Identification of movement-related cortical potentials with optimized spatial filtering and principal component analysis

We present a method for detecting movement intention from multichannel electroencephalographic (EEG) recordings. Movement intention is expressed as a slow negative deflection in amplitude of the EEG signal recorded above the motor cortex. This deflection is known as a movement-related cortical potential (MRCP). Detection of movement intention implies discrimination between MRCPs and noise. The signal-to-noise ratio of MRCPs was improved by an optimized spatial filter. Features were extracted with principal component analysis or locality preserving projections from the spatially filtered signals and classification between MRCPs and noise was performed with a k-nearest neighbors algorithm, modified by adjusting the decision rule to improve specificity, and a support vector machine approach. In one representative subject the sensitivity and specificity in detection were in the range 80–90% and 98–99.5%, respectively. The method seems promising for the development of asynchronous brain–computer interfaces (BCIs) based on MRCPs.     

Decoding Individual Finger Movements from One Hand Using Human EEG Signals

Brain computer interface (BCI) is an assistive technology, which decodes neurophysiological signals generated by the human brain and translates them into control signals to control external devices, e.g., wheelchairs. One problem challenging noninvasive BCI technologies is the limited control dimensions from decoding movements of, mainly, large body parts, e.g., upper and lower limbs. It has been reported that complicated dexterous functions, i.e., finger movements, can be decoded in electrocorticography (ECoG) signals, while it remains unclear whether noninvasive electroencephalography (EEG) signals also have sufficient information to decode the same type of movements. Phenomena of broadband power increase and low-frequency-band power decrease were observed in EEG in the present study, when EEG power spectra were decomposed by a principal component analysis (PCA). These movement-related spectral structures and their changes caused by finger movements in EEG are consistent with observations in previous ECoG study, as well as the results from ECoG data in the present study. The average decoding accuracy of 77.11% over all subjects was obtained in classifying each pair of fingers from one hand using movement-related spectral changes as features to be decoded using a support vector machine (SVM) classifier. The average decoding accuracy in three epilepsy patients using ECoG data was 91.28% with the similarly obtained features and same classifier. Both decoding accuracies of EEG and ECoG are significantly higher than the empirical guessing level (51.26%) in all subjects (p<0.05). The present study suggests the similar movement-related spectral changes in EEG as in ECoG, and demonstrates the feasibility of discriminating finger movements from one hand using EEG. These findings are promising to facilitate the development of BCIs with rich control signals using noninvasive technologies.     

Abnormal Movement Preparation in Task-Specific Focal Hand Dystonia

Electrophysiological and behavioral studies in primary dystonia suggest abnormalities during movement preparation, but this crucial phase preceding movement onset has not yet been studied specifically with functional magnetic resonance imaging (fMRI). To identify abnormalities in brain activation during movement preparation, we used event-related fMRI to analyze behaviorally unimpaired sequential finger movements in 18 patients with task-specific focal hand dystonia (FHD) and 18 healthy subjects. Patients and controls executed self-initiated or externally cued prelearnt four-digit sequential movements using either right or left hands. In FHD patients, motor performance of the sequential finger task was not associated with task-related dystonic posturing and their activation levels during motor execution were highly comparable with controls. On the other hand reduced activation was observed during movement preparation in the FHD patients in left premotor cortex / precentral gyrus for all conditions, and for self-initiation additionally in supplementary motor area, left mid-insula and anterior putamen, independent of effector side. Findings argue for abnormalities of early stages of motor control in FHD, manifesting during movement preparation. Since deficits map to regions involved in the coding of motor programs, we propose that task-specific dystonia is characterized by abnormalities during recruitment of motor programs: these do not manifest at the behavioral level during simple automated movements, however, errors in motor programs of complex movements established by extensive practice (a core feature of FHD), trigger the inappropriate movement patterns observed in task-specific dystonia.     

Online detector of movement intention based on EEG—Application in tremor patients

Patients with tremor can benefit from wearable robots managing their tremor during daily living. To achieve this, the interfaces controlling such robotic systems must be able to estimate the user's intention to move and to distinguish it from the undesired tremor. In this context, analysis of electroencephalographic activity is of special interest, since it provides information on the planning and execution of voluntary movements. This paper proposes an adaptive and asynchronous EEG-based system for online detection of the intention to move in patients with tremor. An experimental protocol with separated self-paced wrist extensions was used to test the ability of the system to detect the intervals preceding voluntary movements. Six healthy subjects and four essential tremor patients took part in the experiments. The system predicted 60 ± 10% of the movements with the control subjects and 42 ± 27% of the movements with the patients. The ratio of false detections was low in both cases (1.5 ± 0.1 and 1.4 ± 0.5 false activations per minute with the controls and patients, respectively). The prediction period with which the movements were detected was higher than in previous similar studies (1.06 ± 1.02 s for the controls and 1.01 ± 0.99 s with the patients). Additionally, an adaptive and fixed design were compared, and it was the adaptive design that had a higher number of movement detections. The system is expected to lead to further development of more natural interfaces between the assistive devices and the patients wearing them.     

Abnormal motor patterns in the framework of the equilibrium-point hypothesis: a cause for dystonic movements?

Until now, the equilibrium-point hypothesis (λ model) of motor control has assumed nonintersecting force-length characteristics of the tonic stretch reflex for individual muscles. Limited data from animal experiments suggest, however, that such intersections may occur. We have assumed the possibility of intersection of the characteristics of the tonic stretch reflex and performed a computer simulation of movement trajectories and electromyographic patterns. The simulation has demonstrated, in particular, that a transient change in the slope of the characteristic of an agonist muscle may lead to temporary movement reversals, hesitations, oscillations, and multiple electromyographic bursts that are typical of movements of patients with dystonia. The movement patterns of three patients with idiopathic dystonia during attempts at fast single-joint movements (in the elbow, wrist, and ankle) were recorded and compared with the results of the computer simulation. This approach considers that motor disorders in dystonia result from faulty control patterns that may not correlate with any morphological or neurophysiological changes. It provides a basis for the high variability of dystonic movements. The uniqueness of abnormal motor patterns in dystonia, that precludes statistical analysis across patients, may result from subtle differences in the patterns of intersecting characteristics of the tonic stretch reflex. The applicability of our analysis to disordered multijoint movement patterns is discussed. Received: 26 July 1993/Accepted in revised form: 22 December 1993     

Equivalence between Step Selection Functions and Biased Correlated Random Walks for Statistical Inference on Animal Movement

Animal movement has a fundamental impact on population and community structure and dynamics. Biased correlated random walks (BCRW) and step selection functions (SSF) are commonly used to study movements. Because no studies have contrasted the parameters and the statistical properties of their estimators for models constructed under these two Lagrangian approaches, it remains unclear whether or not they allow for similar inference. First, we used the Weak Law of Large Numbers to demonstrate that the log-likelihood function for estimating the parameters of BCRW models can be approximated by the log-likelihood of SSFs. Second, we illustrated the link between the two approaches by fitting BCRW with maximum likelihood and with SSF to simulated movement data in virtual environments and to the trajectory of bison (Bison bison L.) trails in natural landscapes. Using simulated and empirical data, we found that the parameters of a BCRW estimated directly from maximum likelihood and by fitting an SSF were remarkably similar. Movement analysis is increasingly used as a tool for understanding the influence of landscape properties on animal distribution. In the rapidly developing field of movement ecology, management and conservation biologists must decide which method they should implement to accurately assess the determinants of animal movement. We showed that BCRW and SSF can provide similar insights into the environmental features influencing animal movements. Both techniques have advantages. BCRW has already been extended to allow for multi-state modeling. Unlike BCRW, however, SSF can be estimated using most statistical packages, it can simultaneously evaluate habitat selection and movement biases, and can easily integrate a large number of movement taxes at multiple scales. SSF thus offers a simple, yet effective, statistical technique to identify movement taxis.     

Evaluation of Harmonic Direction-Finding Systems for Detecting Locomotor Activity

Abstract: We conducted a physical simulation experiment to test the efficacy of harmonic direction finding for remotely detecting locomotor activity in animals. The ability to remotely detect movement helps to avoid disturbing natural movement behavior. Remote detection implies that the observer can sense only a change in signal bearing. In our simulated movements, small changes in bearing (<5.7°) were routinely undetectable. Detectability improved progressively with the size of the simulated animal movement. The average (±SD) of reflector tag movements correctly detected for 5 observers was 93.9 ± 12.8% when the tag was moved ≥11.5°; most observers correctly detected tag movements ≥20.1°. Given our data, one can assess whether the technique will be effective for detecting movements at an observation distance appropriate for the study organism. We recommend that both habitat and behavior of the organism be taken into consideration when contemplating use of this technique for detecting locomotion.     

Relevance of intra-hospital patient movements for the spread of healthcare-associated infections within hospitals - a mathematical modeling study

The aim of this study is to analyze patient movement patterns between hospital departments to derive the underlying intra-hospital movement network, and to assess if movement patterns differ between patients at high or low risk of colonization. For that purpose, we analyzed patient electronic medical record data from five hospitals to extract information on risk stratification and patient intra-hospital movements. Movement patterns were visualized as networks, and network centrality measures were calculated. Next, using an agent-based model where agents represent patients and intra-hospital patient movements were explicitly modeled, we simulated the spread of multidrug resistant enterobacteriacae (MDR-E) inside a hospital. Risk stratification of patients according to certain ICD-10 codes revealed that length of stay, patient age, and mean number of movements per admission were higher in the high-risk groups. Movement networks in all hospitals displayed a high variability among departments concerning their network centrality and connectedness with a few highly connected departments and many weakly connected peripheral departments. Simulating the spread of a pathogen in one hospital network showed positive correlation between department prevalence and network centrality measures. This study highlights the importance of intra-hospital patient movements and their possible impact on pathogen spread. Targeting interventions to departments of higher (weighted) degree may help to control the spread of MDR-E. Moreover, when the colonization status of patients coming from different departments is unknown, a ranking system based on department centralities may be used to design more effective interventions that mitigate pathogen spread.     

Grasp Detection from Human ECoG during Natural Reach-to-Grasp Movements

Various movement parameters of grasping movements, like velocity or type of the grasp, have been successfully decoded from neural activity. However, the question of movement event detection from brain activity, that is, decoding the time at which an event occurred (e.g. movement onset), has been addressed less often. Yet, this may be a topic of key importance, as a brain-machine interface (BMI) that controls a grasping prosthesis could be realized by detecting the time of grasp, together with an optional decoding of which type of grasp to apply. We, therefore, studied the detection of time of grasps from human ECoG recordings during a sequence of natural and continuous reach-to-grasp movements. Using signals recorded from the motor cortex, a detector based on regularized linear discriminant analysis was able to retrieve the time-point of grasp with high reliability and only few false detections. Best performance was achieved using a combination of signal components from time and frequency domains. Sensitivity, measured by the amount of correct detections, and specificity, represented by the amount of false detections, depended strongly on the imposed restrictions on temporal precision of detection and on the delay between event detection and the time the event occurred. Including neural data from after the event into the decoding analysis, slightly increased accuracy, however, reasonable performance could also be obtained when grasping events were detected 125 ms in advance. In summary, our results provide a good basis for using detection of grasping movements from ECoG to control a grasping prosthesis.     

Invasive Silver Carp movement patterns in the predominantly free-flowing Wabash River (Indiana,USA)

Many organisms must move among habitats to fulfill life history requirements. Fish movements have been widely studied and tend to be either fine-scale (i.e., routine) and governed by factors such as food availability and cover, or broad-scale and associated with spawning migrations. However, movements of invasive fishes in non-native ecosystems are comparatively poorly understood despite the often critical importance of fish movement and dispersal for invasion success. We examined invasive Silver Carp (Hypophthalmichthys molitrix) movements using acoustic telemetry to monitor the timing, distance, and direction of fish movements and assessed movements in relation to seasonal, annual, environmental, and individual factors in the Wabash River (Indiana, USA), a largely unregulated Midwestern river. Silver Carp exhibited highly variable movements that could be rapid and large in magnitude; however, tagged individuals remained stationary most of the time. Despite high variability, several trends emerged, indicating the importance of backwater habitats, avoidance of small tributaries, and tendencies of tagged fish to exhibit directed spring and fall broad-scale movements. Summer movements were smaller in magnitude, characterized by lower movement rates, and evenly split between upstream and downstream directions, although tagged Silver Carp moved more frequently during summer months. Our results indicate that specific seasons (i.e., spring and early fall) and locations (i.e., backwaters) are likely targets for Silver Carp control in the Wabash River and should also be useful targets for early detection and control in other largely unconstrained rivers over a broad geographic range (e.g., Great Lakes tributaries and upper Mississippi River mainstem and tributaries).     

Medical robotics

Information and communication technology (ICT) and mechatronics play a basic role in medical robotics and computer-aided therapy. In the last three decades, in fact, ICT technology has strongly entered the health-care field, bringing in new techniques to support therapy and rehabilitation. In this frame, medical robotics is an expansion of the service and professional robotics as well as other technologies, as surgical navigation has been introduced especially in minimally invasive surgery. Localization systems also provide treatments in radiotherapy and radiosurgery with high precision. Virtual or augmented reality plays a role for both surgical training and planning and for safe rehabilitation in the first stage of the recovery from neurological diseases. Also, in the chronic phase of motor diseases, robotics helps with special assistive devices and prostheses. Although, in the past, the actual need and advantage of navigation, localization, and robotics in surgery and therapy has been in doubt, today, the availability of better hardware (e.g., microrobots) and more sophisticated algorithms(e.g., machine learning and other cognitive approaches)has largely increased the field of applications of these technologies,making it more likely that, in the near future, their presence will be dramatically increased, taking advantage of the generational change of the end users and the increasing request of quality in health-care delivery and management.     

Hawk Eyes II: Diurnal Raptors Differ in Head Movement Strategies When Scanning from Perches

Background

Relatively little is known about the degree of inter-specific variability in visual scanning strategies in species with laterally placed eyes (e.g., birds). This is relevant because many species detect prey while perching; therefore, head movement behavior may be an indicator of prey detection rate, a central parameter in foraging models. We studied head movement strategies in three diurnal raptors belonging to the Accipitridae and Falconidae families.

Methodology/Principal Findings

We used behavioral recording of individuals under field and captive conditions to calculate the rate of two types of head movements and the interval between consecutive head movements. Cooper''s Hawks had the highest rate of regular head movements, which can facilitate tracking prey items in the visually cluttered environment they inhabit (e.g., forested habitats). On the other hand, Red-tailed Hawks showed long intervals between consecutive head movements, which is consistent with prey searching in less visually obstructed environments (e.g., open habitats) and with detecting prey movement from a distance with their central foveae. Finally, American Kestrels have the highest rates of translational head movements (vertical or frontal displacements of the head keeping the bill in the same direction), which have been associated with depth perception through motion parallax. Higher translational head movement rates may be a strategy to compensate for the reduced degree of eye movement of this species.

Conclusions

Cooper''s Hawks, Red-tailed Hawks, and American Kestrels use both regular and translational head movements, but to different extents. We conclude that these diurnal raptors have species-specific strategies to gather visual information while perching. These strategies may optimize prey search and detection with different visual systems in habitat types with different degrees of visual obstruction.     

Use of Bioluminescence for Detection of Genetically Engineered Microorganisms Released into the Environment

The persistence and movement of strain JS414 of Xanthomonas campestris pv. campestris, which was genetically engineered to bioluminesce, were monitored during a limited field introduction. Bioluminescence and traditional dilution plate counts were determined. Strain JS414 was applied to cabbage plants and surrounding soil by mist inoculation, by wound inoculation, by scattering infested debris among plants, and by incorporating bacteria into the soil. Bioluminescent X. campestris pv. campestris was detected in plant samples and in the rhizosphere up to 6 weeks after inoculation. Movement to uninoculated plants was detected on one occasion, but movement from the immediate release area was not detected. Strain JS414 was detected in soil samples beneath mist- and wound-inoculated plants only at intentionally infested locations and in aerial samples only on the day of inoculation. Our bioluminescence methods proved to be as sensitive as plating methods for detecting the genetically engineered microorganisms in environmental samples. Our results demonstrate that transgenic incorporation of the luxCDABE operon provides a non-labor-intensive, sensitive detection method for monitoring genetically engineered microorganisms in nature.     

Spatial ecology and habitat use of two-spined blackfish Gadopsis bispinosus in an upland reservoir

The scale and patterns of movement and habitat use are primary considerations in the conservation and management of threatened species. Movement, activity and habitat use of the threatened two-spined blackfish Gadopsis bispinosus were assessed in a small upland reservoir in south-eastern Australia using manual and remote radio-telemetry. Movements and activity of two-spined blackfish (n?=?19) were studied over a 28-day period and exhibited proportionately large directional crepuscular movement and activity with heightened activity continuing throughout the night (although movement was subdued). Two daily movement strategies were observed: movements from diurnal home-shelter habitats (predominantly rock) to macrophytes at night (14 individuals), and occupation of macrophytes during the entire diel period and restricted movement (five individuals). Daily movement strategies were fixed (not plastic) among all individuals, with one exception, for the duration of the study period. Rock, fallen timber and macrophytes were the most commonly used daytime shelter habitat (in order of preference). Although some information exists on movements and habitat use of this species and the congeneric river blackfish G. Marmoratus in lotic environments, we present the first study of movements and habitat use for either species in lentic environments. Given the occupation of lentic environments by this threatened species, the data presented in this study provide insight into the habitat requirements for this species, and offer opportunities for habitat enhancement in existing reservoirs within the species’ geographic range.     

Brain–computer interface: The first experience of clinical use in Russia

Motor imagery can stimulate the same neuroplastic mechanisms of the brain as their actual execution. The motor imagery can be controlled via the brain–computer interface (BCI), which transforms the EEG signals of the brain appearing during the motor imagery into commands for the external device. The results of the two-stage study of the application of a non-invasive BCI for the rehabilitation of patients with marked hemiparesis resulted from a local brain injury. We have shown that the learning to manage the BCI does not depend on the duration of disease, localization of the damaged site, and the severity of neurological deficit. The results of the first stage of the study carried out in a group of 36 patients showed that the rehabilitation therapy was more effective in the group that was trained to manage the BCI (the ARAT score improved from 1 [0; 2] to 5 [0; 16], p = 0.012 in the BCI group; no significant improvement was detected in the control group). In the second phase of the study, 19 patients participated in the testing of a BCI–exoskeleton system. Rehabilitation based on this technology led to an improvement of the motor function of an arm from 2 [0; 37] to 4 [1; 45.5], p = 0.005, according to the ARAT scale, and from 72 [63; 110] to 79 [68; 115], p = 0.005, according to the Fugl-Meyer scale.     

Motion perception and visual signal design in Anolis lizards

Anolis lizards communicate with displays consisting of motion of the head and body. Early portions of long-distance displays require movements that are effective at eliciting the attention of potential receivers. We studied signal-motion efficacy using a two-dimensional visual-motion detection (2DMD) model consisting of a grid of correlation-type elementary motion detectors. This 2DMD model has been shown to accurately predict Anolis lizard behavioural response. We tested different patterns of artificially generated motion and found that an abrupt 0.3° shift of position in less than 100 ms is optimal. We quantified motion in displays of 25 individuals from five species. Four species employ near-optimal movement patterns. We tested displays of these species using the 2DMD model on scenes with and without moderate wind. Display movements can easily be detected, even in the presence of windblown vegetation. The fifth species does not typically use the most effective display movements and display movements cannot be discerned by the 2DMD model in the presence of windblown vegetation. A number of Anolis species use abrupt up-and-down head movements approximately 10 mm in amplitude in displays, and these movements appear to be extremely effective for stimulating the receiver visual system.     

iEMG: Imaging electromyography

Advanced data analysis and visualization methodologies have played an important role in making surface electromyography both a valuable diagnostic methodology of neuromuscular disorders and a robust brain–machine interface, usable as a simple interface for prosthesis control, arm movement analysis, stiffness control, gait analysis, etc. But for diagnostic purposes, as well as for interfaces where the activation of single muscles is of interest, surface EMG suffers from severe crosstalk between deep and superficial muscle activation, making the reliable detection of the source of the signal, as well as reliable quantification of deeper muscle activation, prohibitively difficult. To address these issues we present a novel approach for processing surface electromyographic data. Our approach enables the reconstruction of 3D muscular activity location, making the depth of muscular activity directly visible. This is even possible when deep muscles are overlaid with superficial muscles, such as seen in the human forearm. The method, which we call imaging EMG (iEMG), is based on using the crosstalk between a sufficiently large number of surface electromyographic electrodes to reconstruct the 3D generating electrical potential distribution within a given area. Our results are validated by in vivo measurements of iEMG and ultrasound on the human forearm.     

Searching for Survivors through Random Human-Body Movement Outdoors by Continuous-Wave Radar Array

It is a major challenge to search for survivors after chemical or nuclear leakage or explosions. At present, biological radar can be used to achieve this goal by detecting the survivor’s respiration signal. However, owing to the random posture of an injured person at a rescue site, the radar wave may directly irradiate the person’s head or feet, in which it is difficult to detect the respiration signal. This paper describes a multichannel-based antenna array technology, which forms an omnidirectional detection system via 24-GHz Doppler biological radar, to address the random positioning relative to the antenna of an object to be detected. Furthermore, since the survivors often have random body movement such as struggling and twitching, the slight movements of the body caused by breathing are obscured by these movements. Therefore, a method is proposed to identify random human-body movement by utilizing multichannel information to calculate the background variance of the environment in combination with a constant-false-alarm-rate detector. The conducted outdoor experiments indicate that the system can realize the omnidirectional detection of random human-body movement and distinguish body movement from environmental interference such as movement of leaves and grass. The methods proposed in this paper will be a promising way to search for survivors outdoors.     

Migratory Patterns of Wild Chinook Salmon Oncorhynchus tshawytscha Returning to a Large,Free-Flowing River Basin

Upriver movements were determined for Chinook salmon Oncorhynchus tshawytscha returning to the Yukon River, a large, virtually pristine river basin. These returns have declined dramatically since the late 1990s, and information is needed to better manage the run and facilitate conservation efforts. A total of 2,860 fish were radio tagged during 2002–2004. Most (97.5%) of the fish tracked upriver to spawning areas displayed continual upriver movements and strong fidelity to the terminal tributaries entered. Movement rates were substantially slower for fish spawning in lower river tributaries (28–40 km d^-1) compared to upper basin stocks (52–62 km d^-1). Three distinct migratory patterns were observed, including a gradual decline, pronounced decline, and substantial increase in movement rate as the fish moved upriver. Stocks destined for the same region exhibited similar migratory patterns. Individual fish within a stock showed substantial variation, but tended to reflect the regional pattern. Differences between consistently faster and slower fish explained 74% of the within-stock variation, whereas relative shifts in sequential movement rates between “hares” (faster fish becoming slower) and “tortoises” (slow but steady fish) explained 22% of the variation. Pulses of fish moving upriver were not cohesive. Fish tagged over a 4-day period took 16 days to pass a site 872 km upriver. Movement rates were substantially faster and the percentage of atypical movements considerably less than reported in more southerly drainages, but may reflect the pristine conditions within the Yukon River, wild origins of the fish, and discrete run timing of the returns. Movement data can provide numerous insights into the status and management of salmon returns, particularly in large river drainages with widely scattered fisheries where management actions in the lower river potentially impact harvests and escapement farther upstream. However, the substantial variation exhibited among individual fish within a stock can complicate these efforts.