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How to use low-density EEG [Get more with less]

Low-density EEG is becoming more and more popular. Here, we take a look at some of its advantages and how you can integrate low-density setups into your research. Even if you already have a high-density setup, adding a portable, low-density system can have great advantages.

What is low-density EEG?

If you are working with EEG biomarkers, you probably know that the number of EEG channels you use greatly impacts your data quality. In general, the more channels you have, the more granular your image. 

The current gold standard EEG systems have 256 channels and many people believe accurate source-localization requires at least 64-channel resolution. That is, identifying neural networks and independent components requires three times as many electrodes as a 10-20 setup.

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This rule of thumb ⁠— the more channels, the better the data ⁠— holds true for most experiments. But this is because most experiments are conducted in a controlled environment with stationary participants.

However, more research is being conducted outside the lab, and with more channels comes a greater cost in time and money. 

Why care about low-density EEG systems?

Adding a mobile system to your EEG setup can open new avenues of research.

Ambulatory EEG devices largely account for their low channel count, and so traditional, high-density EEG systems are losing their edge.

Importantly, EEG technology is maturing rapidly. This means some features of mobile EEG have only recently come to light. Here, we consider just a few of the advantages of low-density EEG systems, starting with data quality.

Data quality in low-density EEG

Today, portable EEG systems, like Mentalab Explore, can reliably sample and stream up to 32 channels with a 1kHz sampling rate at 24-bit resolution.

That is on-par with most stationary systems and certainly good enough for most research paradigms. And if you don’t mind using internal memory and analyzing data offline, even higher sampling rates are available.

Unfortunately, it is hard to stream EEG signals at more than 1kHz because Bluetooth and other wireless connections bottleneck data transfer.

Parallel data collection

Cheaper systems with lower channel counts can be used to collect data in parallel from multiple subjects. 

This means that instead of collecting data sequentially, one subject after another, much larger data sets can be generated in a shorter time. Of course, larger sample sizes tend to drive more powerful results.

How many channels is enough?

While the need for high-density EEG data will not disappear anytime soon — it’s the only reliable way for EEG-based source localization — there have been a number of advances in data processing techniques that allow researchers to extract more information from less channels.

To find out more, have a read of our blog post that considers how many channels to use in research

At the end of this article, we have outlined a new paradigm that allows you to extract the most from a combination of high-density and low-density setups.

What are the costs of low-density EEG?

The cost of an EEG system is largely affected by the number of channels it has. As such, mobile, low-density systems are much cheaper than stationary high-density systems.

While FDA-cleared ambulatory EEG devices often come with a hefty price tag, there is a solid selection of research-focused EEG systems with 32 channels or less that don’t break the bank. 

High-density EEG systems can often cost four to ten times more than a low-density system, and they aren’t always necessary!

In fact, you can often buy between four and ten low-density EEG systems for the price of a single 256-channel system!

Access to real-life scenarios

Although lab-based EEG has shed light on some of the brain’s primary physiological processes, each is, in part, biased. This is because lab-based experiments can be ecologically invalid.

Having small and portable EEG equipment allows researchers to collect data outside of the lab, improving ecological validity. It also means scientists don’t need to spend time replicating “real-world” scenarios in the lab.

What is more, mobile setups allow EEG data collection at home. This is especially important for less mobile patients, and can be particularly useful for rehabilitation tracking. 

Reducing inequity in EEG research

By bringing data collection equipment to participants, rather than the other way around, scientists can reduce inequity in EEG research.

Conventionally, most EEG studies are conducted in the Western world. Subjects tend to be Caucasian, educated, and not living in poverty. This contrasts with many areas of the world that would benefit from EEG research.

Having mobile equipment allows researchers to collect data from those who are typically underrepresented in EEG research: underprivileged populations in developing countries and rural areas. 

How do I add low-density setups to my research project?

First, it is important that your low-density EEG system can indeed represent the biomarker you are investigating. Once this is established, however, the following methodology can be employed. 

This method, still in development, combines accurate source localization, mobile data collection, and quick setup times. It focuses on connecting high and low-density data sets in a way that is personalized for each subject. 

The method

  1. Perform an initial, high-density session at the clinic or lab.
  2. Analyze the high-density dataset. Identify the subset of channels that provide the highest statistical power. That is, identify the 8-16 channels that explain the majority of variation in the 128-256 channel recording.
  3. Conduct subsequent sessions with a mobile, low-density system using this channel subset. 
  4. Occasionally conduct high-density EEG sessions to confirm that your low-density channel selection is still appropriate. 

An example of the timeline for a 2-year data collection project is displayed below.

2-year, high density EEG research project
Monthly EEG collection over 2 years using high-density setups only.
2-year, low density EEG research project
Monthly EEG collection over 2 years combing high and low-density EEG sessions.

What are our thoughts about adding a lo-density mobile EEG system to your setup? Where do you see the biggest challenges? We would love to hear about your experiences! To start a conversation, please contact us at