Raphael Vallat

I am a neuroscientist and sleep researcher in the Center for Human Sleep Science at UC Berkeley (Prof. Matt Walker's lab). My research examines how sleep — or the lack of it — impacts human health. My work has been featured in several major news media and podcasts.

In addition, I joined Oura in 2020 as a ML algorithm engineer and sleep advisor. There, I have been co-leading the development of the next generation of sleep algorithms.

Beyond sleep, my domains of expertise include machine learning & signal processing, particularly when applied to polysomnography and/or wearable physiological data (e.g. EEG, ECG, PPG, HRV). Part of my research aims at discovering new sleep biomarkers of various human diseases — including diabetes, atherosclerosis and Alzheimer's disease.

I firmly believe in open science. I am the creator and core maintainer of several open-source libraries in Python, which are used by thousands across the globe: Pingouin (statistics, +500k downloads & taught in several universities), YASA (automatic sleep staging) and AntroPy (complexity of time-series).

In my free time, you can find me enjoying precious moments with my amazing wife and daughter, playing music, or hiking with friends in beautiful California.

Academics

• Education

• Expertise

• Teaching

Publications

Please find below a list of selected publications (last updated June 2022)
PDF versions are provided for individual, noncommercial purposes only. These files may not be reposted without permission. Copyright and all rights therein resides with the respective copyright holders, as stated within each paper.

• Vallat, Shah, and Walker (under review). To sleep perchance to balance blood sugar: coupled sleeping brain waves regulate glucose homeostasis.
• Vallat, Berry, ..., and Walker (2022). How people wake up is associated with previous night's sleep together with physical activity and food intake. Nature Communications.
• Ben Simon, Vallat, Rossi, and Walker (2022). Sleep loss leads to the withdrawal of human helping across individuals, groups, and large-scale societies. PLoS Biology.
• Tsereteli, Vallat, ..., and Franks (2021). Impact of insufficient sleep on dysregulated blood glucose control under standardised meal conditions. Diabetologia.
• Vallat and Walker (2021). An open-source, high-performance tool for automated sleep staging. eLife.
• Vallat, Nicolas and Ruby (2020). Brain functional connectivity upon awakening from sleep predicts inter-individual differences in dream recall frequency. SLEEP.
• Vallat*, Shah*, Redline, Attia and Walker (2020). Broken sleep predicts hardened blood vessels. PLoS Biology. * Co-first authors
• Ben Simon*, Vallat*, Barnes and Walker (2020). Sleep loss and the socio-emotional brain. Trends In Cognitive Sciences. * Co-first authors
• Vallat and Ruby (2019). Is it a good idea to cultivate lucid dreaming? Frontiers in Psychology.
• Plailly, Villalba, Vallat, Nicolas, and Ruby (2019). Incorporation of fragmented visuo-olfactory episodic memory into dreams and its association with memory performance. Scientific Reports, 9, 15687.
• Combrisson, Vallat, ..., and Jerbi (2019). Visbrain: A multi-purpose GPU-accelerated open-source suite for multimodal brain data visualization. Frontiers in Neuroinformatics, 13, 14.
• Vallat (2018). Pingouin: statistics in Python. Journal of Open Source Software, 3(31), 1026.
• Vallat, Meunier, Nicolas, and Ruby (2018). Hard to wake up? The cerebral correlates of sleep inertia assessed using combined behavioral, EEG and fMRI measures. NeuroImage [PDF]
• Vallat, Eichenlaub, Nicolas, and Ruby (2018). Dream recall frequency is associated with medial prefrontal cortex white-matter density. Frontiers in Psychology, 9, 1856.
• Vallat, Eskinazi, Nicolas, and Ruby (2018). Sleep and dream habits in a sample of French college students who report no sleep disorders. Journal of Sleep Research, 27, e12659. [PDF]
• Vallat (2017). Content and frequency of dream reports: psychological and neurophysiological correlates. PhD thesis, Lyon 1 University.
• Combrisson*, Vallat*, ..., and Ruby (2017). Sleep: an open-source python software for visualization, analysis and staging of sleep data. Frontiers in Neuroinformatics, 11. * Co-first authors
• Vallat, Chatard, Blagrove, and Ruby (2017). Characteristics of the memory sources of dreams: a new version of the content-matching paradigm to take mundane and remote memories into account Plos One, 12.
• Vallat, ..., and Ruby (2017). Increased evoked potentials to arousing auditory stimuli during sleep: implication for the understanding of dream recall. Frontiers in Human Neuroscience, 11.

Media outreach

• Sleepyheads need these three habits to get rid of grogginess @ New York Post



• Scientists discover secret to waking up alert and refreshed @ Berkeley News



• Sleep and metabolism @ The Gut Check Series



• The sad truth about sleep-tracking devices and apps @ New York Times



• Why do some people always remember their dreams, while others almost never do? @ Discover Magazine



• Vivid dreams and their role in waking life @ WHYY (NPR)



• The paradox of dreams @ This Is Your Brain



• Fitful nightly sleep linked to chronic inflammation, hardened arteries @ Berkeley News



• Simultaneous EEG and fMRI measure sleep inertia @ PhysicsWorld.com



• Brain scans reveal why it takes so long to wake up in the morning @ Inverse.com

Software development

Please visit my GitHub repository for an exhaustive list of the projects/softwares that I am contributing to.

Pingouin

Pingouin is an open-source Python package for statistics. It is built on top of Pandas and NumPy and provides high-level functions to perform the most common statistical tests. Learn more on the documentation or check the code on GitHub

YASA

YASA (Yet Another Spindle Algorithm) is an open-source Python package for sleep analysis. It implements several state-of-the-art and validated algorithms to score sleep stages, detect spindles & slow-waves, and calculate features from sleep polysomnography recordings. Learn more on the documentation or check the code on GitHub

AntroPy

AntroPy is an open-source Python package for computing several entropy & complexity metrics of time-series. Learn more on the documentation or check the code on GitHub.

Tutorials

Please find below some tutorials regarding the analyses I specialize in.

The Science of Dream Recall

Why do some people remember more of their dreams?

Correlation(s) in Python

A primer on correlation and significance testing between two or more variables in Python.

EEG bandpower

Compute the average bandpower of an EEG signal in Python.