Ward Pettibone keeps his sleep recordings running for about 23 hours a day, so his UCLA project captures sleep in both the light and dark phases.
The schedule follows from his subject. Pettibone studies local sleep, a state in which separate brain regions sit in different sleep states at the same moment.
Local sleep can occur outside the main rest period, in either phase of the day. Capturing it requires near-continuous sleep electrophysiology, the measurement of sleep through the brain’s electrical activity.
Custom electrodes capture four regions at once
Pettibone designed and built custom local field potential electrodes for the project. They pick up activity from the prefrontal cortex, motor cortex, hippocampus and striatum simultaneously.
A local field potential is the combined electrical activity of many neurons near an electrode.
Human sleep labs typically rely on scalp EEG, which measures from the surface of the head. Local field potential electrodes sit inside brain tissue, close to the neurons they measure.
Simultaneous coverage makes local sleep measurable. Two regions can be compared only when both are captured during the same seconds.
This multi-region sleep electrophysiology setup serves a project on local sleep and spatial learning. One aim is to learn whether local sleep affects learning, and another is to learn whether learning alters later local sleep.
Local sleep has been documented in humans and in rodents. The unihemispheric sleep of birds and dolphins is a separate phenomenon, with one half of the brain asleep at a time.
Each region is scored in 10-second epochs
The signal from each region is scored independently. Scoring divides it into 10-second epochs and assigns every epoch one of four states.
The four states are wake, slow-wave sleep, transition-to-REM and REM. Slow-wave sleep is the deepest stage of non-REM sleep, and REM is the stage most associated with vivid dreaming.
Once every region is scored, the results are merged. Wherever one or more regions disagree with the rest, the epoch is marked as local sleep.
Over minutes to hours, the brain moves through a patterned sequence of these states. Transition-to-REM is the short stage that links slow-wave sleep to REM.
Periods of local sleep are sometimes extended. Researchers know little about what purpose, if any, they serve.
Rodents, a common subject in sleep research, sleep in many short bouts spread over the light and dark phases. Adult humans usually gather most of their sleep into one nightly block.
The recordings follow a seven-day learning protocol
Subjects learn the Hidden Goal Task, in which remaining inside an unmarked location leads to a reward. Pettibone designed the fully automated apparatus for the task, then built and programmed it.
After the task, the four regions are captured together while subjects have an opportunity to sleep. The cycle repeats on each of seven days.
Every day starts with a retest on the location learned the previous day. The rewarded location then moves, giving subjects a new place to learn. Each retest measures how well subjects recall the previous day’s location.
The project has logged more than 10,000 hours
The near-continuous schedule has produced more than 10,000 hours of sleep recordings. Analysis of that dataset is ongoing.
Pettibone pairs electrophysiology with behavioral assays and machine learning. The automated apparatus keeps the behavioral side consistent from session to session.
This continuous sleep electrophysiology approach links each day’s sleep to that day’s learning session. Every session is followed by recordings from all four regions.
His current projects also include an exploration of regional sleep after a hippocampal learning task. The hippocampus is a region closely tied to spatial memory.
The brain acquires new information better after a good night’s sleep, and learning suffers after poor or deprived sleep. Those findings concern sleep in general, and the project asks whether local sleep plays a part.
Training in New York preceded the UCLA work
Pettibone earned a bachelor’s degree in neuroscience at New York University. His studies there included undergraduate research on episodic-like memory.
New York University awarded him a Dean’s Undergraduate Research Fund Grant for 2015-16. The Sigma Xi Undergraduate Division Award (The Scientific Research Honor Society) followed in 2016.
Before his graduate studies, he worked as an associate researcher at Mount Sinai. There he studied tau tangles, motor gist learning and sleep. Gist learning is the extraction of a general rule from several specific experiences, and motor gist learning applies that idea to movement.
Pettibone’s sleep electrophysiology work at UCLA began after his time at Mount Sinai. At UCLA, he received the UCLA BRI Flexible Travel Award in 2023 and the UCLA BRI/Semel Institute Graduate Student Travel Award in 2024.
Also in 2024, he took the Poster Award at the UCLA BRI Future of Neuroscience conference. Six research publications list him as an author.
In 2020, The Museum of Science in Boston invited him to give a talk, Multiverse: Your Brain on Sleep. The invitation brought his sleep research to a museum audience.
About Ward Pettibone
Ward Pettibone is a neuroscientist and PhD candidate at UCLA in Los Angeles, California, who studies sleep, learning, and memory. He received the Science Communication Award, UCLA, in 2021, and his honors also include the Frontiers in Neuroscience Editor’s Pick Collection (2021). His publications and honors are listed on the About page of Pettibone’s website.
