Optical Microscopy Observations and Construction of Dupin Cyclides at the Isotropic/Smectic A Phase Transition.

In this work, we are interested in the nucleation of bâtonnets at the Isotropic/Smectic A phase transition of 10CB liquid crystal. Very often, these bâtonnets are decorated with a large number of focal conics. We present here an example of a bâtonnet obtained by optical crossed polarized microscopy in a frequently observed particular area of the sample. This bâtonnet presents bulges and one of them consists of a tessellation of ellipses. These ellipses are two by two tangent, one to each other, and their confocal hyperbolas merge at the apex of the bâtonnet. We propose a numerical simulation with Python software to reproduce this tiling of ellipses as well as the shape of the smectic layers taking the well-known shape of Dupin cyclides within this particular bâtonnet area.

Retrieval mechanisms for autobiographical memories: insights from the frontal variant of frontotemporal dementia.

Very few studies have investigated autobiographical memory in the frontal variant of frontotemporal dementia (fv-FTD). The aim of this study was therefore to unravel the mechanisms of autobiographical memory disruption in general and in the anterograde and retrograde components of amnesia in particular, in patients suffering from fv-FTD. An autobiographical memory task assessing overall (AM) and strictly episodic memories (EM) from five lifetime periods covering the entire lifespan revealed the absence of a temporal gradient for both scores, suggesting the existence of a retrieval deficit. An analysis of the correlation between these two scores and a general cognitive assessment of executive function, working, episodic (i.e. new learning ability) and semantic memory, and behavioural changes highlighted the considerable involvement of executive function, semantic memory and, to a lesser degree, episodic memory and behavioural changes. Moreover, step-wise regression analyses performed on the EM score revealed that the executive function was a better predictor of the retrograde component than of the anterograde component, which was linked principally to new episodic learning ability. All these results confirm the impact of executive dysfunction on autobiographical deficits in fv-FTD, and suggest that the mechanisms at the root of autobiographical memory disruption may also involve difficulties in new episodic learning and semantic storage, though this may be due to the fact that we studied an advanced form of fv-FTD.

Efficacy and safety profile of memantine in patients with cognitive impairment in multiple sclerosis: A randomized, placebo-controlled study.

UNLABELLED: Memantine, an uncompetitive antagonist of N-methyl-D-aspartate (NMDA)-type glutamate receptors that was approved for the treatment of moderate to severe Alzheimer's disease, has been negatively evaluated for the treatment of cognitive disorders of multiple sclerosis, but these studies were conducted only during short-term administration and on a heterogeneous group of patients with different forms of the disease. In addition, many adverse reactions were observed in these patients. AIMS: The purpose of the "EMERITE" (NCT01074619) study was to examine the efficacy and safety of the long-term administration of memantine as a symptomatic treatment for cognitive disorders in patients with relapsing-remitting multiple sclerosis (RR-MS). METHODS: The study was supported by the French Ministry of Health and received additional support from Lundbeck. In this double-blind, placebo-controlled, parallel group, randomized trial, the participants were assigned to receive memantine (20 mg/day) or a placebo for 52 weeks. The participants included males and females, 18-60 years of age, with a diagnosis of RR-MS and presenting with a cognitive complaint and/or demonstrating moderate cognitive impairment. The data were collected in the Department of Neurology in 19 French centers. The primary outcome was the Paced Auditory Serial Addition Test (PASAT) score at week 52. Secondary measurements included additional neuropsychological tests and the annualized relapse rate. The scores were adjusted according to the baseline scores in the analysis. The safety was assessed by the number of adverse events. The random sequence was generated using the Excel software. At each center, only the pharmacist had access to the allocation sequence and could be asked to unblind the trial. RESULTS: Fifty patients were allocated to the memantine group, and 43 to the placebo group. The intent-to-treat (ITT) population included 31 patients in each group. After adjusting for the PASAT scores at baseline, the PASAT scores at the end point did not differ between the memantine and the placebo groups (p=0.88). Adjusted mean score difference (memantine minus placebo), was -0.40 (95% confidence interval: -5.5; +4.7). No significant differences were observed for the secondary outcomes (short term memory and attention scores, EDSS, and relapse rate). The findings remained unchanged after multiple imputation of the missing values. Neurological and psychiatric adverse events were significantly higher in the memantine group than in the placebo group, and these parameters were higher than those reported in the product literature of memantine. CONCLUSIONS: No differences between the placebo and memantine groups were observed. Nevertheless, the tolerability of memantine was significantly worse than expected.

FDG-PET measurement is more accurate than neuropsychological assessments to predict global cognitive deterioration in patients with mild cognitive impairment.

The accurate prediction, at a pre-dementia stage of Alzheimer's disease (AD), of the subsequent clinical evolution of patients would be a major breakthrough from both therapeutic and research standpoints. Amnestic mild cognitive impairment (MCI) is presently the most common reference to address the pre-dementia stage of AD. However, previous longitudinal studies on patients with MCI assessing neuropsychological and PET markers of future conversion to AD are sparse and yield discrepant findings, while a comprehensive comparison of the relative accuracy of these two categories of measure is still lacking. In the present study, we assessed the global cognitive decline as measured by the Mattis scale in 18 patients with amnestic MCI over an 18-month follow-up period, studying which subtest of this scale showed significant deterioration over time. Using baseline measurements from neuropsychological evaluation of memory and PET, we then assessed significant markers of global cognitive change, that is, percent annual change in the Mattis scale total score, and searched for the best predictor of this global cognitive decline. Altogether, our results revealed significant decline over the 18-month follow-up period in the total score and the verbal initiation and memory-recall subscores of the Mattis scale. The percent annual change in the total Mattis score significantly correlated with age and baseline performances in delayed episodic memory recall as well as semantic autobiographical and category word fluencies. Regarding functional imaging, significant correlations were also found with baseline PET values in the right temporo-parietal and medial frontal areas. Age and right temporo-parietal PET values were the most significant predictors of subsequent global cognitive decline, and the only ones to survive stepwise regression analyses. Our findings are consistent with previous works showing predominant delayed recall and semantic memory impairment at a pre-dementia stage of AD, as well as early metabolic defects in the temporo-parietal associative cortex. However, they suggest that only the latter predictor is specifically and accurately associated with subsequent cognitive decline in patients with MCI within 18 months of first assessment.

Dissociating atrophy and hypometabolism impact on episodic memory in mild cognitive impairment.

The present study aims to unravel, in the same study, both morphological and functional specific substrates of encoding versus retrieval deficits in patients with amnestic mild cognitive impairment (MCI). For this purpose, 21 highly screened MCI patients with isolated memory impairment, who attended a memory clinic and fulfilled operational criteria for MCI, underwent (i) two episodic memory subtests designed to assess preferentially either incidental encoding or retrieval capacity; (ii) a high-resolution T1-weighted volume MRI scan; and (iii) a resting state [18F]fluoro-2-deoxy-D-glucose PET study. Using statistical parametric mapping, positive correlations between memory scores on one hand, and grey matter density and normalized partial volume effect-corrected brain glucose utilization (ncCMRglc) on the other hand, were computed. Deficits in both encoding and retrieval were correlated with declines in hippocampal region grey matter density. The encoding subtest also correlated with hippocampal ncCMRglc, whereas the retrieval subtest correlated with the posterior cingulate area ncCMRglc only. The present findings highlight a distinction in the neural substrates of encoding and retrieval deficits in MCI. Furthermore, they unravel a partial dissociation between metabolic and structural correlates, suggesting distinct interpretations. Hippocampal atrophy was related to both encoding and retrieval deficits, possibly reflecting a direct effect on hippocampal functioning, as well as an indirect effect, through remote functional disruption, on posterior cingulate region synaptic function, respectively.