Neuromodulation influences synchronization and intrinsic read-out.

: The roles of neuromodulation in a neural network, such as in a cortical microcolumn, are still incompletely understood. Neuromodulation influences neural processing by presynaptic and postsynaptic regulation of synaptic efficacy. Neuromodulation also affects ion channels and intrinsic excitability.

Logarithmic distributions prove that intrinsic learning is Hebbian.

In this paper, we present data for the lognormal distributions of spike rates, synaptic weights and intrinsic excitability (gain) for neurons in various brain areas, such as auditory or visual cortex, hippocampus, cerebellum, striatum, midbrain nuclei. We find a remarkable consistency of heavy-tailed, specifically lognormal, distributions for rates, weights and gains in all brain areas examined. The difference between strongly recurrent and feed-forward connectivity (cortex vs.

Transfer functions for protein signal transduction: application to a model of striatal neural plasticity.

We present a novel formulation for biochemical reaction networks in the context of protein signal transduction. The model consists of input-output transfer functions, which are derived from differential equations, using stable equilibria. We select a set of "source" species, which are interpreted as input signals.

Learning intrinsic excitability in medium spiny neurons.

We present an unsupervised, local activation-dependent learning rule for intrinsic plasticity (IP) which affects the composition of ion channel conductances for single neurons in a use-dependent way. We use a single-compartment conductance-based model for medium spiny striatal neurons in order to show the effects of parameterization of individual ion channels on the neuronal membrane potential-curent relationship (activation function). We show that parameter changes within the physiological ranges are sufficient to create an ensemble of neurons with significantly different activation functions.

Self-organization of signal transduction.

We propose a model of parameter learning for signal transduction, where the objective function is defined by signal transmission efficiency. We apply this to learn kinetic rates as a form of evolutionary learning, and look for parameters which satisfy the objective. This is a novel approach compared to the usual technique of adjusting parameters only on the basis of experimental data.

Simultaneous magnetoencephalography and intracranial EEG registration: technical and clinical aspects.

The purpose of this study was to describe the methodology necessary for simultaneous recording of intracranial EEG (ICEEG) and magnetoencephalography (MEG) and to assess the sensitivity of whole-head MEG versus depth electrode EEG in the detection and localization of epileptic spikes. Interictal MEG and depth electrode activities from the temporal mesial and occipital lobes were simultaneously recorded from four candidates for epilepsy surgery. Implanted depth electrodes identified neocortical and mesial structures of ictal onset.

Lobar localization information in epilepsy patients: MEG--a useful tool in routine presurgical diagnosis.

Epilepsy surgery is an established therapy for pharmacoresistant focal epilepsy. This study investigated the contribution of routinely used magnetoencepahlography (MEG) in addition to long term video-EEG-monitoring in presurgical evaluation. The distribution of localization results to anatomical lobes was compared with special focus to MEG spike localization results in cases without or with ambiguous EEG findings.

Spatial intralobar correlation of spike and slow wave activity localisations in focal epilepsies: a MEG analysis.

12 patients with focal epilepsy were examined by magnetoencephalography (MEG). Source localisations of interictal epileptiform activity (spikes) yielded clear results. Slow wave dipole density in the frequency range from 2 to 6 Hz, using time selections from an automatic principal component analysis (PCA), was calculated.

Periventricular nodular heterotopia: A challenge for epilepsy surgery.

Pharmacoresistant focal epilepsies due to periventricular nodular heterotopia are a diagnostic and therapeutic challenge because of the need of invasive presurgical diagnostics and the selection of an optimal surgical approach. Invasive investigations in previous studies showed that focal epileptic activity can be correlated predominantly either with one of the nodular heterotopia or with neocortical epileptogenic zones distant to the periventricular nodules. Up to now, invasive recordings were required for localization of epileptic activity and its correlation to heterotopia.

Spatial relationship of source localizations in patients with focal epilepsy: Comparison of MEG and EEG with a three spherical shells and a boundary element volume conductor model.

Epilepsy surgery is an option for patients with pharmacoresistant focal epilepsies, but it requires a precise focus localization procedure. Magnetoencephalography (MEG) and electroencephalography (EEG) can be used for analysis of interictal activity. The aim of this prospective study was to compare clusters of source localization results with MEG and EEG using a three spherical shells (3SS) and a boundary element method (BEM) volume conductor model.

Utilization of magnetoencephalography results to obtain favourable outcomes in epilepsy surgery.

Magnetoencephalography (MEG) is a well-known technique in the presurgical evaluation of epilepsy patients. Like EEG, it can detect and localize epileptic activity. Epilepsy surgery can be used to evaluate MEG source localizations.

Magnetoencephalography (MEG) predicts focal epileptogenicity in cavernomas.

Objective: The aim of this study was to identify the irritative epileptic zone in patients with cavernomas by means of magnetoencephalography (MEG).

Method: Among 82 patients operated for epilepsy, whose presurgical evaluation had included MEG, histological assessment of the tissue removed had confirmed cavernomas in eight. These eight patients had epilepsy since 18.

Regulation of neuromodulator receptor efficacy--implications for whole-neuron and synaptic plasticity.

Membrane receptors for neuromodulators (NM) are highly regulated in their distribution and efficacy-a phenomenon which influences the individual cell's response to central signals of NM release. Even though NM receptor regulation is implicated in the pharmacological action of many drugs, and is also known to be influenced by various environmental factors, its functional consequences and modes of action are not well understood. In this paper we summarize relevant experimental evidence on NM receptor regulation (specifically dopamine D1 and D2 receptors) in order to explore its significance for neural and synaptic plasticity.

Epilepsy surgery, resection volume and MSI localization in lesional frontal lobe epilepsy.

To verify whether interictal noninvasive information detected by magnetoencephalography (MEG) recordings can contribute to localize focal epileptic activity relevant for seizure generation in lesional frontal lobe epilepsy, magnetic source imaging (MSI) localizations of epileptic discharges were compared to the extent of neurosurgical resection and postoperative outcome. Preoperative MEG spike localizations were displayed in postoperative magnetic resonance imaging (MRI) scans to check whether dipole sites were located within the resection cavity. Moreover, MEG localizations were compared with results of prolonged video-EEG monitoring and, in three cases, with invasive EEG recordings.

The musician's brain: functional imaging of amateurs and professionals during performance and imagery.

We compared activation maps of professional and amateur violinists during actual and imagined performance of Mozart's violin concerto in G major (KV216). Execution and imagination of (left hand) fingering movements of the first 16 bars of the concerto were performed. Electromyography (EMG) feedback was used during imagery training to avoid actual movement execution and EMG recording was employed during the scanning of both executed and imagined musical performances.

Magnetic brain source imaging of focal epileptic activity: a synopsis of 455 cases.

Epilepsy surgery is based upon the minute assessment of brain tissue generating epileptic activity. A number of diagnostic methods are employed in the process of presurgical evaluation, supplying information on various morphological and functional aspects, ultimately integrated into the general result fundamental to the final treatment decision. Magnetic source imaging (MSI), combining structural (MRI) and functional (MEG) data, has been playing an increasingly important role among the tools of presurgical epilepsy evaluation.

Determination of distributions of the quadrupole interaction in amorphous solids by 27Al satellite transition spectroscopy.

27Al Satellite transition spectroscopy (SATRAS) has been used to extract both the quadrupole interaction and its distribution width from MAS spectra of glasses. Using this method a measurement at a single magnetic field strength allows one to obtain the true chemical shifts and the quadrupole interaction (and its distributions) with high accuracy, including quantification of the results. In contrast to earlier investigations the central transition MAS lineshapes can be described without assumptions and give correct relative proportions of differently coordinated Al species in glasses.