Are you conscious? Now with our consciousness detector, you can find out!

Hello again! This is the mind-reader reporting to you with updates on my project. I have had quite the scientific adventure since last sharing my research so sit down, grab your tea (or coffee or pop or kool-aide – I don’t judge) and prepare for a rollercoaster.

With no success from LED oddball tasks, I moved to replicate an auditory oddball task from a paper that describes P300 responses from minimally conscious and vegetative subjects. If subjects with severe brain damage are able to produce results from that task, shouldn’t a healthy brain produce them as well? With this thinking in mind, I created a task that produces an Arduino-driven tone from a buzzer that lasts 100 ms, with 900 ms between each tone.  The oddball tone is coded to appear 14% of the time. When this tone appears, the subject makes a tally until we reach 50 tallies, as the P300 signal is reliable after 30 to 40 oddball stimuli have been presented. The signal sent to the buzzer is essentially copied and sent to the EEG so that the tone activation can be seen in the Spike Recorder app, as shown below.

With this information in the app, the data can be averaged around tone onset. I set out to make this work – except it didn’t. Trial after trial returned a flat average. I was finding something that I thought looked like the P300 but the absence of anything substantial from the average suggested that what I was looking at was not consistent enough to be called science.

This lack of success caused me to scale back the project and start from the absolute basics.

One of the current BYB EEG experiments involves finding the alpha wave: a 10 Hz signal that appears from the occipital lobe when the eyes are closed (can be viewed at https://backyardbrains.com/experiments/eeg). This experiment was used as a control to ensure that the EEG was working as it should. We attached three shields to the board to allow for three recording locations: occipital lobe, right temporal lobe, and a forehead control.

To ensure that activity was not dependent on the shield, we cycled the inputs from each recording location so that every location was recorded through each shield. The results confirmed that the alpha wave is most intense over the occipital lobe, less intense but still visible over another cortical location, and nonexistent over a non-cortical location (changes in intensity can be seen in RMS values). With confirmation that the shields are functioning as they should, I climbed to the next control: the flash visual evoked potential.

Flash visual evoked potentials (fVEP) represent electrical signals generated by the occipital region of the cortex when the subject is stimulated with flashes. The main components of the signal are those displayed to the right and are named for their latency, which is highly variable between subject and task, and their polarity. The flash task created to elicit this waveform was powered by an Arduino and a surge protector that has been engineered to receive power inputs through a wire. The Arduino sends constant power to the bulb until the push of a button begins light flashes at a rate of 1/sec for 60 ms each. Each recording begins with an alpha task to ensure that the signal is legitimate. After the signal is verified, the subject sits motionless in my office for one minute and watches the flashing of the bulb. Because of the small amplitude of the fVEP response, the waveform is easily
lost in a raw EEG signal. It is only through averaging of trials that this evoked potential is visible, since the information common to the entire recording will be averaged out. Errors in the Spike Recorder software averaging caused us to call in Matlab for offline data
analysis. One second of data was collected surrounding flash onset and all of these epochs were averaged after eliminating outlier responses. The fVEP mean is then plotted against a Monte Carlo mean to show where and when the data is statistically significant – any data falling within the 95% confidence interval is deemed insignificant. If the data is significant and the waveform components match the literature in latency and amplitude, I considered the trial a success. Several successful trials indicated to me that the fVEP procedure produced what was necessary for the signal to appear and that the data analysis allowed us to see this particular event-related potential. Hoorah! It is possible. Equipped with new Matlab skills and some inspiration, I refocused my project to finding the P300.

My initial set-up for the oddball task was not scientifically sound, so some adjustments to better control and record the stimuli were necessary. With a better designed experiment and several loyal subjects, data collection was in full swing. After collection, the data was run through an adapted Matlab script specific to the task. This script creates a plot of 1.4 seconds surrounding standard tone onset, 1.4 seconds surrounding oddball tone onset, a Monte Carlo simulation, and a plot of all three plotted together for comparison with outlier data excluded, same as before.

The code outputs the largest positive potential between 300 and 600 ms after tone onset, displaying the latency and change in amplitude from baseline for that point. The results are very exciting! We appear to have a P300 on our hands. Nearly half of the recordings taken thus far have had significant results. As I am only three days of data collection in, I’m happy with that! A lack of significance in the other trials could be from poor recording location, high impedance between the electrode and the skin, or simply poor attention allocation on the part of the subject. My goal now is to keep the positive results coming – more collection, more collection, more collection! Replication = science, right?

BYB’s Odd Consciousness Detector

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 🙂