Search

Background and Aims: Glioma growth in eloquent language areas induces adaptive activation changes in the language network. The present study aimed to (1) investigate the pre- to postoperative evolution of neural phoneme perception processes in glioma patients and (2) assess if event-related potentials (ERPs) reflecting phoneme perception can provide added value to the diagnostic approach in individuals undergoing awake surgery. Methods and Procedures: In five persons undergoing an awake craniotomy for the resection of a glioma, pre- and postoperative behavioural language assessment (Aachen Aphasia Test, Comprehensive Aphasia Test and Boston Naming Test) and electrophysiological investigation of phoneme perception was performed. For the latter, ERPs were obtained through the administration of an inattentive (Mismatch Negativity; MMN) and attentive (P300) oddball paradigm containing a phonemic articulation place contrast during EEG recording. Outcomes and Results: Aberrant phoneme categorization processing was evidenced in all five participants preoperatively based on the MMN and P300 amplitude and latency. Moreover, mild behavioural impairments were found in four participants at this time. Postoperatively, three out of five participants reached behavioural ceiling effects, while four individuals displayed normalization of electrophysiological measures. Conclusions: While neural processing of phoneme contrasts was preoperatively affected by glioma-induced disturbances, a high potential for postsurgical plasticity was shown. As four participants presented with a high grade glioma, tumour grade might partially account for this pattern. Addition of electrophysiological tests to the language assessment could provide benefits in both the preand postoperative clinical diagnostic approach in glioma patients. These preliminary results need validation in a larger sample. [ABSTRACT FROM AUTHOR]

The reward positivity (RewP) is an event-related brain potential (ERP) component that emerges approximately 250 to 350 milliseconds (ms) after receiving reward-related feedback stimuli and is believed to be important for reinforcement learning and reward processing. Although numerous localization studies have indicated that the anterior cingulate cortex (ACC) is the neural generator of this component, other studies have identified sources outside of the ACC, fuelling a debate about its origin. Because the results of EEG and MEG source localization studies are severely limited by the inverse problem, we addressed this question by leveraging the high spatial and temporal resolution of intracranial EEG. We predicted that we would identify a neural generator of the RewP in the caudal ACC. We recorded intracranial EEG in 19 refractory epilepsy patients who underwent invasive video-EEG monitoring at Ghent University Hospital, Belgium. Participants engaged in the virtual T-maze task (vTMT), a trial-and-error task known to elicit a canonical RewP, while scalp and intracranial EEG were simultaneously recorded. The RewP was identified using a difference wave approach for both scalp and intracranial EEG. The data were aggregated across participants to create a virtual "meta-participant" that contained all the recorded intracranial ERPs (iERPs) with respect to their intracranial contact locations. We used both a hypothesis-driven (focused on ACC) and exploratory (whole-brain analysis) approach to segment the brain into regions of interest (ROI). For each ROI, we evaluated the degree to which the time course of the absolute current density (ACD) activity mirrored the time course of the RewP, and confirmed the statistical significance of the results using permutation analysis. The grand average waveform of the scalp data revealed a RewP at 309 ms after reward feedback with a frontocentral scalp distribution, consistent with the identification of this component as the RewP. The meta-participant contained iERPs recorded from 582 intracranial contacts in total. The ACD activity of the aggregated iERPs were most similar to the RewP in left caudal ACC, left dorsolateral prefrontal cortex, left frontomedial cortex, and left white matter, with the highest score attributed to caudal ACC, as predicted. To our knowledge, this is the first study that uses intracranial EEG aggregated across multiple human epilepsy patients and current source density analysis to identify the neural generator(s) of the RewP. These results provide direct evidence that the ACC is a neural generator of the RewP., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)