recovery periods; (3) control (CTRL; no exercise). Blood samples were collected pre-exercise, immediately and 90 min post-exercise for the measurement of total PYY and GLP-1. Subjective perceptions of hunger were assessed using a visual analogue scale pre-breakfast and before all blood samples. RESULTS: Concentrations of total PYY and GLP-1 were greater during MICT (P = 0.05) and SIT (P = 0.005) compared to CTRL. Total PYY increased more immediately post-exercise in males than females (P = 0.030). GLP-1 only increased in females following MICT (P = 0.034) and SIT (P = 0.024) compared to CTRL. Perceived hunger was lower immediately post-MICT (P = 0.016) and SIT (P = 0.006) compared to CTRL. CONCLUSIONS: These results suggest that total PYY and GLP-1 respond differently to exercise in males and females over 90 min following various exercise intensities. The observed post-exercise hormonal response would not be expected to create a compensatory increase in energy intake in females.

The Effects of Music Salience on the Gait Performance of Young Adults.

BACKGROUND: The presence of a rhythmic beat in the form of a metronome tone or beat-accentuated original music can modulate gait performance; however, it has yet to be determined whether gait modulation can be achieved using commercially available music. OBJECTIVE: The current study investigated the effects of commercially available music on the walking of healthy young adults. Specific aims were (a) to determine whether commercially available music can be used to influence gait (i.e., gait velocity, stride length, cadence, stride time variability), (b) to establish the effect of music salience on gait (i.e., gait velocity, stride length, cadence, stride time variability), and (c) to examine whether music tempi differentially effected gait (i.e., gait velocity, stride length, cadence, stride time variability). METHODS: Twenty-five participants walked the length of an unobstructed walkway while listening to music. Music selections differed with respect to the salience or the tempo of the music. The genre of music and artists were self-selected by participants. RESULTS: Listening to music while walking was an enjoyable activity that influenced gait. Specifically, salient music selections increased measures of cadence, velocity, and stride length; in contrast, gait was unaltered by the presence of non-salient music. Music tempo did not differentially affect gait performance (gait velocity, stride length, cadence, stride time variability) in these participants. CONCLUSIONS: Gait performance was differentially influenced by music salience. These results have implications for clinicians considering the use of commercially available music as an alternative to the traditional rhythmic auditory cues used in rehabilitation programs.

Manual asymmetries in the kinematics of a reach-to-grasp action.

In the present study, we manipulated the perceived demand of an ecologically valid task to investigate the possible presence of manual asymmetries in a reach-to-grasp action. Participants reached, grasped and sipped from a water glass under low (nearly empty) and high (nearly full) demand conditions. Participants reached to grasp in closed-loop, open-loop and delay visual conditions. Manual asymmetries were found in movement time, peak velocity and maximum grip aperture variability. Consistent with reach-to-point literature: (1) right-handed actions were completed in less time than left-handed actions in visually and memory-guided conditions; (2) right-handed movements were more accurate (i.e., produced more consistent maximum grip apertures) than left-handed movements in visually guided conditions. The results support a theory of left-hemisphere specialization for visual control of action.

Relationship between chiropractic teaching institutions and practice characteristics among Canadian doctors of chiropractic: a random sample survey.

OBJECTIVE: The objectives of this study were to determine if faction membership among Canadian doctors of chiropractic (DCs) is associated with differences in educational program characteristics among English-speaking Canadian and United States chiropractic colleges and to determine if those differences are expressed in terms of surveyed attitudes and behaviors regarding treatment efficacy, radiographic imaging, vaccinations, and interprofessional referrals. This study also aims to identify if educational programs may be a potential source of multiple professional identities. METHODS: A randomly selected sample of Canadian DCs, stratified across the English-speaking provinces, was surveyed by mail. Survey items included school of graduation, self-categorization by chiropractic subgroup, perceptions of condition-specific treatment efficacy, use of plain film radiographic imaging, vaccination attitudes/behaviors, and patient referral patterns. Self-categorization by chiropractic subgroup included: the unorthodox faction (associates the chiropractic subluxation as an encumbrance to the expression of health) and the orthodox perspective (associates with musculoskeletal joint dysfunction, public health, and lifestyle concerns). For data analysis, chiropractic schools were divided into 2 groups according to location: English-speaking Canada and the US. The US was further clustered into liberal ("interested in mixing elements of modern and alternative therapies into the practice of chiropractic") and conservative categories ("chiropractors who believe in continuing the traditions of chiropractic"). RESULTS: Of 740 deliverable questionnaires, 503 were returned for a response rate of 68%. χ(2) Testing revealed significant differences in self-categorized faction membership associated with the clustering of colleges based on ideological viewpoints (χ(2) = 27.06; P = .000). Descriptive results revealed a relationship between school of origin and perceived treatment efficacy, use of radiographic imaging, and vaccination attitudes. No significant differences were found relative to interprofessional referral patterns. CONCLUSION: Chiropractic program attended is a significant predictor of orthodox vs unorthodox faction membership and professional practice characteristics for Canadian DCs. This suggests that the current chiropractic education system may contribute to multiple professional identities.

Hand shaping using hapsis resembles visually guided hand shaping.

The reach-to-grasp movement is composed of a number of movement elements including hand transport, hand shaping, and grasping. These movement elements are featured in grasping when it is guided by vision, when it is guided by haptic input from the non-reaching hand or other body parts, and when it is guided by off-line perceptual (remembered) knowledge. An unanswered question is how is the reach-to-grasp movement achieved when all information about the target must be acquired by the grasping hand? The answer to this question was obtained by asking participants to reach for three randomly presented food items that varied in size: an orange slice, a small round donut ball, or a blueberry. In order to constrain the grasping pattern, participants were asked to pick up an item with the intention of placing it in the mouth. Thus, in the unsighted condition, participants did not know which item they were reaching for until they made haptic contact with it. Hand transport, shaping, and grasping were examined using frame-by-frame video analysis and linear kinematics. These measures showed that in unsighted reaching, hand transport first served to establish haptic contact between either the second or third digit and the target. After haptic identification of the target, the hand and/or grasping digits adjusted their trajectory, reshaped, and reoriented for grasping. A comparison of haptically guided grasping and visually guided grasping indicated that the two were very similar. This similarity is discussed in relation to contemporary ideas concerning the neural mechanisms that guide hand use.

Oral hapsis guides accurate hand preshaping for grasping food targets in the mouth.

Preshaping the digits and orienting the hand when reaching to grasp a distal target is proposed to be optimal when guided by vision. A reach-to-grasp movement to an object in one's own mouth is a natural and commonly used movement, but there has been no previous description of how it is performed. The movement requires accuracy but likely depends upon haptic rather than visual guidance, leading to the question of whether the kinematics of this movement are similar to those with vision or whether the movement depends upon an alternate strategy. The present study used frame-by-frame video analysis and linear kinematics to analyze hand movements as participants reached for ethologically relevant food targets placed either at a distal location or in the mouth. When reaching for small and medium-sized food items (blueberries and donut balls) that had maximal lip-to-target contact, hand preshaping was equivalent to that used for visually guided reaching. When reaching for a large food item (orange slice) that extended beyond the edges of the mouth, hand preshaping was suboptimal compared to vision. Nevertheless, hapsis from the reaching hand was used to reshape and reorient the hand after first contact with the large target. The equally precise guidance of hand preshaping under oral hapsis is discussed in relation to the idea that hand preshaping, and its requisite neural circuitry, may have originated under somatosensory control, with secondary access by vision.

Two types of memory-based (pantomime) reaches distinguished by gaze anchoring in reach-to-grasp tasks.

Comparisons of target-based reaching vs memory-based (pantomime) reaching have been used to obtain insight into the visuomotor control of reaching. The present study examined the contribution of gaze anchoring, reaching to a target that is under continuous gaze, to both target-based and memory-based reaching. Participants made target-based reaches for discs located on a table or food items located on a pedestal or they replaced the objects. They then made memory-based reaches in which they pantomimed their target-based reaches. Participants were fitted with hand sensors for kinematic tracking and an eye tracker to monitor gaze. When making target-based reaches, participants directed gaze to the target location from reach onset to offset without interrupting saccades. Similar gaze anchoring was present for memory-based reaches when the surface upon which the target had been placed remained. When the target and its surface were both removed there was no systematic relationship between gaze and the reach. Gaze anchoring was also present when participants replaced a target on a surface, a movement featuring a reach but little grasp. That memory-based reaches can be either gaze anchor-associated or gaze anchor-independent is discussed in relation to contemporary views of the neural control of reaching.

Novel challenges to gait in Parkinson's disease: the effect of concurrent music in single- and dual-task contexts.

OBJECTIVE: To investigate the effect of concurrent music on parkinsonian gait in single- and dual-task contexts. DESIGN: A counterbalanced repeated-measure design. SETTING: A university balance research laboratory. PARTICIPANTS: People with idiopathic Parkinson's disease (PD) (n=10) (67+/-7 y) and healthy age-matched (65+/-6 y) control subjects (n=10). INTERVENTION: Subjects walked at a self-selected pace along an unobstructed walkway in 4 differing test conditions. Test conditions were differentiated by the presence of music accompaniment (no music/music) and the presence of a secondary cognitive task (single/dual). Single- and dual-task conditions were randomized; trials were blocked by the presence of music and counterbalanced between subjects. Music was self-selected by subjects. The cognitive task consisted of serial subtractions (3's). Subjects were not instructed to attend to the music nor were they provided with instructions regarding task prioritization. MAIN OUTCOME MEASURES: Mean gait velocity, stride length, and the percentage of the gait cycle spent in double-limb support. RESULTS: Gait among the PD patients was adversely affected by concurrent music. In contrast, gait performance in the control subjects showed no significant difference between no music and music conditions. The added requirement of a cognitive task differentially influenced gait performance in PD patients and control subjects, with PD patients displaying a further decrease in spatiotemporal parameters of gait and control subjects displaying a marginal improvement. CONCLUSIONS: Gait impairments associated with PD are exacerbated in the presence of concurrent music, an effect that is further exaggerated by the addition of a cognitive task. These results have implications for patient safety in multitasking situations.

Factors associated with the health status of childcare workers in southern Alberta, Canada.

OBJECTIVE: There is growing evidence that the well-being of childcare workers has important implications for the care provided to children attending childcare centers. To add to the growing body of research in this area and to lay the groundwork for further research, we report the results of a pilot study examining factors that are associated with the health status of childcare workers in southern Alberta, Canada. The factors examined include: health control, employer's interest in the childcare worker's wellbeing, and actions that childcare workers are taking to improve their own health. RESULTS: A total of 260 "Workplace Health and Risks Survey 2008" questionnaires were sent to 13 licensed daycare centers in southern Alberta, Canada. Of these, a total of 110 questionnaires were completed by childcare workers at these centers and returned. Regression analysis results show that control over one's health (Standardized Beta = .504, p < .001), employers' knowledge of negative effects of stress (Standardized Beta = - .328, p = .017), employers' interest in employees' well-being (Standardized Beta = .366, p = .008), and actions that are planned to be taken to improve or maintain health in the future (Standardized Beta = .231, p = .005) are all significant predictors of health status among childcare workers.

Bilateral impairments of skilled reach-to-eat in early Parkinson's disease patients presenting with unilateral or asymmetrical symptoms.

Previous studies have described limb and hand movement abnormalities in a reach-to-eat task in advanced Parkinson's disease (PD) and animal models of PD. The present study was directed toward examining reach-to-eat movements in early PD patients untreated with medication, along with a follow-up examination of a PD patient sub-group who were treated with a symptomatically stable dosage of dopamine replacement. Analysis of the reach-to-eat movement was made using blinded assessment under a validated scoring system, and comparisons were made on the total reach score and reach sub-component scores. In both examinations, PD patients had unilateral deficits or significant deficit asymmetry, as indicated by Unified Parkinson's Disease Rating Scale (UPDRS) scores. UPDRS motor scores were higher for the most-affected side of the body (mean scores of 10.45 and 4.25 for more- and less-affected upper limbs, respectively), whereas reach scores were equivalently impaired for the two sides (median scores of 12.35 and 12.56 for more- and less-affected limbs, respectively). These differences between clinical and experimental assessments of motor impairments persisted among early PD patients treated with medication. Thus, functional reaching shows bilateral and symmetrical abnormalities in early PD patients, even when clinical assessment shows asymmetrical or even unilateral impairment. These findings suggest that functional qualitative reaching evaluation is a sensitive test in early PD, and that significant bilateral abnormalities in reach function are present even in pre-clinical stages of the disease.

Visual guidance for hand advance but not hand withdrawal in a reach-to-eat task in adult humans: reaching is a composite movement.

Many animal species use reaching for food to place in the mouth (reach-to-eat) with a hand, and it may be a primitive movement. Although researchers (I. Q. Whishaw, 2005; A. N. Iwaniuk & I. Q. Whishaw, 2000; M. Gentiluci, I. Toni, S. Chieffi, & G. Pavesi, 1994) have described visual guidance of reaching in both normal and brain-injured human and nonhuman primates, researchers have not described the contribution of vision during advance of the limb to grasp food and during withdrawal of the limb with food to the mouth. To evaluate visual contributions, the authors monitored eye movements in young adults as they reached for food with and without vision. Participants visually engaged the target prior to the 1st hand movement and disengaged it as the food was grasped. Visual occlusion slowed limb advance and altered digit shaping but did not affect withdrawal. The dependence on visual control of advance but not withdrawal suggests that the reach-to-eat movement is a composite of 2 basic movements under visual and tactile/proprioceptive guidance, respectively.