Neural responses to advantageous and disadvantageous inequity

In this paper we study neural responses to inequitable distributions of rewards despite equal performance. We specifically focus on differences between advantageous inequity (AI) and disadvantageous inequity (DI). AI and DI were realized in a hyperscanning functional magnetic resonance imaging (fMRI) experiment with pairs of subjects simultaneously performing a task in adjacent scanners and observing both subjects' rewards. Results showed (1) hypoactivation of the ventral striatum (VS) under DI but not under AI; (2) inequity induced activation of the right dorsolateral prefrontal cortex (DLPFC) that was stronger under DI than under AI; (3) correlations between subjective evaluations of AI evaluation and bilateral ventrolateral prefrontal and left insular activity. Our study provides neurophysiological evidence for different cognitive processes that occur when exposed to DI and AI, respectively. One possible interpretation is that any form of inequity represents a norm violation, but that important differences between AI and DI emerge from an asymmetric involvement of status concerns.

Identifying important nodes in weighted functional brain networks: a comparison of different centrality approaches

We compare different centrality metrics which aim at an identification of important nodes in complex networks. We investigate weighted functional brain networks derived from multichannel electroencephalograms recorded from 23 healthy subject under resting-state eyes-open or eyes-closed conditions. Although we observe the metrics strength, closeness, and betweenness centrality to be related to each other, they capture different spatial and temporal aspects of important nodes in these networks associated with behavioral changes. Identifying and characterizing of these nodes thus benefits from the application of several centrality metrics.

Cliniconeuropathologic correlations show astroglial albumin storage as a common factor in epileptogenic vascular lesions

PURPOSE

Intracerebral vascular malformations including cavernous angiomas (CAs) and arteriovenous malformations (AVMs) are an important cause of chronic pharmacoresistant epilepsies. Little is known about the pathogenetic basis of epilepsy in patients with vascular malformations. Intracerebral deposits of iron-containing blood products have been generally regarded as responsible for the strong epileptogenic potential of CAs. Here, we have analyzed whether blood-brain barrier (BBB) dysfunction and subsequent astrocytic albumin uptake, recently described as critical trigger of focal epilepsy, represent pathogenetic factors in vascular lesion-associated epileptogenesis.

METHODS

We examined the correlation between hemosiderin deposits, albumin accumulation, and several clinical characteristics in a series of 80 drug-refractory epilepsy patients with CAs or AVMs who underwent surgical resection. Analysis of clinical parameters included gender, age of seizure onset, epilepsy frequency, duration of epilepsy before surgery, and postoperative seizure outcome classification according to Engel class scale. Hemosiderin deposits in the adjacent brain tissue of the vascular lesion were semiquantitatively analyzed. Fluorescent double-immunohistochemistry using GFAP/albumin costaining was performed to study albumin extravasation.

KEY FINDINGS

Our results suggest that a shorter duration of preoperative epilepsy is correlated with significantly better postsurgical outcome (p < 0.05), whereas no additional clinical or neuropathologic parameter correlated significantly with the postsurgical seizure situation. Intriguingly, we observed strong albumin immunoreactivity within the vascular lesion and in perilesional astrocytes (57.65 ± 4.05%), but not in different control groups.

SIGNIFICANCE

Our present data on albumin uptake in brain tissue adjacent to AVMs and CAs suggests BBB dysfunction and accumulation of albumin within astrocytes as a new pathologic feature potentially associated with the epileptogenic mechanism for vascular lesions and provides novel therapy perspectives for antiepileptogenesis in affected patients.

Prospective use of subtraction ictal SPECT coregistered to MRI (SISCOM) in presurgical evaluation of epilepsy

PURPOSE

In patients with drug-refractory focal epilepsy, nonlesional magnetic resonance imaging (MRI) or discordant data of presurgical standard investigations leads to failure generating a sufficient hypothesis for electrode implantation or epilepsy surgery. The seizure-onset zone can be further investigated by subtraction ictal single-photon emission computed tomography (SPECT) coregistered to MRI (SISCOM). This is an observational study of a large consecutive cohort of patients undergoing prospective SISCOM to generate hypothesis for electrode implantation or site of epilepsy surgery.

METHODS

One hundred seventy-five consecutive patients undergoing presurgical evaluation with either nonlesional MRI or discordant data of standard investigations preventing the generation of hypothesis for seizure onset were evaluated with SISCOM. Results were compared to gold standard for seizure onset detection, either electrocorticography (ECoG) and/or postoperative outcome.

KEY FINDINGS

One hundred thirty patients had successful SPECT injection. Hypothesis for electrode implantation/site of surgery was generated in 74 patients. Forty patients had gold standard comparison. Twenty-eight patients underwent resective surgery. SISCOM was concordant to site of surgery in 82%. An additional 12 patients underwent invasive EEG monitoring but were not suitable for surgery. SISCOM was concordant multifocal in 75%. Two years postsurgical follow-up of 26 patients showed favorable outcome in 22 (Engel class I and class II).

SIGNIFICANCE

SISCOM is a highly valuable diagnostic tool to localize the seizure-onset zone in nonlesional and extratemporal epilepsies. Outcome in this patient group was unexpectedly good, even in patients with nonlesional MRI. The high correlation with ECoG and site of successful surgery is a strong indicator that outcome prediction in this patient group should be adapted accordingly, which may encourage more patients to undergo electrode implantation and subsequent successful surgery. Statistical analysis showed that SISCOM with shorter duration of seizures, focal seizures, and lesional MRI was more likely to generate implantation hypothesis.

Genome-wide linkage meta-analysis identifies susceptibility loci at 2q34 and 13q31.3 for genetic generalized epilepsies

PURPOSE

Genetic generalized epilepsies (GGEs) have a lifetime prevalence of 0.3% with heritability estimates of 80%. A considerable proportion of families with siblings affected by GGEs presumably display an oligogenic inheritance. The present genome-wide linkage meta-analysis aimed to map: (1) susceptibility loci shared by a broad spectrum of GGEs, and (2) seizure type-related genetic factors preferentially predisposing to either typical absence or myoclonic seizures, respectively.

METHODS

Meta-analysis of three genome-wide linkage datasets was carried out in 379 GGE-multiplex families of European ancestry including 982 relatives with GGEs. To dissect out seizure type-related susceptibility genes, two family subgroups were stratified comprising 235 families with predominantly genetic absence epilepsies (GAEs) and 118 families with an aggregation of juvenile myoclonic epilepsy (JME). To map shared and seizure type-related susceptibility loci, both nonparametric loci (NPL) and parametric linkage analyses were performed for a broad trait model (GGEs) in the entire set of GGE-multiplex families and a narrow trait model (typical absence or myoclonic seizures) in the subgroups of JME and GAE families.

KEY FINDINGS

For the entire set of 379 GGE-multiplex families, linkage analysis revealed six loci achieving suggestive evidence for linkage at 1p36.22, 3p14.2, 5q34, 13q12.12, 13q31.3, and 19q13.42. The linkage finding at 5q34 was consistently supported by both NPL and parametric linkage results across all three family groups. A genome-wide significant nonparametric logarithm of odds score of 3.43 was obtained at 2q34 in 118 JME families. Significant parametric linkage to 13q31.3 was found in 235 GAE families assuming recessive inheritance (heterogeneity logarithm of odds = 5.02).

SIGNIFICANCE

Our linkage results support an oligogenic predisposition of familial GGE syndromes. The genetic risk factor at 5q34 confers risk to a broad spectrum of familial GGE syndromes, whereas susceptibility loci at 2q34 and 13q31.3 preferentially predispose to myoclonic seizures or absence seizures, respectively. Phenotype- genotype strategies applying narrow trait definitions in phenotypic homogeneous subgroups of families improve the prospects of disentangling the genetic basis of common familial GGE syndromes.

A reward prediction error for charitable donations reveals outcome orientation of donators

The motives underlying prosocial behavior, like charitable donations, can be related either to actions or to outcomes. To address the neural basis of outcome orientation in charitable giving, we asked 33 subjects to make choices affecting their own payoffs and payoffs to a charity organization, while being scanned by functional magnetic resonance imaging (fMRI). We experimentally induced a reward prediction error (RPE) by subsequently discarding some of the chosen outcomes. Co-localized to a nucleus accumbens BOLD signal corresponding to the RPE for the subject's own payoff, we observed an equivalent RPE signal for the charity's payoff in those subjects who were willing to donate. This unique demonstration of a neuronal RPE signal for outcomes exclusively affecting unrelated others indicates common brain processes during outcome evaluation for selfish, individual and nonselfish, social rewards and strongly suggests the effectiveness of outcome-oriented motives in charitable giving.

Hippocampal resection length and memory outcome in selective epilepsy surgery

OBJECTIVE

In temporal lobe epilepsy surgery, there is a trend towards becoming more selective in order to achieve seizure control with an optimal neuropsychological outcome. The present study evaluated whether mesial resection length matters for memory outcome after selective amygdalo-hippocampectomy (SAH). Therefore, a sub-analysis of the larger SFB/TR3/A1 multicentre randomised trial on seizure outcome and mesial resection length in temporal lobe surgery was performed.

METHODS

A homogeneous group of 67 selectively operated patients with hippocampal sclerosis as the sole pathology were allocated to a short (2.5 cm, n=34) or a long (3.5 cm, n=33) mesial resection. Repeated memory assessment and three-dimensional MRI data sets served as dependent within group variables, and intraoperatively determined resection lengths (short/long), resected hippocampal volumes (small/large) and side of surgery were independent between group variables.

RESULTS

Resection length did not have a significant effect on seizure or on memory outcome. The resected hippocampal volume also did not affect seizure outcome but it did make a difference with regard to memory outcome. Outcome in verbal learning and memory was poorer after resection of larger left hippocampal volumes. Figural memory outcome was poorer with larger resected volumes on either side.

INTERPRETATION

The data indicate that in SAH, mesial resection length and resected volumes have no differential effect on seizure outcome. The findings on memory outcome are best explained by suggesting that hippocampal volumes take the degree of preoperative pathology into account whereas resection length does not. This suggests resection of non-pathological functional tissues as the basis for memory outcome after SAH.

Identification of preseizure States in epilepsy: a data-driven approach for multichannel EEG recordings

The retrospective identification of preseizure states usually bases on a time-resolved characterization of dynamical aspects of multichannel neurophysiologic recordings that can be assessed with measures from linear or non-linear time series analysis. This approach renders time profiles of a characterizing measure – so-called measure profiles – for different recording sites or combinations thereof. Various downstream evaluation techniques have been proposed to single out measure profiles that carry potential information about preseizure states. These techniques, however, rely on assumptions about seizure precursor dynamics that might not be generally valid or face the statistical problem of multiple testing. Addressing these issues, we have developed a method to preselect measure profiles that carry potential information about preseizure states, and to identify brain regions associated with seizure precursor dynamics. Our data-driven method is based on the ratio S of the global to local temporal variance of measure profiles. We evaluated its suitability by retrospectively analyzing long-lasting multichannel intracranial EEG recordings from 18 patients that included 133 focal onset seizures, using a bivariate measure for the strength of interactions. In 17/18 patients, we observed S to be significantly correlated with the predictive performance of measure profiles assessed retrospectively by means of receiver-operating-characteristic statistics. Predictive performance was higher for measure profiles preselected with S than for a manual selection using information about onset and spread of seizures. Across patients, highest predictive performance was not restricted to recordings from focal areas, thus supporting the notion of an extended epileptic network in which even distant brain regions contribute to seizure generation. We expect our method to provide further insight into the complex spatial and temporal aspects of the seizure generating process.

Genetic analysis of tuberous-sclerosis genes 1 and 2 in nonlesional focal epilepsy

Germline mutations of TSC1 (harmartin) and TSC2 (tuberin) are known to cause tuberous sclerosis (TSC), an autosomal dominant disorder with severe neurological and systemic manifestations. In addition, increasing data indicate aberrant patterns of allelic variants in patients with lesion-associated epilepsy, but absence of other stigmata of TSC. Animal models of TSC suggested that mutations in the TSC2 gene, even in absence of manifest neuropathological changes, induce aberrant neuronal activity. On this basis, we have carried out a mutational analysis of TSC1 and TSC2 in patients with pharmarcoresistant focal epilepsy without evidence of epileptogenic lesions on neuroradiological and histopathological examination (n=10). SSCP analysis revealed an allelic variant of TSC2 to be significantly increased (exon 41: 50.0% vs controls 14%, P=0.0132), which previously was reported to be increased in gangliogliomas and mineralized focal cortical dysplasia as well. Our data suggest allelic imbalances of TSC2 in nonlesional focal epileptic tissue.

Modelling the topography of absolute defects in patients exposed to the anti-epileptic drug vigabatrin and in normal subjects using automated static suprathreshold perimetry of the entire 80° visual field

AIM

(i) To map the spatial distribution of absolute visual field loss (AL) in patients exposed to vigabatrin and to compare the findings with AL in normal individuals, and (ii) to describe the relationship between the major risk factors for absolute loss (gender, age, cumulative dose), and the severity of field loss, expressed as the number of locations with AL per eye.

METHODS

Visual field plots were retrospectively reviewed from 428 individuals. Perimetry was done with the Tübingen Automated Perimeter (using a threshold-oriented, marginally supraliminal strategy, 80° eccentricity, 99 test locations). Three hundred and sixty-one individuals were ophthalmologically normal, and 67 were patients exposed to vigabatrin who had performed reliably during perimetry prior to neurosurgery for epilepsy. Two hundred and sixty-six of the 361 normals were included on the empirical basis that they manifested AL at no more than 19 stimulus locations per eye (the 74th percentile). The frequency per eye of AL at each of 99 stimulus locations was determined for the normals and patients. The effects of age, gender and cumulative dose of vigabatrin on the number of ALs per individual was assessed by an analysis of covariance. A stochastic model was developed to determine the 50% probability of AL at each location.

RESULTS

Thirty-nine of the 67 vigabatrin patients exhibited at least 20 locations with AL. The number of ALs was independent of age (p  =  0.7603). The frequency of AL was 14.8% in the peripheral field and 1.0% in the central field (odds ratio 16.7; 95% CI 15.0-18.6%; p  <  0.0001). Those exposed to vigabatrin exhibited a frequency of 17.1% ALs, compared to 5.2% for the normal individuals (odds ratio 3.77, 95% CI 3.6-4.0%; p  <  0.0001). According to the modelled data, males exhibited 20.9% (95% CI 1.3-44%; p  =  0.0360) more absolute losses than did females. The number of absolute losses per person doubled with an increase in cumulative dose of vigabatrin of 936 g (95% CI 775-1181 g).

CONCLUSIONS

According to this retrospective study, the spatial configuration of absolute defects attributable to vigabatrin indicates sparing of the temporal field up to approximately 60° eccentricity. Such a finding is likely to explain, at least in part, the initially asymptomatic nature of the defect. This study reconfirms a (cumulative) dose effect of vigabatrin on the extent of absolute field loss, with a greater risk for male gender.

Randomized controlled trial of 2.5-cm versus 3.5-cm mesial temporal resection--Part 2: volumetric resection extent and subgroup analyses

BACKGROUND

This paper is addressing outcome differences in interesting subgroups from a previous randomized controlled trial of the extent of mesial temporal lobe resection (TLR) for drug-resistant epilepsy, by looking at effects of randomization, intended resection group, center, and true resection extent on seizure outcome.

METHODS

One hundred and seventy-nine cases with volumetrically assessed resection extent were used. Analyses of the extent of resection and subgroups and within subgroups for the two treatment arms will be performed, looking for confounding factors and using statistical methods (chi-square test, logistic regression analysis, and two-factorial ANOVA).

RESULTS

True resection extent varied considerably. Outcome comparison for right versus left resections, subgroups with mesial temporal sclerosis (MTS), or largest and smallest resections revealed no remarkable difference, compared to overall class I outcome. The intent-to-treat analyses within these subgroups revealed differences for class I outcome, albeit lacking in significance, except for better TLR outcome. Small true resection volume differences or randomization into the two resection groups could not explain the outcome differences between the selective amygdalohippocampectomy (SAH) and TLR subgroups. Logistic regression analysis showed an interaction between intended resection length and surgery type, confirming the impression of different impacts of the intended resection length under the two surgery types. The outcome difference between SAH and TLR was more likely explained by a center effect. In a two-factorial ANOVA for resected hippocampal volume, Engel outcome class I, and resection type, the outcome was not found to be correlated with true resection volume. A multifactorial logistic regression showed a mild interaction between the resection type with center on the Engel outcome class, extent of resection, and surgery type interacted, as did the extent of resection and center.

CONCLUSION

Patients with quite similar extent of resection can be seizure free or non-seizure free. In this cohort, seizure freedom rates fell again when the extent of mesial resection was maximized. Differences in class I outcome for SAH and TLR were not due to erroneous randomization, true resection extent, or presence of MTS, but were influenced by a center effect. Subgroup analyses did not help to provide arguments to favor one surgery type over the other.

Randomized controlled trial of 2.5-cm versus 3.5-cm mesial temporal resection in temporal lobe epilepsy--Part 1: intent-to-treat analysis

BACKGROUND

Only one prospective randomized study on the extent of mesial resection in surgery for temporal lobe epilepsy (TLE) exists. This randomized controlled trial (RCT) examines whether 3.5-cm mesial resection is leading to a better seizure outcome than a 2.5-cm resection.

METHODS

Three epilepsy surgery centers using similar MRI protocols, neuropsychological tests, and resection types for TLE surgery included 207 patients in a RCT with pre- and postoperative volumetrics. One hundred and four patients were randomized into a 2.5-cm resection group and 103 patients into a 3.5-cm resection group, i.e., an intended minimum resection length of 25 versus 35 mm for the hippocampus and parahippocampus. Primary outcome measure was seizure freedom Engel class I throughout the first year. The study was powered to detect a 20% difference in class I outcome. Seizure outcome was available for 207 patients, complete volumetric results for 179 patients. Outcome analysis was restricted to control of successful randomization and an intent-to-treat analysis of seizure outcome.

RESULTS

The mean true resection volumes were significantly different for the 2.5-cm and 3.5-cm resection groups; thus, the randomization was successful. Median resection volume in the 2.5-cm group was 72.86% of initial volume and 83.44% in the 3.5-cm group. At 1 year, seizure outcome Engel class I was 74% in the 2.5-cm and 72.8% in the 3.5-cm resection group.

CONCLUSIONS

The primary intent-to-treat analysis did not show a different seizure freedom rate for the more posteriorly reaching 3.5-cm resection group. It appears possible that not maximal volume resection but adequate volume resection leads to good seizure freedom.

Differential effects of semantic processing on memory encoding

Deeper semantic processing of words leads to enhanced memory encoding (depth of processing effect). The left inferior prefrontal cortex (LIPC) and the left hippocampus are known to be involved in this effect. We tested the hypothesis that different semantic encoding processes contribute qualitatively differently to memory encoding. In a memory experiment using functional magnetic resonance imaging, we compared three different encoding tasks: a nonsemantic alphabetical, an animacy decision, and a size comparison tasks. Recognition memory was tested subsequently. We hypothesized that the size comparison task would activate brain areas involved in the processing of object features and that this would be associated with successful memory encoding. Results showed that the size comparison task led to significantly better memory encoding than the two other tasks. As with the animacy decision task, it led to stronger activation of the LIPC and left hippocampus than the nonsemantic task. Both regions also had stronger activations for later remembered than for nonremembered words. The size comparison task additionally led to stronger activation in the left anterior fusiform gyrus, which was also associated with successful memory encoding. We conclude that different types of semantic processing affect memory encoding based on distinguishable brain processes.

Presence of Temporal Gray-White Matter Abnormalities Does Not Influence Epilepsy Surgery Outcome in Temporal Lobe Epilepsy With Hippocampal Sclerosis

BACKGROUND:

Temporal lobe gray-white matter abnormalities (GWMA) are frequent morphological aberrances observed on MRI in patients with temporal lobe epilepsy (TLE) in addition to hippocampal sclerosis (HS).

OBJECTIVE:

To study the influence of temporal pole GWMA on clinical characteristics and seizure outcome in patients with HS operated on for TLE.

METHODS:

A cohort of 370 patients undergoing surgery for intractable TLE was prospectively collected in an epilepsy surgery data base. Clinical characteristics and seizure outcome of all 58 TLE patients with identified HS and GWMA (group 1) were compared with those of a matched control group of 58 HS patients without GWMA (group 2). Both groups were further subdivided into patients undergoing transsylvian selective amygdalohippocampectomy (sAH) and anterior temporal lobectomy with amygdalohippocampectomy (ATL).

RESULTS:

The HS plus GWMA patients were significantly younger at epilepsy onset than those without GWMA. In the HS plus GWMA group, 41% of patients were younger than 2 years when they experienced their first seizure in contrast to only 17% of patients with pure HS (P = .004). Seizure outcome was not statistically different between the 2 groups: 75.9% of the patients in group 1 were seizure free (Engel class I) compared with 81% of patients in group 2. Seizure outcome in both groups was about equally successful with selective amygdalohippocampectomy and anterior temporal lobectomy (ns).

CONCLUSION:

Limited and standard resections in TLE patients with HS are equally successful regardless of the presence of GWMA.

Mitochondrial dysfunction due to Leber's hereditary optic neuropathy as a cause of visual loss during assessment for epilepsy surgery

Assessment for epilepsy surgery may require invasive measures such as implantation of intracranial electrodes or the Wada test. These investigations are commonly well tolerated. However, complications, including visual disturbances of various etiologies, have been reported. Here we describe two patients with pharmacoresistant temporal lobe epilepsy (TLE) who displayed loss of vision in the context of presurgical assessment and in whom mutations associated with Leber's hereditary optic neuropathy (LHON) were detected. Genetic analysis revealed in one patient the frequent mitochondrial G11778A LHON mutation in ND4. In the second patient, the mitochondrial C4640A mutation in ND2 was detected. This rare LHON mutation enhanced the sensitivity of the patient's muscle and brain tissue to amobarbital, a known blocker of the mitochondrial respiratory chain. Mitochondrial dysfunction has been reported in epilepsy. Thus, the presence of LHON mutations can be a rare cause of visual disturbances in patients with epilepsy and may have predisposed to development of epilepsy.

Congenital prosopagnosia: multistage anatomical and functional deficits in face processing circuitry

Face recognition is a primary social skill which depends on a distributed neural network. A pronounced face recognition deficit in the absence of any lesion is seen in congenital prosopagnosia. This study investigating 24 congenital prosopagnosic subjects and 25 control subjects aims at elucidating its neural basis with fMRI and voxel-based morphometry. We found a comprehensive behavioral pattern, an impairment in visual recognition for faces and buildings that spared long-term memory for faces with negative valence. Anatomical analysis revealed diminished gray matter density in the bilateral lingual gyrus, the right middle temporal gyrus, and the dorsolateral prefrontal cortex. In most of these areas, gray matter density correlated with memory success. Decreased functional activation was found in the left fusiform gyrus, a crucial area for face processing, and in the dorsolateral prefrontal cortex, whereas activation of the medial prefrontal cortex was enhanced. Hence, our data lend strength to the hypothesis that congenital prosopagnosia is explained by network dysfunction and suggest that anatomic curtailing of visual processing in the lingual gyrus plays a substantial role. The dysfunctional circuitry further encompasses the fusiform gyrus and the dorsolateral prefrontal cortex, which may contribute to their difficulties in long-term memory for complex visual information. Despite their deficits in face identity recognition, processing of emotion related information is preserved and possibly mediated by the medial prefrontal cortex. Congenital prosopagnosia may, therefore, be a blueprint of differential curtailing in networks of visual cognition.

Long-term variability of global statistical properties of epileptic brain networks

We investigate the influence of various pathophysiologic and physiologic processes on global statistical properties of epileptic brain networks. We construct binary functional networks from long-term, multichannel electroencephalographic data recorded from 13 epilepsy patients, and the average shortest path length and the clustering coefficient serve as global statistical network characteristics. For time-resolved estimates of these characteristics we observe large fluctuations over time, however, with some periodic temporal structure. These fluctuations can--to a large extent--be attributed to daily rhythms while relevant aspects of the epileptic process contribute only marginally. Particularly, we could not observe clear cut changes in network states that can be regarded as predictive of an impending seizure. Our findings are of particular relevance for studies aiming at an improved understanding of the epileptic process with graph-theoretical approaches.

Distinct patterns of mitochondrial genome diversity in bonobos (Pan paniscus) and humans

BACKGROUND

We have analyzed the complete mitochondrial genomes of 22 Pan paniscus (bonobo, pygmy chimpanzee) individuals to assess the detailed mitochondrial DNA (mtDNA) phylogeny of this close relative of Homo sapiens.

RESULTS

We identified three major clades among bonobos that separated approximately 540,000 years ago, as suggested by Bayesian analysis. Incidentally, we discovered that the current reference sequence for bonobo likely is a hybrid of the mitochondrial genomes of two distant individuals. When comparing spectra of polymorphic mtDNA sites in bonobos and humans, we observed two major differences: (i) Of all 31 bonobo mtDNA homoplasies, i.e. nucleotide changes that occurred independently on separate branches of the phylogenetic tree, 13 were not homoplasic in humans. This indicates that at least a part of the unstable sites of the mitochondrial genome is species-specific and difficult to be explained on the basis of a mutational hotspot concept. (ii) A comparison of the ratios of non-synonymous to synonymous changes (dN/dS) among polymorphic positions in bonobos and in 4902 Homo sapiens mitochondrial genomes revealed a remarkable difference in the strength of purifying selection in the mitochondrial genes of the F0F1-ATPase complex. While in bonobos this complex showed a similar low value as complexes I and IV, human haplogroups displayed 2.2 to 7.6 times increased dN/dS ratios when compared to bonobos.

CONCLUSIONS

Some variants of mitochondrially encoded subunits of the ATPase complex in humans very likely decrease the efficiency of energy conversion leading to production of extra heat. Thus, we hypothesize that the species-specific release of evolutionary constraints for the mitochondrial genes of the proton-translocating ATPase is a consequence of altered heat homeostasis in modern humans.

Organic labeling influences food valuation and choice

Everyday we choose between a variety of different food items trying to reach a decision that fits best our needs. These decisions are highly dependent on the context in which the alternatives are presented (e.g. labeling). We investigate the influence of cognition on food evaluation, using an fMRI experiment in which subjects saw and bid on different foods labeled with (or without) a widely known German emblem for organically produced food. Increased activity in the ventral striatum was found for foods labeled "organic" in comparison to conventionally labeled food. Between-subject differences in activity were related to actual everyday consumption behavior of organic food.

Role of GRM4 in idiopathic generalized epilepsies analysed by genetic association and sequence analysis

BACKGROUND

GRM4 encoding the group III metabotropic glutamate receptor 4 (mGluR4), is located on the chromosomal segment 6p21.3 where tentative susceptibility loci for Juvenile Myoclonic Epilepsy (JME) and Photoparoxysmal Response (PPR) have been mapped. The present candidate gene study examined if variation in GRM4 confers susceptibility to IGE.

PATIENTS AND METHODS

The case-control association sample included 564 unrelated IGE patients and 733 population controls of German descent. Association analysis was carried out for 17 single nucleotide polymorphisms (SNPs) covering the genomic GRM4 sequence for all IGE patients as well as for two common IGE subsyndromes [Juvenile Myoclonic Epilepsy (JME, n=215) and Childhood Absence Epilepsy (CAE, n=175)]. Sequence analysis was performed in 85 IGE and 42 PPR cases and 44 controls.

RESULTS

Nominally significant associations were detected between IGE and seven GRM4 SNPs (with P-values ranging from 0.037 to 0.0036), between JME and five SNPs (P=0.042-0.0106), and between CAE and two SNPs (P=0.0466-0.0021). Four novel SNPs were identified by sequence analysis.

CONCLUSIONS

Our association findings support the hypothesis that GRM4 sequence variants might confer low-risk effects to the etiology of IGE. A minor pathogenetic contribution of the examined variants is possible. These exploratory findings warrant further replication analyses.

Graded effects of social conformity on recognition memory

Previous studies have shown that the opinion of confederates in a group influences recognition memory, but inconsistent results have been obtained concerning the question of whether recognition of items as old and new are affected similarly, possibly because only one or two confederates are present during the recognition phase. Here, we present data from a study where recognition of novel faces was tested in the presence of four confederates. In a long version of this experiment, recognition of items as old and new was similarly affected by group responses. However, in the short version, recognition of old items depended proportionally on the number of correct group responses, while rejection of new items only decreased significantly when all confederates gave an incorrect response. These findings indicate that differential effects of social conformity on recognition of items as old and new occur in situations with an intermediate level of group pressure.

A 24-week multicenter, randomized, double-blind, parallel-group, dose-ranging study of rufinamide in adults and adolescents with inadequately controlled partial seizures

OBJECTIVE

To assess the efficacy, safety, tolerability, and pharmacokinetics of adjunctive rufinamide in adults and adolescents with inadequately controlled partial seizures receiving treatment with one to three concomitant antiepileptic drugs (AEDs).

METHODS

A 24-week multicenter Phase II clinical study was conducted (n=647), comprising a 12-week prospective baseline phase and a 12-week randomized double-blind, parallel-group, five-arm (placebo and rufinamide 200, 400, 800, and 1600mg/day) treatment phase.

RESULTS

The linear trend of dose response for seizure frequency per 28 days in the double-blind treatment phase - the primary efficacy outcome measure - was statistically significant in favor of rufinamide (estimated slope=-0.049, P=0.003; minimally efficacious dose, 400mg/day). Response rates, defined as a >or=50% reduction in seizure frequency per 28 days, also revealed a significant linear trend of dose response (P=0.0019, logistic regression analysis). Adverse events were comparable between placebo and all rufinamide groups except the 1600mg/day group; no safety signals were observed.

CONCLUSIONS

These results suggest that in the dose range of 400-1600mg/day, add-on rufinamide therapy may benefit patients with inadequately controlled partial seizures and is generally well tolerated. These data also suggest that higher doses may confer additional efficacy without adversely affecting safety and tolerability.

Activation of the caudal anterior cingulate cortex due to task-related interference in an auditory Stroop paradigm

Successful information processing requires the focusing of attention on a certain stimulus property and the simultaneous suppression of irrelevant information. The Stroop task is a useful paradigm to study such attentional top-down control in the presence of interference. Here, we investigated the neural correlates of an auditory Stroop task using fMRI. Subjects focused either on tone pitch (relatively high or low; phonetic task) or on the meaning of a spoken word (high/low/good; semantic task), while ignoring the other stimulus feature. We differentiated between task-related (phonetic incongruent vs. semantic incongruent) and sensory-level interference (phonetic incongruent vs. phonetic congruent). Task-related interference activated similar regions as in visual Stroop tasks, including the anterior cingulate cortex (ACC) and the presupplementary motor-area (pre-SMA). More specifically, we observed that the very caudal/posterior part of the ACC was activated and not the dorsal/anterior region. Because identical stimuli but different task demands are compared in this contrast, it reflects conflict at a relatively high processing level. A more conventional contrast between incongruent and congruent phonetic trials was associated with a different cluster in the pre-SMA/ACC which was observed in a large number of previous studies. Finally, functional connectivity analysis revealed that activity within the regions activated in the phonetic incongruent vs. semantic incongruent contrast was more strongly interrelated during semantically vs. phonetically incongruent trials. Taken together, we found (besides activation of regions well-known from visual Stroop tasks) activation of the very caudal and posterior part of the ACC due to task-related interference in an auditory Stroop task.

Enhancing memory for lists by grouped presentation and rehearsal: a pilot study in healthy subjects with unexpected results

List learning is probably the most established paradigm for the psychometric evaluation of episodic memory deficits in different neuropsychiatric conditions including epilepsy. Strategies which are capable of increasing the test performance might be promising candidates for a therapeutic improvement of daily memory performance. Based on the classical 'temporal grouping effect' we wanted to evaluate the memory-enhancing potential of disentangling perceiving, rehearsing and encoding by temporally grouped presentation and group-wise reproduction during acquisition. According to the ethical principle of subsidiary the study was performed in healthy adolescents (N=126) before setting-up a patient study. Subjects had to learn a list of 12 semantically unrelated nouns and a list of 12 figures during two acquisition trials under one of four experimental conditions defined by the size of presented item groups (GS): GS=1 (single items, i.e., 12 x 1 item), GS=3 (4 x 3 items), GS=6 (2 x 6 items), and GS=12 (standard presentation mode, i.e., 1 x 12 items). Repeated measures MANOVA confirmed a positive effect of smaller GS on acquisition performance but the grouping condition obtained no effect on immediate and delayed free recall or on yes/no recognition. For verbal retention, GS=12 even showed a tendency toward an advantage as compared to GS=3. Although appearing reasonable and promising, facilitating acquisition during list learning by temporal grouping and grouped overt rehearsal turned out to be ineffective with regard to long-term memory encoding and retrieval. A strategy however which fails in healthy subjects is unlikely to obtain a therapeutic potential in patients with memory deficits.

Recurrent microdeletions at 15q11.2 and 16p13.11 predispose to idiopathic generalized epilepsies

Idiopathic generalized epilepsies account for 30% of all epilepsies. Despite a predominant genetic aetiology, the genetic factors predisposing to idiopathic generalized epilepsies remain elusive. Studies of structural genomic variations have revealed a significant excess of recurrent microdeletions at 1q21.1, 15q11.2, 15q13.3, 16p11.2, 16p13.11 and 22q11.2 in various neuropsychiatric disorders including autism, intellectual disability and schizophrenia. Microdeletions at 15q13.3 have recently been shown to constitute a strong genetic risk factor for common idiopathic generalized epilepsy syndromes, implicating that other recurrent microdeletions may also be involved in epileptogenesis. This study aimed to investigate the impact of five microdeletions at the genomic hotspot regions 1q21.1, 15q11.2, 16p11.2, 16p13.11 and 22q11.2 on the genetic risk to common idiopathic generalized epilepsy syndromes. The candidate microdeletions were assessed by high-density single nucleotide polymorphism arrays in 1234 patients with idiopathic generalized epilepsy from North-western Europe and 3022 controls from the German population. Microdeletions were validated by quantitative polymerase chain reaction and their breakpoints refined by array comparative genomic hybridization. In total, 22 patients with idiopathic generalized epilepsy (1.8%) carried one of the five novel microdeletions compared with nine controls (0.3%) (odds ratio = 6.1; 95% confidence interval 2.8-13.2; chi(2) = 26.7; 1 degree of freedom; P = 2.4 x 10(-7)). Microdeletions were observed at 1q21.1 [Idiopathic generalized epilepsy (IGE)/control: 1/1], 15q11.2 (IGE/control: 12/6), 16p11.2 IGE/control: 1/0, 16p13.11 (IGE/control: 6/2) and 22q11.2 (IGE/control: 2/0). Significant associations with IGEs were found for the microdeletions at 15q11.2 (odds ratio = 4.9; 95% confidence interval 1.8-13.2; P = 4.2 x 10(-4)) and 16p13.11 (odds ratio = 7.4; 95% confidence interval 1.3-74.7; P = 0.009). Including nine patients with idiopathic generalized epilepsy in this cohort with known 15q13.3 microdeletions (IGE/control: 9/0), parental transmission could be examined in 14 families. While 10 microdeletions were inherited (seven maternal and three paternal transmissions), four microdeletions occurred de novo at 15q13.3 (n = 1), 16p13.11 (n = 2) and 22q11.2 (n = 1). Eight of the transmitting parents were clinically unaffected, suggesting that the microdeletion itself is not sufficient to cause the epilepsy phenotype. Although the microdeletions investigated are individually rare (<1%) in patients with idiopathic generalized epilepsy, they collectively seem to account for a significant fraction of the genetic variance in common idiopathic generalized epilepsy syndromes. The present results indicate an involvement of microdeletions at 15q11.2 and 16p13.11 in epileptogenesis and strengthen the evidence that recurrent microdeletions at 15q11.2, 15q13.3 and 16p13.11 confer a pleiotropic susceptibility effect to a broad range of neuropsychiatric disorders.

NeuroCog FX: computerized screening of cognitive functions in patients with epilepsy

NeuroCog FX, a computerized neuropsychological screening instrument for serial examinations of patients with epilepsy and other neurological diseases, was developed to fill the gap between unspecific ratings and comprehensive assessments. Eight subtests address attention, working memory, verbal and figural memory, and language. The test duration is less than 30min. In research contexts, the test can be applied at multiple sites by nonacademic personnel. Normative data were recorded from healthy subjects (N=244, age range=16-75years; retest: N=44; validation: N=40) and unselected patients from an epileptology unit (N=212; retest: N=94; validation: N=126). Psychometric analyses confirmed sufficient reliability and concurrent validity, particularly in patients. NeuroCog FX memory and overall performance scores showed "fair" to "good" diagnostic utility with respect to deficits revealed by established tests. NeuroCog FX provides reliable and valid measures of cognitive performance and may be used in clinical and research contexts as a screening instrument.

Overlap of musical and linguistic syntax processing: intracranial ERP evidence

The present study investigated the co-localization of musical and linguistic syntax processing in the human brain. EEGs were recorded from subdural electrodes placed on the left and right perisylvian cortex. The neural generators of the early potentials elicited by syntactic errors in music and language were localized by means of distributed source modeling and compared within subjects. The combined results indicated a partial overlap of the sources within the bilateral superior temporal gyrus, and, to a lesser extent, in the left inferior frontal gyrus, qualifying these areas as shared anatomic substrates of early syntactic error detection in music and language.

Working memory representation in atypical language dominance

One of the most important factors controlling material specific processing in the human brain is language dominance, i.e. hemispheric specialization in semantic processes. Although previous studies have shown that lateralized long-term memory processes in the medial temporal lobes are modified in subjects with atypical (right) language dominance, the effect of language dominance on the neural basis of working memory (WM) has remained unknown. Here, we used functional MRI (fMRI) to study the impact of language dominance on the neural representation of WM. We conducted an n-back task in three different load conditions and with both verbal and nonverbal (spatial) material in matched groups of left and right language dominant subjects. This approach allowed us to investigate regions showing significant interactions between language dominance and material. Overall, right dominant subjects showed an increased inter-individual variability of WM-related activations. Verbal WM involved more pronounced activation of the left fusiform cortex in left dominant subjects and of the right inferior parietal lobule in the right dominant group. Spatial WM, on the other hand, induced activation of right hemispheric regions in left dominant subjects, but no specific activations in right dominant subjects. Taken together, these findings indicate that the neural basis of verbal WM processes depends on language dominance and is more mutable in right dominant subjects. The increased variability in right dominant subjects strongly suggests that a standard network of material-dependent WM processes exists in left dominant subjects, and that right dominant subjects use variable alternative networks.