Welcome!

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).

Contact info:
raphaelvallat9 [at] gmail.com
Center for Human Sleep Science (Walker Lab)
University of California, Berkeley

News

PhD thesis online

October 2018

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.
— Aristotle. On Sleep and Sleeplessness. 350 B.C.

The cerebral correlates of sleep inertia

September 2018

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.

Pingouin: a statistical package in Python

April 2018

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.


Post doctoral position at U.C Berkeley

November 2017

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.


New papers out

October 2017

Academics

Link to my full curriculum vitae (pdf format - last updated September 2018)


  • Education

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
  • Expertise

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
  • Teaching

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)
  • Outreach

Elected representative of the doctoral students in Lyon Neuroscience Research Center council
Organizer of the Doctoral Day of the Lyon Federative Research Structure in Health
Invited oral presenter for a general public conference on sleep and dreams (1h, at Lyon town hall)
Organizer of a thematic week on neuroscience for 6 high-school students
Organizer and chairman of "Les Saisons du CRNL" conference on neurosciences and society

Publications

Please find below a list of publications (last updated March 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.

Software development

Visbrain | SLEEP

The SLEEP module of the Visbrain package is an open-source software for visualization and analysis of sleep polysomnographic data. Learn more on the official documentation or read the peer-reviewed publication.

Guides

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

EEG bandpower

Compute the average bandpower of an EEG signal in Python.