Lecture 2 - Acquiring Bioelectrical Signals

A custom integrated circuit that I designed in grad school for conditioning neural signals.

This week's class will be focused on the problem of how one acquires bioelectrical signals from the body. This necessitates an understanding of electrodes and their interactions with the body's electrolytes, as well as analog signal conditioning and digitization. We will use the brain machine interface as an example data acquisition system, since the concepts involved are fairly general and are hence applicable in other domains. Readings include chapters 1 and 3 from my dissertation(!) as well as Chapter 5 from the venerable book "Medical Instrumentation" by Webster.

Here are the discussion topics I emailed to the class:

Dissertation Chapter 1
What are the things you typically have to do when making a biological recording? Describe the pathway from electrode to computer. What are the details along the way that affect design constraints for the engineer?

Dissertation Chapter 3
You can focus your reading on sections 3.1 - 3.3.
Relate the design that I present in this chapter to the general design constraints laid out in Chapter 1. How do the properties of the neural signals I'm trying to capture impact the design of the data acquisition hardware?

Webster Chapter 5 (Electrode/Electrolyte Interface)
Sections 5.6-5.9 can be skimmed (or skipped if you're pressed for time)
What is the electrode/electrolyte interface? How do the chemical processes involved drive electrode designs? What are polarized and non-polarized electrodes? What are the pros and cons of each? What is motion artifact and how do we protect against it? What is the circuit model for the electrode/electrolyte interface and what does it tell us?