Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_6027_Библиотеки_им_академика_М_И_Перельмана.pdf
15 Getting Clean Data: Artifacts and How to Prevent Them 189
Fig. 15.7 EEG signal distortion caused by higher impedance values, manifesting in increased
sensitivity to high-frequency interference. Electrode and cable movements due to whole body
movement introduce random waves of higher amplitudes, which are further masked by 50 Hz
line noise. A few EEG channels with these described artifacts are marked
15.5.4 Movement Artifacts
Although commonly categorized as physiological artifacts, movement-related disturbances often involve a combination of physiological (e.g., EMG) and technical
factors, such as electrode, cap, or cable movement and displacement. This double
impact makes EEG recordings particularly challenging during activities involving
considerable motion, such as walking, dancing, running, or cycling.
15.5.5 Body/Head Movements
As noted previously, different types of body movements produce corresponding
changes in the EEG signal, as illustrated in Fig. 15.8. The intensity and acceleration
movement play a critical role in artifact severity.
of
For example, running on a treadmill can produce rhythmic artifacts in the EEG
signa
l (Gwin et al., 2010). The artifact is often caused by the repetitive, slight lifting
of
electrodes from the skin, which dist urbs the contact between the skin and the
conductive gel.
It is generally recommended to prioritize thorough preparation of the electrode
and to ensure the secure placement of the caps, nets, headsets, and electrodes.
cap
The precise placement and stable attachment of EEG caps and electrodes form the
foundation for all EEG recording scenarios.
190 D. Kadlec et al.
Fig. 15.8 Regular bumps in EEG recordings during running reflect head motion-induced artifacts,
with their amplitude and frequency closely tied to the intensity and acceleration of movement.
Channels are arranged from frontal to posterior regions, progressing from the left to the right
hemisphere. The artifact is especially visible in the second half of the window on the frontal
electrodes
15.5.6 Cable Movement Artifacts
Artifacts caused by cable motion are reflected in the EEG at the frequency of the
cable’s swinging and introduce oscillations that can overlap with the EEG bandwidth of interest. Cable movement can also be mechanically transferred to the
electrodes themselves, as illustrated in the following picture (see Fig. 15.9). Such
s are more visible in passive electrode and dry electrode technology systems,
artifact
where mechanical stability and skin contact are more susceptible to disruption.
15.6 Artifacts in Advanced Applications and Multi-modal Recordings
Some special applications give rise to specific artifacts in addition to those commonly seen in lab environments. It’s beyond the scope of this chapter to cover all of
them in detail; we provide some examples and some references for further reading.
15.6.1 EEG and Functional MRI
In EEG-fMRI, the EEG system is exposed to strong magnetic fields, which can cause
artifacts in the EEG data. These artifacts originate from electromagnetic induction,
15 Getting Clean Data: Artifacts and How to Prevent Them 191
Fig. 15.9 Cable movement artifacts, compounded by 50 Hz line noise, often result from higher
electrode impedance. Mechanical disturbances, like vibrations, tugging, or loose connections, can
introduce voltage shifts
where changing magnetic fields induce voltages in the EEG electrodes and leads,
according to Faraday’s law, for more details see Chap. 33: Combining EEG and
fMRI.
The most prominent and unavoidable artifact is the gradient artifact caused by
rapid magnetic gradient switching used for spatial encoding in MRI. The artifact
appears in large, periodic, and high-amplitude oscillations that reach thousands of
microvolts and completely overlay the EEG signal (Chowdhury et al.,
2019). The
previously mentioned ECG-related artifacts become more visible in the MR environment and can affect all channels. The cardio-ballistic artifact is prominent in
magnetic fields. It is caused by a combination of subtle head and scalp movements,
as well as blood flow in synchrony with the cardiac pulse. In addition to well-known
sources of interference, other forms of motion can significantly contribute to artifacts
us E
in the EEG signal, particularly during simultaneo
instance,
spont
aneous
head
movements alter the position of electrodes within the
EG-fMRI recordings. For
magnetic field, leading to changes in the signal.
Moreover, vibrations can also be problematic in the MR environment. These arise
from several sources, like the scanner’s vibration during sequences, cold heads
associated with the helium pump cooling the MR scanner’s superconducting magnets, or the ventilation system. Good preparation and pilot testing are key to
minimizing the effects of the MR environment on your EEG data.
192 D. Kadlec et al.
15.6.2 EEG and Non-invasive Brain Stimulation
It is becoming increasingly common to measure EEG during brain stimulation. The
stimulation devices can induce artifacts in EEG data. For example, when recording
EEG with concurrent TMS pulses, considerable spikes in the EEG occur, lasting for
a few milliseconds until the signal recovers to baseline (Wischnewski et al.,
Electrical stimulation can induce a current artifact in the EEG data. The most
comm
on forms of stimulation are tDCS (transcranial direct current stimulation),
tACS (transcran ial alternating current stimulation), and ECT (electroconvulsive
therapy). These electrical artifacts exhibit DC voltage shifts that scale with the
current intensity during tDCS. With tACS, a dominant oscillatory artifact, with
amplitudes often several orders higher than the EEG spikes (Feher & Morishima,
2016). This application is described in more detail in Chap. 31: Combining EEG and
Transcra
causi
monly recorded only before and after stimulation, with the EEG cap or net often
removed entirely during the procedure.
nial Brain Stimulation.
ECT typically produces massive voltage spikes during the stimulation, often
ng signal saturation or flatlining in EEG channels. As a result, EEG is com-
2024).
15.7 Optimizing the EEG Recording Quality
A clean EEG signal allows the researcher to analyze and process true brain activity,
leading to reliable, accurate, and meaningful interpretations. An artifact-polluted
EEG will obscure the brain activity signal, which can lead to avoidable artifact
correction processing and filtering steps and difficulties in interpreting the results
appropriately. It is worth considering that artifact attenuation techniques can also
influence your signal of interest and unnecessary processing steps should be
avoided. Therefore, recording clean da ta by preventing artifacts in the first place is
always a priority. However, some artifacts– such as eye blinks are often unavoidable,
and an appropriate artifact handling strategy should be implemented. Below we
provide some tips for how to record a clean EEG signal. For tips on pre-processing
steps for removing unavoidable artifacts, such as eye blinks, refer to Chap.
Pre-pro
cessing and Artifact Handling.
17: EEG
15.7.1 Focus on the Cap Preparation
Select an EEG cap or net that fits the participant properly. A well-fitting cap ensures
stable EEG signal quality over the course of recordings and provides a comfortable
experience for the participant.
15 Getting Clean Data: Artifacts and How to Prevent Them 193
After applying the EEG cap, net, or headset, aim to achieve impedance levels
appropriate for the specific electrode technology in use. Elevated electrode impedance can significantly degrade data quality and signal fidelity (Kappenman & Luck,
2010).
. For standard passive electrodes, it is generally recommended that impedance
values
remain below 10 kOhm to ensure optimal signal quality.
. With advanced active electrodes, impedance values can exceed 20 kOhm without
omising the signal clarity.
compr
. Dry and sponge-based electrodes typically operate at higher impedance levels.
While
they offer faster preparation and more convenience, these are more vul-
nerable to signal artifacts.
That said, the acceptable impedance level also depends on the recording environm
ent. In low-noise environments, EEG recordings may tolerate higher electrode
impedance without compromising the signal quality.
In addition to the impedance measurement, you should check the signal quality.
fact, some systems do not provide an impedance measurement mode, and the
In
electrodes’ contact quality needs to be determined according to the signal during the
monitoring mode, based on waveform stability and noise characteristics.
15.7.2 Optimi ze the Recording Environment
Once the cap preparation is complete, ensure the recording environment is set up for
the best EEG data collection. The general recording environment should be optimized during pilot testing but there are some things you should pay attention to for
each recording to ensure good, clean data. For detailed guidance on lab setup and
environmental conside rations, see Chap.
Collec
tion.
Here are key steps to follow:
. Ensure the participant is seated comfortably, with proper back and head support if
possible. Adjust armrests, distance to keyboards, response pads, monitor, or any
other equipment involved in the study.
. Verify that all cables are securely routed and allow the participant sufficient
m of movement.
freedo
. Use strain reliefs for cables and adjust the amplifier’s position as needed to
minim
ize tugging or tension. Avoid any squeezing of the cables.
. Turn off or unplug any unnecessary electronic devices (e.g., mobile phones,
routers and devices, power strips, etc.) to reduce electromagnetic
Wi-Fi
interference.
. Keep electrical equipment as far away from the participant as possible.
. Guide the
displaying the EEG signal in real time to illustrate the influences on the signal.
participant through simple tasks such as eye blinking. Consider
16: Practical Aspects of EEG Data
194 D. Kadlec et al.
15.7.3 During the Recording
Cautiously observing the participant during data acquisition and making notes can
save you or the data analyst some time in interpreting and explaining the artifact
interferences.
. Closely monitor the signal stream, and the participant’s behavior.
. Use online annotations in the recordings software to document any uncommon
artifact
. Ask for the participant’s feedback during breaks—are they comfortable, are they
becom
. Adjust the position of the participant if required.
. Instruct the participants to relax during the breaks if needed.
. Keep detailed notes in your lab log, including any observations or deviations
from
or behavior.
ing fatigued?
the standard procedure.
15.7.4 Post Recordings
On completion of the EEG session disconnect the participant from the system and
carefully remove the electrode cap or net from their head. This marks the start of
post-session procedures and preparation for the next recordings.
. Ask for participant’s feedback—is there anything you can act on to reduce
artifact
s in subseq uent sessions?
. Maintaining your equipment well ensures proper functioning and reduces the
likelih
ood of artifacts due to, e.g., electrode degradation. Be sure to:
– Clean the electrode caps/nets or headsets according to the manufacturer’s
ions.
instruct
– Perform maintenance checks as specified by the manufacturer.
– Store the equipment, especially the EEG caps and electrodes, according to the
manuf
acturer’s guidelines.
– Inspect the recorded EEG data and note down especially artifacts of technical
e.
natur
– Check the equipment (i.e., electrode surfaces, cables, and connectors)
accordi
ng to the notes.
Most EEG
support to help optimize lab setup. Utilizing these resources can enhance signal
quality and minimize artifacts. Support teams can also assist with setup, troubleshooting, recommend best practices, and apply system-specific adjustments. So,
check whether your EEG system’s manufacturer offers this service.
system vendors provide dedicated materials, documentation, and
15 Getting Clean Data: Artifacts and How to Prevent Them 195
15.8 Conclusion
This chapter provided a comprehensive overview of common EEG artifacts,
explaining both their nature and sources, which is critical for accurate identifi cation
and inte rpretation of the EEG signal. For most arti fact types, practical solutions were
offered to help prevent, reduce, or correct interferences. Being aware of these
artifacts is crucial for ensuring optimal data quality, as it enables EEG researchers
to take appropriate action, whether through preventive measures such as pilot testing
or real-time adjustments during an experiment (e.g., addressing signal loss or
saturation). While some artifacts are unavoidable, their impact can often be reduced
through careful planning, lab setup, and participant preparation, including the use of
offline processing strategies tailored to the specific challenges anticipated in the
study.
References
Amin, U., Nascimento, F. A., Karakis, I., Schomer, D., & Benbadis, S. R. (2023). Normal variants
and artifacts: Importance in EEG interpretation. Epileptic Disorders, 25(5), 591–648.
doi.org/10.1002/epd2.20040. Epub 2023 Jul 27. PMID: 36938895.
Chowdhury, M. E. H., Khandakar, A., Mullinger, K. J., Al-Emadi, N., & Bowtell, R. (2019).
Simultaneous
gradient artifact. Frontiers in Neuroscience, 13, 690. https://doi.org/10.3389/fnins.2019.00690
Fehér, K. D., & Morishima, Y. (2016). Concurrent electroencephalography recording during
transcranial
e53527.
Gwin, J. T., Gramann, K., Makeig, S., & Ferris, D. P. (2010). Removal of movement artifact from
high-density
3526–3534.
PMCID:
Kappenman, E. S., & Luck, S. J. (2010). The effects of electrode impedance on data quality and
statistical
1111/j.1469-8986.2010.01009.x. Epub 2010 Mar 29. PMID: 20374541; PMCID:
PMC2902592.
Lins, O. G., Picton, T. W., Berg, P., & Scherg, M. (1993). Ocular artifacts in EEG and event-related
potentials
BF01234127
Luck, S. J., Stewart, A. X., Simmons, A. M., & Rhemtulla, M. (2021). Standardized measurement
error: A universal metric of data quality for averaged event-related potentials. Psychophysiol-
ogy, 58(6), e13793.
PMCID:
Matsuo, F., Peters, J. F., & Reilly, E. L. (1975). Electrical phenomena associated with movements
of
the eyelid. Electroencephalography and Clinical Neurophysiology, 38(5), 507–511. https://
doi.org/10.1016/0013-4694(75)90191-1. PMID: 50174.
Wischnewski, M.,
P. E., & Opitz, A. (2024). Real-time TMS-EEG for brain state-controlled research and precision
treatment: A narrative review and guide. Journal of Neural Engineering, 21(6), 061001.
doi.org/10.1088/1741-2552/ad8a8e. PMID: 39442548; PMCID: PMC11528152.
EEG-fMRI: Evaluating the effect of the EEG cap-cabling configuration on the
alternating current stimulation (tACS). Journal of Visualized Experiments, 107,
https://doi.org/10.3791/53527. PMID: 26862814; PMCID: PMC4828151.
EEG recorded during walking and running. Journal of Neurophysiology, 103(6),
https://doi.org/10.1152/jn.00105.2010. Epub 2010 Apr 21. PMID: 20410364;
PMC3774587.
significance in ERP recordings. Psychophysiology, 47(5), 888–904. https://doi.org/10.
I: Scalp topography. Brain Topography, 6(1), 51–63. https://doi.org/10.1007/
https://doi.org/10.1111/psyp.13793. Epub 2021 Mar 29. PMID: 33782996;
PMC8169536.
Shirinpour, S., Alekseichuk, I., Lapid, M. I., Nahas, Z., Lim, K. O., Croarkin,
https://
https://
Chapter 16
Practical Aspects of EEG Data Acquisition
Paulo Rodrigo Bazán
Abstract How your lab is set up and how you prepare your participant for the
ment can have an impact on the quality of your EEG recording. In this chapter
experi
we provide tips and tricks regarding the infrastructure and equipment organization in
your lab, as well as data acquisition optimization in different EEG setups. Our
recommendations stand on four pillars: signal quality, experimental control, operational efficiency, and safety. Both stationar y and mobile EEG setups are covered. We
focus on examples of different electrode technologies and on considerations for
special populations, using children as an example, to provide some guidelines that
you can follow in your daily research work.
Keywords EEG data acquisition · EEG laboratory setup · Participant preparation ·
Signal
quality optimization · Experimental control · Data acquisition efficiency ·
EEG Safety · Mobile EEG · Stationary EEG · EEG guidelines
16.1 Introduction
It can be challenging to set up an EEG lab or implement a new EEG study. To help
you achieve such goals, we will first provide advice on the lab infrastructure,
equipment position, and procedures. Then we will discuss practical aspects of data
acquisition using examples of specific EEG setups. Our aim is to maximize the
following:
. Signal quality—We want to make
interest, which is the brain activity related to our experimental task. However, the
measured signal can also include other effects, such as brain activity unrelated to
the task, other physiological activity, and signals from other sources (not directly
from the participant). Therefore, it is very important to reduce the effects of these
P. R. Bazán (✉)
Brain Products GmbH, Gilching, Germany
e-mail:
paulo-rodrigo.bazan@brainproducts.com
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2026
T.
Warbrick (ed.), The EEG Handbook,
https://doi.org/10.1007/978-3-032-20450-9_16
sure that we can properly measure the signal of
197
198 P. R. Bazán
sources of noise (for details on artifacts see Chap. 15, Getting Clean EEG data:
Artifacts and How to Prevent Them).
. Control over the experimental environment—We must consider conditions that
the behavior of the participant and, consequently, the measured signal. The
affect
goal is to make sure the effects we observe in our experiment are due to the
characteristics of the experimental task and the population being evaluated, and
not to uncontrolled variables. Therefore, it is important to reduce distractions and
behaviors that are not related to the study hypothesis. This also strengthens the
reproducibility of the experiment.
. Efficiency—The goal here is to make data acquisition both simpler and faster,
optimizing the resources of the lab.
. Safety—Of course, we must consider safety aspects to prevent risk to the partic-
ipants,
the research team, and the equipment.
16.2 Lab Infrastructure
The specific application will determine the infrastructure requirement such as room
size, number of rooms, or location of rooms. For example, when working with
young participants, it is recommended to have a separate welcoming room with toys
and to let them feel comfortable in the lab environment before moving to the data
acquisition room (Hervé et al.,
welcom
presented by Luck (
planni
tions for optimizing key aspects of an EEG lab.
ing, but without adding distractions or noise sources. The lab setups
2014) and Ledwidge et al. (2018) are good starting points for
ng the layout of an EEG lab. Below, we provi de some general recommenda-
2022). Generally, the data acquisition room should be
16.2.1 Signal Quality
The goal is to optimize the signal-to-noise ratio for the brain signal being measured.
However, the data acquisition room can have several sources of electrical noise,
which can impact data quality. In particular, lighting and temperature control
systems can induce artifacts in the data. This is due to the mains powerline and to
AC-DC (as these devices are AC powered) and DC-DC converters (Luck,
Koya
nagi et al.,
between
aliasing from higher frequency noise, depending on the EEG hardware filters (see
Chap.
12, Hardware for Recording EEG and Peripheral Physiology). If the desired
EEG
signal is close to the AC frequency, it is recommended to reduce their impact
by using DC-powered lights and/or placing the converters away from the EEG
electrodes and amplifier.
2017). These will induce artifacts at the AC frequency (which varies
50 and 60 Hz, depending on the country) and its harmonics, and possibly
2014;
16 Practical Aspects of EEG Data Acquisition 199
Similarly, potential noise from additional devices in multimodal settings must be
considered. It is helpful to limit the electrical devices within the room to those strictly
needed for data acquisition. A good way to avoid noise is to have additional
physiological measures directly connected to the EEG amplifier, avoiding the use
of additional power sources. This is often possible for electromyography, electrocardiography, and electrodermal skin activity, for example.
The room’s electrical installation should be properly grounded to prevent other
coming through the mains connections of the connected devices. Mains noise
noise
can be avoided by using a battery-powered EEG system, as well as having notebooks
running on internal batteries for data acquisition. Avoiding furniture made of metal
or conductive material is also helpful to prevent signal changes in case the participant touches the desk, for example.
Susceptibility to artifacts depends on the type of electrodes used. For example,
ased active electrodes are less impacted by line noise, because active electrodes
gel-b
usually have an impedance conversion on the electrode, reducing the antenna effect
on the cables. If the frequency of the EEG signal of interest does not include the AC
frequency, and/or active electrodes are used, a general, unshielded room should be
enough.
Alternatively, a Faraday cage could be used to filter external noise coming from
the
surrounding environment. For example, rooms with a large concentration of
equipment or big machinery (elevators, motors, treadmills, IT servers) can impact
the EEG data. It is best to have the data acquisition room well away from such noise
sources.
Aside from the external influences on signal quality, it is also important to
der other sources of artifacts that could be influenced by the lab environment.
consi
For example, sweat will change the conductive properties of the skin and cause
low-frequency drifts in the EEG signal. Therefore, it is worth conside ring a temperature control system. However, make sure it is not close to the EEG system to avoid
introducing a source of noise.
16.2.2 Control Over the Experimental Environment
Distractions can impact task performance and should be minimized. For instance, if
the experiment is carried out in a dark room to maximize visual effects, the small
“power on” light of devices should be covered, and the equipment should be
positioned behind the participant.
As researchers
with colleagues or typing observations during the session. If possible, we recommend having a dedicated room for data acquisition/for the participant, and an
adjacent room for monitoring and controlling data acquisition. To allow proper
observation of the participant’s behavior, the room should have a camera system
and/or a window behind the participant. Furthermore, a communication system will
be needed in this case.
we can also be a source of distraction, e.g., by communicating