What can Electrophysiology and Brain Rythms tell us
What can Electrophysiology (and Brain Rythms) tell us about ‘Meditation’ ? Jean-Philippe LACHAUX CNRS - LENA - PARIS INSERM – U 280 – 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
cms spatial resolution meg -eeg fmri pet seeg neurons ms temporal resolution minutes
EEG/MEG in Humans Evoked Potentials EEG Oscillations ‘spontaneous EEG’
EEG Oscillations Synchronization of large neural populations Several characteristic frequency bands with different functional specificities (more or less) d (<4 Hz) q (4 -7 Hz) : working memory, mental load ? a , m (7 -14 Hz) : relax ? ‘idle rythm? ’ b (15 – 30 Hz) : sustained attention ? Relax ? g (> 30 Hz) : attention ? Visual processing ? Motor ? …
G M Gating of the THETA band K response
How is the spontaneous EEG modified during meditative states ?
EEG Oscillations : it’s more complicated than that …. … But more interesting for our main topic
My main point The function of EEG Oscillations depends on where they originate from Therefore, they must be studied and understood at the level of functionally homogeneous neural populations (at first…. ) Then, we should be able to understand what they tell us about meditation
Some proposals on how to use electrophysiology to study meditation Select a set of cognitive tasks …. 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 …
A simple face perception paradigm …. And how it related to visual attention the notion of ‘brain availibility’ and visual imagery
Brain Oscillations during the perception of visual objects Stimuli: 'Mooney' faces Readily recognized when presented in upright orientation Usually seen as meaningless black and white spots when presented upside-down.
Very little freedom …. F 5 -F 4 : Fusiform Gyrus 121 trials std mean
Pat 1, fusiform gyrus III IV I II
Pat 1, fusiform gyrus Mean Deviation [50 – 200 Hz] P NP
Pat 2, Inferior temporal gyrus BA 37 (Bipole e’ 7 e’ 8) Mean Deviation [50 – 200 Hz] P NP Evoked Potential P NP
FUSIFORM GYRUS E’ PRIMARY VISUAL CORTEX O’
Sorry, my brain is busy, I can’t get your call right now … PRIMARY VISUAL CORTEX Fusiform gyrus
Sorry, my brain is busy, I can’t get your call right now … The Attentional blink : how to hide things to the brain Do seasoned meditators Blink attentionally ?
OK, you have my full attention, now
And now, MENTAL IMAGERY and the BETA range
from ( Tallon-Baudry et al. , 01 )
Yes
Yes
A simple occulo-motor paradigm …. And how it related to self (executive) control
Saccade Anti-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
Two simple language paradigms …. And how they related to ‘the little voice in the head’
le il etait petit time une chat fois 1 s adapted from Nobre et al. 1998
: GREEN TARGET : RED TARGET AMPLITUDE MODULATION BETWEEN 30 AND 150 Hz : GREEN IGNORED (z-score / ligne de base [-500 ms : -100 ms]) : RED IGNORED Left Motor Operculum
cheval + SEMAN : living entity or not ? nefoul + PHONO : final sound : vowel or cons. ? xwsxkz + ORTHO : twice the same letter ? + VISUAL : twice the same item ? adapted from Bentin et al. 1999
Amplitude Modulation between 30 and 150 Hz (z-score / base line[-500 ms : -100 ms]) Broca Area Associative Auditory Cortex Motor Operculum Inferior Frontal Gyrus
Some proposals on how to use electrophysiology to study meditation Select a set of cognitive tasks …. 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 Non-invasive dynamic mapping using EEG/MEG and source modelling Real-time Feedback
- Slides: 41