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Millisecond Range (millisecond + range)
Selected AbstractsTime reproduction in finger tapping tasks by children with attention-deficit hyperactivity disorder and/or dyslexiaDYSLEXIA, Issue 4 2004Margaret C. Tiffin-Richards Abstract Aim: Deficits in timing and sequencing behaviour in children with dyslexia and with attention-deficit hyperactivity disorder have already been identified. However many studies have not controlled for comorbidity between dyslexia and ADHD. This study investigated timing performance of children with either dyslexia or ADHD, or ADHD + dyslexia or unaffected children using a finger-tapping paradigm. Method: Four groups of children (ADHD × Dyslexia) with a total of 68 children were compared using a four factorial design with two between-subject factors (ADHD (yes/no), dyslexia (yes/no)) and two within-subject factors, inter-stimulus interval (263, 500, 625, 750, 875 and 1000 ms) and tapping condition (free tapping, synchronous tapping, and unpaced tapping). In addition the complexity of rhythm reproduction pattern (unpaced tapping) was varied (simple/complex). Results: No significant differences were found either in the ability of the ADHD or the dyslexia groups to sustain a self-chosen free tapping rate or to generate a stable inter-response interval either by synchronising to a signal or in reproducing a given interval without the previous pacing signal. Response averages showed the expected asynchrony and variability. In rhythm pattern reproduction the groups did not differ significantly in their ability to reproduce rhythms. However, a significant two way interaction effect between dyslexia and complexity was apparent indicating that the difference in levels of performance for simple versus complex rhythms was more pronounced for dyslexia than for the two other groups. Conclusion: The results indicate that motor timing ability in the millisecond range below 1000 ms in children with ADHD and/or dyslexia is intact. The performance of the comorbid group was revealed to be similar to the performance of the single disorder groups, but both the dyslexic groups were relatively worse than either the ADHD-only or the unimpaired group at reproducing complex versus simple rhythms. Copyright © 2004 John Wiley & Sons, Ltd. [source] Source connectivity analysis with MEG and EEGHUMAN BRAIN MAPPING, Issue 6 2009Jan-Mathijs Schoffelen Abstract Interactions between functionally specialized brain regions are crucial for normal brain function. Magnetoencephalography (MEG) and electroencephalography (EEG) are techniques suited to capture these interactions, because they provide whole head measurements of brain activity in the millisecond range. More than one sensor picks up the activity of an underlying source. This field spread severely limits the utility of connectivity measures computed directly between sensor recordings. Consequentially, neuronal interactions should be studied on the level of the reconstructed sources. This article reviews several methods that have been applied to investigate interactions between brain regions in source space. We will mainly focus on the different measures used to quantify connectivity, and on the different strategies adopted to identify regions of interest. Despite various successful accounts of MEG and EEG source connectivity, caution with respect to the interpretation of the results is still warranted. This is due to the fact that effects of field spread can never be completely abolished in source space. However, in this very exciting and developing field of research this cautionary note should not discourage researchers from further investigation into the connectivity between neuronal sources. Hum Brain Mapp 2009. © 2009 Wiley-Liss, Inc. [source] Timing of potential and metabolic brain energyJOURNAL OF NEUROCHEMISTRY, Issue 5 2007Jakob Korf Abstract The temporal relationship between cerebral electro-physiological activities, higher brain functions and brain energy metabolism is reviewed. The duration of action potentials and transmission through glutamate and GABA are most often less than 5 ms. Subjects may perform complex psycho-physiological tasks within 50 to 200 ms, and perception of conscious experience requires 0.5 to 2 s. Activation of cerebral oxygen consumption starts after at least 100 ms and increases of local blood flow become maximal after about 1 s. Current imaging technologies are unable to detect rapid physiological brain functions. We introduce the concepts of potential and metabolic brain energy to distinguish trans-membrane gradients of ions or neurotransmitters and the capacity to generate energy from intra- or extra-cerebral substrates, respectively. Higher brain functions, such as memory retrieval, speaking, consciousness and self-consciousness are so fast that their execution depends primarily on fast neurotransmission (in the millisecond range) and action-potentials. In other words: brain functioning requires primarily maximal potential energy. Metabolic brain energy is necessary to restore and maintain the potential energy. [source] Photochromism of dihydroindolizines part VII: multiaddressable photophysical properties of new photochromic dihydroindolizines bearing substituted benzo[i]phenanthridine as a fluorescing moiety,JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 8 2007Saleh Abdel-Mgeed Ahmed Abstract Sixteen benzo[i]phenanthridine derivatives 8a-p were prepared via photocyclization of cis-trans substituted 4-styrylquinolines in low-to-moderate yields. The chemical structure of the photocyclized benzo[i]phenanthridine derivatives was unambiguously elucidated by means of both spectral and analytical tools. The photochromic (PC) dihydroindolizines (DHIs) 8a-p based on benzo[i]phenanthridines were prepared in 19,57% yields via nucleophilic addition of benzo[i]phenanthridines 4a-p to spirocyclopropenes 5. The 1D, 2D, NOESY NMR spectra, mass spectrometry, and elemental analysis were used for characterization of the chemical structures of the newly synthesized DHIs 8a-p. Developing and tuning of the photophysical properties of the synthesized compounds by substituents in the base part have been achieved. The absorption maxima (,max) and the half-lives (t1/2) of the colored zwitterionic forms 7a-p were detected in all cases by flash-photolysis measurements due to the fast 1,5-electrocyclization back to the DHI system. Irradiation of DHI 8a-p in'CH2Cl2 solution with polychromatic light leads to the formation of green to green,blue colored betaines 7a-p after cooling with liquid nitrogen. The kinetics of the fast bleaching process of betaines 7a-p to DHIs 8a-p, studied by flash photolysis as well as low temperature FT-UV/VIS, were found to take place in the millisecond range (432,2675,ms) in dichloromethane solution and fitted well a first-order thermal back reaction. The fluorescence spectra as well as the fluorescence quantum yield were studied. Noticeable bathochromic and hypsochromic shifts in the emission spectra by changing the substituents in the base part were monitored. Interestingly, the photo-fatigue resistance of some studied betaines 7a-p showed a higher t30 -value than the standard one (dicyanopyridazine DHI). Large solvatochromic effects on the absorption maxima (,max) as well as a substantial increase in the half-lives (t1/2) with solvent polarity of betaines 7a-p were also observed. The multiaddressable PC properties of DHIs 8a-p will help these compounds to find applications. Copyright © 2007 John Wiley & Sons, Ltd. [source] Fast two-dimensional detection for X-ray photon correlation spectroscopy using the PILATUS detectorJOURNAL OF SYNCHROTRON RADIATION, Issue 5 2009Fabian Westermeier The first X-ray photon correlation spectroscopy experiments using the fast single-photon-counting detector PILATUS (Paul Scherrer Institut, Switzerland) have been performed. The short readout time of this detector permits access to intensity autocorrelation functions describing dynamics in the millisecond range that are difficult to access with charge-coupled device detectors with typical readout times of several seconds. Showing no readout noise the PILATUS detector enables measurements of samples that either display fast dynamics or possess only low scattering power with an unprecedented signal-to-noise ratio. [source] Defects in Ce3+ doped Y2SiO5PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2005T. Aitasalo Abstract The crystal defects in the Ce3+ doped X2 -type yttrium oxyorthosilicate, X2 -Y2SiO5:Ce3+, were studied by high-resolution time-resolved laser excited photoluminescence (PL), thermoluminescence (TL) and EPR spectroscopy. X2 -Y2SiO5:Ce3+ shows two strong 5d1,4f1 emission bands with maxima at about 395 (25300) and 430 nm (23250 cm,1) with ca. 40 ns decay times. In addition, two very weak emission bands at 484 (20660) and 577 nm (17330 cm,1) under wide band UV excitation (maximum at 360 nm) from a pulsed Xe lamp can be observed with decay times in the millisecond range. Under the third harmonic of a Nd:YAG laser (355 nm) excitation these bands are split into a number of sharper bands. The EPR shows the presence of electrons occupying anion vacancies in Y2SiO5 lattice while thermoluminescence revealed the presence of two different traps which are, however, too deep for efficient persistent luminescence materials. The defects play a crucial role in the creation of the Ce3+,Ce4+ charge transfer luminescence. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||