Quantifying the Impact of Motions on Human Aiming Performance: Evidence from Eye Tracking and Bio-Signals.

Working on a moving platform can significantly impede human performance. Previous studies on moving vehicles have often focused on the overall impact on general task performance, whereas our study's emphasis is on precise hand movements, exploring the interaction between body motion and the escalation of task difficulty. We recruited 28 participants to engage in reciprocal aiming tasks, following Paul Fitts's setting, under both in-motion and stationary conditions. The task index of difficulty (ID) was manipulated by varying the width of the targets and the distance between the targets. We measured participants' movement time (MT), performance errors, and monitored their eye movements using an eye-tracking device, heart rate (HR), and respiration rate (RR) during the tasks. The measured parameters were compared across two experimental conditions and three ID levels. Compared to the stationary conditions, the in-motion conditions degraded human aiming performance, resulting in significantly prolonged MT, increased errors, and longer durations of eye fixations and saccades. Furthermore, HR and RR increased under the in-motion conditions. Linear relationships between MT and ID exhibited steeper slopes under the in-motion conditions compared to the stationary conditions. This study builds a foundation for us to explore the control mechanisms of individuals working in dynamic and demanding environments, such as pilots in airplanes and paramedics in ambulances.

A violation of Fitts' Law occurs when a target range is presented before and during movement.

According to Fitts' Law, the time to reach a target (movement time, MT) increases with distance. A violation of Fitts' Law occurs when target positions are outlined before and during movement, as MTs are not different when reaching to the farthest and penultimate targets. One hypothesis posits that performers cognitively process the edges of a target array before the center, allowing for corrective movements to be completed more quickly when moving to edge targets compared to middle targets. The objective of this study was to test this hypothesis by displaying a target range rather than outlines of individual targets in an effort to identify the effects of array edges. Using a touch-screen laptop, participants (N = 24) were asked to reach to one of three targets which would appear within a presented range. Separately, targets were also presented without a range to determine if the display protocol could evoke Fitts' Law. Movements were assessed with the touch screen and optical position measurement. A main effect was found for relative position within a range (touch: F2,44 = 15.4, p < 0.001, η2p = 0.412; position: F2,40 = 15.6, p < 0.001, η2p = 0.439). As hypothesised, MT to the farthest target in a range was not significantly different than MT to the middle target (touch: p = 0.638, position: p = 0.449). No violation was found when a target range was not presented (touch: p = 0.003, position: p = 0.001). Thus, a target range reproduces the Fitts' Law violation previously documented with individually outlined targets, which supports and extends the discussed hypothesis.

Complex motion series performance differs between previously untreated patients with Parkinson's disease and controls.

Motor behaviour in patients with Parkinson's disease is determined with instrumental tests and rating procedures. Results mirror impairment of an individual patient. Objectives were to determine the associations between two kinds of motion series and rating scores in previously untreated 64 patients and to compare outcomes to controls. The line tracing task asks to follow a given path. It measures the needed interval, the number and duration of contacts to the path. The aiming procedure asks to hit contact plates with a pencil and determines the needed time period and the number of accurate, respectively, missed key strokes. Both tests differed between patients and controls. The line tracing task was more sensitive. The line tracing task asks for a complex motion series performance with more cognitive load. The aiming task prompts for a conduction of preponderant simple, repetitive movement series. Only initially, a complex process of aiming is necessary. Performance of complex motion sequences better differs between patients with Parkinson's disease and controls than conduction of simple, repetitive movement series.

Spatial shifts in swiping actions, the impact of "left" and "right" verbalizations.

Movements are often modulated by the meaning of cue words. We explore the interaction between verbal and visual constraints during a movement by investigating if spoken words during movement execution bias late movement control of swiping actions on a tablet when vision of the target is removed during the movement. Verbalization trials required participants to vocalize the spatial directions 'LEFT', 'MIDDLE', or 'RIGHT' of the active target, relative to the other presented targets. A late influence of semantics emerged on movement execution in verbalized trials with action endpoints landing more in the direction of the spoken word than without verbalization. The emergence of the semantic effect as the movement progresses reflects the temporal unfolding of the visual and verbal constraints during the swiping action. Comparing our current results with a similar task using a variant verbalization, we also conclude that, larger semantic content effects are found with spatial direction than numerical magnitude verbalization.

Use of Visual Information by Ant Species Occurring in Similar Urban Anthropogenic Environments.

Many insects, including ants, are known to respond visually to conspicuous objects. In this study, we compared orientation in an arena containing only a black target beacon as local information in six species of ants of widely varying degree of phylogenic relatedness, foraging strategy, and eye morphology (Aphaenogaster, Brachyponera, Camponotus, Formica, and two Lasius spp.), often found associated in similar urban anthropogenic habitats. Four species of ants displayed orientation toward the beacon, with two orienting toward it directly, while the other two approached it via convoluted paths. The two remaining species did not show any orientation with respect to the beacon. The results did not correlate with morphological parameters of the visual systems and could not be fully interpreted in terms of the species' ecology, although convoluted paths are linked to higher significance of chemical signals. Beacon aiming was shown to be an innate behavior in visually naive Formica workers, which, however, were less strongly attracted to the beacon than older foragers. Thus, despite sharing the same habitats and supposedly having similar neural circuits, even a very simple stimulus-related behavior in the absence of other information can differ widely in ants but is likely an ancestral trait retained especially in species with smaller eyes. The comparative analysis of nervous systems opens the possibility of determining general features of circuits responsible for innate and possibly learned attraction toward particular stimuli.

Radio-anatomical study of anterior-posterior placement sacroiliac screw channel.

PURPOSE: The outlet of the classic sacroiliac screw (SIS) cannot be precisely controlled by aiming devices, which may lead to malpositioned implants and neurovascular and visceral injury. This study aimed to radio-anatomically measure the parameters of the channel for anterior-posterior placement SIS (AP-SIS), which can be placed percutaneously with an aiming device. METHODS: Pelvic CT scan data of 80 healthy adults (40 males and 40 females) with an average age of 45 years (range 20-70 years) were collected. The length (L), width (W), height (H), cortical bone spacing (M), camber angle (E), anteversion angle (F), cross-sectional safety angle (P) and sagittal safety angle (Q) of the channel were measured by CT or Mimics software. RESULTS: The L, W, H, M, E, F, P and Q measures of S1 were 109.2 ± 8.0 mm, 18.5 ± 1.9 mm, 21.7 ± 1.7 mm, 8.1 ± 0.4 mm, 44.2 ± 3.2°, 42.4 ± 3.6°, 16.8 ± 1.1°, and 19.4 ± 2.0°, respectively, for S1, and 113.5 ± 9.4 mm, 18.2 ± 1.5 mm, 21.7 ± 1.7 mm, 7.7 ± 0.4 mm, 44.7 ± 3.2°, 31.2 ± 2.7°, 13.8 ± 1.0° and 15.4 ± 1.4°, respectively, for S2. Of the L measures, the intra-iliac segment was slightly longer than the intra-sacral segment. All parameters showed significant sex-related differences (p < 0.05). CONCLUSION: The AP-SIS channels of S1-2 have sufficient width and length to accommodate a cancellous screw with a Φ 7.0-8.0 mm and a length 90-130 mm. The intra-iliac segment is a long channel screw with better mechanical properties over classic SIS.

Contributions of implicit and explicit memories to sensorimotor adaptation of movement extent during goal-directed reaching.

We examined how implicit and explicit memories contribute to sensorimotor adaptation of movement extent during goal-directed reaching. Twenty subjects grasped the handle of a horizontal planar robot that rendered spring-like resistance to movement. Subjects made rapid "out-and-back" reaches to capture a remembered visual target at the point of maximal reach extent. The robot's resistance changed unpredictably between reaches, inducing target capture errors that subjects attempted to correct from one trial to the next. Each subject performed over 400 goal-directed reaching trials. Some trials were performed without concurrent visual cursor feedback of hand motion. Some trials required self-assessment of performance between trials, whereby subjects reported peak reach extent on the most recent trial. This was done by either moving a cursor on a horizontal display (visual self-assessment), or by moving the robot's handle back to the recalled location (proprioceptive self-assessment). Control condition trials performed either without or with concurrent visual cursor feedback of hand motion did not require self-assessments. We used step-wise linear regression analyses to quantify the extent to which prior reach errors and explicit memories of reach extent contribute to subsequent reach performance. Consistent with prior reports, providing concurrent visual feedback of hand motion increased reach accuracy and reduced the impact of past performance errors on future performance, relative to the corresponding no-vision control condition. By contrast, we found no impact of interposed self-assessment on subsequent reach performance or on how prior target capture errors influence subsequent reach performance. Self-assessments were biased toward the remembered target location and they spanned a compressed range of values relative to actual reach extents, demonstrating that declarative memories of reach performance systematically differed from actual performances. We found that multilinear regression could best account for observed data variability when the regression model included only implicit memories of prior reach performance; including explicit memories (self-assessments) in the model did not improve its predictive accuracy. We conclude therefore that explicit memories of prior reach performance do not contribute to implicit sensorimotor adaptation of movement extent during goal-directed reaching under conditions of environmental uncertainty.

The influence of locative expressions on context-dependency of endpoint control in aiming.

It has been claimed that increased reliance on context, or allocentric information, develops when aiming movements are more consciously monitored and/or controlled. Since verbalizing target features requires strong conscious monitoring, we expected an increased reliance on allocentric information when verbalizing a target label (i.e. target number) during movement execution. We examined swiping actions towards a global array of targets embedded in different local array configurations on a tablet under no-verbalization and verbalization conditions. The global and local array configurations allowed separation of contextual-effects from any possible numerical magnitude biases triggered from calling out specific target numbers.The patterns of constant errors in the target directionwere used to assess differences between conditions. Variation in the target context configuration systematically biased movement endpoints in both the no-verbalization and verbalization conditions. Ultimately, our results do not support the assertion that calling out target numbers during movement execution increases the context-dependency of targeted actions.

Energy minimization within target-directed aiming: the mediating influence of the number of movements and target size.

In target-directed aiming, performers tend to more greatly undershoot targets when aiming down compared to up because they try to avoid an overshoot error and subsequently minimize the time and energy expenditure that is required to suddenly combat gravitational forces. The present study aims to further examine this principle of time and energy minimization by directly mediating the perceived cost of potential errors as well as the likelihood of their occurrence by manipulating the number of movements and target size, respectively. Participants executed rapid aiming movements in the up/down direction as part of a one-/two-target movement towards a small/large target. Primary movement endpoints showed greater undershooting when aiming in the downward compared to upward direction and small compared to large targets. Meanwhile, the overall movement time showed that slower movements were generated for down compared to up, but only when aiming toward large targets. The failure to mediate the central tendency as a function of the number of movements and target size indicates that the feature of minimization is highly prominent within the performers' pre-response planning. However, the continued minimization of energy in the presence of large targets may inadvertently cost the movement time.

Examining the equivalence between imagery and execution within the spatial domain - Does motor imagery account for signal-dependent noise?

Motor imagery is suggested to be functionally equivalent to physical execution as they each utilise a common neural representation. The present study examined whether motor imagery correspondingly reflects the spatial characteristics of physically executed movements, including the signal-dependent noise that typically manifests in more variable end locations (as indicated by effective target width; We). Participants executed or imagined a single, upper-limb target-directed aim in the horizontal medio-lateral direction. The start and end of the imagined movements were indexed by the lifting and lowering of the limb over the home position, respectively. Following each imagined movement, participants had to additionally estimate their imagined end location relative to the target. All the movements had to be completed at a pre-specified criterion time (400 ms, 600 ms, 800 ms). The results indicated that the We increased following a decrease in movement time for execution, but not imagery. Moreover, the total error of imagined movements was greater than the actual error of executed movements. While motor imagery may comprise a neural representation that also contributes to the execution of movements, it is unable to closely reflect the random sources of variability. This limitation of motor imagery may be attributed to the comparatively limited efferent motor signals.

Can patients with cerebellar disease switch learning mechanisms to reduce their adaptation deficits?

Systematic perturbations in motor adaptation tasks are primarily countered by learning from sensory-prediction errors, with secondary contributions from other learning processes. Despite the availability of these additional processes, particularly the use of explicit re-aiming to counteract observed target errors, patients with cerebellar degeneration are surprisingly unable to compensate for their sensory-prediction error deficits by spontaneously switching to another learning mechanism. We hypothesized that if the nature of the task was changed-by allowing vision of the hand, which eliminates sensory-prediction errors-patients could be induced to preferentially adopt aiming strategies to solve visuomotor rotations. To test this, we first developed a novel visuomotor rotation paradigm that provides participants with vision of their hand in addition to the cursor, effectively setting the sensory-prediction error signal to zero. We demonstrated in younger healthy control subjects that this promotes a switch to strategic re-aiming based on target errors. We then showed that with vision of the hand, patients with cerebellar degeneration could also switch to an aiming strategy in response to visuomotor rotations, performing similarly to age-matched participants (older controls). Moreover, patients could retrieve their learned aiming solution after vision of the hand was removed (although they could not improve beyond what they retrieved), and retain it for at least 1 year. Both patients and older controls, however, exhibited impaired overall adaptation performance compared to younger healthy controls (age 18-33 years), likely due to age-related reductions in spatial and working memory. Patients also failed to generalize, i.e. they were unable to adopt analogous aiming strategies in response to novel rotations. Hence, there appears to be an inescapable obligatory dependence on sensory-prediction error-based learning-even when this system is impaired in patients with cerebellar disease. The persistence of sensory-prediction error-based learning effectively suppresses a switch to target error-based learning, which perhaps explains the unexpectedly poor performance by patients with cerebellar degeneration in visuomotor adaptation tasks.

The effect of action observation and motor imagery combinations on upper limb kinematics and EMG during dart-throwing.

Recent research has begun to employ interventions that combine action observation and motor imagery (AOMI) with positive results. However, little is known about the underpinning facilitative effect on performance. Participants (n = 50) were randomly allocated to one of five training groups: action observation (AO), motor imagery (MI), simultaneous action observation and motor imagery (S-AOMI), alternate action observation and motor imagery (A-AOMI), and control. The task involved dart-throwing at a concentric circle dartboard at pre- and post-test. Interventions were conducted 3 times per week for 6 weeks. Data were collected from performance outcomes and mean muscle activation of the upper and forearm muscles. Angular velocity and peak angular velocity measurements of the elbow were also collected from the throwing arm. Results showed performance of the A-AOMI group improved to a significantly greater degree than the AO (P = .04), MI (P = .04), and control group (P = .02), and the S-AOMI group improved to a greater degree than the control group (P = .02). Mean muscle activation of the triceps brachii significantly reduced in the S-AOMI and A-AOMI (P < .01) groups, and participants in the AO (P = .04), A-AOMI, and S-AOMI (P < .01) groups significantly reduced activation in the bicep brachii from pre- to post-test. Peak angular velocity significantly decreased from pre- to post-test in both A-AOMI and S-AOMI (P < .01) groups. The results reaffirm the benefits of AOMI for facilitating skill learning and provide an insight how these interventions produce favorable changes in EMG and movement kinematics.

The relationship between multiscale dynamics in tremulous motion of upper limb when aiming and aiming performance in different physical load conditions.

The dynamics of tremulous motion in the upper limb is complex. We aimed to explore the relationship between the complexity of upper limb tremor when aiming and aiming performance and the influences of physical load on the two outcomes. Fifteen modern pentathlon athletes were recruited and completed two 1000-m treadmill running and three 60-s standard aiming task trials: one at baseline and each of the other two immediately after each running. The time series of light spot trace on the target was measured using a high-speed camera. The complexity of this time series was quantified using multiscale entropy. The effective aiming rate was used to assess the aiming performance. We observed that participants with lower tremor complexity had lower effective aiming rate across three physical load conditions (r2 > 0.38, p < 0.01). Physical load decreased both tremor complexity (F = 4.8, p = 0.01) and effective aiming rate (F = 13.5, p < 0.0001), but no difference was observed after 1000-m running compared to that after 2000-m running. The per cent change of tremor complexity associated with the change of effective aiming rate (r2 = 0.55, p < 0.0001). This pilot study demonstrates that multiscale complexity of tremulous motion in the upper limb when aiming may serve as a novel marker to assess the physiologic system functionality when aiming.

Fabrication of a Simple Acrylic Template to Standardize Periapical Radiographs for Implants Retaining Mandibular Bar Overdentures.

A standardized periapical radiograph is still the most suitable technique for monitoring peri-implant osseous destruction during long-term treatment. This article describes a new method for custom fabrication of an acrylic template with standardized reproducible assessment of implants retaining mandibular bar overdentures, without removal of the bar and regardless of the implant system used.

[Action for shield project promoting zero mother-to-child transmission of hepatitis B virus].

The World Health Organization(WHO)has set the goal to eliminate viral hepatitis as a public health threat by 2030, and the key to achieve this ambitious goal lies on the standardized and precise management of pregnant women and their infants by effectively blocking mother-to-child transmission (MTCT) of hepatitis B virus (HBV). Standardized management includes screening and antiviral intervention during pregnancy, infant immunization, and evaluation of immune effect, breastfeeding and mode of delivery. The results of randomized controlled clinical trials and real-world data have confirmed that the comprehensive prevention strategy based on combined immune prophylaxis of neonates can effectively block MTCT of HBV. It is one of the key links to eliminate viral hepatitis in our country, and to formulate a new strategy in line with the public health needs at home and abroad and thereby promote the implementation and application of standardized management process to improve the public's awareness of the disease.

[Organizing an assembly to eliminate hepatitis B virus through a project zero mother-to-child transmission of hepatitis B virus].

The China Foundation of Hepatitis Prevention and Control (CFHPC) initiated a project named, "getting to zero mother-to-child transmission of Hepatitis B," in July 2015, which aims to further reduce the incidence of mother-to-child transmission through standardized follow-up management of pregnant women and their infants with chronic hepatitis B virus infection by means of mobile medical application. Over the past three years, the project has established a nationwide collaborative network for interruption of mother-to-child transmission of hepatitis B virus, with 123 hospitals as project members. In addition, it has formulated a technical guidance document (Clinical Management Algorithm for Interrupting Mother-to-Child Transmission of HBV), which is designed and developed as a mobile medical application (SHIELD APP), and was released in an international conference on the theme to eliminate viral hepatitis. Following the measures mentioned above, the public's awareness rate of hepatitis B have been raised, and a good social atmosphere has been formed, which has played a positive role in promoting the prevention and control of viral hepatitis in China.

Skill level changes the coordination and variability of standing posture and movement in a pistol-aiming task.

The study investigated the coordination and variability of posture and pistol motion for skilled pistol shooters and novices in a pistol-aiming task. The participants stood on a force platform and held a pistol with the preferred arm to aim for accuracy to a target on 30 s trials. The results revealed that the amount of the centre of pressure (COP) and pistol motion was lower for the expert than novice group. The time-varying structure of COP as indexed by multiscale entropy (MSE) and detrended fluctuation analysis (DFA) was also lower for the expert than the novice group. The relative phase between the COP in the anterior-posterior (AP) and pistol in the AP and between the COP in the medial-lateral (ML) and pistol in AP was close to inphase for the both groups. However, for the novice group the coordination patterns of posture and pistol motion were more variable with the pistol motion leading the posture motion while it was lagging in the skilled group. The findings show different qualitative and quantitative dynamics in pistol-aiming as a function of skill level with postural control foundational to supporting the reduced dispersion and complexity of the skilled arm-pistol motion.

The cerebellum does more than sensory prediction error-based learning in sensorimotor adaptation tasks.

Individuals with damage to the cerebellum perform poorly in sensorimotor adaptation paradigms. This deficit has been attributed to impairment in sensory prediction error-based updating of an internal forward model, a form of implicit learning. These individuals can, however, successfully counter a perturbation when instructed with an explicit aiming strategy. This successful use of an instructed aiming strategy presents a paradox: In adaptation tasks, why do individuals with cerebellar damage not come up with an aiming solution on their own to compensate for their implicit learning deficit? To explore this question, we employed a variant of a visuomotor rotation task in which, before executing a movement on each trial, the participants verbally reported their intended aiming location. Compared with healthy control participants, participants with spinocerebellar ataxia displayed impairments in both implicit learning and aiming. This was observed when the visuomotor rotation was introduced abruptly (experiment 1) or gradually (experiment 2). This dual deficit does not appear to be related to the increased movement variance associated with ataxia: Healthy undergraduates showed little change in implicit learning or aiming when their movement feedback was artificially manipulated to produce similar levels of variability (experiment 3). Taken together the results indicate that a consequence of cerebellar dysfunction is not only impaired sensory prediction error-based learning but also a difficulty in developing and/or maintaining an aiming solution in response to a visuomotor perturbation. We suggest that this dual deficit can be explained by the cerebellum forming part of a network that learns and maintains action-outcome associations across trials.NEW & NOTEWORTHY Individuals with cerebellar pathology are impaired in sensorimotor adaptation. This deficit has been attributed to an impairment in error-based learning, specifically, from a deficit in using sensory prediction errors to update an internal model. Here we show that these individuals also have difficulty in discovering an aiming solution to overcome their adaptation deficit, suggesting a new role for the cerebellum in sensorimotor adaptation tasks.

Exploring the quiet eye in archery using field- and laboratory-based tasks.

The 'quiet eye' (QE)-a period of extended gaze fixation on a target-has been reported in many tasks that require accurate aiming. Longer quiet eye durations (QEDs) are reported in experts compared to non-experts and on successful versus less successful trials. The QE has been extensively studied in the field; however, the cognitive mechanisms underlying the QE are not yet fully understood. We investigated the QEDs of ten expert and ten novice archers in the field and in the laboratory using a computer-based archery task. The computer task consisted of shooting archery targets using a joystick. Random 'noise' (visual motion perturbation) was introduced at high and low levels to allow for the controlled examination of the effects of task complexity and processing demands. In this computer task, we also tested an additional group of ten non-archers as controls. In both field and computer tasks, eye movements were measured using electro-oculography. The expert archers exhibited longer QED compared to the novice archers in the field task. In the computer task, the archers again exhibited longer QEDs and were more accurate compared to non-archers. Furthermore, expert archers showed earlier QE onsets and longer QEDs during high noise conditions compared to the novices and non-archers. Our findings show skill-based effects on QED in field conditions and in a novel computer-based archery task, in which online (visual) perturbations modulated experts' QEDs. These longer QEDs in experts may be used for more efficient programming in which accurate predictions are facilitated by attention control.

Quiet eye facilitates sensorimotor preprograming and online control of precision aiming in golf putting.

An occlusion protocol was used to elucidate the respective roles of preprograming and online control during the quiet eye period of golf putting. Twenty-one novice golfers completed golf putts to 6-ft and 11-ft targets under full vision or with vision occluded on initiation of the backswing. Radial error (RE) was higher, and quiet eye was longer, when putting to the 11-ft versus 6-ft target, and in the occluded versus full vision condition. Quiet eye durations, as well as preprograming, online and dwell durations, were longer in low-RE compared to high-RE trials. The preprograming component of quiet eye was significantly longer in the occluded vision condition, whereas the online and dwell components were significantly longer in the full vision condition. These findings demonstrate an increase in preprograming when vision is occluded. However, this was not sufficient to overcome the need for online visual control during the quiet eye period. These findings suggest the quiet eye period is composed of preprograming and online control elements; however, online visual control of action is critical to performance.