Reading Brainwaves

Reading Brainwaves

Hello, all! From the last post about neurons, you might remember I talked about electrical impulses generated by neurons in the brain. Neurons communicate with one another by initiating inhibitory or excitatory activity by means of neurotransmitter release or change in membrane potential at synapses, the connections between neurons. Because our brain is always on, processing sensory information, forming memory, and regulating movement and bodily function, neurons are constantly firing in electrical bursts! 

The Brain…It’s Electric!

The voltage is pretty low on a cellular level, but groups of hundreds or thousands of these cells firing in sync are enough to generate a detectable electrical field that can propagate through tissue and to the surface of the head. Surface electroencephalography, or EEG, is a bioinstrument that can record the electrical activity in the brain by placing electrodes on the scalp. Now that we’ve a better understanding of where electrical activity in the brain comes from, we can discuss how EEG works and its different uses.

How EEG Works

The electrodes are mounted on the scalp using elastic caps and are either dry or wet. Wet electrodes are made so with the use of conductive gel prior to the application of electrodes in specific positions on the cap. The electrodes measure very small signals which are digitized and amplified, then shown on a screen as amplitudes of voltage. These electrodes measure the electrical activity with reliable time resolution, meaning that you can detect spikes of activity in cortical areas at very specific times. Therefore, EEG is a useful tool for studying brain activity at the onset of an event. We call these fluctuations “event-related potentials” or ERP’s.

How To Read EEG

The electrodes are arranged on the cap in very specific locations mapping the areas of the cortex that process information. The recorded signals allow us to understand which areas are active in processing this information at specific time points. These are the areas of interest:

The four areas of the cortex

Not only can the signals be read from specific areas in the brain at a specific time, but the frequency of the “brain waves” can give us information about cognitive processes regarding an event or any other activity. So, the frequency patterns from an EEG may change when you’re asleep to when you’re awake and walking on a treadmill. Depending on the kind of study, each wave has its own association to cognitive processes.

  • Delta (less than 4 Hz): low frequency wave pattern, sleep & memory
  • Theta (4-7 Hz): Memory, difficult cognitive tasks
  • Alpha (7-12 Hz): Relaxation, focus/attention
  • Beta (12-30 Hz): Motor processing, movement
  • Gamma (30-50 Hz): Sensory/information processing

EEG Applications

Based on its excellent temporal (time) resolution, non-invasive EEG is used as a clinical tool in monitoring and diagnosing patients with ailments such as epilepsy and other neurological disorders. Outside of clinical use, dry, surface EEG systems are popular for brain-computer interfaces and controlling prosthetic devices using brain waves for control! Lastly, EEG is a common tool in neuroscience and neuromechanics research.

In most human neuromechanics research, EEG is used as a tool to record brain activity during some task, likely involving movement. Unfortunately, EEG can also record a lot of noise such as shifting of the electrodes or wires (movement artifact), line noise, eye movement, and electric potential from head muscles (jaw clenching is a good example). So, before we can interpret the data, a lot of filtering and pre-processing is required and is typically done with the help of Python or toolboxes in Matlab such as EEGLab. Stay tuned for EEG Part 2, where I will dive into how EEG data is handled!

Neuron Chatter

Neuron Chatter

Mother of Neurons with two neurotransmitting neurons (like firebreathing dragons, except neurons…get it??)

Let’s get excited!

About neurons, specifically. I think it’s clear by my blogging persona that neurons are pretty important to me and without them, I would not be able to do neuromechanics research. Before I dive into what neuromechanists do and share interesting developments in the field, I want my readers to understand why EEG is used to obtain data. Other neuroimaging techniques are used, but I am going to stick with EEG.

Before diving into EEG, however, let’s zoom in a little more and understand what these systems record: electrical activity generated by the brain. More specifically, the electrical activity that we want to read in EEG are the collective signals generated by several neurons in various areas of the brain. And by several, I mean there’s upwards of 85 billion neurons firing off and communicating with each other through these electrical impulses! BECAUSE THEY ARE EXCITED! So, get excited and buckle up as I introduce you to my favorite cells.

Nervous Cells

They’re not anxious – they’re one of the two types of cells in the nervous system: neurons and glial cells! Neurons are the anatomical building block of the nervous system, and they are excitable. Basically this means that these cells are capable of producing action potentials and nerve impulses by conducting electrical impulses along their plasma membrane. They are comprised of a cell body (soma) and processes called dendrites and axons. Dendrites are short processes extending from the cell body that function as signal receptors and transmit information to the cell. Axons (may be short or long, insulated or not) transmit signals away from the cell.

Neurons may look different from one another based on their function and location. For example, motor neurons are categorized as multipolar neurons because they have several dendrites and an axon. You would expect this because motor functions are complex which means input from several sources would need to get to a motor neuron. The two other categories of neurons include bipolar (one main axon on each pole of the cell) and unipolar (with on peripheral and central axon).

Glial cells are non-excitable, support cells for neurons that are also responsible for protection, myelination, among other functions. These cells are also crucial to the nervous system, but I won’t focus on them today.

The Communicators

The neuron’s main function is to pass on information from point A to point B. They are messengers in the command center (our brain), and they pass on messages through electrical impulses known as action potentials. Neurons are in a polarized state which means that the net charge on the inside is negative (resting membrane potential) and the charge on the outside is positive. This polarization is maintained by a Na+/K+ pump that pumps out positive sodium ions and lets in positive potassium ions. This occurs against their concentration gradient – think of this as trying to get water to flow uphill.

If a stimulus is strong enough, the cell membrane opens its Na+ ion channels to allow an influx of positive ions that depolarize the cell by making the inside less negative. Following this, K+ ions leave the cell along their concentration gradient (the outside becomes negative and positive ions like to go where it’s negative). This is induces the action potential and as it propagates through the cell, the membrane potential can spike up to +40 mV. This spike happens in a very short period, called the absolute refractory period, thanks to the opening of the K+ ion channels and closing of the Na+ channels. This period is called the relative refractory period. The Na+/K+ pump then pushes out 3 Na+ ions and brings in 2 K+ ions, repolarizing the cell by making it more negative on the inside and positive on the outside.

Action potential plot, voltage versus time

So, this is the excitatory behavior mentioned before, but what happens after the action potential occurs? Well, neurons come into close contact at what we call a synapse – or, what I like to call the transit station. Synapses form a conducting pathway to communicate with postsynaptic cells and they can be excitatory (depolarize receiving cell to start another action potential) or inhibitory (hyperpolarize receiving cell to prevent excitation). Two types of synapses exist:

  • Chemical – flow of neurotransmitters from one cell to another by release of vesicles from a terminal and binding to receptors on postsynaptic cell
  • Electrical – tunnels between neurons called connexons that allow for a rapid, bidirectional flow of ions
The two types of synapses and how the action potential potential propagates from one cell to another

Conduction Velocity

As I mentioned before, axons may be insulated or not – the difference is the presence of fatty myelin sheaths. Myelin sheaths are insulatory and prevent the loss of ions into the extracellular environment, but they are exposed on the ends (nodes of Ranvier). Ion exchange is possible at these nodes, so the action potential “jumps” rapidly from one node to the other in what is called saltatory conduction. Thus, myelinated axons allow for quicker depolarization and unmyelinated axons have a lower conduction velocity.

What does this all mean?

Synaptic signalling between neurons causes the change in voltage across the cell membrane. Where there is a change in voltage or electrical potential, an electrical field is generated. With the vast amount of neurons in the brain, these small changes in voltage add up to result in a stronger electrical field – one that can be picked up by EEG electrodes.

Hopefully, you have a better understanding of what neurons are and why neuromechanists might be interested in them. We are fundamentally trying to understand how the brain communicates with the body and if we intercept the messengers, we might have a better chance of translating that information.

Now that you are equipped with all this exciting neuron knowledge, stay tuned for a breakdown of EEG in my upcoming post! Last thing: What did the neuron say to the glial cell? “Thanks for the support!”

An Intro to Neuromechanics

An Intro to Neuromechanics

If you’re new to my site, you’re probably wondering why I’ve called my blog persona the “Mother of Neurons” (hint: check out the “About Me” post). Well, my research area is “Neuromechanics“, which is probably not a very commonly used term or a sub-discipline most people know very much about. My goal is to change that, so buckle up and brew yourself a strong cup of tea or coffee: I’m about to dive in and get you all excited about neuromechanics.

Neuromechanics, originally proposed by Roger Enoka in 1988, is the study of the relationship between movement neuroscience and biomechanics. Why did researchers feel the need to combine neuroscience and biomechanics? Well, we know a lot about how our muscles and central nervous system contribute to movement, but we don’t know enough about is how biomechanics and interaction with our environment is involved in neural processing.

Most researchers that study neuromechanics try to understand how our body (or that of animals) works as a whole system works so they can explain what the algorithm is for controlling the system. We want to understand how our brain and body collaborate to execute complex, coordinated movements like walking, balance, running, reaching, squeezing fingers, and the list goes on and on and on and…

So, how do neuromechanists go about this? Why, we experiment and collect information from the body, of course! First, we use sensing systems that collect information from different bodily systems like our brain (EEG or electroencephalography), muscles (EMG or electromyography), and limbs (motion capture or wearable sensors that track limb position). I can literally write an entire post detailing bioinstrumentation (and probably will), but these are just a FEW of the MANY systems available to researchers to collect information needed to conduct neuromechanics research. Then, we conduct movement experiments in lab-controlled environments that mimic real-world interactions and collect data that will tell us more about how our brain, sensing organs, and body communicate while interacting with the environment as well as telling us about how our movement adapts to various conditions.

**As briefly mentioned before, animal studies are included in neuromechanics research and methods may vary when it comes to animal models – I’m just more familiar with human models 🙂 **

All in all, why is neuromechanics important and why should we care about this field? This knowledge is valuable to the clinical assessment of movement disorders typically caused by injury or neurological/musculoskeletal ailments, development of new bio- and wearable technologies such as exoskeletons, and disability-related/rehabilitation engineering (my favorite contribution, and evidently my doctoral research).

Well, there you have it! I hope you’ve been patient on my not-so-brief breakdown on neuromechanics and that you have a new subset of STEM to get excited about. If you’re interested in reading some interesting papers in this field, feel free to send me a message using the contact form and I can refer you to some exciting literature but a lot of good intro papers are, surprisingly, listed under References on the Wikipedia page I linked earlier. I will also probably follow up with a post on how I got into neuromechanics, but for now, please enjoy this feature on my college journey from Valencia College!

Valencia College graduate Lietsel Richardson displays her prototype neuro-rehabilation device in the Biomechanics, Rehabilitation, and Interdisciplinary Neuroscience (BRaIN) lab on the main campus of UCF on November 22, 2019 in Orlando, Fla.
About Me

About Me

Hello and welcome! My name is Lietsel (pronounced Lee-ZUHL) and I am a Mechanical Engineering PhD student at the University of Central Florida. I recently graduated with an M.S. in Biomedical Engineering specializing in biomechanics. My current doctoral research integrates lower limb tasks with interactive art media to determine whether engaging sensorimotor processes involved with creativity and self-exploration are a benefit to lower limb rehabilitation. This endeavor combines everything I love: art, creative expression, neuromechanics, and most importantly, helping others.

A cartoon avatar of the author with a rainbow background.
Mother of Neurons

I am a lesbian, woman of color, and international student – because of these intersections, I feel it is important to share my perspective and experiences. In the last decade, my academic journey has been tumultuous and even though I am right where I was meant to be (a woman in STEM), I know I could have benefited from seeing more representation in my field. Because I feel so strongly about young women seeing someone that looks like them kicking butt in STEM careers, I have performed outreach in classrooms ranging from elementary to high school. But, I want to take it a bit further by branching into science communication! So here’s what you can expect from this blog:

  • my PhD journey
  • mental health advocacy
  • a breakdown of experiences as a minority in STEM, mainly engineering
  • topic reviews on neuromechanics, neurophysiology, biomechanics, and biomedical engineering
  • research updates

Fun Facts

My favorite TV show of ALL TIME is The Office, hence the name of the blog. In my free time, I love to read fantasy novels with a warm cup of tea in hand, obsess over my cat, play The Sims 4 (mostly because I love interior design and it’s the only way I can tap into that passion right now as a grad student), run races (did my first half marathon in December 2019, yay!), spend time and go on adventures with my partner, take care of my plant babies, and explore new places. Speaking of fantasy novels, my love for the genre extends to TV shows, so the origin of “Mother of Neurons” is indubitably from Game of Thrones (I refuse to comment on the show’s ending). I’m from the Dutch Caribbean, so although I grew up speaking both Dutch and English, I have been studying in the U.S.A. for so long that I can only understand/read Dutch now. Please, I beg you. Don’t ask me to say ____ in Dutch in-person 🙂 I will panic.