Good morning.

I want to start answering the 2 questions I had yesterday:

Why is brain activity measured as the difference between two electrodes?

Here's a summary of Claude's response:

There are several reasons why brain activity is measured as the potential difference between electrodes rather than absolute electrical output from specific brain regions.

Brain waves are very weak (measured in microvolts). And there may be external sources of electricity that could affect the reading. That's why measuring the difference between the readings of two electrodes cancels out environmental noise affecting individual readings.

Another reason is because there is no absolute "zero" electrical potential in the body to measure against. We need a base reading to anchor the measurements against. While it's become common practice in EEG reading to place sensors on the patient's earlobes (because earlobes are mostly electrically inactive, easily accessible, and are a consistent reference location across patients) there are other ways to calculate an electrical reference.

I also learned that the electrical activity measured by an EEG are a complex mixture of activity from various brain regions. It's not a measurement of the brain region directly beneath it. Why? Because the conductive properties of brain tissue, cerebrospinal fluid, skill, and scalp cause electrical signals to spread diffusely. And by the time the signals reach the scalp electrodes, signals from different regions have blended together.

And the last reason is also because the skill is a poor electrical conductor. The skull dampens and blurs the electrical signals generated by neurons before they reach the scalp.

Knowing this about the physical limitations of EEG makes me appreciate the technology more, but it also makes me wonder if there are new ways of measuring brain activity using technology that overcome the limitations of EEG.

This morning I finished sketching the general flow of information and data models to record my own sessions using the OpenBCI Ganglion as my device.

After reading more about how brain activity is calculated, I realize I need a base to test my readings against.

And OpenBCI's GUI is a great starting point. They even have their own focus widget. I remember watching this YouTube video and will use it as a guide to setup my OpenBCI GUI + Ganglion sensors to measure my focus levels and test the quality of my connection. Then, once I've validated that, I can run the focus tests with the GUI, record the sessions, and use those as a reference to assess the quality of my computations and recordings using my web app.

I will record some session data tomorrow using the OpenBCI GUI.

I bought Mark H. Libenson's Practical Approach to Electroencephalography. It's a book written by a Neurologist for future neurologists. From what I read online, it's a great introductory book to EEG. I think this book will serve as a foundation to understand the use and importance of EEG in practical clinical settings. And it will also help me think of ideas and see if my intended uses of EEG make sense.

I decided to buy this book yesterday after realizing that I made a very uninformed assumption about how brain activity is measured by EEGs. I need to understand the fundamentals of EEG technology to see how I can use it in innovative ways.

But I first need the basics.

And I think this book will provide the basics as I tinker with the OpenBCI Ganglion and get a more hands-on learning experience.