The pathophysiology of prospective memory failure after diffuse axonal injury - Lesion-symptom analysis using diffusion tensor imaging

<p>Abstract</p> <p>Background</p> <p>Prospective memory (PM) is one of the most important cognitive domains in everyday life. The neuronal basis of PM has been examined by a large number of neuroimaging and neuropsychological studies, and it has been suggested that several cerebral domains contribute to PM. For these activation studies, a constellation of experimental PM trials was developed and adopted to healthy subjects. In the present study, we used a widely used clinical PM assessment battery to determine the lesions attributable to PM failure, with the hypothesis that lesion-symptom analysis using diffusion tensor imaging (DTI) in subjects with diffuse axonal injury (DAI) can reveal the neuronal basis of PM in everyday life.</p> <p>Results</p> <p>Fourteen DAI patients (age: range of 18-36, median 24) participated in this study. PM failure was scored in the range of 0-6 using three sub-tests of the Rivermead Behavioural Memory Test. The PM scores of DAI patients were in the range of 2-6 (median 4.5, inter-quartile range 2.25). The severity of axonal injury following DAI was examined using fractional anisotropy (FA), one of the DTI parameters, at voxel level in each subject. We then obtained clusters correlated with PM failure by conducting voxel-based regression analysis between FA values and PM scores. Three clusters exhibited significant positive correlation with PM score, the left parahippocampal gyrus, left inferior parietal lobe, and left anterior cingulate.</p> <p>Conclusions</p> <p>This is the first lesion-symptom study to reveal the neuronal basis of PM using DTI on subjects with DAI. Our findings suggest that the neuronal basis of PM is in the left parahippocampal gyrus, left inferior parietal lobe, and/or left anterior cingulate. These findings are similar to those of previous activation studies with loading experimental PM tasks.</p

DLTS analysis of interface and near-interface bulk defects induced by TCO-plasma deposition in carrier-selective contact solar cells

We investigate the electrical characteristics of defects at the SiO2/Si interface, within the adjacent Si crystal, and through the depth profile of the bulk defect using three-dimensional deep-level transient spectroscopy (3D-DLTS). These defects are introduced by the reactive plasma deposition technique employed for depositing transparent conductive oxides in the fabrication of carrier-selective contact-type solar cells. To control the surface potential near the Si surface, we apply a varying voltage to obtain DLTS signals as functions of both temperature and Fermi level at the SiO2/Si interface. Using machine learning for 3D-DLTS spectral analysis, we estimate the capture cross sections, energy levels, densities, and depth profiles of these process-induced defects. The experimental results indicate the existence of three types of electron traps within the bulk defects, ranging from the interface to a depth of ∼70 nm. The electrical properties of these bulk defects suggest the presence of oxygen-related defects within Si. On the other hand, regarding the properties of interface defects, the capture cross sections and the defect densities are estimated as a function of their energy levels. They suggest that the defects at the SiO2/Si interface are likely oxygen-related PL centers

Generation of Oxygen-Related Defects in Crystal Silicon Processed by the RPD

Suppression of the formation of crystal defects is essential for the realization of high-efficiency solar cells. The reactive plasma deposition (RPD) process introduces defects in the silicon crystal bulk and at the passivation layer/silicon crystal interface. This study suggests that oxygen impurities can affect the generation of RPD-induced defects. Although the RPD deposition conditions were the same, the number of RPD-induced recombination centers in Cz-Si was larger than that in the Fz wafer. The increase in 950 °C pre-annealing resulted in increased peak intensity corresponding to defect level E1 in the Cz-Si MOS sample. In the case of Fz-Si, the increase in intensity with increasing pre-annealing time was slight. This indicates that oxygen precipitation might be related to the structure of RPD-induced defects

Serial Changes in Delayed Focal Hippocampal Lesions in Patients with Transient Global Amnesia

The etiology of transient global amnesia (TGA) is not well understood. MR studies, including studies using diffusion-weighted imaging (DWI), have been used to investigate the pathophysiology of TGA, and focal hippocampal lesions have been detected in some studies. The aim of this study was to investigate serial changes in MR images from the patients with TGA. In seven TGA patients, serial MRI scans (from the same day of the・ onset to several days after the, onset of symptoms) using a 1.5-T MR unit were prospectively evaluated. Iri four patients, the duration of TGA was over 12 hr. Three of those patients showed small punctate hippocampal hypersensitivity with decreased ADC values on DW images. These lesions were detected in the postacute phase (a time window of 24 - 48 hr after the onset of symptoms). In follow-up studies performed several days after the onset of symptoms, DWI lesions had disappeared in the subacute phase (7-10 days after the TGA episode). The delayed hippocampal lesion on DW images with 1.5-T MRI in patients with TGA appears to be associated with longer duration of symptoms, to persist for several days and to disappear in the chronic phase

Voltage-gated potassium channel antibodies associated limbic encephalitis in a patient with invasive thymoma

Recently, limbic encephalitis (LE) associated with Voltage-gated potassium channel antibody (VGKC-Ab) has been postulated as a new autoimmune disorder. Most previously reported cases of VGKC-Ab-associated LE were non-paraneoplastic, and reports of a paraneoplastic type are rare. Here we describe a 59-year-old woman with paraneoplastic VGKC-Ab-associated LE preceding the recurrence of invasive thymoma. There was a close temporal relationship between the clinical course and the changes of the VGKC-Ab titer. Unlike many of the non-paraneoplastic VGKC-Ab-associated LE cases, our cases showed the more extensive high intensity lesions on MRI and the absence of seizure and hyponatremia

Brain activations in errorless and errorful learning in patients with diffuse axonal injury: A functional MRI study

Primary objective: Errorless learning has been reported to be effective in the rehabilitation of patients with impaired cognitive functions following brain injury. This study compared brain activations in errorless learning (EL) and errorful learning (EF) in patients with diffuse axonal injury (DAI) using a functional magnetic resonance imaging (fMRI). Methods and procedures: The participants were 13 patients with DAI. Thirteen healthy individuals were evaluated as a control group. The participants learned words under the EL and EF conditions in advance and performed the recognition task during fMRI scanning. Main outcomes and results: EL in the control group was significantly faster than EF (p = 0.005), but not in the DAI group. EL in the DAI group scored significantly higher than EF (p = 0.026). An fMRI showed significant activations in the posterior cingulate gyrus (BA 31) and precuneus (BA 7) in the control group when EF EL, but in the precuneus (BA 7, 31) and bilateral inferior parietal lobules (BA 39, 40) in the DAI group. Conclusions: These results indicate the disadvantage of EF and advantage of EL to DAI patients. The findings also reflect brain plasticity in patients with DAI in the chronic phase