Theta Oscillations Support Prefrontal-hippocampal Interactions in Sequential Working Memory

The prefrontal cortex and hippocampus may support sequential working memory beyond episodic memory and spatial navigation.This stereoelectroencephalography(SEEG)study investigated how the dorsolateral prefrontal cortex(DLPFC)interacts with the hippocampus in the online processing of sequential information.Twenty patients with epilepsy(eight women,age 27.6±8.2 years)completed a line ordering task with SEEG recordings over the DLPFC and the hippocampus.Participants showed longer thinking times and more recall errors when asked to arrange random lines clockwise(random trials)than to maintain ordered lines(ordered trials)before recalling the orientation of a particular line.First,the ordering-related increase in thinking time and recall error was associated with a transient theta power increase in the hippocampus and a sustained theta power increase in the DLPFC(3–10 Hz).In particular,the hippocampal theta power increase correlated with the memory precision of line orientation.Second,theta phase coherences between the DLPFC and hippocampus were enhanced for ordering,especially for more precisely memorized lines.Third,the theta band DLPFC→hippocampus influence was selectively enhanced for ordering,especially for more precisely memorized lines.This study suggests that theta oscillations may support DLPFC-hippocampal interactions in the online processing of sequential information.

Harnessing GABAergic Transmission for Slow Oscillations

Oscillatory neuronal activity is the fundamental signature of neural networks.In the EEG literature,the oscillations are described as belonging to different frequency bands that are commonly used in clinical monitoring.

Differences and potential mechanisms of theta oscillation and temporoparietal and temporal-central networks in temporal lobe epilepsy patients with unilateral hippocampal sclerosis

Background There is a lack of further exploration of the epileptogenic network of specific types of epilepsy,such as unilateral hippocampal sclerosis(HS),and there is an urgent need to find exact evidence to confirm the consistency of its brain network changes.Methods We enrolled 22 mesial temporal lobe epilepsy with hippocampal sclerosis(mTLE-HS)patients to compare the differences in brain activity between 22 healthy controls(HCs)and them.Resting-state electroencephalography(EEG)was also measured.Then,we calculated the power spectral density and phase locking values in and between these electrodes.Results The results showed the increased theta power was related to the high severity of epilepsy in the temporal,parietal,and central regions in mTLE-HS patients,and there were positive correlations between theta power in the contralateral temporal region and seizure frequency.Theta power in the ipsilateral parietal lobe is positively correlated with the number of anti-seizure medications(ASMs),but not with the usage of third-generation ASMs.Meanwhile,the temporal lobe of mTLE-HS patients had more connectivity with parietal lobe and central region.