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Usability and Workload of Access Technology for People With Severe Motor Impairment: A Comparison of Brain-Computer Interfacing and Eye Tracking

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Background. Eye trackers are widely used among people with amyotrophic lateral sclerosis, and their benefits to quality of life have been previously shown. On the contrary, Brain-computer interfaces (BCIs) are still quite a novel technology, which also serves as an access technology for people with severe motor impairment. Objective. To compare a visual P300-based BCI and an eye tracker in terms of information transfer rate (ITR), usability, and cognitive workload in users with motor impairments. Methods. Each participant performed 3 spelling tasks, over 4 total sessions, using an Internet browser, which was controlled by a spelling interface that was suitable for use with either the BCI or the eye tracker. At the end of each session, participants evaluated usability and cognitive workload of the system. Results. ITR and System Usability Scale (SUS) score were higher for the eye tracker (Wilcoxon signed-rank test: ITR T = 9, P = .016; SUS T = 12.50, P = .035). Cognitive workload was higher for the BCI (T = 4; P = .003). Conclusions. Although BCIs could be potentially useful for people with severe physical disabilities, we showed that the usability of BCIs based on the visual P300 remains inferior to eye tracking. We suggest that future research on visual BCIs should use eye tracking-based control as a comparison to evaluate performance or focus on nonvisual paradigms for persons who have lost gaze control. © The Author(s) 2015.
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Neurorehabilitation and
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DOI: 10.1177/1545968315575611
Original Research Articles
Because of degenerative neuromuscular diseases or neuro-
logical disorders, such as amyotrophic lateral sclerosis
(ALS), persons with severe physical disabilities can gradu-
ally lose control of speech muscles and limbs and, conse-
quently, the ability to communicate with their voice or with
conventional assistive devices.
Self-expression is funda-
mental for quality of life,
and lack of communication can
result in restrictions of participation, as defined by the
International Classification of Functioning, Disability and
By using gaze, or pupil size, eye trackers enable users to
communicate or control devices.
These systems require
only a short training period
and result in a low workload.
In a comparison between an eye tracker and a single switch
scanning system,
participants with ALS reported less
fatigue and a faster access when using the eye tracker. The
main difficulty in using eye trackers as an access technol-
ogy (AT), is the so-called Midas touch problem.
This refers
to the fact that gaze direction is not always related to the
focus of the attention, causing users to select a command
against their will.
People with ALS were involved only in a small number
of studies regarding the assessment of eye trackers.
Calvo et al
found significant improvement in the quality of
life of people with ALS after being provided with an eye
XXX10.1177/1545968315575611Neurorehabilitation and Neural RepairPasqualotto et al
Université Catholique de Louvain, Louvain-la-Neuve, Belgium
Eberhard Karls Universität, Tübingen, Germany
University of Perugia, Perugia, Italy
Sapienza Università di Roma, Rome, Italy
Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS), Venezia
Lido, Italy
Universität Würzburg, Würzburg, Germany
National Rehabilitation Center for Persons with Disabilities,
Tokorozawa, Japan
Corresponding Author:
Emanuele Pasqualotto, PhD, Université Catholique de Louvain, Avenue
Hippocrate 54, bte B1.54.09, 1200 Brussels, Belgium.
Usability and Workload of Access
Technology for People With Severe Motor
Impairment: A Comparison of Brain-
Computer Interfacing and Eye Tracking
Emanuele Pasqualotto, PhD
, Tamara Matuz, PhD
, Stefano Federici, PhD
Carolin A. Ruf, PhD
, Mathias Bartl
, Marta Olivetti Belardinelli, MA
Niels Birbaumer, PhD
, and Sebastian Halder, PhD
Background. Eye trackers are widely used among people with amyotrophic lateral sclerosis, and their benefits to quality
of life have been previously shown. On the contrary, Brain-computer interfaces (BCIs) are still quite a novel technology,
which also serves as an access technology for people with severe motor impairment. Objective. To compare a visual P300-
based BCI and an eye tracker in terms of information transfer rate (ITR), usability, and cognitive workload in users with
motor impairments. Methods. Each participant performed 3 spelling tasks, over 4 total sessions, using an Internet browser,
which was controlled by a spelling interface that was suitable for use with either the BCI or the eye tracker. At the end of
each session, participants evaluated usability and cognitive workload of the system. Results. ITR and System Usability Scale
(SUS) score were higher for the eye tracker (Wilcoxon signed-rank test: ITR T = 9, P = .016; SUS T = 12.50, P = .035).
Cognitive workload was higher for the BCI (T = 4; P = .003). Conclusions. Although BCIs could be potentially useful for
people with severe physical disabilities, we showed that the usability of BCIs based on the visual P300 remains inferior to
eye tracking. We suggest that future research on visual BCIs should use eye tracking–based control as a comparison to
evaluate performance or focus on nonvisual paradigms for persons who have lost gaze control.
BCI, brain-computer interface, eye tracking, usability, cognitive workload, assistive technology, ALS
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2 Neurorehabilitation and Neural Repair
tracker. The participants in the study were able to communi-
cate independently and rated the communication as easier,
faster, and less effortful than before. Ball et al
the acceptance, training, and extended use patterns of an
eye tracker in a group of 15 people with ALS. The capacity
of the users for social interactions increased considerably.
Indeed, the system was not only used for face-to-face com-
munication, but also for many other functions, such as
group communication (43%), phone calls (71%), e-mail
(79%), and Internet access (86%).
Independent of motor inputs, a brain-computer interface
(BCI) provides a direct connection between the brain and
any device capable of receiving brain signals. Most BCI
systems use electroencephalogram (EEG) signals and
require users to intentionally control specific features of
their own brain activity, such as slow cortical potentials or
the sensorimotor rhythm.
The P300 Speller
has been
successfully used by people with severe motor impair-
The P300 is an event-related potential, recorded
using EEG, evoked by a rare, task-relevant stimulus,
a latency between 200 and 700 ms, and is often related to
attention. P300 BCIs do not require users to learn to modu-
late their brain response.
In a typical P300 paradigm, a participant is presented
with a 6 × 6 alphanumeric matrix, where each row and each
column flashes randomly in a fixed interval, and the user
selects the desired character by focusing the attention on the
corresponding cell. This combined mechanism of focused
attention and random flashing makes the single matrix cell
a rare task-relevant stimulus eliciting the P300 peak
response. The P300 Speller has been adapted to control
to control real and virtual environments,
browse the Internet,
and to paint.
In a recent telephone survey of people with ALS,
Huggins et al
investigated the users’ opinions and priori-
ties on BCI design. Their study reports that the desired BCI
accuracy for people with ALS is at least 90%, but accura-
cies reported in the literature are usually lower. Moreover,
the expected spelling speed would be 15 to 19 letters per
minute, whereas in the published studies, it is only about 5
letters per minute.
Through a recent literature review, we have shown that
although there is a large amount of studies on BCIs, most of
them focus on methodological approaches, neglecting
usability aspects.
Most of the BCI studies, in fact, do not
consider that users often discard assistive technology after
only a few attempts and that personal factors (eg, mood,
motivation, belief, and predispositions) should be taken into
account because they can serve as both barriers and facilita-
tors in sustaining efficient use.
Although the effectiveness of BCIs in terms of character
selection is assessed in most studies, the efficiency and the
satisfaction from the users’ perspective are not always
addressed; however, they are part of a recent area of
Kleih et al
and Nijboer et al
explored the
effects of motivational factors on BCI performance.
Pasqualotto and colleagues
compared 2 prototypes of
BCIs in terms of usability and cognitive workload. Riccio et
investigated the influence of workload on the perfor-
mance of 2 P300-based BCI applications in healthy partici-
pants. Among these studies, only the study by Zickler et al
examined usability and cognitive workload in people with
severe disabilities, even though on a very limited sample.
Anyway, none of these studies compared BCIs with any
other existing AT.
It is our aim to provide a full usability assessment of a
P300-based BCI for controlling an Internet browser. To
accomplish this aim, we compared users’ performance and
usability scores using a P300 BCI and an eye tracking sys-
tem. More specifically, in a group of people with severe dis-
ability, we assessed and compared (1) the accuracy of
correct selections during 3 Internet tasks and (2) usability
indicators, such as control and cognitive workload, and
users’ satisfaction with both communication systems.
This study addresses the issue of whether and under
which conditions a BCI (specifically, the P300-BCI-based
Internet browser) could be a method of choice for users
with severe physical disabilities who still have residual con-
trol over some specific muscle groups and who could,
therefore, use conventional ATs. Furthermore, the study will
provide insights regarding which direction future BCI
research should follow in order to provide a viable alterna-
tive to conventional ATs.
We performed a comparison between the user’s experience
of controlling a BCI and an eye tracker, in a within-subject
design. Through 4 sessions of AT use (2 for the BCI and 2
for the eye tracker), the participants carried out 3 character
selection tasks, which represent common tasks that AT
users may perform when browsing the Internet. In each ses-
sion, participants used one of the ATs and were asked to
complete 2 questionnaires. The study was approved by the
Ethics Committee of the Medical Faculty of the University
of Tübingen and was performed in compliance with the
Code of Ethics of the World Medical Association
(Declaration of Helsinki).
Participants and Procedure
A total of 12 native German-speaking participants (4
women; mean age = 56.5 years; standard deviation =
±10.07) with severe motor impairment (11 affected by ALS,
and 1 affected by Duchenne muscular dystrophy; see Table
1), all naive to the AT assessed, were involved in the study.
All participants had home care assistance. Measurements
were performed in the participants’ homes.
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Pasqualotto et al 3
After obtaining informed consent, we made 4 weekly
appointments, depending on the participants’ availability.
The order of presentation of the technology was balanced
between participants. On average, including calibration,
BCI sessions lasted 4 hours, and eye tracker sessions 2
hours. This difference was because of the longer time
needed to prepare the EEG cap and BCI calibration and the
fixed amount of time required by the BCI for the selection
of characters. Letters selection was, in fact, constrained by
the time required by the Speller to run one, or more, full
cycles of random flashing of columns and rows, in contrast
to the eye tracker where the user could select at his/her own
In the first BCI session and in the first eye tracker ses-
sion, we administered the Amyotrophic Lateral Sclerosis
Functional Rating Scale–Revised (ALSFRS-R).
In each
session, participants were asked to complete 3 copy-spell-
ing tasks (as described below in the Task section) by using
an Internet browser, which was controlled by the BCI or by
the eye tracker. We used the information transfer rate (ITR)
to measure performance. At the end of each session, we
administered the System Usability Scale (SUS)
and the
National Aeronautics and Space Administration–Task Load
Index (NASA-TLX).
Brain-Computer Interface. We used an IBM Thinkpad laptop
to collect data, using the BCI2000 software.
All sessions
were recorded using an electrode cap (Easycap GmbH, Ger-
many) with 16 Ag/AgCl ring electrodes (F3, Fz, F4, T7, C3,
Cz, C4, T8, CP3, CP4, P3, Pz, P4, PO7, PO8, Oz) and
impedance held under 5 kΩ. The electrodes were connected
to a g.USBamp amplifier (g.tec OG, Austria) with a sam-
pling frequency of 256 Hz (bandpass: 0.1-30 Hz; notch:
48-52 Hz). Reference and ground were, respectively, on the
right and left mastoid. The intensifying of rows/columns of
the P300 Speller (see Figure 1) lasted for 62.5 ms, with an
interstimulus interval of 125 ms. The number of intensifica-
tion sequences varied per participant, according to their
calibration, performed at each of the 2 sessions. The cali-
bration consisted in the spelling of the same 2 words for
everyone (Apfelkuchen and Goldfisch in German—respec-
tively, apple pie and goldfish), consisting of 20 letters in
total. We set the number of intensification sequences to the
minimum number needed to reach 70% accuracy offline.
Table 1. Summary of Demographic and Clinical Status of the Participants.
Sex Age Diagnosis
Year of
Diagnosis ALSFRS-R
Degree of
Impairment Communication
(PEG) Ventilation
01 F 53 Spinal 2008 23 Moderate Verbal No No
02 M 55 Spinal 2003 43 Minor Verbal No No
03 F 50 Bulbar 2003 17 Moderate Keyboard text-
No Noninvasive
04 M 55 Spinal 1992 0 LIS Eye blink Yes Invasive
05 M 66 Spinal 1999 2 LIS Eye blink Yes No
06 M 71 Spinal 2005 11 Major Verbal No Noninvasive
07 M 55 Spinal 2006 23 Moderate Verbal No No
08 F 48 Spinal 2007 10 LIS Verbal Yes Noninvasive
09 M 70 Spinal 2008 18 Moderate Verbal No Noninvasive
10 F 54 Spinal 2003 0 LIS Chin joystick Yes Invasive
11 M 36 Duchenne 1976 7 LIS Verbal No Noninvasive
12 M 65 Bulbar 2009 32 Minor Verbal No No
Abbreviations: ALSFRS-R, Amyotrophic Lateral Sclerosis Functional Rating Scale–Revised; LIS, locked-in syndrome; PEG, percutaneous endoscopic
Degree of impairment categories were drawn according to Kübler and Birbaumer (2008).
Figure 1. The P300 matrix contains the complete alphabet
and part of the asterisk commands needed to select a double
code. Every row and column flashes randomly in a fixed interval.
By focusing the attention on a cell, the user can perform the
selection. In this frame, the third row is intensified.
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4 Neurorehabilitation and Neural Repair
The lowest number of sequences reached was 5 and the
highest 8.
Eye Tracker. We used a SeeTech Pro (HumanElektronik
GmbH, Germany) set with a 7 × 7 grid. The SeeTech Pro is
a binocular infrared system with a 32-sample/s camera. The
grid locks the gaze in a cell to obviate the lack of precision.
For character selection, we used a static matrix of letters
modeled on the graphical appearance of the P300 Speller.
Participants could select characters by gazing at the intended
target and closing their eyes for 1.5 s. The visual appearance
of the eye tracker interface was identical to the one used for
the BCI, except for the input modality. The calibration
phase, performed at both sessions, consisted in fixating 9
positions on the screen located in the corners, the center,
and the extremities on the horizontal and vertical middle
lines. The screen, for both the eye tracker and the BCI, was
located at around 50 cm from the participant.
The P300 Browser. For Internet navigation, we used a newer
version (see Figure 1) of the P300 Speller-based browser
described by Mugler et al.
When loading a page, the
browser automatically assigns an alphabetical code to rep-
resent the hyperlinks (eg, the character “A” or a combina-
tion of 2 characters such as “AB”). By means of the Speller,
the user can select the codes corresponding to a particular
hyperlink and thus explore the web pages.
The copy-spelling task is widely used in the BCI field.
The general idea behind this task is to provide the user with
a set of words or sentences to write with the communication
interface. In each session with the BCI or the eye tracker,
participants were asked to select a sequence of predefined
characters in the matrix, representing common Internet
tasks. Each participant performed the same task, with the
same instructions and words to spell. However, the codes
assigned by the browser to the links in the instructions were
not always the same. Participants were allowed to correct
errors, resulting in trials that could differ in length. The first
task consisted in checking the weather forecast by using a
search engine. The participants spelled the name of a
German magazine in the search bar of a search engine Web
site. After selecting the first result of the search, participants
were asked to select the weather section. Then, they had
time to observe the image of the forecast by selecting pause.
Finally, after unpausing they were asked to select the legend
at the bottom of the page, after scrolling the page. A mini-
mum of 15 character selections was required to accomplish
the task. The second task was a search in an online encyclo-
pedia. Starting from the encyclopedia’s main page, partici-
pants performed a search for the term brain (in German,
Gehirn). After checking the resulting page, participants
were asked to select the section about the human brain and
to scroll the page to the bottom. This task required a mini-
mum of 11 selections. The third task involved playing 2
songs on a Web site. Starting from the main page of a music
Web site, the participants performed a search for the term
Jazz. The result was a list of playable songs 30 s in length.
After selecting and then listening to the sixth song on the
list, they were asked to select the “Country” section and
then to listen to the first song. This task needed a minimum
of 14 total selections.
Performance. We used bits per minute (or ITR) to compare
the performance of the BCI and the eye tracker. Bit rate is a
standard measure for communication systems and repre-
sents the amount of information communicated per unit
time, depending on both speed and accuracy.
Based on
Pierce’s formula,
the bit rate is defined as follows:
=+ −−
loglog log
22 2
Here, N represents the number of possible selections in the
matrix and P the accuracy of character selection of the user.
Usability. We used the SUS to assess the usability of the sys-
tems. The SUS is a 10-item scale, with a global subjective
assessment of usability. It consists of 10 sentences with a
5-point Likert scale that ranges from 1 (strongly disagree)
to 5 (strongly agree). The SUS scale provides a score, rang-
ing from 0 to 100, that can be used to compare the usability.
Although, as also stated by the original author of the ques-
tionnaire, usability does not exist in an absolute sense, a
score of 70 has been suggested as the acceptable
Cognitive Workload. The NASA-TLX is a multiscale tool to
evaluate the subjective cognitive workload considering its
possible different sources.
The NASA-TLX consists of 6
scales (mental demands, physical demands, temporal
demands, performance, effort, and frustration level), rated
in 2 stages. In the first stage, the user assigns a value to each
scale. In the second stage, the user is provided with the 15
pairs obtained by combining the 6 scales, with the goal to
choose the scale more relevant to workload from each pair.
This procedure is used to assess the weight of each scale.
The ratings and weights are combined to obtain the final
score, ranging from 0 to 100, with 100 representing the
highest workload experienced by the participant.
Functional Status. To investigate the relationship between
the functional status and the performance and to monitor
potential changes in participants’ functionality, we assessed
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Pasqualotto et al 5
the functionality using the ALSFRS-R.
This scale implies
rating 12 items referring to different functions, such as
speech, swallowing, handwriting, and walking, on a 5-point
scale. The obtained score may range from 0 (most severe
impairment) to 48 (no impairment).
We performed the comparison between the BCI and the eye
tracker using a Wilcoxon signed-rank test, on the averaged
data of the 2 sessions. We used bits per minute and the
scores of SUS and NASA-TLX, as independent variables.
For each technology, we correlated the scores of the ques-
tionnaires and the demographic data with performance data
to investigate how person-related factors affect perfor-
mance. We used stepwise linear discriminant analysis to
classify the EEG signal.
Calibration was performed with
the P300 Classifier tool provided with BCI2000.
All participants were able to use both interfaces to accom-
plish the tasks (see Table 2). The mean ITR with the BCI
was 8.67 bits/min and with the eye tracker, 12.87 bits/min.
Thus, the Wilcoxon signed-rank test showed that the eye
tracker (median = 12.72) had a significantly higher ITR
than the BCI (median = 9.04; T = 9; P = .016, with an effect
size r = −0.68). The outcome of the SUS and the NASA-
TLX yielded similar results. The mean SUS score for the
BCI was 71.15, which according to Bangor et al
is right
above the acceptability threshold (in the third quartile),
whereas the score for the eye tracker was 78.54, which is
just beneath the lower boundary of the fourth quartile. The
direct comparison showed that the difference was signifi-
cant (eye tracker median = 80; BCI median = 71.25; T =
12.50; P = .035; r = −0.60). When using the NASA-TLX,
the absolute values are usually not considered a viable way
of describing the workload, and a comparison (eg, pre/post
measures, 2 different devices) is normally preferred. The
results of the NASA-TLX showed that the cognitive work-
load is higher for the BCI (median = 49.75) than for the eye
tracker (median = 33.53; T = 4; P = .003; r = −0.79).
The Spearman ρ analysis showed correlations between
performance, usability, and workload data with functional
status and disease duration. Age was not significant in our
comparison. The correlations revealed that the lower the
functional status of the participants, the lower their com-
munication rate, both using the BCI (r
= 0.640; P = .001)
and the eye tracker (r
= 0.430; P = .046; see Table 3).
Finally, results show that the longer the disease duration,
the lower the usability of a BCI (r
= −0.547; P = .008) and
the higher the cognitive workload of the BCI (r
= 0.544;
P = .009). We did not find this relation when considering
the eye tracker.
We performed an exploratory study with the aim of compar-
ing 2 access technologies designed for people with severe
motor impairment. Our comparison between these inter-
faces has shown that the eye tracker is a faster and more
accurate technology that allows users to communicate with
a higher ITR than the BCI. The performance measures used
in this study showed the advantages of using the eye tracker
as a communication device. This advantage in performance
matches the findings on the usability and cognitive work-
load of the 2 interfaces. Participants rated the eye tracker as
a more satisfying device and considered the BCI as a tech-
nology requiring more effort and that was more time-con-
suming than the eye tracker. Differences in usability may be
partially a result of the longer time required for the use of
the BCI, and it is known that time can affect the perceived
fatigue, as also pointed out in more recent findings.
Because this time is intrinsic to the way this technology
works, future work on BCIs should address the issue of the
effort required by the end-users. Refined technology, such
as dry and wireless EEG,
and shifts to a classical condi-
tioning paradigm
could enhance not only the perfor-
mance, but also help in reducing the perceived effort of
BCIs. It is interesting to note that with the BCI, disease
duration plays a role with usability and workload, whereas
age does not. This finding, not confirmed with the eye
Table 2. Summary of the BCI and ET Interface Mean
Scores and Standard Deviations for the SUS, the NASA-TLX
Questionnaire for the Cognitive Workload, and the Bits Per
Bits Per Minute SUS NASA-TLX
BCI 8.67 (3.43) 71.15 (11.31) 47.64 (14.87)
ET 12.87 (4.41) 78.54 (13.25) 32.72 (8.83)
Abbreviations: BCI, brain-computer interface; ET, eye tracking; SUS,
System Usability Scale; NASA-TLX, National Aeronautics and Space
Administration–Task Load Index.
Table 3. Summary of the Spearman ρ Correlations.
BCI Eye Tracker
Bits Per
Minute SUS
Bits Per
Minute SUS
ALSFRS-R 0.640** 0.280 −0.202 0.430* 0.241 −0.207
−0.332 −0.547* 0.544** −0.118 −0.328 0.291
Age 0.239 0.153 0.140 −0.217 −0.269 0.002
Abbreviations: BCI, brain-computer interface; SUS, System Usability Scale; NASA-
TLX, National Aeronautics and Space Administration–Task Load Index; ALSFRS-R,
Amyotrophic Lateral Sclerosis Functional Rating Scale–Revised.
*P < .05; **P < .01.
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6 Neurorehabilitation and Neural Repair
tracker, may be also explained by the longer time required
by BCIs. The relation between the functional status and per-
formance is a surprising finding. This result, found both
with the BCI and the eye tracker, seems to be contrary to
that of other studies,
although differences in the per-
formance measures and in the statistical tests should be
taken into account. Consequently, we cautiously abstain
from drawing strong conclusions based on this specific
Because the concept of usability is context related, our
findings should also be confirmed using the same method-
ology in contexts other than Internet use. Using different
control paradigms or classification methods may optimize
the BCI implementation we used, but we decided to evalu-
ate a well-established version of the paradigm for better
compatibility. Moreover, the eye tracker may profit from an
interface tailored specifically for eye tracking, whereas in
our study, it was used to control an interface made for BCIs.
It could also be interesting to investigate the usability of
invasive BCIs. As Hochberg et al
showed, people with
severe motor impairment can use intracortical neuronal
ensemble activity to achieve control, although rudimental,
of neuromotor prostheses. Despite the potential benefits of
a better signal, either because of restrictions on candidacy
or because of personal preferences, even when informed
about the advantages, a large number of patients do not
undergo the procedure.
Nevertheless, it is worth to mention
that the use of the P300 Speller in our implementation is
similar to the one used in previous noninvasive studies.
Although our study is based on a limited number of par-
ticipants in a specific context, we showed in a direct com-
parison that the use of the visual P300 might not be the first
choice as a communication channel for people with severe
physical disabilities. As suggested by our findings, when
users can rely on eye movements, they tend to consider the
eye tracker as a superior technology. As the literature sug-
gests, people with ALS can lose control of their eye move-
Moreover, Brunner et al
have recently shown that
in healthy individuals, the use of the visual P300 BCI may
be dependent on gaze direction. To overcome this issue,
new gaze-independent paradigms have been devel-
However, other studies on neuro-ophthalmic
abnormalities in people with ALS report retinal damage
and loss of visual acuity
associated with the course of the
disease. Considering the implications of our finding together
with the literature, we may conclude that when gaze control
is retained, people with ALS will choose to use the eye
tracker instead of the BCI, but when gaze and acuity are
lost, neither the eye tracker nor the visual BCI will work.
A possible solution to overcome this issue could be the
so-called hybrid BCI, which combines different brain fea-
tures with different data acquisition techniques, or even dif-
ferent non-BCI systems (such as electro-oculography or
electromyography). Hybrid BCIs can be used sequentially
or simultaneously, and in several studies, it has been proved
that they improve accuracy by focusing on the advantages
offered by the combined communication devices. For
example, if the user of an eye tracker has difficulties per-
forming eye blinks for selections and using dwell time gen-
erates too many errors, a BCI can be used to control
selections (brain switch).
Exploring different P300 BCI modalities, such as tac-
and auditory devices,
may be another viable
solution to overcome the issues of the visual P300. Only 1
study on the auditory P300 included clinically relevant end
Moreover, whereas in a single case study on a per-
son in locked-in syndrome (LIS) the authors reported prom-
ising results in the tactile modality,
in another case study
about the transition from LIS to complete LIS (CLIS), the
authors found no vibrotactile brain-evoked response.
Because of the inconclusive results, further research is
needed to determine the value of the tactile-haptic modality
for BCIs. Even though a delayed response in the auditory
areas has been reported in the literature,
we suggest that in
addition, the auditory modality should be further explored.
The present study highlighted that in certain conditions,
people with severe physical disabilities may prefer eye
trackers to visual BCIs, for their performance, usability, and
required cognitive effort. We suggest that future research in
BCIs should take into account these preferences and explore
modalities other than visual.
We would like to thank all the participants involved in this study.
We are very grateful to Humanelektronik GmbH for providing us
with one of their eye trackers and to Sven Körber (SirValUse
Consulting GmbH) for the German version of the System Usability
Scale. This study was carried out with the precious support of
Lasse Wiesinger, Anna-Antonia Pape, and Slavica Von Hartlieb
during the measurements. We are also grateful to the anonymous
reviewers for their suggestions as well as those of Dr Giulia
Liberati, which helped in improving the quality of the article.
Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect
to the research, authorship, and/or publication of this article.
The author(s) disclosed receipt of the following financial support
for the research, authorship, and/or publication of this article: This
study was partially funded by the Inter-University Centre for
Research on Cognitive Processing in Natural and Artificial
Systems (ECONA), the Werner Reichardt Centre for Integrative
Neuroscience (CIN) pool project 2009-10, the Deutsche
Forschungsgemeinschaft (DFG), and the European ICT Program
at Univ Catholique Louvain Bib on March 16, 2015nnr.sagepub.comDownloaded from
Pasqualotto et al 7
Project FP7-288566. SH received funding as international research
fellow from the Japan Society for the Promotion of Science (JSPS)
and the Alexander von Humboldt Foundation.
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... For instance, eye tracking technology can serve as an aid for severely impaired patients and re-enable them to participate and communicate in everyday life (e.g. Ball et al., 2010;Borgestig et al., 2016;Pasqualotto et al., 2015). As eye-tracking technology is becoming increasingly widespread, it is also used in everyday applications (Hyrskykari et al., 2005;Majaranta & Bulling, 2014). ...
... First, our results can form the basis for deeper insights into sense of agency for eye movements, which in turn can be helpful in the development of eyetracking applications. This technology plays a vital role for severely disabled patients in communication and participation in everyday life (e.g., Ball et al., 2010;Borgestig et al., 2016;Pasqualotto et al., 2015) and is being integrated into an increasing number of everyday life applications (e.g., Hyrskykari et al., 2005;Majaranta & Bulling, 2014). ...
... In the last decade, assistive technologies were developed to help people with severe disabilities accomplish their daily tasks, like operating system control. Different sources of information are applied to control the personal computer using, for example, the eyetracking devices [1] and cost-effect brain-computer interface (BCI) [2]. The eye-trackers devices consist of infrared LEDs and one or more infrared cameras capturing the reflection of the infrared light off of the user's eyes and an image processing algorithms applied to determine where the user is looking on a screen. ...
... The eye-trackers devices consist of infrared LEDs and one or more infrared cameras capturing the reflection of the infrared light off of the user's eyes and an image processing algorithms applied to determine where the user is looking on a screen. The main difficulty of using such devices as an access technology is the so-called Midas touch problem because gaze direction is not always related to the focus of the attention, causing users to select a command against their will [1]. Brain-computer interface (BCI) is an alternative applied to control the personal computer by people with severe disabilities. ...
Full-text available
There are many applications controlled by the brain signals to bridge the gap in the digital divide between the disabled and the non-disabled people. The deployment of novel assistive technologies using brain-computer interface (BCI) will go a long way toward achieving this lofty goal, especially after the successes demonstrated by these technologies in the daily life of people with severe disabilities. This paper contributes in this direction by proposing an integrated framework to control the operating system functionalities using Electroencephalography signals. Different signal processing algorithms were applied to remove artifacts, extract features, and classify trials. The proposed approach includes different classification algorithms dedicated to detecting the P300 responses efficiently. The predicted commands passed through a socket to the API system, permitting the control of the operating system functionalities. The proposed system outperformed those obtained by the winners of the BCI competition and reached an accuracy average of 94.5% according to the offline approach. The framework was evaluated according to the online process and achieved an excellent accuracy attaining 97% for some users but not less than 90% for others. The suggested framework enhances the information accessibility for people with severe disabilities and helps them perform their daily tasks efficiently. It permits the interaction between the user and personal computers through the brain signals without any muscular efforts.
... Blink-To-Live follows an Indirect-eye contact tracking approach called a computer-vision-based eye-tracking approach. The comparison considered the results reported from different studies that evaluate different eye-tracking approaches for ALS patient communication 15,19,35,57,58 . The Blink-To-Live system does not rely on special hardware devices or sensors to initiate the patient's communication. ...
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Eye-based communication languages such as Blink-To-Speak play a key role in expressing the needs and emotions of patients with motor neuron disorders. Most invented eye-based tracking systems are complex and not affordable in low-income countries. Blink-To-Live is an eye-tracking system based on a modified Blink-To-Speak language and computer vision for patients with speech impairments. A mobile phone camera tracks the patient’s eyes by sending real-time video frames to computer vision modules for facial landmarks detection, eye identification and tracking. There are four defined key alphabets in the Blink-To-Live eye-based communication language: Left, Right, Up, and Blink. These eye gestures encode more than 60 daily life commands expressed by a sequence of three eye movement states. Once the eye gestures encoded sentences are generated, the translation module will display the phrases in the patient’s native speech on the phone screen, and the synthesized voice can be heard. A prototype of the Blink-To-Live system is evaluated using normal cases with different demographic characteristics. Unlike the other sensor-based eye-tracking systems, Blink-To-Live is simple, flexible, and cost-efficient, with no dependency on specific software or hardware requirements. The software and its source are available from the GitHub repository (
... In addition, a study reported that the conventional control interfaces such as mouse and buttons scored SUS of 84 on average with elderly participants [38]. Given that most of the BCI studies focus on methodological aspects while neglecting usability aspects [39], enhancing the usability of the proposed HA system could be an interesting research topic that has to be pursued in the future study. The usability of the proposed system may be enhanced by i) employing control functions preferred by participants via a pre-experimental survey, or ii) adding functions such as communication as in [38]. ...
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Over the past decades, brain-computer interfaces (BCIs) have been developed to provide individuals with an alternative communication channel toward external environment. Although the primary target users of BCI technologies include the disabled or the elderly, most newly developed BCI applications have been tested with young, healthy people. In the present study, we developed an online home appliance control system using a steady-state visual evoked potential (SSVEP)-based BCI with visual stimulation presented in an augmented reality (AR) environment and electrooculogram (EOG)-based eye tracker. The performance and usability of the system were evaluated for individuals aged over 65. The participants turned on the AR-based home automation system using an eye-blink-based switch, and selected devices to control with three different methods depending on the user’s preference. In the online experiment, all 13 participants successfully completed the designated tasks to control five home appliances using the proposed system, and the system usability scale exceeded 70. Furthermore, the BCI performance of the proposed online home appliance control system surpassed the best results of previously reported BCI systems for the elderly.
... The transition to instrumental communication, such as the Alphabet Board, should preserve the patient's ability to communicate to the greatest extent possible, prior to the onset of "locked-in" syndrome. With the advancement of research and development, eye-tracking technology [2] has come into wide use, and the detection of intent using a brain computer interface is another area where early practical application is anticipated [3,4]. However, malfunctions in communication always threaten the quality of life of patients. ...
Full-text available
Decisions regarding invasive ventilation with tracheostomy (TIV) in patients with amyotrophic lateral sclerosis (ALS) involve serious ethical issues. Cultural differences in the attitudes of patients, caregivers, and physicians toward TIV initiation and withdrawal decisions have been analyzed based on a narrative review approach, comparing the situation between Japan and the U.S. Three main issues were identified regarding the implementation of TIV. The first is the lack of Advance Care Planning. Second, some patients may choose TIV based on the wishes of their physicians or caregivers, even if the patients themselves do not want TIV in the Japanese context. Third is the influence of patient associations, which advocate for the protection of patients’ rights. Next, this study identifies the following issues related to TIV discontinuation. The main concern here is cultural differences in legislation and ethical intuitions regarding the discontinuation of TIV. The treatment guidelines for patients with ALS advise physicians to reassure patients that TIV can be withdrawn at any point. However, TIV withdrawal is not explicitly discussed in Japan. Moreover, Japanese ALS treatment guidelines state that ventilation withdrawal is currently impossible, due to a lack of legal support. Most Japanese physicians have told patients that they are not allowed to stop ventilation via such a request. Unlike in the U.S., withholding and withdrawing ventilators are not ethically equivalent in Japan. In conclusion, the decision-making process regarding TIV is difficult, not only for the patients and caregivers, but also for physicians. Even if patients are legally entitled to refuse unwanted treatment, there have been cases in which Japanese physicians have felt an ethical dilemma in stopping TIV for patients with ALS. However, few studies have investigated in detail why physicians oppose the patient’s right to discontinue TIV in Japan.
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Individuals with amyotrophic lateral sclerosis (ALS) frequently develop speech and communication problems in the course of their disease. Currently available augmentative and alternative communication technologies do not present a solution for many people with advanced ALS, because these devices depend on residual and reliable motor activity. Brain–computer interfaces (BCIs) use neural signals for computer control and may allow people with late-stage ALS to communicate even when conventional technology falls short. Recent years have witnessed fast progression in the development and validation of implanted BCIs, which place neural signal recording electrodes in or on the cortex. Eventual widespread clinical application of implanted BCIs as an assistive communication technology for people with ALS will have significant consequences for their daily life, as well as for the clinical management of the disease, among others because of the potential interaction between the BCI and other procedures people with ALS undergo, such as tracheostomy. This article aims to facilitate responsible real-world implementation of implanted BCIs. We review the state of the art of research on implanted BCIs for communication, as well as the medical and ethical implications of the clinical application of this technology. We conclude that the contribution of all BCI stakeholders, including clinicians of the various ALS-related disciplines, will be needed to develop procedures for, and shape the process of, the responsible clinical application of implanted BCIs.
Purpose: Augmentative and alternative communication (AAC) systems are important to support communication for individuals with complex communication needs. A recent addition to AAC system options is the brain-computer interface (BCI). This study aimed to compare the clinical application of the P300 speller BCI with two more common AAC systems, the EyeLink board, and an eye-tracking camera. Method: Ten participants without communication impairment (18-35 years of age) used each of the three AAC systems to spell three-letter words in one session. Accuracy and speed of letter selection were measured, and questionnaires were administered to evaluate usability, cognitive workload, and user preferences. Results: The results showed that the BCI was significantly less accurate, slower, and with lower usability and higher cognitive workload compared to the eye-tracking camera and EyeLink board. Participants rated the eye-tracking camera as the most favorable AAC system on all measures. Conclusions: The results demonstrated that while the P300 speller BCI was usable by most participants, it did not function as well as the eye-tracking camera and EyeLink board. The clinical use of the BCI is, therefore, currently difficult to justify for most individuals, particularly when considering the substantial cost and setup resourcing needed. Supplemental material:
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page:423 Big Data Analytics for Large Scale Wireless Body Area Networks; Challenges, and Applications
Conference Paper
In recent years through advances in computing methods and hardware it has become easier to solve machine learning and signal processing problems than previous decades. This generated extensive interest in EEG-based Brain Computer Interfaces (EEG-BCI) that could possibly be applied to various assistive technologies that can gain from the hand-free and individual thought translation aspect of this field. Having saud that, most of the research has been at the proof-of-concept stage, rather than at a more practical one. Consequently, there have been few advances in technologies that allow individuals with severely impaired motor systems (humans with Multiple Schlerosis, Amyotrophic Lateral Schlerosis, etc.) to navigate spatially in a simulated 2D or 3D environment. With newer technologies and growing trends of automation and application of artificial intelligence we face newer challenges to bring those newer technologies to the ever-growing diverse population. However, no one has recently investigated the general trends in various aspects of interface design BCI for web applications. In this study, we examined advances in EEG-BCI research over the last decade with the aim of investigating the latest trends in EEG-based web interface design application. In this article, we investigated the number of published BCI publications for each like control mechanism.
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The purpose of this study was to describe a group of individuals with amyotrophic lateral sclerosis training and using the Eye-gaze Response Interface Computer Aid (ERICA) with Type & Talk or LifeMate 1.1 communication software. Fifteen people with ALS participated in the study, and all but one successfully used the ERICA as his or her primary communication device. The sole participant who discontinued use experienced the onset of impaired eyelid control during training. Results indicate that the ERICA was used to support a number of different communication functions, such as face-to-face interaction (100%), group communication (43%), phone calls (71%), e-mail (79%), and Internet access (86%). In an effort to optimize eye-gaze tracking to support communication, a number of environmental, positioning, and calibration adjustments are reported.
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Brain-computer interfaces (BCIs) can serve as muscle independent communication aids. Persons, who are unable to control their eye muscles (e.g., in the completely locked-in state) or have severe visual impairments for other reasons, need BCI systems that do not rely on the visual modality. For this reason, BCIs that employ auditory stimuli were suggested. In this study, a multiclass BCI spelling system was implemented that uses animal voices with directional cues to code rows and columns of a letter matrix. To reveal possible training effects with the system, 11 healthy participants performed spelling tasks on 2 consecutive days. In a second step, the system was tested by a participant with amyotrophic lateral sclerosis (ALS) in two sessions. In the first session, healthy participants spelled with an average accuracy of 76% (3.29 bits/min) that increased to 90% (4.23 bits/min) on the second day. Spelling accuracy by the participant with ALS was 20% in the first and 47% in the second session. The results indicate a strong training effect for both the healthy participants and the participant with ALS. While healthy participants reached high accuracies in the first session and second session, accuracies for the participant with ALS were not sufficient for satisfactory communication in both sessions. More training sessions might be needed to improve spelling accuracies. The study demonstrated the feasibility of the auditory BCI with healthy users and stresses the importance of training with auditory multiclass BCIs, especially for potential end-users of BCI with disease.
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One of the principal application areas for brain-computer interface (BCI) technology is augmentative and alternative communication (AAC), typically used by people with severe speech and physical disabilities (SSPI). Existing word- and phrase-based AAC solutions that employ BCIs that utilize electroencephalography (EEG) are sometimes supplemented by icons. Icon-based BCI systems that use binary signaling methods, such as P300 detection, combine hierarchical layouts with some form of scanning. The rapid serial visual presentation (RSVP) IconMessenger combines P300 signal detection with the icon-based semantic message construction system of iconCHAT. Language models are incorporated in the inference engine and some modifications that facilitate the use of RSVP were performed such as icon semantic role order selection and the tight fusion of language evidence and EEG evidence. The results of a study conducted with 10 healthy participants suggest that the system has potential as an AAC system in real-time typing applications. Ability to construct messages with reduced physical movement demands due to RSVP and increased message construction speed and accuracy due to the incorporation of an icon-based language model in the inference process are the significant findings of this study.
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In order to enable communication through a brain-computer interface (BCI), it is necessary to discriminate between distinct brain responses. As a first step, we probed the possibility to discriminate between affirmative (“yes”) and negative (“no”) responses using a semantic classical conditioning paradigm, within an fMRI setting. Subjects were presented with congruent and incongruent word-pairs as conditioned stimuli (CS), respectively eliciting affirmative and negative responses. Incongruent word-pairs were associated to an unpleasant unconditioned stimulus (scream, US1) and congruent word-pairs were associated to a pleasant unconditioned stimulus (baby-laughter, US2), in order to elicit emotional conditioned responses (CR). The aim was to discriminate between affirmative and negative responses, enabled by their association with the positive and negative affective stimuli. In the late acquisition phase, when the US were not present anymore, there was a strong significant differential activation for incongruent and congruent word-pairs in a cluster comprising the left insula and the inferior frontal triangularis. This association was not found in the habituation phase. These results suggest that the difference in affirmative and negative brain responses was established as an effect of conditioning, allowing to further investigate the possibility of using this paradigm for a binary choice BCI.
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Amyotrophic lateral sclerosis (ALS) is characterized by neuro-ophthalmological abnormalities beyond disturbed oculomotor control such as decreased visual acuity and disturbed visual evoked potentials. Here we report retinal alterations in a cohort of 24 patients with clinically definite (n = 20) or probable (n = 4) ALS as compared to matched controls. High-resolution spectral domain optical coherence tomography with retinal segmentation revealed a subtle reduction in the macular thickness and the retinal nerve fiber layer (RNFL) as well as a marked thinning of the inner nuclear layer (INL). Our data indicate an unprecedented retinal damage pattern and suggest neurodegeneration beyond the motor system in this disease.
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Increasing number of research activities and different types of studies in brain-computer interface (BCI) systems show potential in this young research area. Research teams have studied features of different data acquisition techniques, brain activity patterns, feature extraction techniques, methods of classifications, and many other aspects of a BCI system. However, conventional BCIs have not become totally applicable, due to the lack of high accuracy, reliability, low information transfer rate, and user acceptability. A new approach to create a more reliable BCI that takes advantage of each system is to combine two or more BCI systems with different brain activity patterns or different input signal sources. This type of BCI, called hybrid BCI, may reduce disadvantages of each conventional BCI system. In addition, hybrid BCIs may create more applications and possibly increase the accuracy and the information transfer rate. However, the type of BCIs and their combinations should be considered carefully. In this paper, after introducing several types of BCIs and their combinations, we review and discuss hybrid BCIs, different possibilities to combine them, and their advantages and disadvantages.
The study aimed at revealing electrophysiological indicators of mental workload and fatigue during prolonged usage of a P300 brain-computer interface (BCI). Mental workload was experimentally manipulated with dichotic listening tasks. Medium and high workload conditions alternated. Behavioral measures confirmed that the manipulation of mental workload was successful. Reduced P300 amplitude was found for the high workload condition. Along with lower performance and an increase in the subjective level of fatigue, an increase of power in the alpha band was found for the last as compared to the first run of both conditions. The study confirms that a combination of signals derived from the time and frequency domain of the electroencephalogram is promising for the online detection of workload and fatigue. It also demonstrates that satisfactory accuracies can be achieved by healthy participants with the P300 speller, despite constant distraction and when pursuing the task for a long time.
For many years the reestablishment of communication for people with severe motor paralysis has been in the focus of brain-computer interface (BCI) research. Recently applications for entertainment have also been developed. Brain Painting allows the user creative expression through painting pictures. The second, revised prototype of the BCI Brain Painting application was evaluated in its target function - free painting - and compared to the P300 spelling application by four end users with severe disabilities. According to the International Organization for Standardization (ISO), usability was evaluated in terms of effectiveness (accuracy), efficiency (information transfer rate (ITR)), utility metric, subjective workload (National Aeronautics and Space Administration Task Load Index (NASA TLX)) and user satisfaction (Quebec User Evaluation of Satisfaction with assistive Technology (QUEST) 2.0 and Assistive Technology Device Predisposition Assessment (ATD PA), Device Form). The results revealed high performance levels (M≥80% accuracy) in the free painting and the copy painting conditions, ITRs (4.47-6.65bits/min) comparable to other P300 applications and only low to moderate workload levels (5-49 of 100), thereby proving that the complex task of free painting did neither impair performance nor impose insurmountable workload. Users were satisfied with the BCI Brain Painting application. Main obstacles for use in daily life were the system operability and the EEG cap, particularly the need of extensive support for adjustment. The P300 Brain Painting application can be operated with high effectiveness and efficiency. End users with severe motor paralysis would like to use the application in daily life. User-friendliness, specifically ease of use, is a mandatory necessity when bringing BCI to end users. Early and active involvement of users and iterative user-centered evaluation enable developers to work toward this goal.