What can Electrophysiology (and Brain Rythms) tell us about ‘Meditation’ ? Jean-Philippe LACHAUX CNRS - LENA - PARIS INSERM – U280 – LYON Stirling Workshop June 11-12, 2004 Buddhist inspired Models of the Mind

GENERAL FRAMEWORK ‘Meditation(s)’ … ? Varieties of attention -Focal (‘external’ or ‘internal’ targets) - Open attention (whatever happens, happens) If we can talk about the dynamic of the mind Then meditation has to do with the fine tuning of parameters that determine this dynamic

Mind’s Dynamic Plasticity of Attention Grasping, Frozen Mind, Overexcitment, …

Mind’s Dynamic Deeply Rooted into a Large-Scale Non-linear Dynamical System under constant external perturbations (reactivity vs. inertia)

If the dynamic of the Mind has to do with the dynamic of the Brain, Then it should be possible to understand, or at least witness, the effects of meditation on this dynamic via brain imaging Optimally, it would be nice to describe the neural dynamic at a time-scale that is compatible with the time-scale of subjective experience And at a spatial scale compatible with the spatial scale of the brain’s functional architecture

temporal resolution spatial resolution neurons cms ms minutes meg -eeg seeg pet fmri

EEG/MEG in Humans Evoked PotentialsEEG Oscillations ‘spontaneous EEG’

EEG Oscillations Several characteristic frequency bands with different functional specificities (more or less) Synchronization of large neural populations  (<4Hz)  (4-7 Hz) : working memory, mental load ?  (7-14 Hz) : relax ? ‘idle rythm?’  (15 – 30 Hz) : sustained attention ? Relax ?  (> 30 Hz) : attention ? Visual processing ? Motor ? …

GMresponseK Gating of the THETA band

How is the spontaneous EEG modified during meditative states ?

EEG Oscillations : it’s more complicated than that …. … But more interesting for our main topic

The function of EEG Oscillations depends on where they originate from Then, we should be able to understand what they tell us about meditation My main point Therefore, they must be studied and understood at the level of functionally homogeneous neural populations (at first….)

Select a set of cognitive tasks …. Some proposals on how to use electrophysiology to study meditation In which expert meditators perform much better than ‘normal’ subjects With well-known electrophysiological characteristics (functional anatomy + dynamics) Compare those characteristics between the two groups

Background Study of EEG at the intracerebral level In humans, in a variety of cognitive tasks Visual perception Memory Attention Language Movement …

And how it related to visual attention the notion of ‘brain availibility’ and visual imagery A simple face perception paradigm ….

Stimuli: 'Mooney' faces Readily recognized when presented in upright orientation Usually seen as meaningless black and white spots when presented upside-down. Brain Oscillations during the perception of visual objects

mean std F5-F4 : Fusiform Gyrus 121 trials Very little freedom ….

Pat1, fusiform gyrus I III II IV

Pat1, fusiform gyrus Mean Deviation [50 – 200 Hz] P NP

Pat2, Inferior temporal gyrus BA37 (Bipole e’7e’8) Mean Deviation [50 – 200 Hz] Evoked Potential P NP P NP

O’ E’ FUSIFORM GYRUS PRIMARY VISUAL CORTEX

PRIMARY VISUAL CORTEX Sorry, my brain is busy, I can’t get your call right now … Fusiform gyrus

The Attentional blink : how to hide things to the brain Do seasoned meditators Blink attentionally ? Sorry, my brain is busy, I can’t get your call right now …

OK, you have my full attention, now

And now, MENTAL IMAGERY and the BETA range

from ( Tallon-Baudry et al., 01 )

Yes

And how it related to self (executive) control A simple occulo-motor paradigm ….

SaccadeAnti-Saccade time Look Away !

« This ability to control behaviour flexibly, responding automatically to stimuli in one situation and suppressing this automatic response in favour of an alternative response in a different situation, is the hallmark of executive control. In this review, we describe how the antisaccade task can be used to investigate the volitional control of action » Munoz et al. Nature Reviews Neuroscience 2004

And how they related to ‘the little voice in the head’ Two simple language paradigms ….

leiletaitfoisunepetitchat time 1s adapted from Nobre et al. 1998

AMPLITUDE MODULATION BETWEEN 30 AND 150 Hz (z-score / ligne de base [-500ms : -100ms]) Left Motor Operculum : GREEN TARGET : RED TARGET : GREEN IGNORED : RED IGNORED

SEMAN : living entity or not ? PHONO : final sound : vowel or cons. ? ORTHO : twice the same letter ? VISUAL : twice the same item ? nefoul cheval xwsxkz adapted from Bentin et al. 1999

Amplitude Modulation between 30 and 150 Hz (z-score / base line[-500ms : -100 ms]) Broca Area Motor Operculum Associative Auditory Cortex Inferior Frontal Gyrus

Select a set of cognitive tasks …. Some proposals on how to use electrophysiology to study meditation In which expert meditators perform much better than ‘normal’ subjects With well-known electrophysiological characteristics (functional anatomy + dynamics) Compare those characteristics between the two groups

THE FUTURE Real-time Feedback Non-invasive dynamic mapping using EEG/MEG and source modelling