The brain is a constant hum of activity; individual neurons alight with action potentials, sending messages to one another.
But when we view it at a systems level, that individual chatter becomes a chorus, one that harmonizes in peaks and troughs. Dr Nancy Lai decodes that chorus, trying to find the intention of the signals within the noise of neural oscillations.
“Just like humans communicate with speech and body language, neurons in the brain communicate through electrical signals called action potentials.” Nancy says, “By using specialized electrodes, we can record these signals and essentially listen to how neurons talk to each other.”
Neural oscillations, also known as brain waves, are rhythmic patterns of electrical activity generated by large masses of neurons within the brain. Each neuron produces a small amount of electrical energy
during an action potential, and that energy radiates outward from the neuron through the surrounding fluids and tissues, diminishing as it goes. When a recording electrode is anchored to the scalp (as in typical human EEG) or the surface of the brain (as in cortical EEG), it is able to detect the summation of the electrical activity from nearby neurons. What you find are waves of activity, with varying synchronicity, and varying speed that change depending on the level of wakefulness, awareness, or cognitive activity.
Nancy uses cortical EEG to track brain activity and EMG to correlate brain activity with muscle activation. During her PhD, she used these methods to examine aspects of epilepsy alongside Professor Zhong Cheng. She found fundamental differences in the clustering of
Generalized 3 Hz spike and wave discharges in a child with childhood absence epilepsy.
neurons supporting seizure activity and interictal (between-seizure) activity in the brain and used those differences to develop a potential biomarker for epilepsy.
These days, in her role leading the Neurological Platform at Bios Pharmaceuticals, Nancy is applying those same skills to understanding sleep. “During non-REM sleep the EEG shows high amplitude waves, especially in the delta band, while the EMG shows low muscle tone,” Nancy says, “in contrast, during REM sleep the EEG shows fast low voltage waves in the theta band, and the EMG is almost flat, indicating complete muscle relaxation. Each of these patterns reflect the brain’s needs in different phases.”
“Besides good surgical techniques,” Nancy says, “high-quality EEG and EMG recordings also need a controlled recording environment and reliable equipment.”
High-quality data acquisition and amplification devices are crucial for recording accurate EEG and EMG signals. These are signals that occur in very small ranges and, in the case of EEG, at the millivolt scale, making them susceptible to interference from the typical static of electrical devices. Signal noise or delayed synchronization could mean the difference between EEG activity associated with a muscle movement and a loss of that relationship, extra time spent in post-processing cleaning up noise from the signals, or even an ambiguous EEG pattern. Nancy uses PowerLab C and our redesigned dual bioamplifiers to ensure her EEG and EMG signals are amplified cleanly and synchronized at the sub-microsecond level.
“Brainwaves during sleep and wakefulness are really fascinating,” Nancy says, “And with the help of technology, we are hoping to keep uncovering the mysteries of the brain.”
