Surface EEG Research Articles

Non-restraining EEG Radiotelemetry: Epidural and Deep Intracerebral Stereotaxic EEG Electrode Placement

Implantable EEG radiotelemetry is of central relevance in the neurological characterization of transgenic mouse models of neuropsychiatric and neurodegenerative diseases as well as epilepsies. This powerful technique does not only provide valuable insights into the underlying pathophysiological mechanisms, i.e., the etiopathogenesis of CNS related diseases, it also facilitates the development of new translational, i.e., therapeutic approaches. Whereas competing techniques that make use of recorder systems used in jackets or tethered systems suffer from their unphysiological restraining to semi-restraining character, radiotelemetric EEG recordings overcome these disadvantages. Technically, implantable EEG radiotelemetry allows for precise and highly sensitive measurement of epidural and deep, intracerebral EEGs under various physiological and pathophysiological conditions. First, we present a detailed protocol of a straight forward, successful, quick and efficient technique for epidural (surface) EEG recordings resulting in high-quality electrocorticograms. Second, we demonstrate how to implant deep, intracerebral EEG electrodes, e.g., in the hippocampus (electrohippocampogram). For both approaches, a computerized 3D stereotaxic electrode implantation system is used. The radiofrequency transmitter itself is implanted into a subcutaneous pouch in both mice and rats. Special attention also has to be paid to pre-, peri- and postoperative treatment of the experimental animals. Preoperative preparation of mice and rats, suitable anesthesia as well as postoperative treatment and pain management are described in detail.

Non-restraining EEG Radiotelemetry: Epidural and Deep Intracerebral Stereotaxic EEG Electrode Placement.

Implantable EEG radiotelemetry is of central relevance in the neurological characterization of transgenic mouse models of neuropsychiatric and neurodegenerative diseases as well as epilepsies. This powerful technique does not only provide valuable insights into the underlying pathophysiological mechanisms, i.e., the etiopathogenesis of CNS related diseases, it also facilitates the development of new translational, i.e., therapeutic approaches. Whereas competing techniques that make use of recorder systems used in jackets or tethered systems suffer from their unphysiological restraining to semi-restraining character, radiotelemetric EEG recordings overcome these disadvantages. Technically, implantable EEG radiotelemetry allows for precise and highly sensitive measurement of epidural and deep, intracerebral EEGs under various physiological and pathophysiological conditions. First, we present a detailed protocol of a straight forward, successful, quick and efficient technique for epidural (surface) EEG recordings resulting in high-quality electrocorticograms. Second, we demonstrate how to implant deep, intracerebral EEG electrodes, e.g., in the hippocampus (electrohippocampogram). For both approaches, a computerized 3D stereotaxic electrode implantation system is used. The radiofrequency transmitter itself is implanted into a subcutaneous pouch in both mice and rats. Special attention also has to be paid to pre-, peri- and postoperative treatment of the experimental animals. Preoperative preparation of mice and rats, suitable anesthesia as well as postoperative treatment and pain management are described in detail.

Somatic and movement inductions phantom limb in non-amputees

The illusion of the mirror box is a tool for phantom limb pain treatment; this article proposes the induction of phantom limb syndrome on non-amputees upper limb, with a neurological trick of the mirror box. With two study situations: a) Somatic Induction is a test of the literature reports qualitatively, and novel proposal b) Motor Induction, which is an objective report by recording surface EEG. There are 3 cases proposed for Motor illusion, for which grasped movement is used: 1) Control: movement is made, 2) illusion: the mirror box is used, and 3) Imagination: no movement is executed; the subject only imagines its execution. Three different tasks are registered for each one of them (left hand, right hand, and both of them). In 64% of the subjects for somatic experience, a clear response to the illusion was observed. In the experience of motor illusion, cortical activation is detected in both hemispheres of the primary motor cortex during the illusion, where the hidden hand remains motionless. These preliminary findings in phantom limb on non-amputees can be a tool for neuro-rehabilitation and neuro-prosthesis control training.

Detectability of Fast Ripples (>250Hz) on the Scalp EEG: A Proof-of-Principle Study with Subdermal Electrodes.

To evaluate the possibility of detecting fast ripples (FRs) on the surface EEG of patients with focal pharmacoresistant epilepsy, and to investigate the relationship between scalp FRs and localization of the seizure onset zone (SOZ). We included 10 patients undergoing combined surface-intracranial EEG with ≥10 spikes in the surface EEG during the first 30 consecutive minutes of N3 sleep. FRs (≥4 consecutive oscillations above 250Hz with an amplitude clearly exceeding that of the background) on the surface EEG (F3-C3, C3-P3, Fz-Cz, Cz-Pz, F4-C4, C4-P4) were visually marked, and verified by two EEG experts. FRs were categorized as related to the SOZ, if localized in the brain lobe of the SOZ. Low-amplitude FRs with a rate of 0.09/min were found in 6/10 patients: two exhibited events related to the SOZ, three showed no relationship with the SOZ, and in one patient the SOZ was not identified. It may be possible to detect FRs with surface EEG using subdermal electrodes in patients with focal epilepsy. The relationship between surface FRs and the SOZ remains unclear. Future studies aiming at a higher spatial EEG coverage are needed to elucidate their significance.

ID 405 – Ultra-long term subcutaneous recording system for EEG surveillance

Objective We present a novel subdermal two-channel EEG recording device which promises robust and unobtrusive measurements. Methods Data quality is validated against a state-of-the-art surface EEG electrode technology, as well as a longitudinal comparison of the EEG power in standard frequency band (delta, theta, alpha and beta) over a one month period. Surface electrodes were placed at sites corresponding to the subcutaneous electrodes, and the EEG signals were evaluated quantitatively (power spectral density and coherence analysis) both one week and four weeks after implantation. Results Based on a preliminary trial of two subjects, the quantitative measures were very similar during recordings of resting EEG both at week one and week four. The longitudinal comparison showed no tendency to power change of the different frequency band over time. A full dataset of 10 patients will be shown at the congress. Conclusion and key message The ultra-long term EEG recorder is an unmet clinical need. The subdermal signal recorded by the new convenient and minimally invasive device is comparable to surface EEG in multiple aspects and provides a method of ultra-long term EEG recording in situations where this is required and where a small number of EEG electrodes are sufficient.

Gender-Specific Hippocampal Dysrhythmia and Aberrant Hippocampal and Cortical Excitability in the APPswePS1dE9 Model of Alzheimer's Disease.

Alzheimer's disease (AD) is a multifactorial disorder leading to progressive memory loss and eventually death. In this study an APPswePS1dE9 AD mouse model has been analyzed using implantable video-EEG radiotelemetry to perform long-term EEG recordings from the primary motor cortex M1 and the hippocampal CA1 region in both genders. Besides motor activity, EEG recordings were analyzed for electroencephalographic seizure activity and frequency characteristics using a Fast Fourier Transformation (FFT) based approach. Automatic seizure detection revealed severe electroencephalographic seizure activity in both M1 and CA1 deflection in APPswePS1dE9 mice with gender-specific characteristics. Frequency analysis of both surface and deep EEG recordings elicited complex age, gender, and activity dependent alterations in the theta and gamma range. Females displayed an antithetic decrease in theta (θ) and increase in gamma (γ) power at 18-19 weeks of age whereas related changes in males occurred earlier at 14 weeks of age. In females, theta (θ) and gamma (γ) power alterations predominated in the inactive state suggesting a reduction in atropine-sensitive type II theta in APPswePS1dE9 animals. Gender-specific central dysrhythmia and network alterations in APPswePS1dE9 point to a functional role in behavioral and cognitive deficits and might serve as early biomarkers for AD in the future.

Early auditory processing evoked potentials (N100) show a continuum of blunting from clinical high risk to psychosis in a pediatric sample

BackgroundThe N100 is a negative deflection in the surface EEG approximately 100ms after an auditory signal. It has been shown to be reduced in individuals with schizophrenia and those at clinical high risk (CHR). N100 blunting may index neural network dysfunction underlying psychotic symptoms. This phenomenon has received little attention in pediatric populations. MethodThis cross-sectional study compared the N100 response measured via the average EEG response at the left medial frontal position FC1 to 150 sinusoidal tones in participants ages 5 to 17years with a CHR syndrome (n=29), a psychotic disorder (n=22), or healthy controls (n=17). ResultsLinear regression analyses that considered potential covariates (age, gender, handedness, family mental health history, medication usage) revealed decreasing N100 amplitude with increasing severity of psychotic symptomatology from healthy to CHR to psychotic level. ConclusionsLongitudinal assessment of the N100 in CHR children who do and do not develop psychosis will inform whether it predicts transition to psychosis and if its response to treatment predicts symptom change.

Predictors of surgical outcome in medically-resistant temporal lobe epilepsy with bilateral features on pre-operative evaluation

ObjectiveThis study identifies potential prognostic factors for favorable anterior mesial temporal lobe (AMTL) resection outcomes in patients with medically refractory temporal lobe epilepsy (TLE) with bilateral features on pre-operative examination. MethodsThirty-one patients demonstrated bilateral features defined as: bilateral independent temporal or bitemporal ictal onsets on surface or intracranial EEG, or bitemporal interictal epileptiform abnormalities on surface EEG with bilateral radiographic mesial temporal sclerosis. Surgical outcomes were classified according to reduction in seizure frequency: I (100% reduction), II (≥75% reduction), III (50–74% reduction), IV (<50% reduction). ResultsOf 31 patients, 14 (45%) improved to class I and 9 (29%) had a class II outcome at an average of 4 years after surgery. Eight (26%) patients did not exhibit good surgical outcome (class III, class IV). We found that neuropsychological and Wada memory scores were significantly correlated (p<0.05) with surgical outcome, and logistic regression found neuropsychological evaluation significantly predicted better surgical outcome (p<0.05). ConclusionsWhen bilateral features are present on pre-operative evaluation, neuropsychological and Wada test results can provide unique data to better identify those patients more likely to achieve substantial seizure reduction.

Dynamic causal modelling of EEG and fMRI to characterize network architectures in a simple motor task

Dynamic causal modelling (DCM) has extended the understanding of brain network dynamics in a variety of functional systems. In the motor system, DCM studies based on functional magnetic resonance imaging (fMRI) or on magneto-/electroencephalography (M/EEG) have demonstrated movement-related causal information flow from secondary to primary motor areas and have provided evidence for nonlinear cross-frequency interactions among motor areas. The present study sought to investigate to what extent fMRI- and EEG-based DCM might provide complementary and synergistic insights into neuronal network dynamics. Both modalities share principal similarities in the formulation of the DCM. Thus, we hypothesized that DCM based on induced EEG responses (DCM–IR) and on fMRI would reveal congruent task-dependent network dynamics.Brain electrical (63-channel surface EEG) and Blood Oxygenation Level Dependent (BOLD) signals were recorded in separate sessions from 14 healthy participants performing simple isometric right and left hand grips. DCM–IR and DCM–fMRI were used to estimate coupling parameters modulated by right and left hand grips within a core motor network of six regions comprising bilateral primary motor cortex (M1), ventral premotor cortex (PMv) and supplementary motor area (SMA). We found that DCM–fMRI and DCM–IR similarly revealed significant grip-related increases in facilitatory coupling between SMA and M1 contralateral to the active hand. A grip-dependent interhemispheric reciprocal inhibition between M1 bilaterally was only revealed by DCM–fMRI but not by DCM–IR. Frequency-resolved coupling analysis showed that the information flow from contralateral SMA to M1 was predominantly a linear alpha-to-alpha (9–13Hz) interaction. We also detected some cross-frequency coupling from SMA to contralateral M1, i.e., between lower beta (14–21Hz) at the SMA and higher beta (22–30Hz) at M1 during right hand grip and between alpha (9–13Hz) at SMA and lower beta (14–21Hz) at M1 during left hand grip.In conclusion, the strategy of informing EEG source-space configurations with fMRI-derived coordinates, cross-validating basic connectivity maps and analysing frequency coding allows for deeper insight into the motor network architecture of the human brain. The present results provide evidence for the robustness of non-invasively measured causal information flow from secondary motor areas such as SMA towards M1 and further contribute to the validation of the methodological approach of multimodal DCM to explore human network dynamics.

Signs and symptoms of pediatric brain tumors and diagnostic value of preoperative EEG.

In pediatric patients, brain tumors have been estimated to be the cause for seizures in only 0.2-0.3% of cases, whereas seizures occurred in about 13% of pediatric brain tumor patients at presentation. This survey was conducted to analyze EEG findings in pediatric tumor patients over the past 14 years to evaluate the diagnostic value of preoperative EEG for diagnosis of brain tumors. Surface EEG was obtained in awake patients using the international 10- to 20-electrode placement in all pediatric patients with intracranial neoplasms between 2000 and 2013 at the University Hospital of Leipzig except for those who needed emergency operative treatment. One hundred forty-two pediatric patients with 80 infratentorial and 62 supratentorial tumors (WHO grades I-II: 91 patients; WHO grades III-IV: 46 patients). Symptomatic hydrocephalus was found in 37. Sensitivity and specificity of ophthalmologic examination for predicting hydrocephalus was 0.39 and 0.72. Preoperative EEG has been conducted in 116 patients, showing normal activity in 54 patients (47%). Out of 62 pathologic EEGs, 40 indicated correctly to the site of the lesion, 15 were pathologic despite of infratentorial location of the tumor. Nineteen patients had a history of seizures of which six had normal EEGs. Sensitivity for and specificity of EEG examination for symptomatic epilepsy was 0.68 and 0.7. Conclusion Preoperative routine EEG provides no additional value in the diagnostic algorithm of pediatric train tumors. The low specificity and sensitivity of EEG (even in patients with clinical seizures as primary symptom of a brain tumor) underline that EEG does not contribute to diagnosis and a normal EEG might even delay correct diagnosis.

P142. Pushing the limit of sensitivity for non-invasive high-frequency EEG: Recording human single-trial spike-like SEP in noisy environments

Introduction Human high-frequency EEG responses evoked by median nerve stimulation are non-invasive markers of cortical population spikes. For long, their reliable detection required averaging thousands of trials. Recently, low-noise EEG amplifiers combined with extensive electro-magnetic shielding allowed for a sensitive single-trial non-invasive detection of human high-frequency SEP. Here, using as few as 8 standard surface electrodes we demonstrate how specialized neurotechnology and offline analysis can achieve single-trial hf-SEP recordings without elaborate shielding. Methods In 6 healthy male subjects, 8 sintered Ag/AgCl surface EEG electrodes (reference at nose) were distributed above the left somatosensory cortex with impedances at about 1 kOhm. EEG was recorded upon right median nerve stimulation using a custom-built CE-certified low-noise EEG amplifier, specifically engineered to insulate the EEG from electromagnetic interferences. The signal was filtered spectrally and spatially (canonical correlation analysis variant) and transformed to the time–frequency domain (S transform). Results Bursting activity at about 600 Hz (‘ σ -burst’) in response to median nerve stimulation was detectable in all six subjects, both in the average SEP and in the average time–frequency-transform of single-trial responses. Moreover, this approach allowed to analyze the intrinsic single-trial variability of the hf-SEP. Significance Using tailor-made neurotechnology, evoked human cortical population spikes can be measured non-invasively in single-trial EEG without elaborate shielding and using a small number of standard surface electrodes, thus enabling clinical applicability.

Relationships between interictal epileptic spikes and ripples in surface EEG

ObjectiveRipples (80–250Hz) have been shown to be a more specific biomarker for the epileptogenic zone than epileptic spikes in intracranial EEG and even surface EEG. Ripples often co-occur with spikes. We investigated the spatiotemporal relation between spikes and ripples, and differences between spikes that do and do not co-occur with ripples. MethodsWe marked 50 time points with spikes in bipolar surface EEG during NREM sleep in patients with focal or multifocal epilepsy. We marked ripples that occurred with spikes and calculated parameters relating spikes and ripples: the duration, amplitude and slope of spikes, the timing of the start of ripples and spikes and the proportion of overlap. ResultsIn total 219 ripples and 5995 individual spikes were marked in 31 patients. Spikes with ripples were on average shorter, had higher amplitude and higher slope than spikes without ripples. 64% of ripples started before spikes started. Spikes occurred on 13 (5–26) channels per patient, and ripples on 3 (0–14) channels, which were also spike channels. ConclusionRipples precede rather than follow spikes, so ripples are unlikely to result from spikes. SignificanceRipples and spikes seem not one-on-one coupled, but certain states of the brain can accommodate both.

Detection of epileptiform activity in EEG signals based on time-frequency and non-linear analysis.

We present a new technique for detection of epileptiform activity in EEG signals. After preprocessing of EEG signals we extract representative features in time, frequency and time-frequency domain as well as using non-linear analysis. The features are extracted in a few frequency sub-bands of clinical interest since these sub-bands showed much better discriminatory characteristics compared with the whole frequency band. Then we optimally reduce the dimension of feature space to two using scatter matrices. A decision about the presence of epileptiform activity in EEG signals is made by quadratic classifiers designed in the reduced two-dimensional feature space. The accuracy of the technique was tested on three sets of electroencephalographic (EEG) signals recorded at the University Hospital Bonn: surface EEG signals from healthy volunteers, intracranial EEG signals from the epilepsy patients during the seizure free interval from within the seizure focus and intracranial EEG signals of epileptic seizures also from within the seizure focus. An overall detection accuracy of 98.7% was achieved.

Transition dynamics of EEG-based network microstates during mental arithmetic and resting wakefulness reflects task-related modulations and developmental changes.

We studied how maturation influences the organization of functional brain networks engaged during mental calculations and in resting state. Surface EEG measurements from 20 children (8-12years) and 25 students (21-26years) were analyzed. Interregional synchronization of brain activity was quantified by means of Phase Lag Index and for various frequency bands. Based on these pairwise estimates of functional connectivity, we formed graphs which were then characterized in terms of local structure [local efficiency (LE)] and overall integration (global efficiency). The overall data analytic scheme was applied twice, in a static and time-varying mode. Our results showed a characteristic trend: functional segregation dominates the network organization of younger brains. Moreover, in childhood, the overall functional network possesses more prominent small-world network characteristics than in early acorrect in xmldulthood in accordance with the Neural Efficiency Hypothesis. The above trends were intensified by the time-varying approach and identified for the whole set of tested frequency bands (from δ to low γ). By mapping the time-indexed connectivity patterns to multivariate timeseries of nodal LE measurements, we carried out an elaborate study of the functional segregation dynamics and demonstrated that the underlying network undergoes transitions between a restricted number of stable states, that can be thought of as "network-level microstates". The rate of these transitions provided a robust marker of developmental and task-induced alterations, that was found to be insensitive to reference montage and independent component analysis denoising.

The value of susceptibility-weighted imaging (SWI) in patients with non-neonatal hypoxic-ischemic encephalopathy

ObjectiveIn susceptibility-weighted imaging (SWI) in the normal brain, cortical veins appear hypointense due to paramagnetic properties of deoxy-hemoglobin. Global cerebral anoxia decreases cerebral oxygen metabolism, thereby increasing oxy-hemoglobin levels in cerebral veins. We hypothesized that a lower cerebral oxygen extraction fraction in comatose patients with non-neonatal hypoxic-ischemic encephalopathy (IHE) produces a pattern of global rarefied or pseudo-diminished cortical veins due to higher oxy-hemoglobin. Purpose(1) To investigate the topographic relationship between susceptibility effects in cortical veins and related diffusion restrictions on diffusion-weighted imaging (DWI) in patients with IHE. (2) To relate imaging findings to patterns of altered resting activity on surface EEG. MethodsTwenty-three IHE patients underwent MRI. EEG patterns were used to classify the depth of coma. Regional vs. global susceptibility changes on SWI and patterns of DWI restrictions were compared with the depth of coma. ResultsAll patients exhibited areas of restricted cortical diffusion and SWI abnormalities. The dominant DWI restrictions encompassed widespread areas along the precuneus, frontal and parietal association cortices and basal ganglia. For SWI, nineteen patients had generalized bi-hemispherical patterns, the EEG patterns correlated with coma grades III–V. Four patients had focal decreases of deoxy-hemoglobin following DWI restrictions; associated with normal EEGs. ConclusionFocal patterns of diamagnetic effects on SWI according to relative decreases in deoxy-hemoglobin due to reduced metabolic demand are associated with normal EEG in IHE patients. Global patterns indicated increased depth of coma and widespread cortical damage. Clinical relevanceThe results indicate a potential diagnostic value of SWI in patients with IHE.

Anodal transcranial direct current stimulation (tDCS) increases frontal–midline theta activity in the human EEG: A preliminary investigation of non-invasive stimulation

Rhythmical brain activity in the range between four and eight Hz acquired over frontal–midline EEG recording sites – so called frontal–midline theta activity – is regarded as one of the most prominent neural signatures of sustained attention. It is reported to parametrically increase with cognitive load and is thought to be generated in medial prefrontal cortex. Here we explored the possibility of using anodal transcranial direct current stimulation over frontal sites to enhance frontal–midline theta activity and to increase sustained attention performance. We used a small preliminary sample to test a novel direct current stimulation electrode configuration by which we were able to significantly increase frontal–midline theta amplitude in a resting condition after the end of the stimulation period. Using standardised low resolution electromagnetic tomography analysis the effect in the surface EEG was localised to right prefrontal and left medial prefrontal brain areas. Transcranial direct current stimulation did, however, not have any impact on behavioural performance during a sustained attention task. This most likely was due to a very fast washout of the stimulation’s after effect on theta activity. Although these are only preliminary results from a rather small sample, this study demonstrates that transcranial direct current stimulation can be used to rather selectively enhance frontal–midline theta amplitude.

EEG Signal Quality of a Subcutaneous Recording System Compared to Standard Surface Electrodes

Purpose. We provide a comprehensive verification of a new subcutaneous EEG recording device which promises robust and unobtrusive measurements over ultra-long time periods. The approach is evaluated against a state-of-the-art surface EEG electrode technology.Materials and Methods. An electrode powered by an inductive link was subcutaneously implanted on five subjects. Surface electrodes were placed at sites corresponding to the subcutaneous electrodes, and the EEG signals were evaluated with both quantitative (power spectral density and coherence analysis) and qualitative (blinded subjective scoring by neurophysiologists) analysis.Results. The power spectral density and coherence analysis were very similar during measurements of resting EEG. The scoring by neurophysiologists showed a higher EEG quality for the implanted system for different subject states (eyes open and eyes closed). This was most likely due to higher amplitude of the subcutaneous signals. During periods with artifacts, such as chewing, blinking, and eye movement, the two systems performed equally well.Conclusions. Subcutaneous measurements of EEG with the test device showed high quality as measured by both quantitative and more subjective qualitative methods. The signal might be superior to surface EEG in some aspects and provides a method of ultra-long term EEG recording in situations where this is required and where a small number of EEG electrodes are sufficient.

Correlates of a single cortical action potential in the epidural EEG

To identify the correlates of a single cortical action potential in surface EEG, we recorded simultaneously epidural EEG and single-unit activity in the primary somatosensory cortex of awake macaque monkeys. By averaging over EEG segments coincident with more than hundred thousand single spikes, we found short-lived (≈0.5ms) triphasic EEG deflections dominated by high-frequency components >800Hz. The peak-to-peak amplitude of the grand-averaged spike correlate was 80nV, which matched theoretical predictions, while single-neuron amplitudes ranged from 12 to 966nV. Combining these estimates with post-stimulus-time histograms of single-unit responses to median-nerve stimulation allowed us to predict the shape of the evoked epidural EEG response and to estimate the number of contributing neurons. These findings establish spiking activity of cortical neurons as a primary building block of high-frequency epidural EEG, which thus can serve as a quantitative macroscopic marker of neuronal spikes.

Usability of the FLAIR Image in Temporal Lobe Epilepsy

It is necessary to identify the epileptogenic zone in patients with intractable epilepsy. It is, however, difficult to identify thelesion in conventional MRI including T1WI and T2WI. Another pulse sequence, FLAIR (Fluid-attenuated inversion recovery) image,may give a clue to identify the epileptogenic lesion in MRI. This study included 20 patients, who did not show discrete unilateralhippocampal atrophy or sclerosis, and who showed unilateral hippoccampal atrophy and contralateral sclerosis in T1WI or T2WI.Preoperatively, all patients had chronic video-EEG (Electroencephalography) monitoring with standard surface electrodes anddepth electrodes in bilateral hippocampus. Standard anterior temporal lobectomy was performed in 17 patients, and selectiveamygdalohippocampectomy was done in three. MRI including T1WI and T2WI recognized unilateral hippocampal atrophy andsclerosis in three, unilateral hippocampal atrophy and contralateral hippocampal sclerosis in three. The rest of the patients didnot show any identifiable lesion in MRI. FLAIR image, however, identified high signal intensity of the unilateral hippocampus in12, bilateral hippocampus in three, and showed none of change in five. Anterior temporal lobectomy was performed based onthe data of the MRI with FLAIR image and depth EEGs. Histopathologic findings revealed hippocampal sclerosis in all. 18patients were seizure free at the follow-up period of 16- 28 months. In patients with intractable temporal lobe epilepsy whohad difficulty in lateralizing the epileptogenic temporal lobe in semiology, surface EEG, and the conventional MRI including T1WIand T2WI, FLAIR image is of value in identifying the epileptoge nic hippocampus.

Basal forebrain cholinergic modulation of sleep transitions.

The basal forebrain cholinergic system is involved in cognitive processes that require an attentive state, an increased level of arousal, and/ or cortical activation associated with low amplitude fast EEG activity. The activity of most neurons in the basal forebrain cholinergic space is tightly correlated with the cortical EEG and the activity state. While most cholinergic neurons fire maximally during waking and REM sleep, the activity of other types of basal forebrain neurons vastly differs across different arousal and sleep states. Numerous studies have suggested a role for the basal forebrain cholinergic neurons in eliciting cortical activation and arousal. However, the intricate local connectivity within the region requires the use of cell-specific manipulation methods to demonstrate such a causal relationship. Here we have combined optogenetics with surface EEG recordings in freely moving mice in order to investigate the effects of acute cholinergic activation on the dynamics of sleep-to-wake transitions. We recorded from naturally sleeping animals and analyzed transitions from NREM sleep to REM sleep and/ or wakefulness in response to photo-stimulation of cholinergic neurons in substantia innominata. Our results show that optogenetic activation of BF cholinergic neurons during NREM sleep is sufficient to elicit cortical activation and facilitate state transitions, particularly transitions to wakefulness and arousal, at a time scale similar to the activation induced by other subcortical systems. Our results provide in vivo cell-specific demonstration for the role of basal forebrain cholinergic system in induction of wakefulness and arousal.