Poster C121, Sunday, March 26, 5:00 – 7:00 pm, Pacific Concourse
pMTG and dlPFC involvement in top-down contextual effects during the perception of other people's actions
Lucia Amoruso1, Alessandra Finisguerra1, Cosimo Urgesi1,2; 1University of Udine, Italy, 2Scientific Institute (IRCCS) Eugenio Medea
Single-pulse TMS studies suggest that motor activity can be modulated by high-level contextual representations. Specifically, in a series of previous experiments, we observed a facilitation of M1 activity during the observation of actions embedded in congruent contexts and a decrease when these were embedded in incongruent ones. However, direct evidence about the neural areas involved in these modulations is lacking. Here, we used a perturb-and-measure TMS approach, which offers the unique possibility of i) disrupting neural activity in regions of interest using continuous theta burst stimulation, and to ii) measure the consequent functional modulation of M1 activity to observed actions via online spTMS. We administered cTBS over the dorsolateral prefrontal cortex (dlPFC), and the posterior middle temporal gyrus (pMTG). After each “perturb session” participants underwent a “measure session”. During the measure session, motor evoked potentials (MEPs) were recorded from hand and arm muscles while participants watched videos of everyday actions embedded in congruent, incongruent or neutral contexts. Video ending was occluded from view and participants had to predict action unfolding. We found that, when interfering with dlPFC activity, both effects were abolished. When disrupting pMTG activity, we observed a facilitation for actions embedded in either congruent or incongruent contexts. Overall, these results suggest that i) the dlPFC might exert a top-down modulation in motor responses by providing contextual information necessary to estimate the probability of a given outcome; and that ii) the pMTG might be involved in a process of semantic retrieval when processing actions embedded in natural contexts.
Topic Area: PERCEPTION & ACTION: Other