Long-term memory deficits in temporal lobe epilepsy

MicroRNA-mediated regulation of neurotransmitter receptors in epilepsy: A systematic review

BACKGROUND

Pathogenesis of epilepsy involves dysregulation of the neurotransmitter system contributing to hyper-excitability of neuronal cells. MicroRNA (miRNAs) are small non-coding RNAs known to play a crucial role in post-transcriptional regulation of gene expression.

METHODS

The present review was prepared following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines, employing a comprehensive search strategy to identify and extract data from published research articles. Keywords suchas epilepsy, micro RNA (micro RNAs, miRNA, miRNAs, miR), neurotransmitters (specific names), and neurotransmitter receptors (specific names) were used to construct the query.

RESULTS

A total of 724 articles were identified using the keywords epilepsy, microRNA along with select neurotransmitter and neurotransmitter receptor names. After exclusions, the final selection consisted of 17 studies, most of which centered on glutamate and gamma-aminobutyric acid (GABA) receptors. Singular studies also investigated miRNAs affecting cholinergic, purinergic, and glycine receptors.

CONCLUSION

This review offers a concise overview of the current knowledge on miRNA-mediated regulation of neurotransmitter receptors in epilepsy and highlights their potential for future clinical application.

Hippocampal transcriptomic analyses reveal the potential antiapoptotic mechanism of a novel anticonvulsant agent Q808 on pentylenetetrazol-induced epilepsy in rats

Brain apoptosis is one of the main causes of epileptogenesis. The antiapoptotic effect and potential mechanism of Q808, an innovative anticonvulsant chemical, have never been reported. In this study, the seizure stage and latency to reach stage 2 of pentylenetetrazol (PTZ) seizure rat model treated with Q808 were investigated. The morphological change and neuronal apoptosis in the hippocampus were detected by hematoxylin and eosin (HE) and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) staining, respectively. The hippocampal transcriptomic changes were observed using RNA sequencing (RNA-seq). The expression levels of hub genes were verified by quantitative reverse-transcription PCR (qRT-PCR). Results revealed that Q808 could allay the seizure score and prolong the stage 2 latency in seizure rats. The morphological changes of neurons and the number of apoptotic cells in the DG area were diminished by Q808 treatment. RNA-seq analysis revealed eight hub genes, including Map2k3, Nfs1, Chchd4, Hdac6, Siglec5, Slc35d3, Entpd1, and LOC103690108, and nine hub pathways among the control, PTZ, and Q808 groups. Hub gene Nfs1 was involved in the hub pathway sulfur relay system, and Map2k3 was involved in the eight remaining hub pathways, including Amyotrophic lateral sclerosis, Cellular senescence, Fc epsilon RI signaling pathway, GnRH signaling pathway, Influenza A, Rap1 signaling pathway, TNF signaling pathway, and Toll-like receptor signaling pathway. qRT-PCR confirmed that the mRNA levels of these hub genes were consistent with the RNA-seq results. Our findings might contribute to further studies exploring the new apoptosis mechanism and actions of Q808.

Canonical Wnt activator Chir99021 prevents epileptogenesis in the intrahippocampal kainate mouse model of temporal lobe epilepsy

The Wnt signaling pathway mediates the development of dentate granule cell neurons in the hippocampus. These neurons are central to the development of temporal lobe epilepsy and undergo structural and physiological remodeling during epileptogenesis, which results in the formation of epileptic circuits. The pathways responsible for granule cell remodeling during epileptogenesis have yet to be well defined, and represent therapeutic targets for the prevention of epilepsy. The current study explores Wnt signaling during epileptogenesis and for the first time describes the effect of Wnt activation using Wnt activator Chir99021 as a novel anti-epileptogenic therapeutic approach. Focal mesial temporal lobe epilepsy was induced by intrahippocampal kainate (IHK) injection in wild-type and POMC-eGFP transgenic mice. Wnt activator Chir99021 was administered daily, beginning 3 h after seizure induction, and continued up to 21-days. Immature granule cell morphology was quantified in the ipsilateral epileptogenic zone and the contralateral peri-ictal zone 14 days after IHK, targeting the end of the latent period. Bilateral hippocampal electrocorticographic recordings were performed for 28-days, 7-days beyond treatment cessation. Hippocampal behavioral tests were performed after completion of Chir99021 treatment. Consistent with previous studies, IHK resulted in the development of epilepsy after a 14 day latent period in this well-described mouse model. Activation of the canonical Wnt pathway with Chir99021 significantly reduced bilateral hippocampal seizure number and duration. Critically, this effect was retained after treatment cessation, suggesting a durable antiepileptogenic change in epileptic circuitry. Morphological analyses demonstrated that Wnt activation prevented pathological remodeling of the primary dendrite in both the epileptogenic zone and peri-ictal zone, changes in which may serve as a biomarker of epileptogenesis and anti-epileptogenic treatment response in pre-clinical studies. These findings were associated with improved object location memory with Chir99021 treatment after IHK. This study provides novel evidence that canonical Wnt activation prevents epileptogenesis in the IHK mouse model of mesial temporal lobe epilepsy, preventing pathological remodeling of dentate granule cells. Wnt signaling may therefore play a key role in mesial temporal lobe epileptogenesis, and Wnt modulation may represent a novel therapeutic strategy in the prevention of epilepsy.

Dental stem cells improve memory and reduce cell death in rat seizure model

Epilepsy is a common neurological disorder that significantly affects the quality of life of patients. In this study, we aim to evaluate the effectiveness of dental pulp stem cell (DPSC) transplantation in decreasing inflammation and cell death in brain cells, thus reducing seizure damage. We induced seizures in rats using intraperitoneal injections of pentylenetetrazole (PTZ). In the PTZ + DPSC group, we conducted bilateral hippocampal transplantation of DPSCs in PTZ-lesioned rat models. After 1 month, we performed post-graft analysis and measured some behavioral factors, such as working memory and long-term memory, using a T-maze test and passive avoidance test, respectively. We investigated the immunohistopathology and distribution of astrocyte cells through light microscopy and Sholl analysis. Additionally, we employed the Voronoi tessellation method to estimate the spatial distribution of the cells in the hippocampus. Compared to the control group, we observed a reduction in astrogliosis, astrocyte process length, the number of branches, and intersections distal to the soma in the hippocampus of the PTZ + DPSC group. Further analysis indicated that the grafted DPSCs decreased the expression of caspase-3 in the hippocampus of rats with induced seizures. Moreover, the DPSCs transplant protected hippocampal pyramidal neurons against PTZ toxicity and improved the spatial distribution of the hippocampal neurons. Our findings suggest that DPSCs transplant can be an effective modifier of astrocyte reactivation and inflammatory responses.

Distinct changes to hippocampal and medial entorhinal circuits emerge across the progression of cognitive deficits in epilepsy

Temporal lobe epilepsy (TLE) causes pervasive and progressive memory impairments, yet the specific circuit changes that drive these deficits remain unclear. To investigate how hippocampal-entorhinal dysfunction contributes to progressive memory deficits in epilepsy, we performed simultaneous in vivo electrophysiology in hippocampus (HPC) and medial entorhinal cortex (MEC) of control and epileptic mice 3 or 8 weeks after pilocarpine-induced status epilepticus (Pilo-SE). We found that HPC synchronization deficits (including reduced theta power, coherence, and altered interneuron spike timing) emerged within 3 weeks of Pilo-SE, aligning with early-onset, relatively subtle memory deficits. In contrast, abnormal synchronization within MEC and between HPC-MEC emerged later, by 8 weeks after Pilo-SE, when spatial memory impairment was more severe. Furthermore, a distinct subpopulation of MEC layer 3 excitatory neurons (active at theta troughs) was specifically impaired in epileptic mice. Together, these findings suggest that hippocampal-entorhinal circuit dysfunction accumulates and shifts as cognitive impairment progresses in TLE.

Electroencephalographic microstates as a potential neurophysiological marker differentiating bilateral from unilateral temporal lobe epilepsy

OBJECTIVE

Electroencephalographic (EEG) microstate abnormalities have been documented in different neurological disorders. We aimed to assess whether EEG microstates are altered also in patients with temporal epilepsy (TLE) and whether they show different activations in patients with unilateral TLE (UTLE) and bilateral TLE (BTLE).

METHODS

Nineteen patients with UTLE, 12 with BTLE, and 15 healthy controls were enrolled. Resting state high-density electroencephalography (128 channels) was recorded for 15 min with closed eyes. We obtained a set of stable scalp maps representing the EEG activity, named microstates, from which we acquired the following variables: global explained variance (GEV), mean duration (MD), time coverage (TC), and frequency of occurrence (FO). Two-way repeated measures analysis of variance was used to compare groups, and Spearman correlation was performed to study the maps in association with the clinical and neuropsychological data.

RESULTS

Patients with BTLE and UTLE showed differences in most of the parameters (GEV, MD, TC, FO) of the four microstate maps (A-D) compared to controls. Patients with BTLE showed a significant increase in all parameters for the microstates in Map-A and a decrease in Map-D compared to UTLE and controls. We observed a correlation between Map-A, disease duration, and spatial short-term memory, whereas microstate Map-D was correlated with the global intelligence score and short-term memory performance.

SIGNIFICANCE

A global alteration of the neural dynamics was observed in patients with TLE compared to controls. A different pattern of EEG microstate abnormalities was identified in BTLE compared to UTLE, which might represent a distinctive biomarker.

Lack of causal association between epilepsy and dementia: A Mendelian randomization analysis

OBJECTIVE

Epidemiological studies have reported an association between epilepsy and dementia. However, the causal relationship between epilepsy and the risk of dementia is not clear. We aimed to inspect the causal effect of epilepsy on memory loss and dementia.

METHODS

We analyzed summary data of epilepsy, memory loss, and dementia from the genome-wide association study (GWAS) using the two-sample Mendelian randomization (MR) method. We used the estimated odds ratio of memory loss and dementia associated with each of the genetically defined traits to infer evidence for a causal relationship with the following exposures: all epilepsy, focal epilepsy (including focal epilepsy with hippocampal sclerosis, lesion-negative focal epilepsy, and focal epilepsy with other lesions), and genetic generalized epilepsy (including childhood absence epilepsy, generalized tonic-clonic seizures alone, Juvenile absence epilepsy, and Juvenile myoclonic epilepsy).

RESULTS

According to the result of MR using the inverse variance weighted method (IVW), we found that genetically predicted epilepsy did not causally increase the risk of memory loss and dementia (p > 0.05). Results of the MR-Egger and weighted median method were consistent with the IVW method.

CONCLUSIONS

No evidence has been found to support the notion that epilepsy can result in memory loss and dementia. The associations observed in epidemiological studies could be attributed, in part, to confounding or nongenetic determinants.

Concordance of verbal memory and language fMRI lateralization in people with epilepsy

BACKGROUND AND PURPOSE

This work investigates verbal memory functional MRI (fMRI) versus language fMRI in terms of lateralization, and assesses the validity of performing word recognition during the functional scan.

METHODS

Thirty patients with a diagnosis of epilepsy underwent verbal memory, visuospatial memory, and language fMRI. We used word encoding, word recognition, image encoding, and image recognition memory tasks, and semantic description, reading comprehension, and listening comprehension language tasks. We used three common lateralization metrics: network spatial distribution, maximum statistical value, and laterality index (LI).

RESULTS

Lateralization of signal spatial distribution resulted in poor similarity between verbal memory and language fMRI tasks. Signal maximum lateralization showed significant (>.8) but not perfect (1) similarity. Word encoding LI showed significant correlation only with listening comprehension LI (p = .016). Word recognition LI was significantly correlated with expressive language semantic description LI (p = .024) and receptive language reading and listening comprehension LIs (p = .015 and p = .019, respectively). There was no correlation between LIs of the visuospatial tasks and LIs of the language tasks.

CONCLUSIONS

Our results support the association between language and verbal memory lateralization, optimally determined by LI quantification, and the introduction of quantitative means for language fMRI interpretation in clinical settings where verbal memory lateralization is imperative.

Diurnal circadian clock gene expression is altered in models of genetic and acquired epilepsy

OBJECTIVES

Growing evidence demonstrates a relationship between epilepsy and the circadian system. However, relatively little is known about circadian function in disease states, such as epilepsy. This study aimed to characterize brain and peripheral core circadian clock gene expression in rat models of genetic and acquired epilepsy.

METHODS

For the Genetic Absence Epilepsy Rats from Strasbourg (GAERS) study, we used 40 GAERS and 40 non-epileptic control (NEC) rats. For the kainic acid status epilepticus (KASE) study, we used 40 KASE and 40 sham rats. Rats were housed in a 7 am:7 pm light-dark cycle. Hypothalamus, hippocampus, liver, and small intestine samples were collected every 3 h throughout the light period. We then assessed core diurnal clock gene expression of per1, cry1, clock, and bmal1.

RESULTS

In the GAERS rats, all tissues exhibited significant changes in clock gene expression (P < 0.05) when compared to NEC. In the KASE rats, there were fewer effects of the epileptic condition in the hypothalamus, hippocampus, or small intestine (P > 0.05) compared with shams.

SIGNIFICANCE

These results indicate marked diurnal disruption to core circadian clock gene expression in rats with both generalized and focal chronic epilepsy. This could contribute to epileptic symptomology and implicate the circadian system as a viable target for future treatments.

Plastic rearrangement of basal forebrain parvalbumin-immunoreactive neurons in the kainite model of epilepsy

Temporal lobe epilepsy (TLE) is the most prevalent form of epilepsy, through the neuronal mechanisms of this syndrome remain elusive. In addition to the temporal lobe structures, it was found that the basal forebrain cholinergic cells are also involved in epileptogenesis. However, little is known about the involvement of the basal forebrain GABAergic neurons in epilepsy; despite this, they largely project to the temporal lobe and are crucial for the regulation of the hippocampal circuitry. In this study, we assessed epilepsy-induced changes in parvalbumin (PARV) immunoreactive neurons of the medial septum (MS) and of the magnocellular preoptic nucleus (MCPO) using the kainic acid (KA) model in rats. In addition, we estimated the respective changes in the cholinergic varicosities in the MS, where we observed a significant reduction in the PARV cell number (12849 ± 2715 vs. 9372 ± 1336, p = .029) and density (16.2 ± 2.62 vs. 10.5 ± 1.00 per .001 mm3, p =.001), and an increase in the density of cholinergic varicosities (47.9 ± 11.1 vs. 69.4 ± 17.8 per 30,000 µm2, p =.036) in KA-treated animals. In the MCPO, these animals showed a significant increase in somatic volume (827.9 ± 235.2 µm3 vs. 469.9 ± 79.6 µm3, p = .012) and total cell number (2268.6 ± 707.1 vs. 1362.4 ± 262.0, p =.028). These results show that the basal forebrain GABAergic cell populations undergo numerical and morphological changes in epileptic animals, which may contribute to an increased vulnerability of brain circuits to epilepsy and epilepsy-related functional impairments.

Antiepileptogenic Effects of Anakinra, Lamotrigine and Their Combination in a Lithium-Pilocarpine Model of Temporal Lobe Epilepsy in Rats

Temporal lobe epilepsy is a common, chronic disorder with spontaneous seizures that is often refractory to drug therapy. A potential cause of temporal lobe epilepsy is primary brain injury, making prevention of epileptogenesis after the initial event an optimal method of treatment. Despite this, no preventive therapy for epilepsy is currently available. The purpose of this study was to evaluate the effects of anakinra, lamotrigine, and their combination on epileptogenesis using the rat lithium-pilocarpine model of temporal lobe epilepsy. The study showed that there was no significant difference in the number and duration of seizures between treated and untreated animals. However, the severity of seizures was significantly reduced after treatment. Anakinra and lamotrigine, alone or in combination, significantly reduced neuronal loss in the CA1 hippocampus compared to the control group. However, the drugs administered alone were found to be more effective in preventing neuron loss in the hippocampal CA3 field compared to combination treatment. The treatment alleviated the impairments in activity level, exploratory behavior, and anxiety but had a relatively weak effect on TLE-induced impairments in social behavior and memory. The efficacy of the combination treatment did not differ from that of anakinra and lamotrigine monotherapy. These findings suggest that anakinra and lamotrigine, either alone or in combination, may be clinically useful in preventing the development of histopathological and behavioral abnormalities associated with epilepsy.

Higher education level as a protective factor against executive dysfunction in patients with epilepsy in Mataram, Indonesia

OBJECTIVE

Since the concept of cognitive reserve is applicable in epilepsy-associated cognitive impairment, the role of cognitive reserve components as a protective factor against epilepsy-associated executive dysfunction needs further investigation. This study aimed at investigating the association between cognitive reserve components and the frequency of epilepsy-associated executive dysfunction in Mataram, Indonesia.

METHODS

This case-control study involved both epilepsy outpatient and healthy participants recruited consecutively in 5 hospitals in Mataram, between October 2021 and September 2022. Data on sociodemographic, cognitive reserve components, and executive function status were collected from both groups, while data on seizure were collected only from epilepsy participants. The association between cognitive reserve components and the frequency of epilepsy-associated executive dysfunction was tested using logistic regression.

RESULTS

A total of 119 epilepsy patients and 93 healthy participants were recruited. The frequency of epilepsy-associated executive dysfunction was 50.4%. Multivariate logistic regression analysis showed that higher education level was the only cognitive reserve component protective against epilepsy-associated executive dysfunction (odds ratio [OR]: 3.36; 95% confidence interval [CI]: 1.33 - 8.50).

CONCLUSION

A high frequency of epilepsy-associated executive dysfunction was observed in Mataram. Higher education level was a cognitive reserve component protective against executive dysfunction in these patients.

Xenon inhalation attenuates neuronal injury and prevents epilepsy in febrile seizure Sprague-Dawley pups

Background

Febrile seizures (FS) usually occur in childhood and may cause irreversible neuronal damage, cognitive functional defects, and an increase in the risk of epilepsy later in life. Anti-epileptic drugs (AEDs), currently used to treat FS in children, can relieve seizures. However, their effects in preventing the risk of developing epilepsy in later life are unsatisfactory. Moreover, AEDs may damage child brain development. Here, we evaluated the efficiency of xenon in treating prolonged FS (PFS) and preventing epilepsy in Sprague-Dawley pups.

Methods

Prolonged FS was induced by hyperthermic treatment. After 90 min of PFS, the pups in the xenon treatment group were immediately treated with 70% xenon/21% oxygen/9% nitrogen for 60 min. The levels of glutamate, mitochondrial oxidative stress, mitophagy, and neuronal injury, seizures, learning, and memory functions were measured at specific time points.

Results

Neonatal period PFS led to spontaneous seizure, learning and memory dysfunction, accompanied by increased levels of glutamate, mitochondrial oxidative stress, mitophagy, and neuronal injury. Xenon treatment alleviated the changes caused by PFS and reduced the risk of PFS developing into epilepsy later.

Conclusion

Our results suggest that xenon inhalation could be a potential therapeutic strategy to attenuate neuronal injury and prevent epilepsy in patients with FS.

Identification of key potassium channel genes of temporal lobe epilepsy by bioinformatics analyses and experimental verification

One of the most prevalent types of epilepsy is temporal lobe epilepsy (TLE), which has unknown etiological factors and drug resistance. The detailed mechanisms underlying potassium channels in human TLE have not yet been elucidated. Hence, this study aimed to mine potassium channel genes linked to TLE using a bioinformatic approach. The results found that Four key TLE-related potassium channel genes (TERKPCGs) were identified: potassium voltage-gated channel subfamily E member (KCNA) 1, KCNA2, potassium inwardly rectifying channel, subfamily J, member 11 (KCNJ11), and KCNS1. A protein-protein interaction (PPI) network was constructed to analyze the relationship between TERKPCGs and other key module genes. The results of gene set enrichment analysis (GSEA) for a single gene indicated that the four TERKPCGs were highly linked to the cation channel, potassium channel, respiratory chain, and oxidative phosphorylation. The mRNA-TF network was established using four mRNAs and 113 predicted transcription factors. A ceRNA network containing seven miRNAs, two mRNAs, and 244 lncRNAs was constructed based on the TERKPCGs. Three common small-molecule drugs (enflurane, promethazine, and miconazole) target KCNA1, KCNA2, and KCNS1. Ten small-molecule drugs (glimepiride, diazoxide, levosimendan, and thiamylal et al.) were retrieved for KCNJ11. Compared to normal mice, the expression of KCNA1, KCNA2, KCNJ11, and KCNS1 was downregulated in the brain tissue of the epilepsy mouse model at both the transcriptional and translational levels, which was consistent with the trend of human data from the public database. The results indicated that key potassium channel genes linked to TLE were identified based on bioinformatics analysis to investigate the potential significance of potassium channel genes in the development and treatment of TLE.

Alpha-pinene moderates memory impairment induced by kainic acid via improving the BDNF/TrkB/CREB signaling pathway in rat hippocampus

Introduction

The potential benefits of natural ingredients in the alleviation of neurodegenerative disorders are of great interest. Alpha-pinene (APN) is an essential oil belonging to monoterpenes with multiple beneficial effects. In this study, the possible improving effects of alpha-pinene on memory impairment induced by kainic acid and the underlying molecular mechanisms were examined.

Methods

Memory impairment was induced by i.c.v. injection of kainic acid (KA) in male Wistar rats. Alpha-pinene (50 mg/kg/day, i.p.) was injected for 21 days, including 14 days before the KA injection and seven days afterward. Spatial working memory and inhibitory avoidance (IA) memory performance were assessed five and even days following KA injection, respectively. The hippocampal protein levels of brain-derived neurotrophic factor (BDNF), tropomyosin-like receptor kinase B (TrkB), cAMP response element binding protein (CREB), and neuronal loss in the CA1 region were also examined.

Results

Results revealed that the i.c.v. injection of KA triggered memory impairment, which was notably diminished by alpha-pinene pre-and post-treatment. Histopathological evaluation revealed that alpha-pinene significantly moderated the attenuation in CA1 alive neurons induced by KA injection. Western blotting analysis confirmed that alpha-pinene pre-and post-treatment significantly reversed the KA-induced decreases in the hippocampal levels of BDNF, TrkB, phosphorylated TrkB, CREB, and phosphorylated CREB.

Discussion

These findings suggest that alpha-pinene pre-and post-treatment moderate memory impairment induced by KA by restoring the BDNF/TrkB/CREB signaling pathway in the rat hippocampus.

Beneficial Effects of Probiotic Bifidobacterium longum in a Lithium-Pilocarpine Model of Temporal Lobe Epilepsy in Rats

Epilepsy is a challenging brain disorder that is often difficult to treat with conventional therapies. The gut microbiota has been shown to play an important role in the development of neuropsychiatric disorders, including epilepsy. In this study, the effects of Bifidobacterium longum, a probiotic, on inflammation, neuronal degeneration, and behavior are evaluated in a lithium-pilocarpine model of temporal lobe epilepsy (TLE) induced in young adult rats. B. longum was administered orally at a dose of 10⁹ CFU/rat for 30 days after pilocarpine injection. The results show that B. longum treatment has beneficial effects on the TLE-induced changes in anxiety levels, neuronal death in the amygdala, and body weight recovery. In addition, B. longum increased the expression of anti-inflammatory and neuroprotective genes, such as Il1rn and Pparg. However, the probiotic had little effect on TLE-induced astrogliosis and microgliosis and did not reduce neuronal death in the hippocampus and temporal cortex. The study suggests that B. longum may have a beneficial effect on TLE and may provide valuable insights into the role of gut bacteria in epileptogenesis. In addition, the results show that B. longum may be a promising drug for the comprehensive treatment of epilepsy.

The relationship between memory and quality of life is mediated by trait anxiety in patients with temporal lobe epilepsy

PURPOSE

Memory deficits are very frequent in patients with drug-resistant epilepsy, but they predict a small proportion of variance of their quality of life (QOL) in previous studies, possibly due to the lack of consideration of mediating factors of this relationship. This study aimed to examine whether trait anxiety mediates the relationship between memory and QOL in this population, controlling the influence of demographic and seizure-related factors.

METHODS

In this cross-sectional study, 119 adults with drug-resistant temporal lobe epilepsy (TLE) underwent a neuropsychological evaluation, in which memory, anxiety, and QOL were assessed.

RESULTS

In the total sample, better delayed memory had an effect on better QOL indirectly through lower trait anxiety (B = 0.13, SE = 0.06, p = 0.04, ab_cs = 0.13; κ² = 0.18; PM_ind = 0.76). Additionally, delayed memory has not a direct association with QOL (B = 0.04, SE = 0.09, p = 0.64, Cohen's f ² = 0.005; PM_dir = 0.24), and the total effect of delayed memory on QOL tended to reach statistical significance (B = 0.17, SE = 0.10, p = 0.08). The proposed mediation model yielded excellent fit (CFI = 1.00, RMSEA = 0.0001, SRMR = 0.009, and χ² (1) = 0.50, p = 0.48) and explained 38% of the variance of QOL.

CONCLUSION

These findings suggest that trait anxiety is an important factor in understanding the relationship between memory and QOL in patients with TLE, considering the influence of demographic and seizure-related variables, and may have relevant implications for decision-making in this population.

Cerebellar functional disruption and compensation in mesial temporal lobe epilepsy

Background

Cerebellar functional alterations are common in patients with mesial temporal lobe epilepsy (MTLE), which contribute to cognitive decline. This study aimed to deepen our knowledge of cerebellar functional alterations in patients with MTLE.

Methods

In this study, participants were recruited from an ongoing prospective cohort of 13 patients with left TLE (LTLE), 17 patients with right TLE (RTLE), and 30 healthy controls (HCs). Functional magnetic resonance imaging data were collected during a Chinese verbal fluency task. Group independent component (IC) analysis (group ICA) was applied to segment the cerebellum into six functionally separated networks. Functional connectivity was compared among cerebellar networks, cerebellar activation maps, and the centrality parameters of cerebellar regions. For cerebellar functional profiles with significant differences, we calculated their correlation with clinical features and neuropsychological scores.

Result

Compared to HCs and patients with LTLE, patients with RTLE had higher cerebellar functional connectivity between the default mode network (DMN) and the oculomotor network and lower cerebellar functional connectivity from the frontoparietal network (FPN) to the dorsal attention network (DAN) (p < 0.05, false discovery rate- (FDR-) corrected). Cerebellar degree centrality (DC) of the right lobule III was significantly higher in patients with LTLE compared to HC and patients with RTLE (p < 0.05, FDR-corrected). Higher cerebellar functional connectivity between the DMN and the oculomotor network, as well as lower cerebellar degree centrality of the right lobule III, was correlated with worse information test performance.

Conclusion

Cerebellar functional profiles were altered in MTLE and correlated with long-term memory in patients.

Amplitude synchronization of spontaneous activity of medial and lateral temporal gyri reveals altered thalamic connectivity in patients with temporal lobe epilepsy

In this study, we examined whether amplitude synchronization of medial (MTL) and lateral (LTL) temporal lobes can detect unique alterations in patients with MTL epilepsy (mTLE) with mesial temporal sclerosis (MTS). This was a retrospective study of preoperative resting-state fMRI (rsfMRI) data from 31 patients with mTLE with MTS (age 23-69) and 16 controls (age 21-35). fMRI data were preprocessed based on a multistep preprocessing pipeline and registered to a standard space. Using each subject's T1-weighted scan, the MTL and LTL were automatically segmented, manually revised and then fit to a standard space using a symmetric normalization registration algorithm. Dual regression analysis was applied on preprocessed rsfMRI data to detect amplitude synchronization of medial and lateral temporal segments with the rest of the brain. We calculated the overlapped volume ratio of synchronized voxels within specific target regions including the thalamus (total and bilateral). A general linear model was used with Bonferroni correction for covariates of epilepsy duration and age of patient at scan to statistically compare synchronization in patients with mTLE with MTS and controls, as well as with respect to whether patients remained seizure-free (SF) or not (NSF) after receiving epilepsy surgery. We found increased ipsilateral positive connectivity between the LTLs and the thalamus and contralateral negative connectivity between the MTLs and the thalamus in patients with mTLE with MTS compared to controls. We also found increased asymmetry of functional connectivity between temporal lobe subregions and the thalamus in patients with mTLE with MTS, with increased positive connectivity between the LTL and the lesional-side thalamus as well as increased negative connectivity between the MTL and the nonlesional-side thalamus. This asymmetry was also seen in NSF patients but was not seen in SF patients and controls. Amplitude synchronization was an effective method to detect functional connectivity alterations in patients with mTLE with MTS. Patients with mTLE with MTS overall showed increased temporal-thalamic connectivity. There was increased functional involvement of the thalamus in MTS, underscoring its role in seizure spread. Increased functional thalamic asymmetry patterns in NSF patients may have a potential role in prognosticating patient response to surgery. Elucidating regions with altered functional connectivity to temporal regions can improve understanding of the involvement of different regions in the disease to potentially target for intervention or use for prognosis for surgery. Future studies are needed to examine the effectiveness of using patient-specific abnormalities in patterns to predict surgical outcome.

An aqueous extract of Syzygium cumini protects against kainate-induced status epilepticus and amnesia: evidence for antioxidant and anti-inflammatory intervention

Temporal lobe epilepsy is the most common drug-resistant epilepsy. To cure epilepsy, drugs must target the mechanisms at the origin of seizures. Thus, the present investigation aimed to evaluate the antiepileptic- and anti-amnesic-like effects of an aqueous extract of Syzygium cumini against kainate-induced status epilepticus in mice, and possible mechanisms of action. Mice were divided into 7 groups and treated as follows: normal group or kainate group received po distilled water (10 mL/kg), four test groups received Syzygium cumini (28.8, 72, 144, and 288 mg/kg, po), and the positive control group treated intraperitoneally (ip) with sodium valproate (300 mg/kg). An extra group of normal mice was treated with piracetam (200 mg/kg, po). Treatments were administered 60 min before the induction of status epilepticus with kainate (15 mg/kg, ip), and continued daily throughout behavioral testing. Twenty-four hours after the induction, T-maze and Morris water maze tasks were successively performed. The animals were then sacrificed and some markers of oxidative stress and neuroinflammation were estimated in the hippocampus. The extract significantly prevented status epilepticus and mortality. In the T-maze, the aqueous extract markedly increased the time spent and the number of entries in the discriminated arm. In the Morris water maze, the extract significantly increased the time spent in the target quadrant during the retention phase. Furthermore, the aqueous extract induced a significant reduction of oxidative stress and neuroinflammation. These results suggest that the aqueous extract of Syzygium cumini has antiepileptic- and anti-amnesic-like effects, likely mediated in part by antioxidant and anti-inflammatory activities.

A Classification Model of EEG Signals Based on RNN-LSTM for Diagnosing Focal and Generalized Epilepsy

Epilepsy is a chronic neurological disorder caused by abnormal neuronal activity that is diagnosed visually by analyzing electroencephalography (EEG) signals.

BACKGROUND

Surgical operations are the only option for epilepsy treatment when patients are refractory to treatment, which highlights the role of classifying focal and generalized epilepsy syndrome. Therefore, developing a model to be used for diagnosing focal and generalized epilepsy automatically is important.

METHODS

A classification model based on longitudinal bipolar montage (LB), discrete wavelet transform (DWT), feature extraction techniques, and statistical analysis in feature selection for RNN combined with long short-term memory (LSTM) is proposed in this work for identifying epilepsy. Initially, normal and epileptic LB channels were decomposed into three levels, and 15 various features were extracted. The selected features were extracted from each segment of the signals and fed into LSTM for the classification approach.

RESULTS

The proposed algorithm achieved a 96.1% accuracy, a 96.8% sensitivity, and a 97.4% specificity in distinguishing normal subjects from subjects with epilepsy. This optimal model was used to analyze the channels of subjects with focal and generalized epilepsy for diagnosing purposes, relying on statistical parameters.

CONCLUSIONS

The proposed approach is promising, as it can be used to detect epilepsy with satisfactory classification performance and diagnose focal and generalized epilepsy.

The Parietal Lobe in Alzheimer’s Disease and Blindness

The progressive aging of the population will notably increase the burden of those diseases which leads to a disabling situation, such as Alzheimer’s disease (AD) and ophthalmological diseases that cause a visual impairment (VI). Eye diseases that cause a VI raise neuroplastic processes in the parietal lobe. Meanwhile, the aforementioned lobe suffers a severe decline throughout AD. From this perspective, diving deeper into the particularities of the parietal lobe is of paramount importance. In this article, we discuss the functions of the parietal lobe, review the parietal anatomical and pathophysiological peculiarities in AD, and also describe some of the changes in the parietal region that occur after VI. Although the alterations in the hippocampus and the temporal lobe have been well documented in AD, the alterations of the parietal lobe have been less thoroughly explored. Recent neuroimaging studies have revealed that some metabolic and perfusion impairments along with a reduction of the white and grey matter could take place in the parietal lobe during AD. Conversely, it has been speculated that blinding ocular diseases induce a remodeling of the parietal region which is observable through the improvement of the integration of multimodal stimuli and in the increase of the volume of this cortical region. Based on current findings concerning the parietal lobe in both pathologies, we hypothesize that the increased activity of the parietal lobe in people with VI may diminish the neurodegeneration of this brain region in those who are visually impaired by oculardiseases.

Pentylenetetrazole-induced seizures cause impairment of memory acquisition and consolidation in zebrafish (Danio rerio)

Epilepsy is characterized by the occurrence seizures, and the high prevalence of epilepsy-associated comorbidities affects the quality of patients' life. We investigated the effects of pentylenetetrazole (PTZ) exposure in zebrafish cognitive performance on inhibitory avoidance test. The animals were exposed to the 7.5mM PTZ for 10minutes, in the acquisition (before training) and in the consolidation memory phases (after training). In the acquisition phase, the animals were submitted to PTZ-induced seizures and trained in periods of 1, 24, or 48hours after exposure, and 24hours after training were tested. In the consolidation phase, animals were trained and exposed to PTZ 10minutes after training and were tested 24hours later. Control groups in periods of 1, 24, or 48hours before or 10minutes after training showed a significantly increased latency to enter the dark compartment. The latencies between training and test sessions did not differ in PTZ groups of animals exposed and trained 1 and 24hours or exposed to PTZ 10minutes after training. At 48hours, animals exposed to PTZ showed an increased latency to enter the dark compartment. Animals exposed to PTZ and trained 1h after increased the traveled distance, when compared to the control group. Traveled distance did not differ in animals that were exposed to PTZ and trained 24 and 48hours, or 10minutes after training. Our findings indicate that PTZ causes a cognitive deficit in the pre-and post-training phase, allowing us to explore the influence of seizures at different memory phases.

Blood-brain barrier: emerging trends on transport models and new-age strategies for therapeutics intervention against neurological disorders

The integrity of the blood–brain barrier (BBB) is essential for normal central nervous system (CNS) functioning. Considering the significance of BBB in maintaining homeostasis and the neural environment, we aim to provide an overview of significant aspects of BBB. Worldwide, the treatment of neurological diseases caused by BBB disruption has been a major challenge. BBB also restricts entry of neuro-therapeutic drugs and hinders treatment modalities. Hence, currently nanotechnology-based approaches are being explored on large scale as alternatives to conventional methodologies. It is necessary to investigate the in-depth characteristic features of BBB to facilitate the discovery of novel drugs that can successfully cross the barrier and target the disease effectively. It is imperative to discover novel strategies to treat life-threatening CNS diseases in humans. Therefore, insights regarding building blocks of BBB, activation of immune response on breach of this barrier, and various autoimmune neurological disorders caused due to BBB dysfunction are discussed. Further, special emphasis is given on delineating BBB disruption leading to CNS disorders. Moreover, various mechanisms of transport pathways across BBB, several novel strategies, and alternative routes by which drugs can be properly delivered into CNS are also discussed.

Similar Profile and Magnitude of Cognitive Impairments in Focal and Generalized Epilepsy: A Pilot Study

Introduction: Cognitive impairments in epilepsy are not well-understood. In addition, long-term emotional, interpersonal, and social consequences of the underlying disturbances are important to evaluate.

Purpose: To compare cognitive function including language in young adults with focal or generalized epilepsy. In addition, quality of life and self-esteem were investigated.

Patients and Methods: Young adults with no primary intellectual disability, 17 with focal epilepsy and 11 with generalized epilepsy participated and were compared to 28 healthy controls. Groups were matched on age (mean = 26 years), sex, and education. Participants were administered a battery of neuropsychological tasks and carried out self-ratings of quality of life, self-esteem, and psychological problems.

Results: Similar impairments regarding cognitive function were noted in focal and generalized epilepsy. The cognitive domains tested were episodic long-term memory, executive functions, attention, working memory, visuospatial functions, and language. Both epilepsy groups had lower results compared to controls (effect sizes 0.24–1.07). The total number of convulsive seizures was predictive of episodic long-term memory function. Participants with focal epilepsy reported lower quality of life than participants with generalized epilepsy. Lowered self-esteem values were seen in both epilepsy groups and particularly in those with focal epilepsy. Along with measures of cognitive speed and depression, the total number of seizures explained more than 50% of variation in quality of life.

Conclusion: Interestingly, similarities rather than differences characterized the widespread cognitive deficits that were seen in focal and generalized epilepsy, ranging from mild to moderate. These similarities were modified by quality of life and self-esteem. This study confirms the notion that epilepsy is a network disorder.

Effect of repeated seizures on spatial exploration and immediate early gene expression in the hippocampus and dentate gyrus

Immediate early genes (IEGs) are coordinately activated in response to neuronal activity and can cause activation of secondary response genes that modulate synaptic plasticity and mediate long-lasting changes in behaviour. Excessive neuronal stimulation induced by epileptic seizures induce rapid and dramatic changes in IEG expression. Although the impact of acute seizure activity on IEG expression has been well studied, less is known about the long-term effects of chronic seizures on IEG induction during seizure free periods where behavioural and cognitive impairments are frequently observed in people with epilepsy and in animal models of epilepsy. The present study sought out to examine the impact of chronic pentylenetetrazole evoked seizures (PTZ kindling) on spatial exploration induced in IEG expression (c-Fos, ΔFosB, Homer1a, Egr1, Npas4, Nr4a1) in the hippocampus (CA1 and CA3 subfields) and dentate gyrus of rats. Male rats underwent two weeks of PTZ kindling (every 2 days) or received vehicle injections and were placed into a novel open field arena for 30 min either 24 hrs or 4 weeks after the last treatment. Although exploratory activity was similar between PTZ kindled and vehicle controls when examined 24 hrs after the last treatment, we observed a significant reduction in spatial exploration induced expression of c-Fos, Egr1, and ΔFosB in the hippocampus and dentate gyrus, and reduced expression of Nr4a1 in the dentate gyrus and Homer1a in the hippocampus only. When testing was conducted after a 4-week recovery period, only c-Fos continued to show reduced expression after exposure a novel environment in previously PTZ kindled animals. Interestingly, these animals also showed reduced activity in the center region of the open field suggestive of heightened anxiety-like behaviour. Collectively, these results suggest that repeated seizures may lead to longterm downregulation in hippocampal IEG expression that can extend into seizure free periods thereby providing a critical mechanism for the development of cognitive and behavioural deficits that arise during chronic epilepsy

Mapping of Language-and-Memory Networks in Patients With Temporal Lobe Epilepsy by Using the GE2REC Protocol

Preoperative mapping of language and declarative memory functions in temporal lobe epilepsy (TLE) patients is essential since they frequently encounter deterioration of these functions and show variable degrees of cerebral reorganization. Due to growing evidence on language and declarative memory interdependence at a neural and neuropsychological level, we propose the GE2REC protocol for interactive language-and-memory network (LMN) mapping. GE2REC consists of three inter-related tasks, sentence generation with implicit encoding (GE) and two recollection (2REC) memory tasks: recognition and recall. This protocol has previously been validated in healthy participants, and in this study, we showed that it also maps the LMN in the left TLE (N = 18). Compared to healthy controls (N = 19), left TLE (LTLE) showed widespread inter- and intra-hemispheric reorganization of the LMN through reduced activity of regions engaged in the integration and the coordination of this meta-network. We also illustrated how this protocol could be implemented in clinical practice individually by presenting two case studies of LTLE patients who underwent efficient surgery and became seizure-free but showed different cognitive outcomes. This protocol can be advantageous for clinical practice because it (a) is short and easy to perform; (b) allows brain mapping of essential cognitive functions, even at an individual level; (c) engages language-and-memory interaction allowing to evaluate the integrative processes within the LMN; (d) provides a more comprehensive assessment by including both verbal and visual modalities, as well as various language and memory processes. Based on the available postsurgical data, we presented preliminary results obtained with this protocol in LTLE patients that could potentially inform the clinical practice. This implies the necessity to further validate the potential of GE2REC for neurosurgical planning, along with two directions, guiding resection and describing LMN neuroplasticity at an individual level.

The Role of Brain-Derived Neurotrophic Factor in Epileptogenesis: an Update

Epilepsy, which is characterized by spontaneous recurrent seizures, is one of the most common and serious chronic neurological diseases in the world. 30% patients failed to control seizures with multiple anti-seizure epileptic drugs, leading to serious outcomes. The pathogenesis of epilepsy is very complex and remains unclear. Brain-derived neurotrophic factor (BDNF), as a member of the neurotrophic factor family, is considered to play an important role in the survival, growth and differentiation of neurons during the development of the central nervous system. Recent years, a series of studies have reported that BDNF can maintain the function of the nervous system and promotes the regeneration of neurons after injury, which is believed to be closely related to epileptogenesis. However, two controversial views (BDNF inhibits or promotes epileptogenesis) still exist. Thus, this mini-review focuses on updating the new evidence of the role of BDNF in epileptogenesis and discussing the possibility of BDNF as an underlying target for the treatment of epilepsy.

Hidden Objective Memory Deficits Behind Subjective Memory Complaints in Patients With Temporal Lobe Epilepsy

OBJECTIVE

To test the hypothesis that temporal lobe epilepsy (TLE) patients with subjective initial memory complaints (not confirmed by an objective standard assessment) and various phenotypes also show objective very long-term memory deficit with accelerated long-term forgetting. We tested TLE patients with two surprise memory tests after three weeks: the standard Free and Cued Selective Reminding Test (FCSRT), and Epireal, a new test specifically designed to capture more ecological aspects of autobiographical memory.

METHODS

47 TLE patients (12 hippocampal sclerosis, 12 amygdala enlargement, 11 extensive lesions, 12 normal MRI) who complained about their memory, but for whom the standard neuropsychological assessment did not reveal any memory impairment after a standard delay of 20 minutes, underwent two surprise memory tests after three weeks. They were compared to 35 healthy control subjects.

RESULTS

After three weeks, FCSRT and Epireal recall scores were significantly lower in patients than in controls (p<0.001). There was no significant correlation between FCSRT and Epireal scores (p=0.99). Seventy-six percent of TLE patients had objective impairment on at least one of these very long-term memory tests, regardless of the existence and type of lesion or response to antiseizure medication. Easily applicable, Epireal had a higher effect size, detected deficits in 28% more patients, and is a useful addition to the standard workup.

CONCLUSION

Assessing long-term memory should be broadened to a wide spectrum of TLE patients with a memory complaint, regardless of the epileptic syndrome, whether or not associated with a lesion. This could lead to rethinking TLE nosology associated with memory.

Identification and Validation of a Dysregulated miRNA-Associated mRNA Network in Temporal Lobe Epilepsy

Objectives

This study is aimed at exploring the relationships between miRNAs and mRNAs and to characterize their biological functions in temporal lobe epilepsy (TLE).

Methods

Novel clinical significant miRNAs and target genes and their potential underlying mechanisms have been discovered and explored by mining miRNAs and mRNA expression data of TLE patients using various bioinformatics methods. Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to validate the bioinformatic analysis results.

Results

A total of 6 dysregulated miRNAs and 442 differentially expressed genes (DEGs) related to TLE were obtained from GEO database (GSE114701 and GSE127871 datasets). A protein-protein interaction (PPI) network containing the 442 DEGs was established. mRNA response elements from the 6 dysregulated miRNAs were predicted using the miRDB and TargetScan bioinformatic tools. By merging the identified targets of the dysregulated miRNAs and the 247 downregulated DEGs, a miRNA-mRNA network was constructed revealing the interaction of miR-484 with eight mRNAs (ABLIM2, CEP170B, CTD-3193O13.9, EFNA5, GAP43, PRKCB, FXYD7, and NCAN). A weighted correlation network analysis (WGCNA) based on the eight genes was established and demonstrated that these mRNAs, except FXYD7 and NCAN, were hub genes in the network. Gene Oncology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis revealed that the six hub genes were mainly involved in cellular-related biological functions and the neurotransmitter synapse pathway. The differences in expression levels of the miR-484 and the three hub genes (CTD-3193O13.9, EFNA5, and PRKCB) observed experimentally in TLE patients compared to those of healthy controls were consistent with the WGCNA prediction.

Conclusion

Our study suggests that understanding the miRNA-mRNA interactions will provide insights into the epilepsy pathogenesis. In addition, our results indicate that miR-484 may be a promising novel biomarker for TLE.

Prediction of the clinical and naming status after anterior temporal lobe resection in patients with epilepsy

By assessing the cognitive capital, neuropsychological evaluation (NPE) plays a vital role in the perioperative workup of patients with refractory focal epilepsy. In this retrospective study, we used cutting-edge statistical approaches to examine a group of 47 patients with refractory temporal lobe epilepsy (TLE), who underwent standard anterior temporal lobectomy (ATL). Our objective was to determine whether NPE may represent a robust predictor of the postoperative status, two years after surgery. Specifically, based on pre- and postsurgical neuropsychological data, we estimated the sensitivity of cognitive indicators to predict and to disentangle phenotypes associated with more or less favorable outcomes. Engel (ENG) scores were used to assess clinical outcome, and picture naming (NAM) performance to estimate naming status. Two methods were applied: (a) machine learning (ML) to explore cognitive sensitivity to postoperative outcomes; and (b) graph theory (GT) to assess network properties reflecting favorable vs. less favorable phenotypes after surgery. Specific neuropsychological indices assessing language, memory, and executive functions can globally predict outcomes. Interestingly, preoperative cognitive networks associated with poor postsurgical outcome already exhibit an atypical, highly modular and less densely interconnected configuration. We provide statistical and clinical tools to anticipate the condition after surgery and achieve a more personalized clinical management. Our results also shed light on possible mechanisms put in place for cognitive adaptation after acute injury of central nervous system in relation with surgery.

Interactive mapping of language and memory with the GE2REC protocol

Previous studies have highlighted the importance of considering cognitive functions from a dynamic and interactive perspective and multiple evidence was brought for a language and memory interaction. In this study performed with healthy participants, we present a new protocol entitled GE2REC that interactively accesses the neural representation of language-and-memory network. This protocol consists of three runs related to each other, providing a link between tasks, in order to assure an interactive measure of linguistic and episodic memory processes. GE2REC consists of a sentence generation (GE) in the auditory modality and two recollecting (2REC) memory tasks, one recognition performed in the visual modality, and another one recall performed in the auditory modality. Its efficiency was evaluated in 20 healthy volunteers using a 3T MR imager. Our results corroborate the ability of GE2REC to robustly activate fronto-temporo-parietal language network as well as temporal mesial, prefrontal and parietal cortices in encoding during sentence generation and recognition. GE2REC is useful because it: (a) requires simultaneous and interactive language-and-memory processes and jointly maps their neural basis; (b) explores encoding and retrieval, managing to elicit activation of mesial temporal structures; (c) is easy to perform, hence being suitable for more restrictive settings, and (d) has an ecological dimension of tasks and stimuli. GE2REC may be useful for studying neuroplasticity of cognitive functions, especially in patients with temporal lobe epilepsy who show reorganization of both language and memory networks. Overall, GE2REC can provide valuable information in terms of the practical foundation of exploration language and memory interconnection.

Genetic influence of Apolipoprotein E gene ε2/ε3/ε4 isoforms on odds of mesial temporal lobe epilepsy

OBJECTIVE

The potential correlation between the ε2/ε3/ε4 variants of the ApoE (Apolipoprotein E) gene and the odds of mesial temporal lobe epilepsy was investigated.

METHODS

The database searching for eligible studies was performed in October 2020. A series of pooling analyses were conducted.

RESULTS

We enrolled a total of twelve case-control studies for pooling. Within the pooling analysis of ε4, there was an increased risk of mesial temporal lobe epilepsy in cases under the models of carrier ε4 vs. ε3, ε3ε4 vs. ε3ε3, and ε3ε4+ε4ε4 vs. ε3ε3 [P < 0.05, odds ratio (OR) > 1], compared with controls. Moreover, we observed similar positive results in the subgroup analyses of "China" and "Population-based control" under the genetic models of ε4 (P < 0.05, OR > 1). Nevertheless, we did not detect the significant difference between the mesial temporal lobe epilepsy cases and controls in the pooling analyses of ε2 (all P > 0.05).

CONCLUSION

The ε3ε4 genotype of ApoE seems to be linked to the risk of mesial temporal lobe epilepsy for patients in China. More sample sizes are required to confirm the potential role of ApoE isoforms in the susceptibility to diverse types of epilepsy from different origins.

Reconfiguration dynamics of a language-and-memory network in healthy participants and patients with temporal lobe epilepsy

Current theoretical frameworks suggest that human behaviors are based on strong and complex interactions between cognitive processes such as those underlying language and memory functions in normal and neurological populations. We were interested in assessing the dynamic cerebral substrate of such interaction between language and declarative memory, as the composite function, in healthy controls (HC, N = 19) and patients with temporal lobe epilepsy (TLE, N = 16). Our assumption was that the language and declarative memory integration is based on a language-and-memory network (LMN) that is dynamic and reconfigures according to task demands and brain status. Therefore, we explored two types of LMN dynamics, a state reconfiguration (intrinsic resting-state compared to extrinsic state assessed with a sentence recall task) and a reorganization of state reconfiguration (TLE compared to HC). The dynamics was evaluated in terms of segregation (community or module detection) and integration (connector hubs). In HC, the level of segregation was the same in both states and the mechanism of LMN state reconfiguration was shown through module change of key language and declarative memory regions with integrative roles. In TLE patients, the reorganization of LMN state reconfiguration was reflected in segregation increase and extrinsic modules that were based on shorter-distance connections. While lateral and mesial temporal regions enabled state reconfiguration in HC, these regions showed reduced flexibility in TLE. We discuss our results in a connectomic perspective and propose a dynamic model of language and declarative memory functioning. We claim that complex and interactive cognitive functions, such as language and declarative memory, should be investigated dynamically, considering the interaction between cognitive networks.

Accelerated forgetting in temporal lobe epilepsy: When does it occur?

OBJECTIVE

The main goal of the study was to analyse differences in the forgetting rates of Temporal Lobe Epilepsy (TLE) patients at different intervals (30 sec, 10 min, 1 day and 1 week) compared with those of healthy controls. A secondary aim of this research was to provide an assessment of the relationship between clinical epilepsy-related variables and forgetting rates in TLE patients.

METHOD

The sample was composed of 14 TLE patients and 14 healthy matched controls. All participants underwent a full standardised neuropsychological assessment including general intelligence, executive functioning, memory, language and other variables, such as depression, anxiety or everyday memory failures. Two specific memory tasks, consisting of cued recall of 4 short stories and 4 routes, were carried out at four different intervals.

RESULTS

There was a significant difference between groups at 10-min interval on the stories task, with the TLE group displaying greater forgetting than healthy controls. None of the other intervals on either task showed significant group differences. No differences were found when controlling for clinical epilepsy-related variables.

CONCLUSION

Forgetting of verbal information at 10 min was greater in patients with TLE compared with controls, but accelerated longer term forgetting was not found. This study suggests that a late consolidation process is not necessarily impaired in TLE patients.

Excitatory synaptic transmission in hippocampal area CA1 is enhanced then reduced as chronic epilepsy progresses

This study examines changes in synaptic transmission with progression of the chronic epileptic state. Male Sprague-Dawley rats (P40-45) were injected with either saline or pilocarpine. In rats injected with pilocarpine, status epilepticus ensued. Hippocampal slices were cut 20-60 days or 80-110 days post-treatment. Evoked and miniature EPSCs (mEPSCs) were recorded from CA1 pyramidal neurons using whole-cell voltage-clamp. Fiber volleys were also recorded from stratum radiatum. Evoked EPSCs from the pilocarpine-treated cohort showed enhanced amplitudes 20-60 days post-treatment compared to the saline-treated cohort, whereas mEPSCs recorded from the same age group showed no change in event frequency and a slight but significant decrease in mEPSC amplitude distribution. In contrast, comparing evoked EPSCs and mEPSCs recorded 80-110 days after treatment indicated reduced amplitudes from pilocarpine-treated animals compared to controls. mEPSC inter-event interval decreased. This could be explained by a partial depletion of the ready releasable pool of neurotransmitter vesicles in Schaffer collateral presynaptic terminals of the pilocarpine-treated rats. In both saline- and pilocarpine-treated cohorts, concomitant decreases in mEPSC amplitudes as time after treatment progressed suggest that age-related changes in CA1 circuitry may be partially responsible for changes in synaptic transmission that may influence the chronic epileptic state.

Pentylenetetrazol-induced seizures in adult rats are associated with plastic changes to the dendritic spines on hippocampal CA1 pyramidal neurons

Epilepsy is a chronic neurobehavioral disorder whereby an imbalance between neurochemical excitation and inhibition at the synaptic level provokes seizures. Various experimental models have been used to study epilepsy, including that based on acute or chronic administration of Pentylenetetrazol (PTZ). In this study, a single PTZ dose (60 mg/kg) was administered to adult male rats and 30 min later, various neurobiological parameters were studied related to the transmission and modulation of excitatory impulses in pyramidal neurons of the hippocampal CA1 field. Rats experienced generalized seizures 1-3 min after PTZ administration, accompanied by elevated levels of Synaptophysin and Glutaminase. This response suggests presynaptic glutamate release is exacerbated to toxic levels, which eventually provokes neuronal death as witnessed by the higher levels of Caspase-3, TUNEL and GFAP. Similarly, the increase in PSD-95 suggests that viable dendritic spines are functional. Indeed, the increase in stubby and wide spines is likely related to de novo spinogenesis, and the regulation of neuronal excitability, which could represent a plastic response to the synaptic over-excitation. Furthermore, the increase in mushroom spines could be associated with the storage of cognitive information and the potentiation of thin spines until they are transformed into mushroom spines. However, the reduction in BDNF suggests that the activity of these spines would be down-regulated, may in part be responsible for the cognitive decline related to hippocampal function in patients with epilepsy.

Investigating the Effects of Seizures on Procedural Memory Performance in Patients with Epilepsy

Memory complaints are frequently reported by patients with epilepsy and are associated with seizure occurrence. Yet, the direct effects of seizures on memory retention are difficult to assess given their unpredictability. Furthermore, previous investigations have predominantly assessed declarative memory. This study evaluated within-subject effects of seizure occurrence on retention and consolidation of a procedural motor sequence learning task in patients with epilepsy undergoing continuous monitoring for five consecutive days. Of the total sample of patients considered for analyses (N = 53, M_age = 32.92 ± 13.80 y, range = 18–66 y; 43% male), 15 patients experienced seizures and were used for within-patient analyses. Within-patient contrasts showed general improvements over seizure-free (day + night) and seizure-affected retention periods. Yet, exploratory within-subject contrasts for patients diagnosed with temporal lobe epilepsy (n = 10) showed that only seizure-free retention periods resulted in significant improvements, as no performance changes were observed following seizure-affected retention. These results indicate general performance improvements and offline consolidation of procedural memory during the day and night. Furthermore, these results suggest the relevance of healthy temporal lobe functioning for successful consolidation of procedural information, as well as the importance of seizure control for effective retention and consolidation of procedural memory.

The Clinical Significance of miR-135b-5p and Its Role in the Proliferation and Apoptosis of Hippocampus Neurons in Children with Temporal Lobe Epilepsy

Temporal lobe epilepsy (TLE) is the most familiar localized epilepsy in children. MicroRNAs (miRNAs) are essential for the inhibition or promotion of numerous diseases. This study aimed to detect the expression of miR-135b-5p and primarily uncover its underlying function and mechanism in children with TLE. Quantitative real-time polymerase chain reaction was used to evaluate the expression of miR-135b-5p in children with TLE and in a rat model of epilepsy. MTT assay and flow cytometric apoptosis assay were conducted to evaluate the effects of miR-135b-5p on cell viability and apoptosis. Additionally, the dual luciferase reporter assay was performed to confirm the direct target of miR-135b-5p. Our data showed that the expression of miR-135b-5p was significantly decreased in children with TLE and in the epileptic rat neuron model. The dysregulation of miR-135b-5p could serve as a promising diagnostic biomarker for children with TLE. The overexpression of miR-135b-5p moderated the adverse influence on cell viability and apoptosis induced by magnesium-free medium. SIRT1 was identified as a target gene of miR-135b-5p. These results proved that miR-135b-5p might serve as a potential diagnostic biomarker in children with TLE. Overexpression of miR-135b-5p alleviates the postepileptic influence on cell viability and apoptosis by targeting SIRT1.

miR-128 regulates epilepsy sensitivity in mice by suppressing SNAP-25 and SYT1 expression in the hippocampus

Epilepsy is accompanied by abnormal neurotransmission, and microRNAs, as versatile players in the modulation of gene expression, are important in epilepsy pathology. Here, we found that miR-128 expression was elevated in the acute seizure phase and decreased during the recurrent seizure phase after status epilepticus in mice. Both SNAP-25 and SYT1 are regulated by miR-128 in vitro and in vivo. Overexpressing miR-128 in cultured neurons decreased neurotransmitter released by suppressing SNAP-25 and SYT1 expression. Anti-miR-128 injection before kainic acid (KA) injection increased the sensitivity of mice to KA-induced seizures, while overexpressing miR-128 at the latent and recurrent phases had a neuroprotective effect in KA-induced seizures. Our study shows for the first time that miR-128, a key regulator of neurotransmission, plays an important role in epilepsy pathology and that miR-128 might be a potential candidate molecular target for epilepsy therapy.

A Review of Accelerated Long-Term Forgetting in Epilepsy

Accelerated long-term forgetting (ALF) is a memory disorder that manifests by a distinct pattern of normal memory for up to an hour after learning, but an increased rate of forgetting during the subsequent hours and days. The topic of ALF has gained much attention in group studies with epilepsy patients and the phenomenon has been shown to have contradictory associations with seizures, epileptiform activity, imaging data, sleep, and antiepileptic medication. The aim of this review was to explore how clinical and imaging data could help determine the topographic and physiological substrate of ALF, and what is the possible use of this information in the clinical setting. We have reviewed 51 group studies in English to provide a synthesis of the existing findings concerning ALF in epilepsy. Analysis of recently reported data among patients with temporal lobe epilepsy, transient epileptic amnesia, and generalized and extratemporal epilepsies provided further indication that ALF is likely a disorder of late memory consolidation. The spatial substrate of ALF might be located along the parts of the hippocampal-neocortical network and novel studies reveal the increasingly possible importance of damage in extrahippocampal sites. Further research is needed to explore the mechanisms of cellular impairment in ALF and to develop effective methods of care for patients with the disorder.

Circular RNA Circ_ANKMY2 Regulates Temporal Lobe Epilepsy Progression via the miR-106b-5p/FOXP1 Axis

Temporal lobe epilepsy (TLE) is common intractable epilepsy that affects the patient's lives. The circular RNA circ_ANKMY2 (circ_ANKMY2) has been reported to be abnormally expressed in TLE. Nevertheless, the role and mechanism of circ_ANKMY2 in TLE are unclear. A human neuroblastoma cell line (SK-N-AS) was used for a series of studies. Expression levels of circ_ANKMY2, miR-106b-5p, and Forkhead Box Protein 1 (FOXP1) mRNA in TLE tissues were assessed through quantitative real-time polymerase chain reaction (qRT-PCR). Cell colony formation, proliferation, and apoptosis were determined by cell colony formation, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), or flow cytometry assays. The levels of FOXP1 protein, Ki67, B cell lymphoma (Bcl-2), Bcl-2 Associated X (Bax), and Cleaved caspase-3 were evaluated by western blot analysis. The relationship between circ_ANKMY2 or FOXP1 and miR-106b-5p was verified with dual-luciferase reporter assay. We observed that circ_ANKMY2 and FOXP1 expression were reduced while miR-106b-5p expression was increased in TLE tissues. Overexpression of circ_ANKMY2 decreased spontaneous recurrent seizures (SRSs) in rat TLE model and blocked cell colony formation, proliferation, and induced cell apoptosis in SK-N-AS cells. Importantly, circ_ANKMY2 was verified as a sponge for miR-106b-5p. In addition, miR-106b-5p mimics abolished circ_ANKMY2 elevation-mediated effects on colony formation, proliferation, and apoptosis of SK-N-AS cells. Also, FOXP1 served as a target for miR-106b-5p. And FOXP1 silencing overturned the effects of miR-106b-5p inhibitors on the colony formation, proliferation, and apoptosis of SK-N-AS cells. In sum, circ_ANKMY2 modulated TLE advancement via regulation of FOXP1 expression through sponging miR-106b-5p, and circ_ANKMY2 might be an underlying target for the improvement of TLE.

Lactation in large litters influences anxiety, memory, and spreading depression in adult male rats that were chronically subjected to a non-convulsive pilocarpine dose

Objectives: Unfavorable lactation influences brain excitability and behavioral reactions in adults. Administration early in life of the cholinergic agonist, pilocarpine, even at non-convulsive doses, alters the brain excitability-related phenomenon known as cortical spreading depression (CSD), and produce anxiogenic-like behavior. However, the influence of unfavorable lactation on the CSD- and memory-effects of pilocarpine administration late in life has not been investigated. Herein, we analyzed the ponderal, electrophysiological (CSD), and behavioral effects of chronic treatment with a non-convulsive dose of pilocarpine, in adult rats suckled under favorable and unfavorable conditions.Methods: Wistar rats were suckled in litters with 9 or 15 pups (groups L₉ and L₁₅, respectively). A very low dose of pilocarpine (45/mg/kg/day) was chronically administered in mature rats from postnatal day (PND) 69-90. Behavioral tests occurred at PND91 [elevated plus maze (EPM)], PND93 [open field (OF)], and PND94-95 [object recognition memory (ORM)]. CSD was recorded between PND96-120.Results: Pilocarpine-treated rats performed worse in the anxiety and memory tests, and displayed lower CSD propagation velocity when compared with saline-treated controls. In addition, L₁₅ rats showed an increase in the distance traveled and a decrease in the immobility time in the EPM, impaired ORM, and accelerated CSD propagation when compared with L₉ rats (p ≤ 0.05).Discussion: These data suggest that sub-convulsive pilocarpine treatment in adult rats can affect behavioral and excitability-related reactions. In addition, unfavorable lactation increases the ambulatory effects of pilocarpine. Further studies should investigate the possible cholinergic molecular mechanisms involved in these effects.

Long-term efficacy and cognitive effects of bilateral hippocampal deep brain stimulation in patients with drug-resistant temporal lobe epilepsy

PURPOSE

Temporal lobe epilepsy patients treated with hippocampal deep brain stimulation (Hip-DBS) have rarely been reported before. Preoperative and postoperative cognitive function is seldom analyzed.

METHODS

Seven patients with drug-resistant temporal lobe epilepsy were included in this study. Bilateral Hip-DBS was performed in these patients. The stimulator was activated 1 month after the implantation. Then, the patients returned for further adjustments 4 months after the surgery and reprogramming every year. The seizure frequency, Wechsler Adult Intelligence Scale-IV, and Wechsler memory scale-IV were assessed blindly as the outcomes at each follow-up.

RESULTS

After a mean 48-month follow-up, the mean seizure frequency significantly decreased (p = 0.011, paired t test; decrease of 78.1%). One patient (14.3%) was seizure-free by the last follow-up; six of seven (85.7%) patients had reductions in seizure frequency of at least 50%; one patient (14.3%) who did not comply with the antiepileptic drug instructions had a less than 50% reduction in seizure frequency. In addition, there were no significant decreases in intelligence or verbal and visual memory from baseline to the last follow-up (p = 0.736, paired t test; p = 0.380, paired t test, respectively).

CONCLUSION

Hip-DBS could provide acceptable long-term efficacy and safety. For patients with drug-resistant temporal lobe epilepsy who are not suitable for resective surgery, Hip-DBS could become a potential therapeutic option.

Effects of Antiepileptic Drug Tapering on Episodic Memory as Measured by Virtual Reality Tests

Antiepileptic drugs impair episodic memory in patients with epilepsy, but this effect has so far only been examined with tests that do not provide first-person experience-an aspect that is crucial for episodic memory. Virtual reality techniques facilitate the development of ecologically valid tests. In the present study, we measure the effect of antiepileptic drug changes in a within-subject design using a virtual reality test in order to provide direct evidence for effects of antiepileptic drugs on episodic memory. Among 106 recruited patients, 97 participated in a virtual reality test up to six times during a 4-day hospitalization, and 78 patients underwent changes in drug load during this period. There were six parallel versions of a virtual town test, with immediate recall and delayed recall after about 12 h. The test requires recall of elements, details, sequence of experience, and egocentric and allocentric spatial memory. We determined drug load by defined daily dose, and compared test performance at lowest antiepileptic drug load to highest antiepileptic drug load. Across the six towns, performance was lower in delayed compared to immediate recall. There was an overall effect of medication when comparing patients taking vs. not taking antiepileptic drugs and/or psychoactive drugs (p = 0.005). Furthermore, there was a within-subject effect of antiepileptic drug load (p = 0.01), indicating lower test performance at higher drug load. There was no effect of gender, daytime, circadian type, depression, seizures, lesions, and epilepsy. For patients with temporal lobe epilepsy, there was no effect of lateralization. The present study provides direct evidence for episodic memory impairment due to antiepileptic drugs, suggesting that a small change in drug load can matter. This study can serve as a proof of principle for the methodology, but a larger sample is needed to examine the differential effects of individual antiepileptic drugs.

Role of c-Jun N-Terminal Kinases (JNKs) in Epilepsy and Metabolic Cognitive Impairment

Previous studies have reported that the regulatory function of the different c-Jun N-terminal kinases isoforms (JNK1, JNK2, and JNK3) play an essential role in neurological disorders, such as epilepsy and metabolic-cognitive alterations. Accordingly, JNKs have emerged as suitable therapeutic strategies. In fact, it has been demonstrated that some unspecific JNK inhibitors exert antidiabetic and neuroprotective effects, albeit they usually show high toxicity or lack therapeutic value. In this sense, natural specific JNK inhibitors, such as Licochalcone A, are promising candidates. Nonetheless, research on the understanding of the role of each of the JNKs remains mandatory in order to progress on the identification of new selective JNK isoform inhibitors. In the present review, a summary on the current gathered data on the role of JNKs in pathology is presented, as well as a discussion on their potential role in pathologies like epilepsy and metabolic-cognitive injury. Moreover, data on the effects of synthetic small molecule inhibitors that modulate JNK-dependent pathways in the brain and peripheral tissues is reviewed.