Combined EEG-fMRI and tractography to visualise propagation of epileptic activity

In a patient with refractory temporal lobe epilepsy, EEG-fMRI showed activation in association with left anterior temporal interictal discharges, in the left temporal, parietal and occipital lobes. Dynamic causal modelling suggested propagation of neural activity from the temporal focus to the area of occipital activation. Tractography showed connections from the site of temporal lobe activation to the site of occipital activation. This demonstrates the principle of combining EEG-fMRI and tractography to delineate the pathways of propagation of epileptic activity

Reduced anisotropy of water diffusion in structural cerebral abnormalities demonstrated with diffusion tensor imaging

We used diffusion tensor imaging (DTI) to investigate the behavior of water diffusion in cerebral structural abnormalities. The fractional anisotropy, a measure of directionality of the molecular motion of water, and the mean diffusivity, a measure of the magnitude of the molecular motion of water, were measured in 18 patients with longstanding partial epilepsy and structural abnormalities on standard magnetic resonance imaging and the results compared with measurements in the white matter of 10 control subjects. Structural abnormalities were brain damage (postsurgical brain damage, nonspecific brain damage, perinatal brain damage, perinatal infarct, ischemic infarct, perinatal hypoxia, traumatic brain damage (n = 3), mitochondrial cytopathy and mesiotemporal sclerosis), dysgenesis (cortical dysplasia (n = 2) and heterotopia) and tumors (meningioma (n = 2), hypothalamic hamartoma and glioma). Anisotropy was reduced in all structural abnormalities. In the majority of abnormalities this was associated with an increased mean diffusivity; however, 30% of all structural abnormalities (some patients with brain damage and dysgenesis) had a normal mean diffusivity in combination with a reduced anisotropy. There was no correlation between fractional anisotropy and mean diffusivity measurements in structural abnormalities (r = -0.1). Our findings suggest that DTI is sensitive for the detection of a variety of structural abnormalities, that a reduced anisotropy is the common denominator in structural cerebral abnormalities of different etiologies and that mean diffusivity and fractional anisotropy may be, in part, independent. Combined measurements of mean diffusivity and fractional anisotropy are likely to increase the specificity of DTI

The impact of automatic exaggeration of the visual articulatory features of a talker on the intelligibility of spectrally distorted speech

Visual speech information plays a key role in supporting speech perception, especially when acoustic features are distorted or inaccessible. Recent research suggests that for spectrally distorted speech, the use of visual speech in auditory training improves not only subjects’ audiovisual speech recognition, but also their subsequent auditory-only speech recognition. Visual speech cues, however, can be affected by a number of facial visual signals that vary across talkers, such as lip emphasis and speaking style. In a previous study, we enhanced the visual speech videos used in perception training by automatically tracking and colouring a talker’s lips. This improved the subjects’ audiovisual and subsequent auditory speech recognition compared with those who were trained via unmodified videos or audio-only methods. In this paper, we report on two issues related to automatic exaggeration of the movement of the lips/ mouth area. First, we investigate subjects’ ability to adapt to the conflict between the articulation energy in the visual signals and the vocal effort in the acoustic signals (since the acoustic signals remained unexaggerated). Second, we have examined whether or not this visual exaggeration can improve the subjects’ performance of auditory and audiovisual speech recognition when used in perception training. To test this concept, we used spectrally distorted speech to train groups of listeners using four different training regimes: (1) audio only, (2) audiovisual, (3) audiovisual visually exaggerated, and (4) audiovisual visually exaggerated and lip-coloured. We used spectrally distorted speech (cochlear-implant-simulated speech) because the longer-term aim of our work is to employ these concepts in a training system for cochlear-implant (CI) users. The results suggest that after exposure to visually exaggerated speech, listeners had the ability to adapt alongside the conflicting audiovisual signals. In addition, subjects trained with enhanced visual cues (regimes 3 and 4) achieved better audiovisual recognition for a number of phoneme classes than those who were trained with unmodified visual speech (regime 2). There was no evidence of an improvement in the subsequent audio-only listening skills, however. The subjects’ adaptation to the conflicting audiovisual signals may have slowed down auditory perceptual learning, and impeded the ability of the visual speech to improve the training gains

Site investigation for the effects of vegetation on ground stability

The procedure for geotechnical site investigation is well established but little attention is currently given to investigating the potential of vegetation to assist with ground stability. This paper describes how routine investigation procedures may be adapted to consider the effects of the vegetation. It is recommended that the major part of the vegetation investigation is carried out, at relatively low cost, during the preliminary (desk) study phase of the investigation when there is maximum flexibility to take account of findings in the proposed design and construction. The techniques available for investigation of the effects of vegetation are reviewed and references provided for further consideration. As for general geotechnical investigation work, it is important that a balance of effort is maintained in the vegetation investigation between (a) site characterisation (defining and identifying the existing and proposed vegetation to suit the site and ground conditions), (b) testing (in-situ and laboratory testing of the vegetation and root systems to provide design parameters) and (c) modelling (to analyse the vegetation effects)

Radiative Corrections to Double Dalitz Decays: Effects on Invariant Mass Distributions and Angular Correlations

We review the theory of meson decays to two lepton pairs, including the cases of identical as well as non-identical leptons, as well as CP-conserving and CP-violating couplings. A complete lowest-order calculation of QED radiative corrections to these decays is discussed, and comparisons of predicted rates and kinematic distributions between tree-level and one-loop-corrected calculations are presented for both pi-zero and K-zero decays.Comment: 25 pages, 18 figures, added figures and commentar

Vector-meson contributions do not explain the rate and spectrum in K_L -> pi0 gamma gamma

We analyze the recent NA48 data for the reaction K_L -> pi0 gamma gamma with and without the assumption of vector meson dominance (VMD). We find that the data is well described by a three-parameter expression inspired by O(p^6) chiral perturbation theory. We also find that it is impossible to fit the shape of the decay distribution and the overall rate simultaneously if one imposes the VMD constraints on the three parameters. We comment on the different fits and their implications for the CP-conserving component of the decay K_L -> pi0 e+ e-.Comment: Version accepted for publication on Phys. Rev. D. 19 pages, LaTeX, 8 figures, uses epsf.st

Search for the Rare Decay KL --> pi0 ee

The KTeV/E799 experiment at Fermilab has searched for the rare kaon decay KL--> pi0ee. This mode is expected to have a significant CP violating component. The measurement of its branching ratio could support the Standard Model or could indicate the existence of new physics. This letter reports new results from the 1999-2000 data set. One event is observed with an expected background at 0.99 +/- 0.35 events. We set a limit on the branching ratio of 3.5 x 10^(-10) at the 90% confidence level. Combining the results with the dataset taken in 1997 yields the final KTeV result: BR(KL --> pi0 ee) < 2.8 x 10^(-10) at 90% CL.Comment: 4 pages, three figure