Poster A60, Saturday, March 25, 5:00 – 7:00 pm, Pacific Concourse
Time-course of motor involvement in literal and metaphoric action sentence processing: A TMS study
Megan Reilly1, Olivia Howerton1, Rutvik Desai1; 1University of South Carolina
There is ample evidence that the motor cortex is involved in reading sentences that contain an action verb ("The lengthy spike was hammered into the ground"). This also holds for metaphoric sentences ("The weak army was hammered again in battle"). One view suggests that verbs such as 'hammered' are homonyms, with one meaning related to the literal action (physical hammering) and one to the abstract meaning (defeat badly). Another view holds that such verbs are polysemous, and the two senses are related and not independent. The metaphoric or abstract sense is grounded in the literal sense. Using single-pulse transcranial magnetic stimulation (TMS), we investigated whether disruption to motor areas affects literal and metaphoric sentence comprehension. In the primary motor cortex, stimulation 300 ms post-verb presentation impaired comprehension of both literal and metaphor sentences relative to control sentences. This supports grounded semantic views, where sensory-motor areas play a causal role in comprehension. These results also suggest that the literal meaning of an action verb remains activated during metaphor comprehension, even after the temporal window during which homophones are disambiguated (around 200 ms). This suggests that such verbs are polysemous rather than homonymous, and both senses are related and grounded in motor cortex. A second experiment using stimulation to the left anterior inferior parietal lobe suggests that TMS to a higher-order motor region selectively inhibits metaphor processing.
Topic Area: LANGUAGE: Semantic