Abstract
The capacity to respond to novel events is crucial for adapting to the constantly changing environment. Here, we recorded 29-channel Event Related Brain Potentials (ERPs) during an active auditory novelty oddball paradigm and used for the first time Current Source Density-transformed Event Related Brain Potentials and associated time-frequency spectra to study target and novelty processing in a group of epileptic patients with unilateral damage of the hippocampus (N = 18) and in healthy matched control participants (N = 18). Importantly, we used Voxel-Based Morphometry to ensure that our group of patients had a focal unilateral damage restricted to the hippocampus and especially its medial part. We found a clear deficit for target processing at the behavioral level. In addition, compared to controls, our group of patients presented (i) a reduction of theta event-related synchronization (ERS) for targets and (ii) a reduction and delayed P3a source accompanied by reduced theta and low-beta ERS and alpha event-related synchronization (ERD) for novel stimuli. These results suggest that the integrity of the hippocampus might be crucial for the functioning of the complex cortico-subcortical network involved in the detection of novel and target stimuli.
Highlights
Integrity of the hippocampus does not predict the amplitude of the P3b component to targets in temporal-lobe epileptic patients with unilateral sclerotic hippocampus (TLE-UHS)[27]
We used CSD-transformed Event Related Brain Potentials (ERPs) and associated time-frequency spectra to compare a group of temporal-lobe epileptic patients with unilateral sclerotic hippocampus to a group of healthy participants during an active novelty auditory oddball task
We found a higher number of misses and slower Reaction times (RTs) in the TLE-UHS group than in the control group suggesting a deficit for target processing at the behavioral level
Summary
Integrity of the hippocampus does not predict the amplitude of the P3b component to targets in temporal-lobe epileptic patients with unilateral sclerotic hippocampus (TLE-UHS)[27]. Compared to controls, patients presented an attenuation of alpha ERD to targets but a similar pattern of CSD-transformed ERPs to novel stimuli These results are in line with previous findings showing an increase of alpha ERD during an active auditory oddball task as compared to a passive condition[44]. The main goal of the present study was to explore the electrophysiological correlates of target and novelty processing in patients with unilateral hippocampal sclerosis With this aim and following previous reports[26, 41], we used for the first time CSD-transformed ERPs and associated TF spectra to compare a group of epileptic patients with unilateral damage restricted to the hippocampus to a group of healthy matched control participants. Within the group of patients, we were not expecting a clear effect of lesion side but a negative effect of GABAergic medication on these measures
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
