Delta Components Research Articles

F-VEPs IN ZEN MEDITATION

The observation of the inner-light perception in deep Zen meditation14 has aroused our attention. Based on the recording of F-VEPs (flash visual evoked potentials), this study was thus designed to investigate the characteristics of visual nervous pathway for the Zen-meditation practitioners (experimental group), in comparison with that for the normal, healthy subjects (control group). Flash stimuli were applied before, during and after meditation/relaxation in experimental/control subjects. We focused on the F-VEPs at the occipital site Oz, central site Cz and frontal site Fz. Our results show that amplitudes of late latency components N3-P3 and P3-N4 at Oz decrease for the experimental subjects during meditation, whereas they increase in the control group. Both Cz and Fz amplitudes increase during meditation, yet decrease during relaxation for the control group. The latencies of some components were increased under relaxation in control group, yet little variation (except P2) is observed in the meditators. We also applied discrete wavelet transform to F-VEPs to analyze the frequency components. Our results showed that delta, theta and alpha components increased during meditation at some specific time periods. According to our findings, Zen meditation induces particular effects on the visual nervous system and cortex that are distinct from the normal relaxation.

Theta responses during passive listening depend on cognitive abilities in children

Event Abstract Back to Event Theta responses during passive listening depend on cognitive abilities in children Vasil Kolev1*, P. Nanova1 and Juliana Yordanova1 1 Bulgarian Academy of Sciences, Bulgaria Cognitive development in children is accompanied by changes in frequency content of the spontaneous and event-related EEG activity. Event-related theta (4-7 Hz) and alpha (8-13 Hz) oscillations have been implicated with cognitive information processing in both children and adults. Typically, the functional relevance of EEG frequency responses is evaluated in task processing conditions. This type of assessment does not permit to reliably distinguish between task-related functional involvement and neurophysiological maturity of different EEG rhythms. The present study addressed this issue by comparing event-related oscillatory responses to passive (no task) stimuli of children at 6-8 years of age, who varied with respect to their cognitive performance in a working memory task (see accompanying abstract). According to verbal and reaction time criteria, twenty six normal healthy children were divided into two groups of good and bad performers (each comprising 13 subjects, mean group age 85 months, p>0.8). Auditory event-related potentials (ERPs) in response to 50 identical tones presented in a passive listening condition were recorded. Time-domain ERP analysis demonstrated that the latencies of N1 and P2 components were significantly shorter in good relative to bad performers. Also, in contrast to bad performers, a prominent positive wave P330 characterized in ERPs of good performers. Time-frequency ERP analysis demonstrated that theta but not delta (0.5-4 Hz) and alpha frequency ERP components differentiated passive stimulus processing in the two groups. As shown on the Figure, strongly enhanced theta oscillations within 250-500 ms after stimulus occurred synchronously at the three electrodes only in the group of good performers. Also, corresponding to latency shifts, oscillatory theta responses were phase delayed in bad performers, mostly at the central and parietal sites. These distinct patterns of oscillatory theta responses observed between the two groups during passive processing conditions imply that differences in memory performance are accompanied by specific organization of the underlying neural substrate. * Supported by the National Science Fund at the Ministry of Science and Education, Sofia, Bulgaria (L-1501/2005). pic1 pic tn_pic1 Conference: 10th International Conference on Cognitive Neuroscience, Bodrum, Turkey, 1 Sep - 5 Sep, 2008. Presentation Type: Poster Presentation Topic: Brain Electrical Oscillations in Cognition Citation: Kolev V, Nanova P and Yordanova J (2008). Theta responses during passive listening depend on cognitive abilities in children. Conference Abstract: 10th International Conference on Cognitive Neuroscience. doi: 10.3389/conf.neuro.09.2009.01.129 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 05 Dec 2008; Published Online: 05 Dec 2008. * Correspondence: Vasil Kolev, Bulgarian Academy of Sciences, Sofia, Bulgaria, vasil_kolev@yahoo.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Vasil Kolev P. Nanova Juliana Yordanova Google Vasil Kolev P. Nanova Juliana Yordanova Google Scholar Vasil Kolev P. Nanova Juliana Yordanova PubMed Vasil Kolev P. Nanova Juliana Yordanova Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Effects Of Strength TVaining By Electrostimulation On Skeletal Muscle Oxidative Metabolism

Strength training is frequently associated with endurance exercise during training and rehabilitation. The effects of strength training (particularly when obtained by electrostimulation) per se on skeletal muscle oxidative metabolism are not well known. PURPOSE: To evaluate the effects of strength training by electrostimulation on variables of functional evaluation of oxidative metabolism specifically aimed at skeletal muscle. METHODS: Measurements were conducted on 7 young untrained subjects, during incremental cycloergometric exercises up to voluntary exhaustion and 6-min constant-load exercises below and above the gas exchange threshold (GET). Measurements were carried out before (B) and after (A) a strength training period (25 sessions of neuromuscular electrical stimulation of both quadriceps, over 8 weeks), which determined a 24% increase in force during maximal voluntary contraction. Breath-by-breath pulmonary O2 uptake (VO2) and vastus lateralis oxygenation indices by continuous-wave near-infrared spectroscopy (NIRS) were determined. Skeletal muscle O2 extraction was estimated by NIRS on the basis of changes in concentration of deoxygenated hemoglobin + myoglobin (Delta[deoxy(Hb+Mb)]), expressed as a percentage of values obtained during transient limb ischemia. RESULTS: VO2 peak and Delta[deoxy(Hb+Mb)] peak were, respectively, 44.5 ± 3.1 (x ± SE) ml/kg/min in B vs. 47.8 ± 2.2 in A; and 84.2 ± 6.0 % in B vs. 85.4 ± 6.3 in A. GET occurred at 66.6 ± 2.8 % of VO2 peak in B, vs. 67.6 ± 3.5 in A. The time-constant of VO2 kinetics during the transition to constant-load exercise below GET was 34.7 ±6.8 s in B vs. 32.3 ± 4.3 in A. During constant-load exercise above GET slow components of VO2 and Delta[deoxy(Hb+Mb)] kinetics were observed. For VO2, the slow component amplitude, expressed as a percentage of the total response, was 17.8 ± 3.3 % in B, vs. 11.7 ± 2.5 in A. With exception of force, all differences, in A vs. B, were not statistically significant. CONCLUSIONS: In young subjects a strength training program by electrostimulation of the vastus lateralis, capable of significantly increasing muscle force, did not significantly affect VO2 peak and other variables of functional evaluation specifically aimed at skeletal muscle oxidative metabolism.

ALTERED BRAIN WAVE ACTIVITY IN PERSONS WITH CHRONIC SPINAL CORD INJURY

This study investigated brain wave activity associated with spinal cord injury (SCI). Electroencephalograms (EEG) were compared between 10 individuals with SCI and 10 age and sex matched able-bodied controls using a 64-channel EEG montage. SCI participants had chronic (>12 months) paraplegic clinically complete injuries. The 64 channels of EEG data were spread diffusely over the cortex and were compared for delta (2–4 Hz), theta (4–8 Hz), alpha (8–13 Hz), and beta (13–30 Hz) wave components of the EEG frequency spectra. No significant magnitude or directional changes were found in the delta (2–4 Hz) or theta (4–8 Hz) wave frequency bands between these two groups. However, significant and consistent decreased alpha wave (8–13 Hz) and increased beta wave activity (13–30 Hz) were found in the SCI participants across the cortex compared to the able-bodied control group. These findings suggest that the SCI group have increased neural processing compared to the able-bodied individuals, which may be related to ongoing reorganization of brain structures following SCI.

Structure–Function Analysis of Delta Trafficking, Receptor Binding and Signaling in Drosophila

The transmembrane proteins Delta and Notch act as ligand and receptor in a conserved signaling pathway required for a variety of cell fate specification events in many organisms. Binding of Delta to Notch results in a proteolytic cascade that releases the Notch intracellular domain, allowing it to participate in transcriptional activation in the nucleus. Recent research has implicated the endocytic and ubiquitylation machinery as essential components of Delta-Notch signaling. Our analysis of chimeric and missense Delta variants has delineated a number of structural requirements for Delta trafficking, receptor binding, and signaling. We find that while the Delta N-terminal domain is necessary and sufficient for binding to Notch, the integrity of the epidermal-growth-factor-like repeat (ELR) 2 is also required for Notch binding. Screening of 117 Delta mutant lines for proteins that exhibit aberrant subcellular trafficking has led to the identification of 18 Delta alleles (DlTD alleles) that encode "trafficking-defective" Delta proteins. We find, unexpectedly, that many DlTD alleles contain missense mutations in ELRs within the Delta extracellular domain. Finally, we find that two DlTD alleles contain lysine missense mutations within the Delta intracellular domain (DeltaICD) that may identify residues important for DeltaICD mono-ubiquitylation and subsequent Delta endocytosis and signaling.

Is extinction the hallmark of operant discrimination? Reinforcement and S(Delta) effects.

Using a successive discrimination procedure with rats, three experiments investigated the contribution of reinforcement rate and amount of S(Delta) exposure on the acquisition of an operant discrimination. S(D) components and were always 2 min in length, while S(Delta) (extinction) components were either 1 min or 4 min in length; responses in S(D) were reinforced on one of four schedules. In Experiment 1, each of eight groups were exposed to one possible combination of rate of reinforcement and S(Delta) component length. At every level of reinforcement, the 4 min S(Delta) groups acquired the discrimination more quickly. However, within each level of reinforcement, the proportions of responding in S(D) as a function cumulative S(Delta) exposure were equivalent, regardless of the number of reinforcers earned in S(D), suggesting that extinction is the "hallmark" of discrimination. Experiment 2 sought to replicate these results in a within-subjects design, and although the 4 min S(Delta) conditions always produced superior discriminations, the lack of discriminated responding in some conditions suggested that stimulus disparity was reduced. Experiment 3 clarified those results and extended the finding that the acquisition of operant discrimination closely parallels extinction of responding in S(Delta). In sum, it appears that higher reinforcement rates and longer S(Delta) exposure facilitate the acquisition of discriminated operant responding.

Comparative analysis of event-related potentials during Go/NoGo and CPT: Decomposition of electrophysiological markers of response inhibition and sustained attention

Neuropsychological tests target specific cognitive functions; however, numerous cognitive subcomponents are involved in each test. The aim of this study was to decompose the components of two frontal executive function tests, Go/NoGo (GNG) and cued continuous performance task (CPT), by analyzing event-related potentials (ERPs) of 24 subjects both in time and time-frequency domains. In the time domain, P1, N1, P2, N2 and P3 peak amplitudes and latencies and mean amplitudes of 100 ms time windows of the post-P3 time period were measured. For GNG, the N1 amplitude and for both GNG and CPT N2 amplitudes were significantly higher in the NoGo condition compared with the Go condition. P3 had a central maximum in the NoGo conditions of both paradigms in contrast to a parietal maximum in the Go conditions. All peaks except P1 and mean amplitudes of the post-P3 period were more positive in CPT compared to those of GNG. N1, N2 and P3 latencies were longer for the NoGo condition than the Go condition in the CPT. In time-frequency analyses, the NoGo condition evoked higher theta coefficients than the Go condition, whereas the CPT and GNG paradigms differed mainly in the delta band. These results suggest that theta component reflects response inhibition in both GNG and CPT, whereas delta component reflects the more demanding sustained attention requirement of the CPT. The latency prolongation observed with the NoGo condition of the CPT paradigm was thought to be due to perseverance/inhibition conflict enhanced by the primer stimuli in CPT.

A NEW APPROACH FOR IDENTIFYING SLEEP APNEA SYNDROME USING WAVELET TRANSFORM AND NEURAL NETWORKS

This paper describes a new technique to classify and analyze the electroencephalogram (EEG) signal and recognize the EEG signal characteristics of Sleep Apnea Syndrome (SAS) by using wavelet transforms and an artificial neural network (ANN). The EEG signals are separated into Delta, Theta, Alpha, and Beta spectral components by using multi-resolution wavelet transforms. These spectral components are applied to the inputs of the artificial neural network. We treated the wavelet coefficient as the kind of the training input of artificial neural network, might result in 6 groups of wavelet coefficients per second signal by way of characteristic part processing technique of the artificial neural network designed by our group, we carried out the task of training and recognition of SAS symptoms. Then the neural network was configured to give three outputs to signify the SAS situation of the patient. The recognition threshold for all test signals turned out to have a sensitivity level of approximately 69.64% and a specificity value of approximately 44.44%. In neurology clinics, this study offers a clinical reference value for identifying SAS, and could reduce diagnosis time and improve medical service efficiency.

Genome-wide profiling of PRC1 and PRC2 Polycomb chromatin binding in Drosophila melanogaster

Polycomb group (PcG) proteins maintain transcriptional repression of developmentally important genes and have been implicated in cell proliferation and stem cell self-renewal. We used a genome-wide approach to map binding patterns of PcG proteins (Pc, esc and Sce) in Drosophila melanogaster Kc cells. We found that Pc associates with large genomic regions of up to approximately 150 kb in size, hereafter referred to as 'Pc domains'. Sce and esc accompany Pc in most of these domains. PcG-bound chromatin is trimethylated at histone H3 Lys27 and is generally transcriptionally silent. Furthermore, PcG proteins preferentially bind to developmental genes. Many of these encode transcriptional regulators and key components of signal transduction pathways, including Wingless, Hedgehog, Notch and Delta. We also identify several new putative functions of PcG proteins, such as in steroid hormone biosynthesis. These results highlight the extensive involvement of PcG proteins in the coordination of development through the formation of large repressive chromatin domains.

Phase transition of L‐Ser monohydrate crystal studied by 13C solid‐state NMR

We used gravimetric analysis (GA) and (13)C solid-state nuclear magnetic resonance (NMR) to study solid-phase transition from the transparent single crystal of L-serine (L-Ser) monohydrate to a turbid powder. We found that L-Ser monohydrate loses water molecules and transforms into an anhydrate, thus experimentally demonstrating Frey's assumption. Application of a handmade cross-polarization (CP) NMR probe with a saddle-type coil to the oriented crystal of the L-Ser monohydrate revealed the dehydration mechanism. Furthermore, the chemical shift tensor components of the carboxyl carbon in L-Ser monohydrate were determined. The difference in the tensor component of delta(22) between the monohydrate and anhydrate forms was more than 7 ppm, probably owing to differences in the hydrogen-bonding structure of each form.

Delta and Spindle Components in the Integrated Eeg during Nocturnal Sleep for Infants with Developmental Disabilities

The delta and spindle components in the integrated EEG for 121 infants with developmental disabilities (from 4 mo. to 6 yr. of age: M=1.79, SD=0.14; 57 girls and 64 boys) were studied throughout nocturnal sleep. In 80 (66.1%, Group A) of 121 subjects, periodic changes of delta and spindle rhythm powers were noted in measurements of EEG made during sleep. In 28 (23.1%, Group B), delta but not spindle rhythm powers were found, and in the remaining 13 subjects (10.7%, Group C) neither delta nor spindle rhythm powers were found throughout measurements of EEG made during sleep. The Tsumori-Inage Questionnaire for Infants was administered to the parents to estimate subjects' behavioral developmental level as Developmental Quotients. Significantly lower mean Developmental Quotients were found for Groups B and C than Group A. These findings suggested that the presence or absence of delta and spindle rhythm powers in EEG measurements made during nocturnal sleep could be taken as an index of the severity of developmental disorders in infants with developmental disabilities.

Aging and Error Processing

Abstract: Objectives: To determine age-related changes in the frequency content, temporal dynamics, and functional reactivity of error-related potentials. Methods: Two groups of subjects, young (mean age 22.5 years) and older (mean age 58.3 years) were studied with a four-choice reaction time task. Response-related potentials (RRPs) to correct and error responses were decomposed by means of wavelet transform. Time-frequency (TF) components of correct and error responses were identified. Effects of aging were evaluated for the phase-locked TF power at FCz. Results: (1) Error-related potentials in both groups were characterized by phase-locked activity from the delta (1.5-3.5 Hz) frequency band that was error-specific and was significantly enhanced for errors. (2) In contrast to young adults, no pronounced phase-locked theta (4-7 Hz) RRP components were generated at FCz for either correct or error responses, nor did the theta power manifest any sensitivity to error processing in older subjects. Conclusion: In older subjects, RRPs at FCz do not contain a theta TF component, thus, demonstrating that the frequency content of error-related potentials changes with aging. A common error-specific delta component is present in the two age groups, but its reactivity is significantly reduced and delayed with aging. These qualitative and quantitative differences between young and older subjects may reflect a functional suppression of the underlying frontomedial structures involved in performance and movement monitoring.

13C NMR chemical shifts of the triclinic and monoclinic crystal forms of valinomycin.

Two different crystalline polymorphs of valinomycin, the triclinic and monoclinic forms, have been studied by high resolution, solid state (13)C CP-MAS NMR spectroscopy. Although the two polymorphs of the crystal are remarkably similar, there are distinct differences in the isotropic chemical shifts between the two spectra. For the triclinic form, the carbon chemical shift tensor components for the alpha carbons adjacent to oxygen in the lactic acid and hydroxyisovaleric acid residues and the ester carbonyls of the valine residue were obtained using the FIREMAT experiment. From the measured components, it was found that the behavior of the isotropic chemical shift, delta(iso), for valine residue ester carbonyl carbons is predominately influenced by the intermediate component, delta(22). Additionally it was found that the smallest shift component, delta(33), for the L -lactic acid ( L -Lac) and D -alpha-hydroxyisovaleric acid ( D -Hyi) C(alpha)-O carbon was significantly displaced depending upon the nature of individual amino acid residues, and it is the delta(33) component that governs the behavior of delta(iso) in these alpha carbons.

Changed Energy State and Increased Mitochondrial β-Oxidation Rate in Liver of Rats Associated with Lowered Proton Electrochemical Potential and Stimulated Uncoupling Protein 2 (UCP-2) Expression: EVIDENCE FOR PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR-α INDEPENDENT INDUCTION OF UCP-2 EXPRESSION

Lowering of plasma triglyceride levels by hypolipidemic agents is caused by a shift in the liver cellular metabolism, which become poised toward peroxisome proliferator-activated receptor (PPAR) alpha-regulated fatty acid catabolism in mitochondria. After dietary treatment of rats with the hypolipidemic, modified fatty acid, tetradecylthioacetic acid (TTA), the energy state parameters of the liver were altered at the tissue, cell, and mitochondrial levels. Thus, the hepatic phosphate potential, energy charge, and respiratory control coefficients were lowered, whereas rates of oxygen uptake, oxidation of pyridine nucleotide redox pairs, beta-oxidation, and ketogenesis were elevated. Moderate uncoupling of mitochondria from TTA-treated rats was confirmed, as the proton electrochemical potential (Delta(p)) was 15% lower than controls. The change affected the Delta(Psi) component only, leaving the (Delta)pH component unaltered, suggesting that TTA causes induction of electrogenic ion transport rather than electrophoretic fatty acid activity. TTA treatment induced expression of hepatic uncoupling protein 2 (UCP-2) in rats as well as in wild type and PPARalpha-deficient mice, accompanied by a decreased double bond index of the mitochondrial membrane lipids. However, changes of mitochondrial fatty acid composition did not seem to be related to the effects on mitochondrial energy conductance. As TTA activates PPARdelta, we discuss how this subtype might compensate for deficiency of PPARalpha. The overall changes recorded were moderate, making it likely that liver metabolism can maintain its function within the confines of its physiological regulatory framework where challenged by a hypolipemic agent such as TTA, as well as others.

Additivity theorem for constrained optimum filters in the presence of colored noise

It is well known that the optimum filter in presence of an additive stationary noise of spectral density N( ω) and an input signal composed by a sum of delta-like components is obtained as the sum of the optimum filters for the single delta components, each weighted by the amplitude of the corresponding delta component. This holds if no constraints are enforced in the filter weighting function (WF). However, this no longer holds if constraints are introduced in the filter WF, such as finite duration and area balance. Recently, it has been observed that if such constraints are enforced the optimum filter seems again to be given by a weighted sum of the optimum WFs for the single delta components of the signal. However, each weight is given in this case by the product of the delta-pulse amplitude with the inverse of the variance associated to the corresponding WF. A rigorous proof for this additivity property will be given, while considering the typical white and non-white noises of a spectrometer of ionizing radiations using semiconductor detectors.

Spectral analysis of all-night human sleep EEG in narcoleptic patients and normal subjects.

To investigate the pathophysiology of narcoleptic patients' sleep in detail, we analysed and compared the whole-night polysomnograms of narcoleptic patients and normal human subjects. Eight drug-naive narcoleptic patients and eight age-matched normal volunteers underwent polysomnography (PSG) on two consecutive nights. In addition to conventional visual scoring of the polysomnograms, rapid eye movement (REM)-density and electroencephalograph (EEG) power spectra analyses were also performed. Sleep onset REM periods and fragmented nocturnal sleep were observed as expected in our narcoleptic patients. In the narcoleptic patients, REM period duration across the night did not show the significant increasing trend that is usually observed in normal subjects. In all narcoleptic patient REM periods, eye movement densities were significantly increased. The power spectra of narcoleptic REM sleep significantly increased between 0.3 and 0.9 Hz and decreased between 1.0 and 5.4 Hz. Further analysis revealed that non-rapid eye movement (NREM) period duration and the declining trend of delta power density in the narcoleptic patients were not significantly different from the normal subjects. Compared with normal subjects, the power spectra of narcoleptic NREM sleep increased in the 1.0-1.4 Hz and 11.0-11.9 Hz frequency bands, and decreased in a 24.0-26.9 Hz frequency band. Thus, increased EEG delta and decreased beta power densities were commonly observed in both the NREM and REM sleep of the narcoleptic patients, although the decrease in beta power during REM sleep was not statistically significant. Our visual analysis revealed fragmented nocturnal sleep and increased phasic REM components in the narcoleptic patients, which suggest the disturbance of sleep maintenance mechanism(s) and excessive effects of the mechanism(s) underlying eye movement activities during REM sleep in narcolepsy. Spectral analysis revealed significant increases in delta components and decreases in beta components, which suggest decreased activity in central arousal mechanisms. These characteristics lead us to hypothesize that two countervailing mechanisms underlie narcoleptic sleep pathology.

Quantitative analysis of mannitol polymorphs. X-ray powder diffractometry—exploring preferred orientation effects

Mannitol is a polymorphic pharmaceutical excipient, which commonly exists in three forms: alpha, beta and delta. Each polymorph has a needle-like morphology, which can give preferred orientation effects when analysed by X-ray powder diffractometry (XRPD) thus providing difficulties for quantitative XRPD assessments. The occurrence of preferred orientation may be demonstrated by sample rotation and the consequent effects on X-ray data can be minimised by reducing the particle size. Using two particle size ranges (<125 and 125–500 μm), binary mixtures of beta and delta mannitol were prepared and the delta component was quantified. Samples were assayed in either a static or rotating sampling accessory. Rotation and reducing the particle size range to <125 μm halved the limits of detection and quantitation to 1 and 3.6%, respectively. Numerous potential sources of assay errors were investigated; sample packing and mixing errors contributed the greatest source of variation. However, the rotation of samples for both particle size ranges reduced the majority of assay errors examined. This study shows that coupling sample rotation with a particle size reduction minimises preferred orientation effects on assay accuracy, allowing discrimination of two very similar polymorphs at around the 1% level.

Nonlinear analysis of EEG after repetitive transcranial magnetic stimulation.

The purpose of this study was to investigate whether repetitive transcranial magnetic stimulation (rTMS) can change nonlinear dynamic properties of the cerebral cortex. Two rTMS trains (10 Hz, 3 seconds, 100% of motor threshold) were administered to the left frontal area in healthy subjects. EEG signals were collected at 14 electrode sites before and after stimulation, and were filtered digitally into delta, theta, alpha, beta, and gamma bands. Basing on an improved algorithm introduced in the authors' recent study, dimension estimates were calculated on these signals as well as on the corresponding surrogate data. Sham treatment was designed into this study. The data showed that EEG signals obviously exhibited lower dimension estimates than the surrogate data, whereas the theta and alpha rhythms presented the lowest values among the frequency components. rTMS increased the dimension estimates of EEG signals during the first 2 minutes. Similar findings were also obtained on the delta and beta components. This study revealed that EEG signals in the normal state can be described by a nonlinear dynamic process. This process can be affected temporarily by rTMS. Neuronal networks revealed by EEG signals show more complicated properties after stimulation.

Distinguishing subtypes of temporal lobe epilepsy with background hippocampal activity.

Two subtypes of temporal lobe epilepsy (TLE) can be defined through clinical observations and analysis of hippocampal tissue resected during surgical procedures for intractable TLE: (a) mesial temporal sclerosis (MTS), which is characterized by extensive changes to the hippocampus and good surgical outcome; and (b) paradoxical temporal lobe epilepsy (PTLE), which is characterized by minimal cell loss and comparatively poorer surgical outcome. Patients in both subtypes have seizures that appear to begin in the medial temporal lobe, but documented differences in substrate and outcome between these subtypes has defined a need to distinguish MTS and PTLE patients before surgery. This report describes a retrospective study to investigate the feasibility of doing so during intracranial monitoring. Background EEG epochs, 5 min in duration, were recorded from the anterior hippocampus in 14 (10 MTS and four PTLE) patients with consistent localization of seizure onset to medial temporal structures. The power spectral density (PSD) of the EEG epochs was calculated by a Fourier spectral estimator, and the total signal power and power of the delta, theta, alpha, beta, and gamma frequency bands were submitted to group-to-group comparison. Spectral peaks were observed in the delta band in all PSD estimates and in the theta band in nine of 14 (seven MTS, two PTLE) estimates. The MTS and PTLE subtypes could be distinguished by the total signal power and delta band power. These power measurements were greater in the PTLE subtype. Both delta and theta spectral components are present in hippocampal background EEGs recorded from patients with TLE. The results indicate that group differences exist in spectral measures of background hippocampal signals recorded from MTS and PTLE subtypes. This suggests both that substrate differences in cellular composition and connectivity are reflected in hippocampal background EEGs and that spectral measurements of these signals may hold promise for tests to identify the group membership of individual patients.

The human homologue of fission Yeast cdc27, p66, is a component of active human DNA polymerase delta.

An essential eukaryotic DNA polymerase, DNA polymerase delta (pol delta), synthesizes DNA processively in the presence of proliferating cell nuclear antigen (PCNA). Recently, a 66 kDa polypeptide (p66) that displays significant homology within its PCNA binding domain to that of fission yeast cdc27 was identified as a component of mouse and calf thymus pol delta. Our studies show that p66 interacts tightly with other subunits of pol delta during size fractionation of human cell extracts, and co-immunoprecipitates with these subunits along with PCNA-dependent polymerase activity. Active human pol delta could be reconstituted by co-expressing p125, p50, and p66 recombinant baculoviruses, but not by co-expressing p125 and p50 alone. Interaction studies demonstrated that p66 stabilizes the association between p125 and p50. Pull-down assays with PCNA-linked beads demonstrated that p66 increases the overall affinity of pol delta for PCNA. These results indicate that p66 is a functionally important subunit of human pol delta that stabilizes the pol delta complex and increases the affinity of pol delta for PCNA.