The time course of idiom processing.

Recent neuropsychological and neurophysiological studies have suggested that the neural correlates of idiom processing are predominantly
located in the left Brodmann’s area (BA) 22 and, to some extent, in the prefrontal cortex. The present study explores the temporal dynamics of left
prefrontal and temporal cortex in idiom processing by using repetitive transcranial magnetic stimulation (rTMS) in normal subjects.
Forty-five opaque highly familiar idioms and 45 literal sentences were used. Forty-three subjects completed 5 blocks of 18 trials (9 idioms,
9 literal sentences) corresponding to 4 stimulation conditions (left prefrontal, left temporal, vertex, no-stimulation baseline). Each subject was
assigned to one of three groups, which differed in the timing of stimulation delivery.
A selective impairment in accuracy for idioms was found when rTMS was applied to the prefrontal and temporal cortex 80ms after picture
presentation, confirming the role of these regions in this task. Moreover, rTMS to the prefrontal cortex, but not to the temporal cortex, continued
to affect the performance with idiomatic sentences at the later time of 120 ms. The results seem to suggest that the prefrontal region is involved
in both the retrieval of the figurative meaning from semantic memory and the monitoring of the response by inhibiting alternative interpretations
when a picture-matching task is used.