[HN Gopher] EEG channels with low-cost PiEEG device
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EEG channels with low-cost PiEEG device
Author : ron_87
Score : 72 points
Date : 2024-03-29 19:49 UTC (1 days ago)
(HTM) web link (pieeg.com)
(TXT) w3m dump (pieeg.com)
| brcmthrowaway wrote:
| Is this how the Neuralink device works?
| _Microft wrote:
| NeuraLink is using a specialized robot to surgically insert
| very thin electrodes into the brain.
|
| This device here uses good old wet or dry EEG electrodes that
| are touching the outside of the head (e.g. on an EEG cap).
| roughly wrote:
| As a bad analogy, I've heard the difference between EEG and
| implants described as pointing microphones at the outside of
| a building vs having them inside the room.
| hasmanean wrote:
| Well at least you can tell if there's a party going on in
| room 106.
| plastic-enjoyer wrote:
| Well, EEG is more like undirected microphones that record
| the voices of several thousand people at the same time
| outside of a building, whereas implants are more like
| directed microphones inside the building that only record
| the voices of a few people...
| nextaccountic wrote:
| It's worth noting that if each electrode is thin enough
| to be placed in extracellular medium getting signals from
| several neurons around it, you can do some fairly simple
| signal processing to separate the signals of individual
| neurons. This is called spike sorting [0] (a "spike" is
| an impulse transmitted by a single neuron).
|
| So, continuing with the microphone analogy, with the
| right setup, recording a few voices is almost as good as
| recording each voice separately. It's not perfect because
| sometimes people talk over each other, and people distant
| from the mic may have muffed voices, and stuff like that.
| But generally speaking, we can roughly understand each
| individual people in a recording, because each people
| speak in a different way (and just like that, neurons
| spike in a different way).
|
| Here's some academic code that does this [1] (it has
| accompanying articles [2] [3]) (Random article found in
| Google, no affiliation).
|
| The first thing it does is removing the low frequency
| component of the signal (the LFP [4], that doesn't
| originate from any specific neuron), then it stores each
| individual spike waveform as a time series (a vector of N
| dimensions, where each dimension is the value of the
| signal at a moment in time), and then just does some
| k-means clustering to separate spikes in clusters, then
| assign each cluster to an individual neuron (by
| hypothesizing that each neuron likes to spike in a
| specific way which depends on its characteristics). This
| is all very vanilla / undergraduate stuff, and it's been
| done for more than 10 years [5] or perhaps even 20 years
| or more.
|
| Trouble is, with EEG all you have is essentially an
| average of the LFP over a large area; you don't get
| single-neuron spikes. So EEG fundamentally can't listen
| to each neuron individually. However it isn't right to
| simply throw away LFP information, and you can still do
| stuff with it.
|
| [0] http://www.scholarpedia.org/article/Spike_sorting
|
| [1] https://github.com/akcarsten/spike_sorting
|
| [2] https://towardsdatascience.com/using-signal-
| processing-to-ex...
|
| [3] https://towardsdatascience.com/whos-talking-using-k-
| means-cl...
|
| [4] https://en.wikipedia.org/wiki/Local_field_potential
|
| [5] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3657693/
| brcmthrowaway wrote:
| How does the neuralink get an advantage though, do neuron
| spike signals contain any information
| ron_87 wrote:
| of course not
| wpietri wrote:
| I like the idea, but $350 plus a Pi plus getting electrodes is
| beyond my "impulse by to try it out" price for sure.
| ron_87 wrote:
| yes, hat electrodes + plus about 300 dollars
| y-curious wrote:
| I work at a relatively unique EEG startup, and our single-
| patient-use EEG headbands cost a bit more than this project.
|
| That said, doing an EEG on yourself is a bit disappointing imo;
| You won't get much interesting output.
| m_kos wrote:
| If you are at liberty to share, how many channels and are the
| electrodes dry or wet?
| y-curious wrote:
| Sure :) (this is all publically available, fyi, no trade
| secrets here)
|
| 8 channel headband with individual gel packets for each
| electrode. You pop the gel packets and then you have wet
| electrodes!
|
| The company is called Ceribell; Happy to answer more
| questions if you have them. We do not sell to individuals,
| but if you're in the research space, I'm happy to get in
| touch.
| gorkish wrote:
| This seems as if it could be cool, but the board is $350 with a
| BoM of about 50 bucks. Considering the current nascent state of
| things, this doesn't really feel like a project on a successful
| path.
| ron_87 wrote:
| why 50 ?
| _Microft wrote:
| The Elecrow page says that the analog front end used on the
| board is a ADS1299. The eight channel version of it is
| 60EUR+VAT on Digikey. The rest of the parts is most likely
| very cheap.
| ron_87 wrote:
| yes, but also ICs for Voltage! I use with the low noise.
| Also price for PCB board and for soldering and in my case
| also included software) But anyway I will try make price
| lower in the near future
| _Microft wrote:
| The BoM is of course only a small part of the cost and
| there is lots of work time and prototypes that need to be
| paid off by selling finished devices. I'm sorry if that
| sounded like I thought that the price might be too high.
| Thanks for your efforts!
| mt_ wrote:
| What are good papers to get started on BCI in tandem with the
| recent advancements in Large Language Models?
| tbenst wrote:
| Our preprint does exactly that :).
| https://arxiv.org/abs/2403.05583
| dmarto wrote:
| There is also the OpenEEG project[0], the boards are way cheaper
| (sub 100eur[1]) and also they are both open source and open
| hardware.
|
| [0] - https://openeeg.sourceforge.net/doc/index.html
|
| [1] - https://www.olimex.com/Products/EEG/OpenEEG/
| ron_87 wrote:
| is is possible measure EEG with 8 bits ADC ?
| dmarto wrote:
| With an active electrode, it should be good enough. After
| all, we are talking about hobby-grade results.
|
| The Olimex ones are 10-bit (supporting both active and
| passive electrodes), while it's claimed[0] that 12-bit
| resolution is sufficient for EEG.
|
| However, it's worth noting that there are obvious advantages
| to the higher resolution.
|
| [0] https://www.biosemi.com/faq/24bitsystem.htm
| ron_87 wrote:
| EEG in microvolts, if ADC 12 bits, then reference for ADC
| should be in millivolts
| mlyle wrote:
| He mentions active probes. Active probes have
| amplification.
|
| As his link makes clear, your ADC just needs enough
| resolution to measure the signal when the (amplified)
| offset voltages don't saturate it.
| ron_87 wrote:
| yes, I told about digital EEG device from this website.
| To clarify analog device, I need a little more time
| Kiboneu wrote:
| I've been wondering about this for a while.... have you
| tried?
|
| I'm not a EEG designer but I've experimenting and learning
| about it. Sounds like you make PiEEG? This is really cool and
| I appreciate the docs on the github.
|
| After amplification, you could get the signal 0-100uV to
| ~0-Vanalog; so then the entire 8-bit range could ideally be
| used. Realistically, after filtering, due to roll-off /
| artifacts one could probably use 3/4ths of that space -- so ~
| 192 voltage levels that can be determined by the ADC per
| sample. Does this sound right?
|
| It'd probably depend on what level of control / reliability
| one would want from the EEG data; I imagine that you could
| probably cut a lot of corners if, say, you were only
| measuring for hemispheric coherence in a small set of
| frequency bands, or stages of REM sleep (and maybe ERPs like
| p300).
|
| I don't know, this is in my upcoming experiments. Originally
| this was an attempt to build an EEG amplifier / filter
| circuit for an atmega328p 10-bit ADC but for my purposes I
| settled for a 12-bit (and possibly hardware oversampling) on
| an EFM32.
| QuantumG wrote:
| Is someone maintaining a big list of BCIs somewhere? If you're
| going with extra-cranial hardware, I think the best available
| involves Microwave Brain Stimulation along with passive sensing
| methods like this. Unidirectional brain -> computer is neat but
| so long as the feedback is via sight or sound it's just another
| move-the-mouse alternative.
| ron_87 wrote:
| Forgot to say, 8 channels now and 16 in the few months
| pedalpete wrote:
| I was going to point to openBCI as another option, but the
| definitely are not a low-cost option. I don't remember spending
| this much on the Cyton board a few years ago.
|
| https://shop.openbci.com/collections/frontpage
| ron_87 wrote:
| yes, thank you!
| seeknotfind wrote:
| Anyone recommend particular electrodes for this or have a good
| comparison with alternatives?
| lukeinator42 wrote:
| I recently discovered that you can attach an external electrode
| or two to a Muse headset:
| https://hackaday.io/project/162169-muse-eeg-headset-making-e....
| This is a fairly cheap way to hack around with an EEG system that
| has four electrodes at the front and then an extra electrode you
| can place anywhere else you want. I think it would probably work
| pretty well for simple stuff like detecting P300s or SSVEP.
|
| But yeah you definitely get what you pay for with EEG. In the lab
| I'm in, we have a $150k EGI system and a $40k cognionics system
| and even the cognionics system is way more glitchy/low quality
| compared to the more expensive systems.
|
| Also, I wonder what happens safety/electrical noise-wise if
| you're plugging a raspberry pi into the wall? Generally, EEG
| systems are either battery-powered or use an isolation
| transformer. I wonder if it's best to power the pi with a
| battery.
| MPSimmons wrote:
| Without some serious fuse/filtering, I don't think I'd feel
| good about plugging it into the wall. It's easy enough to get a
| battery pack that can provide enough juice to run this for
| testing sessions, so why risk it, even if the risk is small?
| ron_87 wrote:
| only from battery, thank for your message! for details write me
| here https://www.linkedin.com/in/ildar-rakhmatulin-262a66112/
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