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Post-doctoral position

 

Location: Paris , FRANCE

Neurosciences Cognitives et Imagerie Fonctionnelle Cérébrale / Cognitive Neuroscience and Functional Brain Mapping (CNRS laboratory, UPR 640-LENA, Director : Line Garnero)

Name of the Project:  Towards a neurophysiology of metacognition

In charge of the project :

Bernnard RENAULT , Jean LORENCEAU,  Joëlle PROUST.

A general presentation of this collaborative project involving 7 teams can be found on http://mpscesf.free.fr/

Consciousness studies and cognitive human neurophysiology has a long history that was fueled between 1965 and early eighties by the discovery and the study of the so-call “endogenous” or “cognitive” event-related potentials (ERPs); see Gaillard & Ritter (1983). One notable feature of these endogenous ERPs is that they can be elicited by a variety of stimuli or events from any stimulus modality. The only requirement is that the events have distinct onsets and that they are classifiable into two or more categories. In that case they elicit the N2m-P3b response, which is composed by a negative “modality specific” wave (N2m) whose duration varies with that of the processing and is followed by a positive parietal (P3b) wave (Renault et al. 1982). A lot of studies have also reported that another type of response, the N2-P3a “vertex complex”, can also be elicited by unpredictable shifts in an ongoing sequence of stimuli and reflects automatic and irrepressible processes involved in the involuntary capture of attention without awareness of the exact meaning of the stimulus. Quite interestingly it has also been shown that unconscious recognition (without awareness) of well-known faces by prosopagnosic patients only evokes the N2-P3a “vertex complex” whereas the few trials where conscious face recognition was done did evoked the N2m-P3b response (Renault et al. 1989). These results support that for control subjects, during tasks where a response choice should be made, the amplitude balance between P3a and P3b waves would be in favour of the P3b for conscious decisions but in favour of the P3a for unconscious decision. However such a demonstration had not yet been clearly achieved (see Sergent et al. 2005) and this is one of the main objectives of our project for metacognitive decisions.

Moreover, a significant number of studies have also shown local synchronization in the gamma band (between 30-80 Hz: see Gray et al, 1989 for an example) in single cells studies recorded from animals during cognitive acts. More recently, we reported long-range synchrony in humans, between occipital, parietal and frontal areas, during the conscious perception of complex significant visual stimuli whereas these synchronizations disappeared when the stimulus was not significant (Rodriguez et al. 1999). Subsequently, based on the search for long distance synchronization in specific frequency EEG band, we also described “waves of consciouness” during binocular rivalry (Cosmelli et al; 2004). In this latter experiment we analyzed, in human, phase relations between cortical sources driven by a frequency tagged stimulus (at 5 Hz) during the ongoing conscious succession of dominance and suppression periods.

The Post Doctoral researcher will have to concentrate on the following main objectives:

1)             to test the existence of different indices of conscious and unconscious processing of human subjects (ERPs and long distance EEG rhythms synchronization) during adequate experimental  paradigms. Good knowledge of human neurophysiology and psychophysics are needed.

2)             to obtain very precise brain mapping of the induced activations both along time (with a  msec precision) and for their brain locations (with a few mm precision) by using MEG and EEG and reconstruction procedure based on individual subject brain anatomy obtained from MRI.

3)             Moreover, he will also study phase synchronizations due to frequency tagging procedure in order to better describe the functional brain network involved during the perception-decision processes.

 These analyses should thus contribute to reveal specific networks with different brain spatio-temporal dynamics for each kind of subject’ responses that could then become templates for studying the possibility of  metacognition in other species.

REFERENCES

Cosmelli D., David O., Lachaux J.-P., Martinerie J., Garnero L., Renault B. & Varela F. (2004). Waves of Consciousness: Ongoing Cortical Patterns during Binocular Rivalry. NeuroImage, 23, 128-140.  Gaillard A.W.K. & Ritter W.  (Eds.) , (1983). Tutorials in Event Related Potential Research: Endogenous Components. Advances in Psychology, North-Holland, Amsterdam.  Gray, C.M., Kônig, P., Engel, A;K. & Singer, W. (1989) Oscillatory responses in cat visual cortex exhibit intercolumnar synchronization which reflects global stimulus properties. Nature, 338, 334-337.  Renault B., Ragot R., Lesèvre N. and Rémond A. (1982) Brain events: their onset and offset as indices of mental chronometry. Science, 215, 1413-1415. Renault B., Signoret J.L., Debruille B., Breton F. and Bolgert F. (1989) Brain potentials reveal covert facial recognition in prosopagnosia. Neuropsychologia, 27, 905-912. Rodriguez, E., George, N., Lachaux, J. P., Martinerie, J., Renault, B. & Varela, F. J. (1999) Perception's shadow: long-distance synchronization of human brain activity. Nature, 397, 430-433.  Sergent C.. Baillet, S.,  Dehaene, S. 2005. Timing of the brain events underlying access to consciousness during the attentional blink. Nature Neuroscience, 8, 1390-1400  

Candidate' skills : 

Candidates should be familiar with human neurophysiology and brain mapping: MEG-EEG, event-related potentials (ERPs), and long distance EEG or MEG synchronizations. Additional knowledge on fMRI recording and analysis and good level of MATLAB programming will be welcome. Competence in psychophysics and statistical analysis are a plus.

Contact Bernard.Renault@chups.jussieu.fr   _______________________________

Bernard RENAULT, DSci

Directeur de Recherche CNRS

CNRS UPR 640-LENA

Hôpital Pitié-Salpêtrière,

47 Bd de l'Hôpital,

75651 Paris Cedex 13