1,720,988 research outputs found
PERICLES: A performance evaluation platform for indoor localization systems
No full textPeople Localization and Tracking (PLT) systems are in charge of providing information about mobile agents to components providing higher level services. This low level knowledge usually consists of the dynamic position (or more generally the dynamic pose) of mobile agents and can sometimes include the identity of mobile agents. Currently, both commercial and accademic/research PLT systems exist, but a comparison among them is difficult, as it is often difficult to compare experiments and to reproduce them in different systems. This has motivated our work in designing and realizing an evaluation platform, namely pericles, based on the use of off-the-shelf hardware. In this work we present the platform, to be used by the community for experimenting and testing different PLTs, its design choices, the implementation details and we discuss how it has been validated by using it for the testing of a PLT sytems we are currently developing (but which is out of the scope of the present paper)
P300-based brain-computer interface for environmental control: An asynchronous approach
No full textBrain-computer interface (BCI) systems allow people with severe motor disabilities to communicate and interact with the external world. The P300 potential is one of the most used control signals for EEG-based BCIs. Classic P300-based BCIs work in a synchronous mode; the synchronous control assumes that the user is constantly attending to the stimulation, and the number of stimulation sequences is fixed a priori. This issue is an obstacle for the use of these systems in everyday life; users will be engaged in a continuous control state, their distractions will cause misclassification and the speed of selection will not take into account users' current psychophysical condition. An efficient BCI system should be able to understand the user's intentions from the ongoing EEG instead. Also, it has to refrain from making a selection when the user is engaged in a different activity and it should increase or decrease its speed of selection depending on the current user's state. We addressed these issues by introducing an asynchronous BCI and tested its capabilities for effective environmental monitoring, involving 11 volunteers in three recording sessions. Results show that this BCI system can increase the bit rate during control periods while the system is proved to be very efficient in avoiding false negatives when the users are engaged in other tasks
Toward domotic appliances control through a self-paced P300-based BCI
Full text linkDuring recent years there has been a growing interest in Brain Computer Interface (BCI) systems as an alternative means of interaction with the external world for people with severe motor disabilities. The use of the P300 event-related potentials as control feature allows users to choose between various options (letters or icons) requiring a very short calibration phase. The aim of this work is to improve performances and flexibility of P300 based BCIs. An efficient BCI system should be able to understand user's intentions from the ongoing EEG, abstaining from doing a selection when the user is engaged in a different activity, and changing its speed of selection depending on current user's attention level. Our self-paced system addresses all these issues representing an important step beyond the classical synchronous P300 BCI that forces the user in a continuous control task. Experimentation has been performed on 10 healthy volunteers acting on a BCI-controlled domestic environment in order to demonstrate the potential usability of BCI systems in everyday life. Results show that the self-paced BCI increases information transfer rate with respect to the synchronous one, being very robust, at the same time, in avoiding false negatives when the user is not engaged in a control task
Monitoring mood states in everyday life: A new device for patients with cerebellar ataxia.
No full textThirty patients with cerebellar ataxia and 40 healthy volunteers underwent 7 days of mood monitoring using a new device requiring a low motor load. Its convergent validity and compliance were tested. The measurements resulted consistent with validated scale scores. Patients’ motor impairment did not affect the compliance
Pattern and path encoding: new tool for unwelding visuo-spatial memory through the use of a sensorized platform
No full textIt has been demonstrated that the processing of visuospatial information in reaching or navigational space is supported by independent systems.
Moreover, it has been proposed that visuospatial information may require a pattern or a path encoding. The pattern encoding is specifically used when the task requires a simultaneous processing of spatial positions, while the path encoding is used in sequential processing that allows to link different spatial positions in correct succession.
The aim of the present study was to disentangle these different components of visuospatial information processing in navigational tasks by the development of an innovative sensorized platform, and to verify if subjects use the same strategies when similar tasks are performed in reaching space. We assessed the performance of 70 healthy volunteers on the sensorized platform to investigate topographical orientation (route memory) in three different tasks that required a sequential strategy (named Route A and Route B tasks, which differ for sequential load required for their implementation) or a simultaneous strategy (named Simultaneous Walking Test).
Subsequently, similar tasks were performed in reaching space, (by means Corsi Block tapping Test and a Modified Corsi Test for the sequential strategy and Simultaneous Paper Test for the simultaneous strategy).
The six tasks were submitted to factor analysis (Principal Axis Factoring). This analysis showed four factors that explaining the 51.3% of the total variance: Corsi Block tapping Test (.501); Simultaneous Paper and Walking Test (-.74 and -.51, respectively); Route A (-.38); Modified Corsi Test and the Route B (.72 and .67, respectively). This clustering demonstrates that - the sensorized platform, set up in the present study, allows to identify the different strategies performed to correctly solve visuo-spatial tasks in navigational space – the same strategies can be also used in reaching space according to the task demand
Asynchronous gaze-independent event-related potential-based brain-computer interface
No full textObjective: In this study a gaze independent event related potential (ERP)-based brain computer interface (BCI) for communication purpose was combined with an asynchronous classifier endowed with dynamical stopping feature. The aim was to evaluate if and how the performance of such asynchronous system could be negatively affected in terms of communication efficiency and robustness to false positives during the intentional no-control state. Material and methods: The proposed system was validated with the participation of 9 healthy subjects. A comparison was performed between asynchronous and synchronous classification technique outputs while users were controlling the same gaze independent BC! interface. The performance of both classification techniques were assessed both off-line and on-line by means of the efficiency metric introduced by Bianchi et al. (2007). This latter metric allows to set a different misclassification cost for wrong classifications and abstentions. Robustness was evaluated as the rate of false positives occurring during voluntary no-control states. Results: The asynchronous classifier did not exhibited significantly higher accuracy or lower error rate with respect to the synchronous classifier (accuracy: 74.66% versus 87.96%, error rate: 7.11% versus 12.04% respectively). However, the on-line and off-line analysis revealed that the communication efficiency was significantly improved (p < .05) with the asynchronous classification modality as compared with the synchronous. Furthermore, the asynchronous classifier proved to be robust to false positives during intentional no-control state which occur during the ongoing visual stimulation (less than 1 false positive every 6 min). Conclusion: As such, the proposed ERP-BCI system which combines an asynchronous classifier with a gaze independent interface is a promising solution to be further explored in order to increase the general usability of ERP-based BCI systems designed for severely disabled people with an impairment of the voluntary control of eye movements. In fact, the asynchronous classifier can improve communication efficiency automatically adapting the number of stimulus repetitions to the current user's state and suspending the control if he/she does not intend to select an item. (C) 2013 Elsevier B.V. All rights reserved
Modern electrophysiological methods for brain-computer interfaces.
No full textModern electrophysiological studies in animals show that the spectrum of neural oscillations encoding relevant information is broader than previously thought and that many diverse areas are engaged for very simple tasks. However, EEG-based brain-computer interfaces (BCI) still employ as control modality relatively slow brain rhythms or features derived from preselected frequencies and scalp locations. Here, we describe the strategy and the algorithms we have developed for the analysis of electrophysiological data and demonstrate their capacity to lead to faster accurate decisions based on linear classifiers. To illustrate this strategy, we analyzed two typical BCI tasks. (1) Mu-rhythm control of a cursor movement by a paraplegic patient. For this data, we show that although the patient received extensive training in mu-rhythm control, valuable information about movement imagination is present on the untrained high-frequency rhythms. This is the first demonstration of the importance of high-frequency rhythms in imagined limb movements. (2) Self-paced finger tapping task in three healthy subjects including the data set used in the BCI-2003 competition. We show that by selecting electrodes and frequency ranges based on their discriminative power, the classification rates can be systematically improved with respect to results published thus far
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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