I am a French research scientist specialized in sleep and dreaming.
I obtained in December 2017 a PhD in neuroscience, with honors, from Lyon 1 University. My doctoral project was conducted with Dr. Perrine Ruby, and aimed at understanding how and why we sometimes recall our dreams and sometimes forget them, using several approaches such as EEG, fMRI and dream content analysis. Since Feb 2018, I am working with Pr. Matthew Walker, at U.C Berkeley, studying the impact of sleep deprivation on the brain.
I also have a strong research interest in statistics, machine-learning and signal processing. I am the (co)-founder of three Python open-source packages that are currently under active development: Sleep (sleep scoring and analysis, part of the Visbrain package), Pingouin (general statistics) and EntroPy (EEG signal processing).
raphaelvallat9 [at] gmail.com
Center for Human Sleep Science (Walker Lab)
University of California, Berkeley
I have decided to upload the full PDF (and LaTeX files) of my PhD thesis. It's a long read but (hopefully) an up-to-date review of what we - sleep and dream scientists - know and do not know about dreaming. In short, the goal of this thesis is to give some elements of answer to a question asked by Aristotle more than two thousand years ago:
We must also inquire what the dream is, and from what cause sleepers sometimes dream, and sometimes do not; or whether the truth is that sleepers always dream but do not always remember (their dream); and if this occurs, what its explanation is.
I am thrilled to announce that our article on sleep inertia is published in NeuroImage.
Ever felt groggy, sleepy, and disoriented when awakening from a long mid-afternoon nap?
In this article, we have investigated this phenomenom, called "sleep inertia", using a combination of behavioral tasks, resting-state fMRI scans and continuous EEG. We have measured the brain function of 34 participants before an afternoon nap, 5 minutes straight after awakening and 25 minutes after. Our results show that sleep-specific brain activity does not disappear immediately after we wake up but instead persists for several minutes, as illustrated by decreased cognitive performance, increased EEG delta power and disruption of brain functional networks (the two latter being typically observed during sleep). In addition, we have found that this sleep inertia progressively dissipates across the first half hour after awakening and that its severity and duration is related to the depth of sleep prior to awakening.
I am very happy to introduce my new open-source Python package, called Pingouin. Pingouin is born out of a personal need to reduce and simplify the number of steps in my statistical analyses. Pingouin provides simple and easy-to-grasp statistical functions for computing ANOVA, post-hoc tests, robust correlations, Bayes factors and effect sizes. Pingouin is based on Pandas and therefore allows to leverage the power of this latter. Learn more on the documentation or check the code on GitHub.
I am thrilled to announce that I will join Pr. Matthew Walker at U.C Berkeley (USA) for a two-years post-doctoral position starting February 2018.
Link to my full curriculum vitae (pdf format - last updated September 2018)
|2018-Present||Postdoctoral fellow, Walker lab, U.C. Berkeley|
|2014-17||PhD in Neuroscience, with honors, Lyon 1 University||2012-14||Master degree in Neuroscience, cum laude, Lyon 1 University|
|2009-12||Bachelor degree of Cognitive Sciences, summa cum laude (ranked 1st), Lyon 2 University|
|Methods||Polysomnography, sleep studies, actigraphy, combined EEG-fMRI, resting-state and task-based fMRI, behavioural studies|
|Analysis||Sleep scoring, ERP, EEG and fMRI signal processing, functional and connectivity MRI analyses, machine-learning, dream content analysis|
|Programming||Python, Matlab, CONN Toolbox, SPM, FSL, HTML, LateX, Shell, R, PsychoPy|
|Neurobiology / Neuroanatomy, 1st and 2nd year of Bachelor Degree in Biology (145h)|
|Social science, 1st year of Medicine (50h)|
|Neuro-imaging (fMRI analysis), Neuroscience Master degree (~10h)|
Please find below a list of publications (last updated November 2018)
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.
Sleep inertia study
Vallat et al., NeuroImage, 2018
SleepViz is the MATLAB prototype of SLEEP. Click here for a quick start guide.
Please find below some tutorials regarding the analyses I specialize in.
A simple and efficient wavelet-based sleep spindles detector in Python.
Compute the average bandpower of an EEG signal in Python.
Two-way mixed-design ANOVA in Python using the Pingouin package.
Extract and plot functional connectivity matrices from the CONN toolbox second-level results folder (Python and Matlab)
A short guide on how to plot BOLD timeseries of one or two regions of interests (ROIs) from CONN toolbox second-level results folder