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Posts tagged “EEG

An early present

Since my deadline has come and gone I can look around for a moment, but more importantly I don’t feel the pressure to hyperfocus on a single project. So today instead of working on that dataset I’m switching to a dataset I need to get done before my PhD proposal defense. It’s data that will (assuming I find something) further help make my case for studying my new “super secret” technique for the next 2-3 years depending on how long everything takes.

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Back to EEG processing…

It’s the day after thanksgiving and I made my annual I don’t want to have to cook for the next week or two spread of tasty foods. I don’t do the traditional Thanksgiving foods though, I prefer Mexican dishes (since I’m Mexican). Namely I make a huge batch of tamales, since they are a bit of work I tend to make a comically large amount, think 100 or more. So while I have food to last, I need to get back to my main focus and that’s work!

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How can we record from the brain non-invasively?

Still my favorite photo, which I took showing the EEG setup process we use these days!

We can read your mind! Okay, not quite, we can read the electrical activity going on in the brain and we can do this non-invasively. That’s right, you can do it from your own home if you wanted (here). It’s easy and since you don’t have to break the skin, it’s about as safe as can be. The real question here is why does this even work? For that we need to talk a bit on biology so let’s do this!

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EEG Cleaning: ICA and Dipoles

This is (a very, very, small portion) of the data I’m working with for this post!

Let it be known that I’m a person of my word and today we’re going to give a rather broad overview of ICA and dipoles. Don’t know what those words mean? Well start here and that will give you a high level view of the entire process. Today we’re going to do a slightly deeper dive into what the heck a dipole is, why we use it for ICA and why ICA is so helpful in EEG data processing. Sound like a lot? Well it is, but let’s take a crack at it anyway!

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How to process EEG data

This is what Raw EEG data looks like. That big spike in the middle of the screen across most of the channels, that’s (probably) eye movement.

For those just tuning in, I’ve been busy! I made my deadline, barely. Unfortunately that was one of two. The second requires me to have all the work done, not just part of it. I managed to finish one of ten (yes ten) of the datasets I had, so now I have less than two weeks to finish the rest of it Let’s take it from the top and discuss how we process EEG data!

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EEG, not quite mind reading

Still one of the best photos showing how we set up EEG, that syringe has a blunt tipped needle and we use it to apply gel to the scalp. Don’t worry, we don’t break the skin, so it just looks scary, but it’s really safe.

Well I’m behind schedule and even though I was given an extra week (6 days now) I don’t know that I’m going to meet my deadline. It’s not me, it’s my computer, things take time to run so I’m stuck waiting for it to do its thing. Today let’s talk about what EEG is and how we make sense of it.

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Into the unknown

Time to cross that bridge…

Today is going to be a somewhat anxious day for me. It’s the day I get to crack open my data and see what spills out. There was a process to get to this point of course, it took me about a week, but today with just a few clicks I’m going to see if I have something or if my idea was never meant to be.

Read more… if you dare!

Day 143: Meeting with my two PI’s

Exo

Some of our exoskeletons from the lab

Today was an interesting set of events. I had my meeting with my two PI’s (which I still think would make a hilarious television show). The meeting went well, I’m very excited, but I’m also getting ready to be very, VERY busy. Let’s breakdown how it went shall we?

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Day 142: So you want to record from the brain…

EEG setup

My college helping me set up for the experiment I just did. This is how we add gel to the head, there is a tiny hole by each sensor, we then insert a blunt tip needle (we do NOT puncture the skin!) to add the gel between the sensor and the top of the head to eliminate the air gap caused by the hair. Unfortunately it looks scary, but we need something tiny to get around the sensor (if you look close you can seethe tiny, tiny opening each senor has). The lights on each sensor tell us how good of a connection we have, red means bad, yellow means we’re getting close, and green means good.

Today’s post was inspired by a conversation I was having yesterday in the comment section (you know who you are and thank you for the questions). I thought I would elaborate on how we record from the brain and why. There are a lot of different ways we can do this, some of them are super invasive and others are non-invasive. In the lab I work in now, we do things non-invasively there are good things about this and bad things about this, so let’s get into it!

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Day 110: Experiment!

EEG setup

This is an actual photo from my experiment setup, one of my colleagues is adding gel to the sensors. While the giant syringe looks scary, it isn’t. It’s full of conductive gel that gets placed between the head and the sensor. There is no pain or puncturing of the skin involved. Afterwards the gel washes out of the hair. The real pain is sitting for ~30 minutes or so while we gel each electrode enough to get a good reading.

A few days ago I mentioned I did a thing, well an experimental thing really. It was… fun? It was definitely something. Overall it went well, but I said I would give everyone an update and I try to be a man of my word, so let’s do this.

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Day 106: Super Busy!!!!!

Today I had my experiment (yay), so now I need to process the data. I also sat in another PhD defense for one of our lab members, so now that I have a free second I wanted to give an update. Expect a longer post tomorrow, but for today, I have sooooo much work to do!

Until next time, don’t stop learning!


Day 105: Defense day #1

phd defense

This basically sums up today’s post…

Here we are another day another post. Today I will be spending the bulk of my time studying and getting my slides ready for the confrence I’ll be attending next week. That will be … fun? However today is also an important day for one of my fellow students, he’s defending his PhD.

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Day 104: Experiment Prep

EEG headset

It looks like things are moving a little quicker than I thought for me. As you may or may not know, I’m getting ready to do an experiment. Well, we finally (finally!) finalized the protocol and just in time too. While I won’t make the deadline for my project update, I will have some data to show when we get to the conference, which is a good consolation prize.

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Day 2: Power Spectral Density (pmtm)

Day 2 - EKG

A example EKG signal

This is a (somewhat) continuation on what we were discussing in the previous post. We covered the pwelch MATLAB function, this time we will cover the PMTM function, this function uses the Thomson multitaper method to calculate power spectral density. We can do a deep dive into the differences between the two next time, but for now let’s talk about the command itself.*

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Day 1: Power Spectral Density (pwelch)

EEG

Some EEG data that I’ve aligned, processed, and made look nice and pretty.

Signal processing, it’s complex, there are a million ways to go about processing a signal, and like life, there is no best way to go about doing it. Trust me, it is as frustrating as it sounds. Today’s scratch pad note is on power spectral density or PSD for short. So let’s dive in.*

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