Gamma EEG activity induced by semantic violation during sentence reading.

In the present research changes in electroencephalographic (EEG) power spectrum induced by semantic violations in Italian sentences were examined. Significant effects related to the sentence correctness were found only within gamma frequency range (approximately 30-100 Hz), with well-formed sentences showing higher gamma levels than sentences containing the violation. Lower gamma band (approximately 30-45 Hz) marked semantic violation at the level of the target word and did not show specific scalp topography. Instead, in addition to the same violation effect, analyses of the two upper gamma bands (upper-1 gamma: approximately 55-75 Hz; upper-2 gamma: approximately 75-100 Hz) revealed, for the word following the target, significant greater gamma levels for correct vs. incorrect sentences specifically over anterior right sites. The functional significance of gamma band and its contribution to psycholinguistic field are discussed, by highlighting its use as an additional tool, with respect to evoked potentials, for investigating linguistic network dynamics associated to sentence processing.