A new insight into sentence comprehension: The impact of word associations in sentence processing as shown by invasive EEG recording

Abstract

The effect of word association on sentence processing is still a matter of debate. Some studies observe no effect while others found a dependency on sentence congruity or an independent effect. In an attempt to separate the effects of sentence congruity and word association in the spatio-temporal domain, we jointly recorded scalp- and invasive-EEG (iEEG). The latter provides highly localized spatial (unlike scalp-EEG) and high temporal (unlike fMRI) resolutions. We recorded scalp- and iEEG in three patients with refractory epilepsy. The stimuli consisted of 280 sentences with crossed factors of sentence congruity and within sentence word-association. We mapped semantic retrieval processes involved in sentence comprehension onto the left temporal cortex and both hippocampi, and showed for the first time that certain localized regions participate in the processing of word-association in sentence context. Furthermore, simultaneous recording of scalp- and iEEG gave us a direct overview of signal change due to its propagation across the head tissues.

Semantic and perceptual priming activate partially overlapping brain networks as revealed by direct cortical recordings in humans

“…In ECoG, the said effect was most pronounced in later time-windows (in particular during the N400) and was spatially localized mainly in the left superior and middle temporal gyri and, to a considerably lesser extent, in the right temporal cortex (middle temporal and fusiform gyri). This observation suggests that semantic priming reflected by the N400 ERP is mainly concentrated in the left temporal cortex, as previously reported (Khachatryan et al, 2018;Ghosh Hajra et al, 2018).…”

“…This is additionally supported by the observed ERSs in the alpha band during the said time windows in response to primes and ERDs in response to related targets, as an increase in alpha power has been linked to inhibition (Klimesch, 2012). Some previous studies (Khachatryan et al, 2018;Migliaccio et al, 2016) suggest the involvement of the middle part of the left middle temporal gyrus (mMTG) in semantic processing and locate the semantic hub in the anterior temporal cortex (ATL) (Patterson et al, 2007), also based on observations of N400 in that area (Lau et al, 2013;Jackson et al, 2015). In the current study, we observed an N400 effect in the left middle temporal cortex spanning to ATL, as well as an increase in high-gamma power around the N400 time window in response to related targets, which confirms the involvement of this area in semantic processing.…”

“…S1; for the MNI coordinates of each electrode, see SI, Table S4). First, we conduct the ERP analysis that has been long considered for studying the temporal dynamics of priming in both scalp- recorded (Khachatryan et al, 2016a;Kovalenko et al, 2012) and intracranial EEG (Nobre and McCarthy, 1995;Khachatryan et al, 2016bKhachatryan et al, , 2018. After that, we conduct a time-frequency analysis looking for event-related synchronization/desynchronization (ERS/ERD) in the high-gamma (80-120 Hz), alpha (8-12 Hz) and theta (4-7.5 Hz) bands, each of which reflects certain conditions (e.g., focal activation for high-gammas) in the brain.…”

“…For the remaining electrodes, epochs containing interictal or ictal epileptic activity or excessive abnormal slowing were also rejected. To the remaining ECoG data we first applied a conventional ERP analysis, generally identical to the procedure for scalp-recorded EEG, except for the higher epoch rejection threshold ( AE500 μV), as in general ECoG data has larger magnitude, and instead of re-referencing to the mastoids, each electrode in each grid was re-referenced to its common average reference (CAR), as usually done in ECoG data analysis (Khachatryan et al, 2018;Wittevrongel et al, 2017).…”

Time to Face Language: Embodied Mechanisms Underpin the Inception of Face-Related Meanings in the Human Brain

“…2010 ; Ponz et al. 2013 ; Khachatryan et al. 2018 ) studies and that, assuming average response latencies in the order of 700 ms, trials would be roughly 2000 ms apart from each other.…”