Experimental Setup Review – Seeking Feedback Before Equipment Purchase
mckworkman
USA
Hi all,
I'm planning a polyelectrophysiology study focused on resting-state slow-wave oscillatory activity across multiple systems, and I’d really appreciate feedback before purchasing gear.
The subject will lie supine and enter various resting, meditative, or altered states of consciousness. We aim to capture slow, low-amplitude oscillations across central and peripheral tissues, including some speculative low-frequency signals in fascia and postural muscle.
Summary Table of Targets and Planned Setups
| Target & Signal Type | Frequency Range | Amplitude (Est.) | Electrode Type | Electrode Placement | Setup Type |
|---|---|---|---|---|---|
| Overall brain state (EEG: alpha, beta, theta, etc.) | 0.5 – 40 Hz | µV range | Ag/AgCl | FP1, FP2 (forehead) | Unipolar |
| Heartbeat (ECG) | ~1 Hz | mV range | Ag/AgCl | Chest or forearm | Bipolar |
| Resting muscle activity (EMG) | 10 – 500 Hz | mV range | Ag/AgCl | Targeted muscle groups | Bipolar |
| Pre-movement potentials (motor intent) | <1 Hz | Low µV | Ag/AgCl | Motor cortex & target muscle | Bipolar |
| Fascial contractile rhythms (hypothetical) | <0.1 – 0.5 Hz | Very low µV | Ag/AgCl | Near fascial planes | Bipolar |
| Postural idle muscle rhythms (low-frequency) | ~0.05 – 0.2 Hz | Low µV | Ag/AgCl | Back, neck, core | Bipolar |
| Mayer waves (vascular pressure oscillations) | ~0.1 Hz | — (pressure) | — | — | Accelerometer |
| CSF oscillations (craniospinal fluid pulsation) | ~0.3-1 Hz | — (pressure) | — | — | Accelerometer |
Hardware Plan
We plan to use 4 EEG-related channels (FP1, FP2, and both earlobes), and 3 bipolar peripheral pairs on different muscle or fascial regions, all referenced to one ground.
- Board: OpenBCI Cyton (8-channel)
- Electrodes: Ag/AgCl sticky electrodes
- Cables: 0.5m snap electrode cables (shorter to reduce noise??)
Brain State Strategy (EEG)
- Planning a unipolar setup with FP1/FP2 and earlobe references.
- The goal is general brain state classification (relaxed, focused, dreaming, etc.), not fine localization.
- We prefer forehead-only electrodes for participant comfort while lying down.
→ Will this be sufficient for detecting overall brain states like focused, relaxed, meditative, or deep sleep?
Peripheral Signal Strategy
- All non-EEG signals will use a bipolar configuration.
- We're focusing on slow (<1 Hz) and low-amplitude rhythms.
- These will be captured as differential voltages between paired electrodes as traveling waves move across muscle or fascia.
→ Is this bipolar set ideal for measuring slow, traveling low-frequency waves (<1 Hz)?
→ Will the 8-channel Cyton support simultaneous EEG and multiple peripheral bipolar measurements effectively?
Thanks so much for your feedback
—
MR
Comments
Hi McK,
I'll comment on some of what you posted here on the Forum. I'd also suggest you email sales at openbci.com and confirm that they understand your project and needs.
re: 4 channels of EEG
Your post above just mentions Fp1 and Fp2. So you get 2 more EEG channels where you can pick their 10-20 scalp locations. The reference and ground ('Bias') electrodes do not count as channels, they are separate connections to the ADC. All EEG works this way.
Your Summary chart mentions 'motor cortex', yet you have no electrodes at the motor strip (C3 C4 Cz, etc.)
Yes, shorter cables for the EEG will reduce motion artifact.
re: "Will this be sufficient for detecting overall brain states like focused, relaxed, meditative, or deep sleep?"
This is not straightforward and may require training something like machine learning models. There is an entire field called PSG for sleep recording, do a search on PSG with the 'Google Advanced Search' button. EEG in meditation is another large subject area.
re: 'all referenced to one ground'
Your chart mentions bipolar differential channels for ECG and EMG, yet EMG is generally measured differentially across a muscle group, not with a common reference / ground. Also EMG tends to be high frequency, hundreds or more Hz. I'm not sure I've heard of trying to measure < 1 Hz EMG potentials. May be possible, perhaps cite some literature. Your chart items 3 through 6 mention 'low uV' potentials at these body points. Yet you may have difficulty distinguishing this from movement artifact.
re: slow < 1 Hz recording.
Yes, Cyton can do this because it is a DC-coupled amplifer, (TI ADS1299). Generally for ILF Infra-Low Frequencies you need wet silver chloride based electrodes. If you are using the dry ear clips sold in the shop, you may want to wet the ear lobes first for better connection.
re: "Will the 8-channel Cyton support simultaneous EEG and multiple peripheral bipolar measurements effectively?"
Yes, see this docs page:
https://docs.openbci.com/GettingStarted/Biosensing-Setups/ExGSetup/
Regards, William
Thank you for your detailed reply. We will look into everything you mentioned!
Here is one of the low frequency oscillation studies. https://journals.physiology.org/doi/full/10.1152/jn.2002.88.3.1177
They don't share much about their equipment set up however. Just that its at about 10% of regular EMG amplitude and <.3 Hz
Interesting. Here is the ADC they used, according the paper. A HUGE device. Not sure how they gathered sleep data with this.
https://www.strteknikk.no/Previous products/Premed Physiometer.pdf
After the amplitudes were sampled with that gizmo, it was recorded in this HP device:
https://www.google.com/search?q=HP+200LX
As the paper was from 2002 (23 years ago), there may be more recent studies available. You may want to contact the authors or other papers mentioned in the references.
re: very slow Hz activity.
So as you can read in the paper, what they are tracking is the sEMG, average amplitude, the RMS value. Sample rate only 10 Hz. So your previous question regarding very low frequency sampling, and my answer mentioning the DC-coupling of the ADS1299, is not really relevant. Because this average EMG amplitude is very easy to capture with any ADC system.