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Background: A common problem in neurophysiology is to identify stimuli that elicit neuronal responses in a given brain region. Particularly in situations where electrode positions are fixed, this can be a time-consuming task that requires presentation of a large number of stimuli. Such a screening for response-eliciting stimuli is employed, e.g., as a standard procedure to identify 'concept cells' in the human medial temporal lobe., New Method: Our new method evaluates neuronal responses to stimuli online during a screening session, which allows us to successively exclude stimuli that do not evoke a response. Using this method, we can screen a larger number of stimuli which in turn increases the chances of finding responsive neurons and renders time-consuming offline analysis unnecessary., Results: Our method enabled us to present 30% more stimuli in the same period of time with additional presentations of the most promising candidate stimuli. Our online method ran smoothly on a standard computer and network., Comparison With an Existing Method: To analyze how our online screening procedure performs in comparison to an established offline method, we used the Wave_Clus software package. We did not observe any major drawbacks in our method, but a much higher efficiency and analysis speed., Conclusions: By transitioning from a traditional offline screening procedure to our new online method, we substantially increased the number of visual stimuli presented in a given time period. This allows to identify more response-eliciting stimuli, which forms the basis to better address a great number of questions in cognitive neuroscience., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Background: Detailed neuropathological information on the structural brain lesions underlying seizures is valuable for understanding drug-resistant focal epilepsy., Methods: We report the diagnoses made on the basis of resected brain specimens from 9523 patients who underwent epilepsy surgery for drug-resistant seizures in 36 centers from 12 European countries over 25 years. Histopathological diagnoses were determined through examination of the specimens in local hospitals (41%) or at the German Neuropathology Reference Center for Epilepsy Surgery (59%)., Results: The onset of seizures occurred before 18 years of age in 75.9% of patients overall, and 72.5% of the patients underwent surgery as adults. The mean duration of epilepsy before surgical resection was 20.1 years among adults and 5.3 years among children. The temporal lobe was involved in 71.9% of operations. There were 36 histopathological diagnoses in seven major disease categories. The most common categories were hippocampal sclerosis, found in 36.4% of the patients (88.7% of cases were in adults), tumors (mainly ganglioglioma) in 23.6%, and malformations of cortical development in 19.8% (focal cortical dysplasia was the most common type, 52.7% of cases of which were in children). No histopathological diagnosis could be established for 7.7% of the patients., Conclusions: In patients with drug-resistant focal epilepsy requiring surgery, hippocampal sclerosis was the most common histopathological diagnosis among adults, and focal cortical dysplasia was the most common diagnosis among children. Tumors were the second most common lesion in both groups. (Funded by the European Union and others.).

Refractory mesial temporal lobe epilepsy (mTLE) is a debilitating condition potentially amenable to resective surgery. However, between 40 and 50% patients continue to experience postoperative seizures. The development of imaging prognostic markers of postoperative seizure outcome is a crucial objective for epilepsy research. In the present study, we performed analyses of preoperative cortical thickness and subcortical surface shape on MRI in 115 of patients with mTLE and radiologically defined hippocampal sclerosis being considered for surgery, and 80 healthy controls. Patients with excellent (International League Against Epilepsy outcome (ILAE) I) and suboptimal (ILAE II-VI) postoperative outcomes had a comparable distribution of preoperative atrophy across the cortex, basal ganglia, and amygdala. Conventional volumetry of whole hippocampal and extrahippocampal subcortical structures, and of global gray and white matter, could not differentiate between patient outcome groups. However, surface shape analysis revealed localized atrophy of the thalamus bilaterally and of the posterior/lateral hippocampus contralateral to intended resection in patients with persistent postoperative seizures relative to those rendered seizure free. Data uncorrected for multiple comparisons also revealed focal atrophy of the ipsilateral hippocampus posterior to the margins of resection in patients with persistent seizures. This data indicates that persistent postoperative seizures after temporal lobe surgery are related to localized preoperative shape alterations of the thalamus bilaterally and the hippocampus contralateral to intended resection. Imaging techniques that have the potential to unlock prognostic markers of postoperative outcome in individual patients should focus assessment on a bihemispheric thalamohippocampal network in prospective patients with refractory mTLE being considered for temporal lobe surgery., (© 2015 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.)

Recent functional imaging studies that examined functional connectivity in the resting brain have demonstrated various intrinsic connectivity networks (ICNs). Certain patterns of over- and underactivity in various ICNs have been hypothesized to form the neural basis of psychiatric disorders. Furthermore, activity in the ICNs does not reflect ongoing mental activity but the maintenance of neural circuits in a ready state suggesting not only relationships between ICNs and disorders but also correlations between ICNs and personality. In the present study, we assess the relationship between trait anxiety, a well established endophenotype of anxiety disorders, and functional connectivities within the insular salience ICN in a sample of healthy female subjects. Based on a previous study that demonstrated the functional relevance of the insular salience ICN for state anxiety, we used the harm avoidance scale from the Temperament and Character Inventory (TCI) as a trait marker to demonstrate increased functional connectivity within the insular salience ICN. Specifically, the functional connectivity between the anterior insula and the anterior cingulate and between the anterior insula and the dorsolateral prefrontal cortex were positively correlated with individual harm avoidance scores. The results fit into previous work, provide evidence for a potential biomarker of anxiety disorders and, most importantly, demonstrate a direct neural correlate of the personality trait harm avoidance in the absence of external stimulation., (Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.)

The aim of this functional magnetic resonance imaging (fMRI) study was to investigate the correlation between the severity of malocclusion and brain activation. The fMRI was used to measure blood-oxygenation- level-dependent (BOLD) signals of twelve healthy human subjects while they clenched in two different ways to simulate two types of malocclusion. In each malocclusion model, a custom-made splint forced the mandible to each of two retrusive positions (0.5 mm, 0.7 mm). A no-modification splint provided the control. We compared the BOLD signals measured at each clenching position with those measured during the corresponding resting conditions. The BOLD signals were significantly stronger in the amygdala and the prefrontal area (PFA) when subjects clenched in the two retrusive positions compared during clenching in the control position. In addition, the BOLD signal in the PFA increased as the simulated malocclusion became more severe. These results indicate that we may be able to objectively assess the severity of malocclusion via focus on the brain activity.

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., (Copyright 2010 Elsevier Inc. All rights reserved.)

This case concerns a 17-year-old boy, who was given the diagnosis of Alpers syndrome only postmortem when a homozygous 1399G-->A (A467T) mutation was found in the linker-region of POLG1. Serial muscle and liver biopsies as well as brain MRI scans in our patient ranging from early childhood to postmortem analyses showed that (i) routine diagnostic procedures can be normal in the early stage of the disorder and that (ii) central nervous system and further organ affection may only develop in the time course of the disease. Consecutive diagnostic examinations clearly reflected the devastating clinical course and cerebral deterioration evolving over time in Alpers syndrome.

In 1928, Hugo Friedrich Kufs reported on a family with cerebral, retinal, and cutaneous cavernous malformations. Since then, more than 300 families with inherited cavernous malformations have been reported. Genetic studies showed three loci, on chromosomes 7q21-q22 (with the gene CCM1), 7p15-p13 (CCM2), and 3q25.2-q27 (CCM3). The gene product of CCM1 is Krit 1 (Krev interaction trapped 1), a protein interacting with angiogenesis by various mechanisms. Recently, CCM2 has also been identified; its product is a protein which might have a function similar to that of Krit 1. However, the CCM3 gene has still not been found. In this study, we present clinical and genetic findings on 15 German families.

We report the case of a two years old boy showing gelastic fits as the leading clinical symptom of a rare complex cerebral malformation with closed-lip schizencephaly, an arachnoid cyst and a partial agenesis of the corpus callosum. After 5 uneventful interictal electroencephalograms the patient underwent 24 h EEG with telemetry while finally presenting two laughing fits with associated spike-wave discharges in the right-centroparietal region. Medical treatment with carbamacepine was initiated and the seizure frequency decreased significantly. This is the first cited case of gelastic fits occurring in schizencephaly. In contrast to previously cited cases with laughing fits we observed a good response to anticonvulsive treatment. Moreover our patient presented a surprisingly favourable psycho-mental and motor development during an 8 months observation period.

Objective: To correlate MRI and histopathologic findings in patients with Rasmussen's encephalitis (RE)., Patients and Methods: MRI features of 10 patients with RE were studied on serial scans. In surgical specimens from these patients, densities of T lymphocytes, microglial cells and nodules, and reactive astrocytes were evaluated., Results: Densities of T cells, microglial nodules, and astrocytes were inversely correlated to disease duration. MRI abnormalities had a focal onset and spread across one hemisphere. The following course of MRI abnormalities in a given brain region was observed: on very early scans, the cortex was swollen and showed a hyperintense T2/fluid-attenuated inversion recovery signal. Consecutively, progressive atrophy of the affected hemisphere occurred. Correlation of MRI features with quantitative histopathology revealed that there was a higher number of T cells and reactive astrocytes in the earlier MRI stages compared with the late (merely atrophic) stage., Conclusion: These data suggest a disease course in RE with the highest inflammatory intensity in the early stages and a subsequent decrease in inflammation. The MRI abnormalities and their characteristic sequence may help to identify patients with RE and to obtain informative biopsies.

We compare dynamical properties of brain electrical activity from different recording regions and from different physiological and pathological brain states. Using the nonlinear prediction error and an estimate of an effective correlation dimension in combination with the method of iterative amplitude adjusted surrogate data, we analyze sets of electroencephalographic (EEG) time series: surface EEG recordings from healthy volunteers with eyes closed and eyes open, and intracranial EEG recordings from epilepsy patients during the seizure free interval from within and from outside the seizure generating area as well as intracranial EEG recordings of epileptic seizures. As a preanalysis step an inclusion criterion of weak stationarity was applied. Surface EEG recordings with eyes open were compatible with the surrogates' null hypothesis of a Gaussian linear stochastic process. Strongest indications of nonlinear deterministic dynamics were found for seizure activity. Results of the other sets were found to be inbetween these two extremes.

There is increasing clinical and experimental evidence that hormones, in particular sex steroid hormones, influence neuronal excitability and other brain functions. The term 'neuroactive steroids' has been coined for steroids that interact with neurotransmitter receptors. One of the best characterized actions of neuroactive steroids is the allosteric modulation of GABA(A)-receptor function via binding to a putative steroid-binding site. Since neuroactive steroids may interact with a variety of other membrane receptors, excitatory as well as inhibitory, they may have an impact on the excitability of specific brain regions. Neuronal excitability is enhanced by estrogen, whereas progesterone and its metabolites exert anticonvulsant effects. Testosterone and corticosteroids have less consistent effects on seizure susceptibility. Apart from these particular properties, neuroactive steroids may regulate gene expression via progesterone receptors. Based on their molecular properties, these compounds appear to have a promising therapeutical profile for the treatment of different neuropsychiatric diseases including epilepsy. This review focuses on the effects of neuroactive steroids on neuronal excitability and their putative impact on the physiology of epileptic disorders.

An enzyme-mediated metabolism of androgens and estrogens including 17beta-HSD activity in the brain of vertebrates was discovered approximately 30 years ago. Mainly 5alpha-reductase and aromatase have been studied in detail. Recently we could demonstrate reductive and oxidative 17beta-HSD activity as well as considerable mRNA expression of the 17beta-HSD types 3 and 4 in the human brain. In the present study, we report on 17beta-HSD type 5 mRNA expression in brain tissue of women and men. Data analysis did not reveal sex specific differences, but we determined a significantly higher mRNA concentration in the subcortical white matter (SC) than in the cerebral cortex (CX). Investigation of reductive 17beta-HSD in vitro activity with 2 microM androstenedione as the substrate revealed no sex specific differences. Testosterone formation was significantly higher in SC than in CX. Moreover, enzyme activity was significantly higher in brain tissue of adults compared to that of children.

We present and apply a method for single trial analysis of event related potentials (ERPs) that combines techniques from non-linear time series analysis with the wavelet transform. For this method, convincing results have already been achieved for simulated data as well as for intracranially recorded ERPs (Physica D 140 (2000) 257). However, ERPs are affected by a variety of external and internal experimental parameters, which makes the appropriate configuration of single trial analysis difficult. Thus, several pitfalls may occur in realistic applications. In this paper, we applied the method of non-linear de-noising with wavelets to both intra- and extracranially recorded ERPs, and show examples of how and where this single trial analysis can be used to obtain additional information on dynamic neural processes.

The safety of single and repetitive (paired and quadruple) focal transcranial magnetic stimuli as possible inducers of epileptic discharges or clinically manifest seizures was investigated in 21 patients with intractable epilepsy during invasive presurgical monitoring. Subdural and/or intracerebral depth electrodes had been implanted in close proximity to the suspected epileptogenic zone, and the anticonvulsant medication had been reduced. Focal transcranial magnetic stimuli were applied by a Magstim QuadroPulse magnetic stimulator over the hand area of the motor cortex ipsilateral to the epileptogenic focus at intensities of 120% and 150% of motor threshold and additionally as close as possible to the suspected epileptogenic zone at 40-100% of maximal stimulator output. Stimulation did not induce any complex partial or secondary generalized tonic-clonic seizures. One patient with hippocampal sclerosis experienced an aura associated with rhythmic electroencephalographic discharges restricted to the ipsilateral intrahippocampal depth electrode after stimulation over his left temporal lobe. This patient, however, also had frequent spontaneously occurring auras with focal ictal discharges originating from this hippocampus. Interictal discharges were not influenced significantly by single or repetitive magnetic stimuli. In conclusion, from this study there is no evidence that single or serial focal transcranial magnetic stimuli activate epileptogenic foci. At least four high-frequency repetitive stimuli of high intensity may thus be applied with a low risk of seizure induction even in patients with low seizure threshold.

Purpose: Because a low IQ score indicates global brain damage, several authors consider it a contraindication for resective epilepsy surgery. This study reports the postoperative results of a small group of subaverage-intelligence patients with epilepsy who underwent focal resections., Methods: We report on 16 patients who underwent focal resections (no callosotomy or hemispherectomy). All had IQ's <85 and were >13 years of age at the time of surgery. Low IQ was psychometrically assessed (mean IQ = 70) and confirmed by the patients' educational/occupational status. Clinical characteristics, findings from the preoperative workup, and the surgical treatment are described in detail. Postoperative outcome was evaluated with respect to seizure relief and cognitive/ socioeconomic development., Results: Three months after surgery, 14 (87%) of 16 patients were completely seizure free, and nine (64%) of 14 were seizure free at the 1-year follow-up. Patients' cognitive abilities and socioeconomic status were mostly unchanged and in some cases improved. Seizure outcome was not related to IQ level, and there was no evidence of multiple epileptic foci in the patients with continued seizures., Conclusions: A low IQ level does not entail the presence of extended epileptogenic regions or multiple epileptic foci. Seizure-relief rates in our group concurred with the rates in patients of average intelligence, and the cognitive/socioeconomic outcome was favorable. We conclude that focal surgery in intellectually impaired patients can be recommended if the preoperative diagnostics confirm a circumscribed seizure onset.

Brain electrical activity of 16 patients with temporal lobe epilepsy, recorded intracranially during seizure-free intervals as well as during transitions to the seizure state, was analysed using methods derived from the theory of non-linear dynamics. Long-lasting and marked changes towards low-dimensional system states were found to occur specifically up to 25 min prior to epileptic seizures and allow to predict the occurrence of individual seizures in time. These findings reflect a continuous increase in the degree of synchronicity, and thus open a window for the study of mechanisms generating seizures in humans. This offers new possibilities for therapeutic interventions.

Aim: Today, MRI is an integral part of the presurgical evaluation of patients suffering from partial epilepsy. These patients frequently show focal morphological abnormalities with potential epileptogenic character and surgical resection of these lesions is associated with superior postsurgical outcome as to seizure frequency. Apart from easily detectable defects, such as post-traumatic lesions or cerebral infarction, as wide variety of mainly small abnormalities can be detected using MRI., Methods: In this study, 484 patients suffering from partial epilepsy of temporal or frontal onset were evaluated for the incidence of different lesions in this population., Results: All lesions found were included without evaluating their potential epileptogenicity, which remains to be proven using other procedures (EEG, SPECT, PET, etc.). Involvement of the hippocampal formation was a major finding in temporal lobe epilepsy, which could be detected as sclerosis (T2w-images), atrophy (T2w-TSE or T1w-IR-images) or both (15%). In addition and in declining frequency various tumors (14%), post-traumatic lesion (-5%), and focal cortical dysplasia or other disturbances of cortical integrity (-4%) were found. These lesions are detectable with best contrast on different sequences. As a consequence it is suggested to acquire sequences in 3 dimensions including a T1w-SE, two (coronal and axial) double-echo-SE sequences and similarly two T1w-IR-sequences. The application of contrast media can be restricted to special questions, derived either from the first imaging results or from the patients history., Conclusion: Using qualitative data for interpretation, the sensitivity as to the detection of any focal pathology of a recent-generation MRI in this population was 75%, with 79% for temporal lobe epilepsies and 67% for frontal lobe epilepsies. Quantitative measurements of hippocampal volume or signal seem to be able to increase the sensitivity of the method.

Previous research has suggested that methohexital, a short-term barbiturate, alters activity in the primary epileptogenic area. It can be assumed that drug-induced activation of the epileptogenic focus provides a rapid and safe method to obtain a sufficient amount of information relevant for the lateralization and localisation of the primary epileptogenic area. This study shows that methohexital changes spectral power in the beta band derived from magnetoencephalographic (MEG) signals over the hemisphere ipsilateral to the primary epileptogenic area. This effect was demonstrated for 10/13 of the investigated patients suffering from unilateral temporal lobe epilepsy (TLE). The side and location of the primary epileptogenic area of these patients (5 left TLE, 8 right TEL) was determined invasively during presurgical evaluation. During a 1-2 minute interval after intravenous bolus injection of 100 mg methohexital a clear lateralization effect in the beta band was observed, which differed marginally between fronto-central, fronto-temporal and temporo-parietal brain regions. In addition, bilateral spectral power changes were obtained in the theta, alpha and gamma bands that differed between brain regions. Analyses of simultaneously recorded scalp electroencephalographic (EEG) data revealed effects consistent with those of the MEG analysis. The reduced enhancement of beta band spectral power of MEG recordings provides a potential application for the non-invasive lateralization of the primary epileptogenic area.

Purpose and Methods: The aim of this study was to analyze clinical, radiologic, and histopathologic findings in 60 consecutive patients with medically intractable extratemporal epilepsy who were operated on between November 1987 and May 1993., Results: Histologically, there were distinct structural abnormalities in 50 (83%) of the surgical specimens. Signal abnormalities on magnetic resonance imaging (MRI) were present in all patients with neoplastic lesions (n = 17) and in 94% of patients with nonneoplastic focal lesions (n = 32). Overall, structural abnormalities were detected by MRI in 47 (96%) of 49 patients with focal lesions. During a mean follow-up of 4 years, 30 (54%) patients remained completely seizure free, 11 (20%) had < or = 2 seizures per year, seven (12%) showed a seizure reduction of > or = 75%, and eight (14%) had < 75% reduction in seizure frequency. The fraction of seizure-free patients was 12 (80%) of 15 in patients with neoplastic lesions, 16 (52%) of 31 in patients with nonneoplastic focal lesions, and two (20%) of 10 for those without histopathologic abnormalities. The differences in seizure outcome between patients with and without focal lesions were statistically significant (p < 0.05), if seizure-free outcome was compared with persistent seizures., Conclusions: Focal lesions and particularly neoplasms are associated with improved postoperative seizure control compared with patients without histopathologic abnormalities. We advise caution in considering surgery to treat extratemporal epilepsy in patients who have normal MRI scans, because the outcome with the approach described in this study is poor in such cases.

Unlabelled: In childhood epilepsy, it is difficult, but of critical importance, to determine whether surgical intervention might be beneficial for an individual patient. Because both established procedures-MRI and electroencephalography (EEG)-have limitations, interictal and ictal regional cerebral blood flow (rCBF) SPECT has proven to be a valuable adjunctive method in the presurgical evaluation of children., Methods: We evaluated the usefulness of the new rCBF tracer 99mTc-ECD in 14 children with focal epilepsy (mean age 9.7 yr). Eleven interictal and 8 ictal studies were performed. Results were correlated with ictal and interictal surface EEG, MRI and histological findings and the postsurgical outcome., Results: On the basis of the presurgical evaluation, nine patients underwent surgery. MRI studies demonstrated pathological features with possible relation to epilepsy in 50%. Overall, interictal 99mTc-ECD SPECT showed areas of hypoperfusion in 80% of patients. Ictal rCBF SPECT was informative in all patients, including one who showed bifrontal hyperperfusion in accordance with EEG results., Conclusion: Technetium-99m-ECD has proven to be of value for interictal and ictal rCBF SPECT in childhood epilepsy. No side effects during or after tracer administration were noticed. Ictal and interictal rCBF SPECT showed good correlation with MRI and EEG results in patients in whom correlation with the postoperative situation was possible and presented additional significant information in those patients with normal MRI and uninterpretable EEG results. No false lateralizations occurred. In children with focal epilepsy, interictal rCBF SPECT may accelerate the application of long-term electrocorticography (ECoG) in patients with normal MRI results. Ictal rCBF SPECT may also help to avoid ECoG, if a focal hyperperfusion correlates with a focal MRI abnormality, and the surface EEG gives no contradictory information.

Electrocorticograms of 192 complex partial seizures which were recorded via chronically implanted subdural electrodes during presurgical evaluation of 64 patients with medically intractable epilepsy were visually analysed. The objective was to assess the diagnostic and prognostic relevance of postictal slow foci (PISF) in the electrocorticogram which were defined as focal isoelectric activity or as a focal burst-suppression pattern. The following results were obtained: (1) PISF were seen in a total of 114 of 192 seizures (59.4%), (2) 48 of 64 patients (75%) demonstrated at least 1 PISF in 3 seizures, (3) PISF were more frequent in seizures of temporal lobe origin (66%) than in those of extratemporal origin (33.3%), (4) no PISF developed if the electrographic seizure duration was < 32 sec, (5) PISF were (predominantly) localized in the lobe of seizure origin in 85% of the seizures, (6) there was a strong correlation between frequent occurrence of temporal PISF and favourable seizure outcome following temporal lobe surgery. In conclusion, PISF contribute valuable data as to the localization of the epileptogenic zone during presurgical evaluation of epilepsy and indicate favourable seizure outcome following temporal lobe surgery.

Unlabelled: The aim of this study was to evaluate the use of 99mTc-ethyl cysteinate dimer (ECD), also known as 99mTc-bicisate, in the presurgical evaluation of patients suffering from medically intractable epilepsy., Methods: Twenty-three brain SPECT studies (8 ictally and 15 interictally) were performed on 16 patients with a high-resolution annular SPECT system (CERASPECT). For the ictal studies, the tracer was injected in the very early phase of the seizure. The delay between seizure onset and 99mTc-ECD injection was 2-20 sec., Results: Interictally, all patients showed circumscribed hypoperfusions. In four patients, the SPECT lesion represented only structural defects. Circumscribed increased tracer uptake was observed in all ictal studies. For all patients with temporal lobe epilepsy without significant mass lesion, in whom an interictal and ictal 99mTc-ECD-SPECT study could be obtained, the asymmetry index was 0.88 +/- 0.03 for the interictal and 1.23 +/- 0.08 for the ictal studies., Conclusion: The data suggest that 99mTc-ECD is an effective marker of cerebral perfusion imaging in epilepsy. In comparison to other tracers, it has a high in vitro stability and is therefore particularly useful for ictal studies in the very early phase after seizure onset.

The clinical application of technetium-99m bicisate (ethyl cysteinate dimer, ECD) for ictal and interictal studies of regional cerebral blood flow (rCBF) in a patient suffering from medically intractable simple and complex partial seizures is reported. The interictal study was performed 60 min p.i. and the ictal studies were performed at 60 min p.i. using an annular crystal single photon emission tomography (SPET) system dedicated for high-resolution brain SPET imaging. Visual evaluation of the studies was carried out, as well as semiquantitative measurement of regional tracer uptake. Magnetic resonance imaging (MRI) scans revealed atrophy of almost the complete left frontal lobe and the ventral parts of the left temporal lobe, including in part the temporomesial structures. The left parietal and occipital structures and the right hemisphere were normal. The interictal study showed a large perfusion defect involving the whole left frontal lobe as well as the left temporal lobe with remaining small areas of normal cortical tracer uptake. The ictal studies detected circumscribed hyperperfusion within the left mesial temporal lobe (ventral part of the hippocampus). Additionally an increase in perfusion could be seen within the entire remaining left temporal lobe. Semiquantitative evaluation of tracer uptake comparing both studies detected markedly increased uptake within the focus compared to the remaining left temporal lobe. On this basis the newly available tracer for studies of rCBF, 99mTc-bicisate, seems to be of value for the detection of epileptogenic foci. Additionally, the value of ictal rCBF studies in the presurgical evaluation of those patients presenting severe morphological alterations on MRI is clearly underlined by this case.

Physical aspects favour subdural registrations: as the solid angle under which a source is seen from a nearby electrode, the potential is large; there is no distortion by high impedence between source and electrode, nor by perpendicular short circuits; the frequency response is quasi-linear. Technical aspects and implantation strategy are outlined. Interictal and ictal ECoG patterns of diagnostical relevance and activation procedures are discussed. Advantages of subdural electrodes are: They provide detailed information on the epileptogenic zone, data on prognosis, are free of artefacts, allow electrical stimulation to determine eloquent cortex areas; by mathematical analysis methods the localizing power is increased. Disadvantages are: closed fields can be missed (recordable only by depth electrodes), in comparison to EEG, costs are considerably higher. Risks are practically absent with strip electrodes. In about half of the investigated patients, subdural electrodes were necessary to minimize the area of resection on a rational basis.

As a part of presurgical evaluation, bilateral intracarotid amobarbital procedures (IAPs) were performed in 42 patients (84 tests) with long-standing, medically intractable complex-partial seizures. During the IAPs, electrocorticographic (ECoG) recording was carried out via bilaterally implanted subdural electrodes. Five distinct patterns of suppression of electrical brain activity were observed: (1) an isoelectric line; (2) a burst-suppression pattern; (3) polyphasic waves; (4) high-voltage beta; and (5) low-voltage beta activity. Further, two types of specific reactions of the epileptic focus were detectable: (1) spike-burst-suppression patterns (SBS; 11 left; 7 right; 6 in both IAPs) and amobarbital-induced spikes (7 left; 4 right). ECoG suppression patterns as well as SBS and spike induction showed great variability in duration and overall occurrence. To determine the influence of these amobarbital-induced ECoG changes on results of IAP memory testing, performance in a verbal learning task was analyzed according to the ECoG patterns predominant during encoding. In left IAPs, it was found that SBS at the beginning of or during encoding had a significant negative effect on verbal memory. In right IAPs, verbal memory performance improved significantly with the decline of ECoG suppression. Hence, verbal memory performance in IAPs is significantly affected by specific ECoG suppression patterns and activation of the epileptic focus.

48 patients with medically intractable epilepsy were submitted to a total of 60 series of transcranial magnetic stimulation. Effects of transcranial magnetic stimulation were monitored via subdural electrodes. The aim of the study was to investigate the use and reliability of the method for the localization and delineation of the epileptic focus in the process of presurgical evaluation of epilepsy. The following effects of transcranial magnetic stimulation could be observed: (i) Induction of complex partial seizures or auras during (n = 3) or within 5 min after (n = 3) serial stimulation. (ii) Necessity of the presence of additional provocative circumstances for the induction of seizures. (iii) Induction of short-lived epileptiform afterdischarge potentials selectively in the epileptogenic area (or areas) (n = 22). (iv) Enhancement as well as suppression of epileptiform potentials in patients with continuously spiking epileptic foci (n = 7). (v) Temporary interruption of epileptiform paroxysms for 1-3 sec (n = 9). (vi) Persistent suppression of spontaneous spikes (n = 1). (vii) Induction of focal theta or delta activity (n = 26). (viii) No clear-cut response of the epileptic focus (n = 18). (ix) Action of anticonvulsant medication against epileptiform afterdischarge or seizure induction. In conclusion, transcranial magnetic stimulation provides complementary information about the location of the epileptic focus in the process of presurgical evaluation. However, its practical use is limited mainly by its low capability to induce seizures.

Transient elevation of serum levels of prolactin has been observed following several types of epileptic seizures and after electrical stimulation of limbic temporal lobe structures via implanted electrodes. Transcranial magnetic stimulation has been found to selectively induce epileptiform afterdischarges in the epileptic focus of candidates for epilepsy surgery who suffered from temporal lobe epilepsy. Lateralized serial transcranial magnetic stimulation was therefore used and serum levels of prolactin or luteinizing hormone were measured to find if it could be used as a non-invasive diagnostic tool. The investigation was performed on six patients and five healthy volunteers. In the patients the induction of epileptiform potentials was continuously monitored via subdural electrodes. A transient surge of prolactin and luteinizing hormone was found in only one patient, in whom a complex partial seizure was induced. Thus, transcranial magnetic stimulation appeared not to be helpful for the lateralization of the (primary) epileptic focus during presurgical evaluation.

After non-invasive stimulation of the motor cortex by brief electromagnetic pulses evoked potentials were biolaterally recorded in 29 healthy individuals. Normal values for the following target muscles were calculated: abductor pollicis brevis (APB), biceps brachii (BIC), tibialis anterior (TIB) and extensor digitorum brevis (EDB). In a subgroup (N = 12) results for APB and EDB were compared with those obtained by electrical stimulation techniques.

N-Isopropyl-p-123I-amphetamine (123I-IMP) single photon emission computer tomography studies were performed on 17 patients suffering from amyotrophic lateral sclerosis (ALS). All patients displayed varying degrees of impaired fixation of 123I-IMP in the whole brain. These findings were not related to the clinical variants of ALS and the age of the patients. A correlation between the severity of the disease and the degree of impaired fixation could be observed. In addition, patients suffering from ALS for longer periods showed more pronounced impairment of 123I-IMP fixation.

Whether social comparison affects individual well-being is of central importance for understanding behavior in any social environment. Traditional economic theories focus on the role of absolute rewards, whereas behavioral evidence suggests that social comparisons influence well-being and decisions. We investigated the impact of social comparisons on reward-related brain activity using functional magnetic resonance imaging (fMRI). While being scanned in two adjacent MRI scanners, pairs of subjects had to simultaneously perform a simple estimation task that entailed monetary rewards for correct answers. We show that a variation in the comparison subject's payment affects blood oxygenation level-dependent responses in the ventral striatum. Our results provide neurophysiological evidence for the importance of social comparison on reward processing in the human brain. [ABSTRACT FROM AUTHOR]