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Abstract
Cognitive workload recognition is pivotal to maintain the operator's health and prevent
accidents in the human-robot interaction condition. So far, the focus of workload
research is mostly restricted to a single task, yet cross-task cognitive workload
recognition has remained a challenge. Furthermore, when extending to a new workload
condition, the discrepancy of electroencephalogram (EEG) signals across various cognitive
tasks limits the generalization of the existed model. To tackle this problem, we propose
to construct the EEG-based cross-task cognitive workload recognition models using
domain adaptation methods in a leave-one-task-out cross-validation setting, where
we view any task of each subject as a domain. Specifically, we first design a fine-grained
workload paradigm including working memory and mathematic addition tasks. Then, we
explore four domain adaptation methods to bridge the discrepancy between the two different
tasks. Finally, based on the supporting vector machine classifier, we conduct experiments
to classify the low and high workload levels on a private EEG dataset. Experimental
results demonstrate that our proposed task transfer framework outperforms the non-transfer
classifier with improvements of 3% to 8% in terms of mean accuracy, and the transfer
joint matching (TJM) consistently achieves the best performance.
We have developed a toolbox and graphic user interface, EEGLAB, running under the crossplatform MATLAB environment (The Mathworks, Inc.) for processing collections of single-trial and/or averaged EEG data of any number of channels. Available functions include EEG data, channel and event information importing, data visualization (scrolling, scalp map and dipole model plotting, plus multi-trial ERP-image plots), preprocessing (including artifact rejection, filtering, epoch selection, and averaging), independent component analysis (ICA) and time/frequency decompositions including channel and component cross-coherence supported by bootstrap statistical methods based on data resampling. EEGLAB functions are organized into three layers. Top-layer functions allow users to interact with the data through the graphic interface without needing to use MATLAB syntax. Menu options allow users to tune the behavior of EEGLAB to available memory. Middle-layer functions allow users to customize data processing using command history and interactive 'pop' functions. Experienced MATLAB users can use EEGLAB data structures and stand-alone signal processing functions to write custom and/or batch analysis scripts. Extensive function help and tutorial information are included. A 'plug-in' facility allows easy incorporation of new EEG modules into the main menu. EEGLAB is freely available (http://www.sccn.ucsd.edu/eeglab/) under the GNU public license for noncommercial use and open source development, together with sample data, user tutorial and extensive documentation.
Domain adaptation allows knowledge from a source domain to be transferred to a different but related target domain. Intuitively, discovering a good feature representation across domains is crucial. In this paper, we first propose to find such a representation through a new learning method, transfer component analysis (TCA), for domain adaptation. TCA tries to learn some transfer components across domains in a reproducing kernel Hilbert space using maximum mean miscrepancy. In the subspace spanned by these transfer components, data properties are preserved and data distributions in different domains are close to each other. As a result, with the new representations in this subspace, we can apply standard machine learning methods to train classifiers or regression models in the source domain for use in the target domain. Furthermore, in order to uncover the knowledge hidden in the relations between the data labels from the source and target domains, we extend TCA in a semisupervised learning setting, which encodes label information into transfer components learning. We call this extension semisupervised TCA. The main contribution of our work is that we propose a novel dimensionality reduction framework for reducing the distance between domains in a latent space for domain adaptation. We propose both unsupervised and semisupervised feature extraction approaches, which can dramatically reduce the distance between domain distributions by projecting data onto the learned transfer components. Finally, our approach can handle large datasets and naturally lead to out-of-sample generalization. The effectiveness and efficiency of our approach are verified by experiments on five toy datasets and two real-world applications: cross-domain indoor WiFi localization and cross-domain text classification.
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