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Adaptive Assistance for Brain-Computer Interfaces by Online Prediction of Command Reliability

  • Authors: Saeedi, Sareh; Chavarriaga, Ricardo; Leeb, Robert; Millán, José del R.

One of the challenges of using brain-computer interfaces (BCIs) over extended periods of time is the variation of the users’ performance across different experimental days. The goal of the current study is to propose a performance estimator for an electroencephalography-based motor imagery BCI by assessing the reliability of a command (i.e., predicting a ‘short’ or ‘long’ command delivery time, CDT). Using a short time window (< 1.5 s, shorter than the delivery time) of the mental task execution and a linear discriminant analysis classifier, we could reliably differentiate between long and short CDT (AUC around 0.8) for 9 healthy subjects. Moreover, we assessed the feasibility of providing online adaptive assistance using the performance estimator in a BCI game, comparing two conditions: (i) allowing a ‘fixed timeout’ to deliver each command or (ii) providing ‘adaptive assistance’ by giving more time if the performance estimator detects a long CDT. The results revealed that providing adaptive assistance increases the ratio of correct commands significantly (p < 0.01). Moreover, the task load index (measured via the NASA TLX questionnaire) shows a significantly higher user acceptance in case of providing adaptive assistance (p < 0.01). Furthermore, the results obtained in this study were used to simulate a robotic navigation scenario, which showed how adaptive assistance improved performance.

Posted on: October 13, 2015

Making the most of context-awareness in brain-computer interfaces

  • Authors: Saeedi, Sareh; Carlson, Tom; Chavarriaga, Ricardo; Millán, José del R.

In order for brain-computer interfaces (BCIs) to be used reliably for extended periods of time, they must be able to adapt to the users evolving needs. This adaptation should not only be a function of the environmental (external) context, but should also consider the internal context, such as cognitive states and brain signal reliability. In this work, we propose three different shared control frameworks that have been used for BCI applications: contextual fusion, contextual gating, and contextual regulation. We review recently published results in the light of these three context-awareness frameworks. Then, we discuss important issues to consider when designing a shared controller for BCI.

Posted on: April 29, 2013

Prediction of Command Delivery Time for BCI

  • Authors: Saeedi, Sareh; Carlson, Tom; Chavarriaga, Ricardo; Iturrate, Inaki; Millán, José del R.

One of the challenges in using brain computer interfaces over extended periods of time is the uncertainty in the system. This uncertainty can be due to the user’s internal states, the non stationarity of the brain signals, or the variation of the class discriminative information over time. Therefore, the users are often unable to maintain the same accuracy and time efficiency in delivering BCI commands. In this paper, we tackle the issue of variation in BCI command delivery time for a motor imagery task with the aim of providing assistance through adaptive shared control. This is important mainly because having long delivery of mental commands leads to uncertainty in the user’s intent classification and limits the responsiveness of the system. In order to address this issue, we separate the trials into “long” and “short” groups so that we have the same number of trials in each group. We demonstrate that using only a few samples at the beginning of the trial, we are able to predict whether the current trial will be short or long with high accuracies (70% – 86%). Eventually, this prediction enables us to tune the shared control parameters to overcome the issue of uncertainty.

Posted on: July 11, 2014

Real-time Prediction of Fast and Slow Delivery of Mental Commands in a Motor Imagery BCI: An Entropy-based Approach

  • Authors: Saeedi, Sareh; Chavarriaga, Ricardo; Gastpar, Michael C.; Millán, José del R.

Providing adaptive shared control for Brain- Computer Interfaces (BCIs) can result in better performance while reducing the user’s mental workload. In this respect, online estimation of accuracy and speed of command delivery are important factors. This study aims at real-time differentiation between fast and slow trials in a motor imagery BCI. In our experiments, we refer to trials shorter than the median of trial lengths as “fast” trials and to those longer than the median as “slow” trials. We propose a classifier for real-time distinction between fast and slow trials based on estimates of the entropy rates for the first 2-3 s of the electroencephalogram (EEG). Results suggest that it can be predicted whether a trial is slow or fast well before a cutoff time. This is important for adaptive shared control especially because 55% to 75% of trials (for the five subjects in this study) are longer than that cutoff time

Posted on: July 16, 2012

Towards Independence: A BCI Telepresence Robot for People with Severe Motor Disabilities

  • Authors: Leeb, Robert; Tonin, L.; Rohm, M.; Desideri, L.; Carlson, T.; Millán, José del R.

This paper presents an important step forward towards increasing the independence of people with severe motor disabilities, by using brain-computer interfaces (BCI) to harness the power of the Internet of Things. We analyze the stability of brain signals as end-users with motor disabilities progress from performing simple standard on-screen training tasks to interacting with real devices in the real world. Furthermore, we demonstrate how the concept of shared control —which interprets the user’s commands in context— empowers users to perform rather complex tasks without a high workload. We present the results of nine end-users with motor disabilities who were able to complete navigation tasks with a telepresence robot successfully in a remote environment (in some cases in a different country) that they had never previously visited. Moreover, these end-users achieved similar levels of performance to a control group of ten healthy users who were already familiar with the environment.

Posted on: April 27, 2015