1,720,959 research outputs found
Developing a prolonged neurophysiological monitoring protocol to detect windows of responsiveness in minimally conscious state patients: foundation for a passive brain- computer interface system
Full text linkBrain-Computer Interfaces (BCIs) are systems designed to record brain activity and translate it into artificial output to replace, restore, enhance, supplement, or improve natural brain functions (Wolpaw et al., 2020). Among BCI applications, it is possible to find the replacement of communication and control for individuals with severe disabilities (Riccio et al., 2016). BCIs can be classified as either active or passive systems. An active BCI requires the user to consciously modulate brain activity or to engage in specific tasks to generate output and control an external device. In contrast, a passive BCI decodes mental and emotional states from spontaneous brain activity without necessitating the user's active participation (Zander et al., 2009). Disorders of consciousness (DoC) are clinical conditions resulting from severe acquired brain injuries, characterized by absent or diminished vigilance and awareness of self and the environment. These conditions include coma, vegetative state/unresponsive wakefulness syndrome (VS/UWS), and minimally conscious state (MCS), existing on a continuum where patients may transition sequentially through these states. Patients with DoC are considered potential candidates for BCI interventions, supported by substantial evidence suggesting that they may possess covert awareness - characterized by a dissociation between severely limited motor abilities and preserved cognitive functioning (Schiff, 2015). The initial efforts to establish an alternative communication channel for these patients were conducted by Monti et al. (2010), based on prior findings by Owen et al. (2006). They employed a mental imagery fMRI paradigm to assess command-following abilities in 54 patients with DoC, identifying five patients capable of intentionally modulating their mental activity. Notably, one patient diagnosed with MCS demonstrated successful communication. Despite these preliminary findings, the effectiveness of BCIs for communication with DoC patients remains uncertain (Spüler, 2019). Various factors may hinder the ability of DoC patients to utilize a BCI for communication, including sensory deficits, cognitive impairments, and fluctuations of responsiveness. Fluctuations of responsiveness are a hallmark of MCS diagnosis, which is defined by the presence of cognitively mediated behaviors that can be reliably differentiated from reflexive behaviors, despite occurring inconsistently over time. We propose that fluctuations of responsiveness give rise to what we term “Windows of Responsiveness” (WoR), defined as temporal windows during which an MCS patient exhibits higher level of responsiveness and potential interaction with their environment with respect “No Windows of Responsiveness” (NoWoR, i.e. interval time of low responsiveness). While fluctuations have been extensively examined from a behavioral perspective (Candelieri et al., 2011; Cortese et al., 2015; Wannez et al., 2017), they have received limited attention from a neurophysiological standpoint (Piarulli et al., 2016; Sitt et al., 2014). The objective of the present thesis is to investigate fluctuations of responsiveness from a neurophysiological perspective to identify a range of indices that may describe windows of responsiveness. This neurophysiological investigation into fluctuations of responsiveness will contribute to developing a model to characterize responsiveness and will constitute the foundation for implementing a passive BCI to automatically detect WoR. Chapter 1 presents a systematic review of the current state of BCI applications in patients with DoC, resulted in a publication in an international journal (Galiotta et al., 2022). The review aims to: i) describe the characteristics of BCI systems based on electroencephalography (EEG) developed for DoC patients, including the control signals employed, paradigm characteristics, classification algorithms, and applications; and ii) evaluate the performance of DoC patients using BCIs. The systematic review included twenty-seven studies. It was determined that the control signals utilized for BCI operation primarily consisted of the P300 component of the event-related potential (ERP), either in isolation or in conjunction with Steady-State Visual Evoked Potentials (hybrid systems), as well as sensorimotor rhythms. Potential applications of BCI in DoC patients include assessment, communication, prognosis, and rehabilitation, with a prevalence of the assessment application. Although BCIs appear to be promising tools in managing DoC patients - especially in supporting diagnostic and prognostic evaluations - the findings remain preliminary, with no definitive conclusions drawn, particularly regarding their utility and effectiveness for communication. Chapter 2 details the implementation and validation of a prolonged monitoring protocol aimed at detecting fluctuations of responsiveness from a neurophysiological perspective. This study specifically addresses a clinical population defined by the presence of such fluctuations, i.e. MCS patients, alongside a control group of healthy subjects. The protocol involved four hours of monitoring primarily conducted in resting state, during which multiple biosignals, including EEG, were recorded. The monitoring sessions were punctuated by two active tasks: an auditory oddball task and a motor command task. The EEG responses to these tasks were analyzed to determine patients' levels of responsiveness at various points throughout the monitoring. This chapter focuses exclusively on the oddball task. To validate the protocol, I examined the P300 ERP component in response to the oddball task, investigating whether the variability in its amplitude and latency was greater in patients than in healthy participants. My findings supported this hypothesis, revealing higher variability in both amplitude and latency among patients compared to healthy controls. These results substantiate the suitability of the P300 ERP component for detecting fluctuations of responsiveness within our protocol. Following the validation, I established a criterium based on P300 amplitude and latency to classify each monitoring moment as either WoR or NoWoR for each subject. Chapter 3 explores biosignals in the resting state immediately preceding each task presentation to evaluate significant differences in these indices between WoR and NoWoR. This analysis focuses on EEG and electrocardiographic (ECG) signals among those recorded. I computed a series of spectral EEG indices, as well as heart rate (HR) and heart rate variability (HRV). Initial comparisons were made between patients and healthy subjects, selecting only measures that exhibited significant differences between the two groups. Subsequently, I compared the selected indices between WoR and NoWoR to identify any significant differences. Notably, the Power Ratio Index (PRI) from the EEG and the HR from the ECG were found to be significantly higher in NoWoR than WoR, while the HRV was elevated in WoR compared to NoWoR. This investigation into EEG and ECG indices aims to contribute to the development of a neurophysiological model of responsiveness, which could facilitate the implementation of a passive BCI for the detection of the presence of WoR
P300-based Brain-Computer Interface for communication in assistive technology centers: influence of users’ profile on BCI access
No full textObjective. Assistive technology (AT) refers to any product that enables people to live independently and with dignity and to participate in activities of daily life. A Brain-Computer Interface (BCI) is an AT that provides an alternative output, based on neurophysiological signals, to control an external device. The aim of the study is to screen patients accessing an AT-center to investigate their eligibility for BCI access and the factors influencing the BCI control.
Approach. Thirty-five users and 11 healthy controls were included in the study. Participants were required to operate a P300-speller BCI. We investigated differences in BCI performance metrics (online accuracy and Information Transfer Rate) between end-user and control groups and we evaluated the influence of clinical diagnosis, socio-demographic factors, level of dependence and disability of users, neuropsychological profile on BCI performance.
Main results. 7.1% of the users controlled the system with a mean accuracy of 93.6±8.0%, while 8 users had an online accuracy below 70%. We found that the neuropsychological profile significantly affected online accuracy and ITR.
Significance. The percentage of users who had an accuracy considered as functional communication is an encouraging data in terms of BCI effectiveness. The results regarding accuracy and to the factors influencing (and not influencing) it, are a contribution to the process of introducing BCIs in the AT-centers, considering the BCI for communication as an additional input to provide multimodal access to AT
Usability of a Hybrid System Combining P300-Based Brain-Computer Interface and Commercial Assistive Technologies to Enhance Communication in People With Multiple Sclerosis
Full text linkBrain-computer interface (BCI) can provide people with motor disabilities with an alternative channel to access assistive technology (AT) software for communication and environmental interaction. Multiple sclerosis (MS) is a chronic disease of the central nervous system that mostly starts in young adulthood and often leads to a long-term disability, possibly exacerbated by the presence of fatigue. Patients with MS have been rarely considered as potential BCI end-users. In this pilot study, we evaluated the usability of a hybrid BCI (h-BCI) system that enables both a P300-based BCI and conventional input devices (i.e., muscular dependent) to access mainstream applications through the widely used AT software for communication “Grid 3.” The evaluation was performed according to the principles of the user-centered design (UCD) with the aim of providing patients with MS with an alternative control channel (i.e., BCI), potentially less sensitive to fatigue. A total of 13 patients with MS were enrolled. In session I, participants were presented with a widely validated P300-based BCI (P3-speller); in session II, they had to operate Grid 3 to access three mainstream applications with (1) an AT conventional input device and (2) the h-BCI. Eight patients completed the protocol. Five out of eight patients with MS were successfully able to access the Grid 3 via the BCI, with a mean online accuracy of 83.3% (± 14.6). Effectiveness (online accuracy), satisfaction, and workload were comparable between the conventional AT inputs and the BCI channel in controlling the Grid 3. As expected, the efficiency (time for correct selection) resulted to be significantly lower for the BCI with respect to the AT conventional channels (Z = 0.2, p < 0.05). Although cautious due to the limited sample size, these preliminary findings indicated that the BCI control channel did not have a detrimental effect with respect to conventional AT channels on the ability to operate an AT software (Grid 3). Therefore, we inferred that the usability of the two access modalities was comparable. The integration of BCI with commercial AT input devices to access a widely used AT software represents an important step toward the introduction of BCIs into the AT centers’ daily practice
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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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