Welcome! This is Kylie Smith, a Michigan State University undergraduate writing to you from a basement in Ann Arbor. I am studying behavioral neuroscience and cognition at MSU and have been fortunate enough to have landed an internship with the one and only Backyard Brains for the summer. I am working on The Consciousness Detector – an effort to bring neuroscience equipment to the DIY realm in a way that allows us to learn about EEGs, attention, and consciousness. It is my mission to create an oddball task that elicits the P300 signal in such a way that can be detected on BYB’s EEG machine. Let me break it down:
An oddball task is an attentional exercise in which a participant sees or listens to a series of repeating stimuli. These stimuli are infrequently interrupted by a novel stimulus called the oddball stimulus. The participant is asked to count or press a button for each oddball stimulus that is seen. Named so for its positive change in voltage occurring around 300 ms after the appearance of the oddball, the P300 can be seen when the participant is attending to the stimuli and the oddball they had been waiting for arrives. This signal can be detected by an electroencephalogram, or EEG. EEGs use a series of small, flat discs, called electrodes, in contact with the scalp to detect changes in voltage through the skull. The EEG detects the changes in the electrical activity of neurons and transmits the detected signals to a polygraph to be analyzed. Outside of my project, EEGs can be used to help diagnose certain neurological disorders and help pinpoint locations of activity during seizures.
So why is this project worthwhile? Consistent with BYB’s mission statement, we want to bring neuroscience to everyone. Your average neuroscientist spends years learning the mechanisms behind brain funtion in order to use this knowledge practically. Then the equipment must be conquered – it is often complicated and lots of time is dedicated to mastery. By hacking their own EEG and producing it from basic electronic components, BYB is able to bring this machinery to you – and that is an incredible thing. Learning the principles behind EEG recording and how to use such a machine is something that few have the opportunity to do – and now you can do it in your living room! The idea behind The Consciousness Detector is used in the medical field. Patients with severe brain damage can be given an auditory oddball task to objectively predict recovery of consciousness through the P300 that is or is not present (If interested, please see: Cavinato et al. (2010) Event-related brain potential modulation in patients with severe brain damage). We are bringing medical techniques used to predict prognosis to you. Yay!
The current BYB EEG headband is being employed to record from the parietal lobe, as this is where the P300 is detected the strongest. A better apparatus for holding electrodes in place will most likely be introduced down the line. I have high hopes to pop some rivets into a home-made brain hat and begin an EEG cap trend. For now, this is what I’m working with:
Backyard Brain’s EEG system uses two active electrodes, the electrodes recording activity, and a ground to eliminate noise common to the head. I have attempted to begin as simply as possible to determine what kind of oddball task is required to elicit the P300. The arduino shield produced by BYB has a series of LEDs, shown in the picture to the right, that I have used in my first version of the task. We coded the LEDs to flash in a random sequence with the oddball stimulus flashing 10% of the time, as a smaller probability of seeing the oddball predicts a larger amplitude and more easily detectable P300. The standard and oddball LEDs were assigned to corresponding digital outputs on the arduino and were wired into the analog input so that each flash could be detected on the Spike Recorder app. In the picture below, the green signals represent the standard LED flash and the red represents the oddball LED. Using this method, we can see what occurs 300 ms after the oddball LED is flashed. To ensure that attention is required to detect the oddball, we began by using one green LED as the standard stimulus and the other green LED as the oddball flashing 10% of the time. After getting no response in that department we tried other colored LEDs as the oddball, thinking that two green LEDs may be too similar since the oddball stimulus is intended to be more novel than the standard. No P300 was observed there, either.
We have written another oddball task using LEDs in which the LEDs randomly flash two at a time. The task of EEG-wearer is to count how often symmetric stimulation occurs across the LED midline. This task gives a more novel oddball and hopefully an easily detectable P300! More oddball options are in the works, including small images for a visual oddball and auditory tasks as well! Stay tuned 🙂