Integration or Predictability? A Further Specification of the Functional Role of Gamma Oscillations in Language Comprehension

Abstract

Gamma-band neuronal synchronization during sentence-level language comprehension has previously been linked with semantic unification. Here, we attempt to further narrow down the functional significance of gamma during language comprehension, by distinguishing between two aspects of semantic unification: successful integration of word meaning into the sentence context, and prediction of upcoming words. We computed event-related potentials (ERPs) and frequency band-specific electroencephalographic (EEG) power changes while participants read sentences that contained a critical word (CW) that was (1) both semantically congruent and predictable (high cloze, HC), (2) semantically congruent but unpredictable (low cloze, LC), or (3) semantically incongruent (and therefore also unpredictable; semantic violation, SV). The ERP analysis showed the expected parametric N400 modulation (HC < LC < SV). The time-frequency analysis showed qualitatively different results. In the gamma-frequency range, we observed a power increase in response to the CW in the HC condition, but not in the LC and the SV conditions. Additionally, in the theta frequency range we observed a power increase in the SV condition only. Our data provide evidence that gamma power increases are related to the predictability of an upcoming word based on the preceding sentence context, rather than to the integration of the incoming word’s semantics into the preceding context. Further, our theta band data are compatible with the notion that theta band synchronization in sentence comprehension might be related to the detection of an error in the language input.

Basic composition and enriched integration in idiom processing: An EEG study.

“…power increase in the lower Gamma (35-45Hz) has been associated with the processing of correct sentences compared to sentences containing semantic violations (Hald et al, 2006;Wang et al, 2012; but see the increase in gamma for world knowledge violations observed in Hagoort et al, 2004); also the power increase in middle gamma range (50-70Hz) has been reported for successful sentence processing (Penolazzi et al, 2009;Monsalve, Perez & Molinaro, 2014). Despite the different frequency ranges of lower and middle gamma bands, and the different time development of the effects observed (sustained in time, Hald et al, 2006;Penolazzi et al, 2009;Wang et al, 2012;or short lasting, Monsalve et al, 2014), according to a recent interpretation of these changes the increase in gamma power would reflect reverberatory activity triggered by a successful match "between the pre-activation of the neural representation of the predicted word, and the neural representation of the actually incoming word" (Wang et al,p.11).…”

“…Despite the different frequency ranges of lower and middle gamma bands, and the different time development of the effects observed (sustained in time, Hald et al, 2006;Penolazzi et al, 2009;Wang et al, 2012;or short lasting, Monsalve et al, 2014), according to a recent interpretation of these changes the increase in gamma power would reflect reverberatory activity triggered by a successful match "between the pre-activation of the neural representation of the predicted word, and the neural representation of the actually incoming word" (Wang et al,p.11). This explanation (see also Lewis & Bastiaansen, 2015) processes involved in processing highly predictable strings.…”

“…In fact, power increase in lower and middle gamma frequency bands (approximately between 35-75 Hz) has been associated with successful semantic unification mechanisms (e.g., Hald, Bastiaansen & Hagoort, 2006;Penolazzi, Angrilli & Job, 2009;Wang, Zhu & Bastiaansen, 2012). Lewis and Bastiaansen (2015) proposed that such activity "reflects a match between strong top-down predictions and bottom-up linguistic input" (p.159).…”

Females with schizophrenia have abnormal functional cortical connectivity in the gamma frequency during an auditory oddball task using magnetoencephalography

“…Hypothalamic abnormalities in schizophrenia were associated with endocrine dysfunction the stress response and the hypothalamic-pituitary-adrenal (HPA) axis [54]. Patients with schizophrenia spectrum had a larger pituitary volume (larger in female than male patients), reflecting hyperactivity of the HPA axis, which may be related to a common vulnerability to stress in patients [63].…”

“…Gamma ERS has been implicated in the coordination of activity between distributed neuronal assemblies in the service of sensory registration of stimuli and perceptual binding of their features, and schizophrenia patients have demonstrated deficits in the magnitude and/or phase synchrony of stimulus-evoked gamma oscillations [53]. Gamma ERS during sentence-level language comprehension has previously been linked with semantic unification, and increased gamma power was related to the predictability of an upcoming word based on the preceding sentence context [54]. Gamma ERS was associated with cortical activation while imagining the movement of body parts, and appeared to be located near somatosensory and motor areas [55].…”