|Reference code: ||PT/FB/BL-2008-192.04|
|Location: ||Arquivo PCA - Pasta 8/2008|
|Cortical dynamics underlying the intentions behind speech-acts: A MEG study|
|Publication year: ||2009|
Intention is an essential dimension of language-in-action. Using language, we do more than things such as stating, requesting, and refusing (Searle, 1969; Austin, 1980): we realize spontaneous, voluntary actions.
Our intended speech acts rely crucially on the matching between the output of our verbal actions and a prior intention (what the speaker decides to express using language, Levelt, 1989). However, how intention is generated in the brain during speech is an open question.
In the action domain, motor control theories postulate that, during action execution, the Central Nervous System generates “forward models” in order to predict the sensory consequences of our upcoming movements (Wolpert and Ghahramani, 2000). The parietal cortex is a key region for activating and maintaining these models. Indeed, left inferior parietal lesions alter the ability to report the time of conscious intention to act (Sirigu et al., 2004).
Does the intention to act depend on similar neurocognitive mechanisms also in other domains such as speech?
Our hypothesis is indeed that the parietal regions are involved in intentional processes that encompass both action and language.
In order to test this hypothesis, we adopted a Libet’s paradigm based on a temporal judgment task (Libet et al., 1983), in which 16 healthy subjects were asked to pronounce a one-word-like utterance and then to report verbally:
(a) the time when they first intended to speak (Intention condition)
(b) the time when they actually spoke (Speech condition)
Subject gave their verbal responses based on the position of a clock-hand turning around a clock-face on 2,560ms.
We used Magnetoencephalography to explore the neural dynamics associated with the awareness of the intention to speak.
We observed a negative rise of magnetic field over right parietal sensors, which was significantly higher in Intention than Speech (p<0.05) from -776 ms to -390ms before speech onset. This effect preceded the subjects’ reported time of their intention to speak (-352ms before speech onset). Furthermore, a right parietal source of brain activity emerged during the Intention condition within a time window from -890 to -290ms before speech onset. Left temporal regions were selectively engaged in the Speech task.
Taken together, the findings strongly support the view that the parietal cortex plays a key multimodal role in the conscious intention to act, whether this involves hand action or a linguistic act. These results are discussed in the perspective of the link between action and language in multimodal communication.
|Accessibility: ||Document exists in file|
|Secondary author(s): |
|Posada, A., Harquel, S., Delpuech, C., Sirigu, A.|
|Document type: |
|Number of reproductions: |
|Carota, F., Posada, A., Harquel, S., Delpuech, C., & Sirigu, A. (2009). Cortical dynamics underlying the intentions behind speech-acts: A MEG study. In Abstract Book of 11th International Pragmatics Conference, Melbourne, Australia (pp. 218-219).|
|Indexed document: ||No|
|Keywords: ||Spoken language / Action intention / Parietal cortex|
Cortical dynamics underlying the intentions behind speech-acts: A MEG study