Seminaire: Asaf Bachrach, Alpage, lundi 9 mars

[Thierry Hamon]

Date: Mon, 2 Mar 2009 14:33:38 +0100
From: Benoit Crabbé <bcrabbe at linguist.jussieu.fr>
Message-Id: <54E2A065-7213-49B3-AAAE-5B0A24314C9F at linguist.jussieu.fr>

******************* Séminaire Alpage *******************

         Séminaire de l'école doctorale de Paris 7

Il s'agit du séminaire de recherche en linguistique informatique
organisé par l'équipe Alpage, Alpage est une nouvelle équipe mixte
Inria -- Paris 7 issue de la fusion des équipes Atoll et Talana.
L'équipe centre ses intérêts scientifiques autour de l'analyse
syntaxique automatique et du traitement du discours pour la langue
française.

Ce séminaire remplace l'ancien séminaire Talana. Il se tient le lundi
de ***14.00*** à ***16.00*** tous les 15 jours.
Il a lieu en salle 131 au 30 rue du Château des Rentiers 75013 Paris
(premier étage)

Toute personne intéressée est la bienvenue.


Lundi 9 mars, Asaf Bachrach (INSERM/CEA  Cognitive Neuroimaging Unit)  
nous parlera de :

MRI investigation of incremental language processing in a  
naturalistic context »

Résumé :

Our study examined brain activation in a naturalistic language
processing task, with a particular focus on the temporal dynamics
inherent to this complex cognitive task.
Sentence processing, in particular in the auditory modality, is
incremental. The structure and associated compositional meaning of a
sentence are not provided to the listener instantaneously, but require
integration over multiple temporally spaced inputs.  Behavioral and
electrophysiological evidence (a small sample of which will be
reviewed) point out that the human parser makes use of an `eager'
strategy, incrementally constructing the eventual sentential
representation based on partial input. In addition, it appears that
this incremental strategy is probabilistic and parallel. The parser
considers potentially multiple alternative analyses, which are
probabilistically weighted.

Most behavioral and imaging paradigms used to explore aspects of
incremental auditory sentence processing have been limited by the use
of qualitative or binary contrasts and by a sparse sampling approach
(often only one data point per sentence). In this talk we will present
the results of a novel imaging paradigm that attempts to overcome the
above limitations.

We used functional Magnetic Resonance Imaging (fMRI) to monitor brain
activation while subjects passively listen to short narratives. The
texts were written so as to introduce various syntactic complexities
(relative clauses, embedded questions, etc.) not usually found (in
such density) in actual corpora.
With the use of computationally implemented probabilistic parser
(taken to represent an 'ideal listener') we have calculated a number
of temporally dense (one per word) parametric measures reflecting
different aspects of the incremental processing of each sentence.  We
used the resulting measures to model the observed brain activity
(BOLD). We were able to identify different brain networks that support
incremental linguistic processing and characterize their particular
function.

In the talk we will present data regarding the effect of contextually
based prediction (or surprisal), distinguishing lexical and syntactic
prediction, and the effect of local entropy or uncertainty.



Calendrier *prévisionnel* des séminaires à venir :

Joakim Nivre (Uppsala) : 16/3
Alexis Nasr (Marseilles) :  6/4
Mirella Lapata (Edinburgh) : 27/4
Jennifer Foster (Dublin):  4/5

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