ORCID Profile
0000-0002-0838-354X
Current Organisation
University of Sydney
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Publisher: Elsevier BV
Date: 06-2016
DOI: 10.1016/J.BANDC.2016.03.007
Abstract: Increasingly studied, episodic future thought (EFT) impairment negatively affects patients' daily life. Along these lines, working with relapsing-remitting multiple sclerosis (RR-MS) patients, we documented the clinical effectiveness of a mental visual imagery (MVI)-based facilitation programme on EFT impairment related to executive function difficulties. We aimed at improving the characterisation of the cognitive and neural underpinnings of RR-MS patients' EFT amelioration, by exploring the structural and functional brain changes following the MVI programme. Seventeen non-depressed RR-MS patients were recruited and randomly assigned in the (i) experimental group (n=10), who followed the MVI programme or in the control group (n=7), who followed a verbal control programme. Using an adapted version of the Autobiographical Interview to assess EFT, after facilitation, significant improvement was observed in the experimental group only. This was accompanied by increased activation in the prefrontal region during the generation of future events and was positively correlated with grey matter volume increase in this same brain area. Increased activations in the parahippoc al and the middle temporal gyri were also observed in the experimental group in post-facilitation. Likewise, functional connectivity changes were observed in the posterior brain regions after facilitation. Only minor cerebral changes were observed in the control group, likely reflecting practice effects. Our study showed that EFT improvement following the MVI programme led to functional and structural changes in brain regions sustaining contextual processing, visual imagery, the integration and maintenance of multimodal information. Taken together, these findings suggest that a cognitive intervention focusing on scene construction can be efficient to alleviate EFT impairment related to executive dysfunction. As such, this study opens the way to the development of tailor-made rehabilitation programmes using the different cognitive mechanisms involved in EFT.
Publisher: Frontiers Media SA
Date: 23-06-2016
Publisher: Elsevier BV
Date: 10-2017
DOI: 10.1016/J.CORTEX.2017.06.019
Abstract: The Self is a complex construct encompassing distinct components, including episodic and semantic autobiographical memory, the Self-concept, and the subjective sense of Self, which highest level consists of Self-awareness. The neuro-anatomical correlates are complex, and it is debated as to whether a common region could support these different components of the Self, with a particular interest for the cortical midline structures and the medial prefrontal cortex (MPFC). Alzheimer's disease (AD) constitutes an interesting model for the study of Self as autobiographical memory typically deteriorates as the disease progresses. Here, we report the unexpected case of Henry, a patient with MCI due to AD who was unable to produce any personal autobiographical memories, nor describe his Self-concept, had a poor personal semantic memory, and disclosed unusual anosognosia for this stage of the disease. His cognitive performance was compared to a group of matched AD patients and a group of healthy controls confirming that the main components of his Self were degraded. We hypothesized that it was due to a marked atrophy within the cortical midline, as visually assessed on his MRI. We further elucidated these findings through Voxel-based morphometry analysis, which confirmed a significant atrophy of the MPFC that was specific to this patient. Moreover, this revealed significant atrophy within the bilateral insular cortex. Given the stage of the disease, the degradation of the Self is unlikely to be accounted for by deficient mnemonic processes, especially as the presence of discrete temporal atrophy was noted. We suggest that this specific pattern of MPFC and insular atrophy is responsible for the systematic collapse of the patient's Self, through the breakdown of the subjective sense of Self, which is proposed as a prerequisite to all other components, according to the model proposed by Prebble, Addis, and Tippett (2013).
Publisher: Elsevier BV
Date: 10-2020
Publisher: SPIE
Date: 19-03-2015
DOI: 10.1117/12.2075643
Publisher: Elsevier BV
Date: 02-2014
DOI: 10.1016/J.JNEUMETH.2013.11.014
Abstract: During the last years, many investigations focused on spontaneously active cerebral networks such as the default-mode network. A data-driven technique, the independent component analysis, allows segregating such spontaneous (co-)activity maps (SAM) from noise in functional magnetic resonance imaging (fMRI) time series. The inter-rater reliability of manual selection of not only the default-mode network but all SAMs remained to be assessed. The current study was performed on 20 min (400 volumes) fMRI time series of 30 healthy participants. SAMs' selection criteria were first established on past experience and from the literature. The inter-rater reliability of SAMs vs non-SAMs manual selection was then investigated from 250 independent components per participant. Inter-rater Kappa coefficient was of 0.89 ± 0.01 on whole analysis, and 0.88 ± 0.09 on participant per participant analysis. Without focusing on specific and predetermined SAMs only, our criteria allow a reliable selection of all SAMs including the idiosyncratic networks. The proposed SAM's selection criteria are reliable enough to allow scientific exploration of all SAMs at the single subject level.
Publisher: Springer Science and Business Media LLC
Date: 25-08-2017
DOI: 10.1038/S41598-017-08667-7
Abstract: Diffuse atrophy including the insula was previously demonstrated in dementia with Lewy bodies (DLB) patients but little is known about the prodromal stage of DLB (pro-DLB). In this prospective study, we used SPM8-DARTEL to measure gray matter (GM) and white matter (WM) atrophy in pro-DLB patients (n = 54), prodromal Alzheimer’s disease (pro-AD) patients (n = 16), DLB patients at the stage of dementia (mild-DLB) (n = 15), and Alzheimer’s disease patients at the stage of dementia (mild-AD) (n = 28), and compared them with healthy elderly controls (HC, n = 22). Diminished GM volumes were found in bilateral insula in pro-DLB patients, a trend to significance in right hippoc us and parahippoc al gyrus in pro-AD patients, in left insula in mild-DLB patients, and in medial temporal lobes and insula in mild-AD patients. The comparison between prodromal groups did not showed any differences. The comparison between groups with dementia revealed atrophy around the left middle temporal gyrus in mild-AD patients. Reduced WM volume was observed in mild-DLB in the pons. The insula seems to be a key region in DLB as early as the prodromal stage. MRI studies looking at perfusion, and functional and anatomical connectivity are now needed to better understand the role of this region in DLB.
Publisher: Elsevier BV
Date: 02-2016
Publisher: S. Karger AG
Date: 2018
DOI: 10.1159/000486780
Abstract: b i Aims: /i /b Limited research has been done on the functional connectivity in visuoperceptual regions in dementia with Lewy bodies (DLB) patients. This study aimed to investigate the functional connectivity differences between a task condition and an inter-task resting state condition within a visuoperceptual paradigm, in DLB patients compared with Alzheimer disease (AD) patients and healthy elderly control subjects. b i Methods: /i /b Twenty-six DLB, 29 AD, and 22 healthy subjects underwent a detailed clinical and neuropsychological examination along with a functional MRI during the different conditions of a visuoperceptual paradigm. Functional images were analyzed using group-level spatial independent component analysis and seed-based connectivity analyses. b i Results: /i /b While the DLB patients scored well and did not differ from the control and AD groups in terms of functional activity and connectivity during the task conditions, they showed decreased functional connectivity in visuoperceptual regions during the resting state condition, along with a temporal impairment of the default-mode network activity. Functional connectivity disturbances were also found within two attentional-executive networks and between these networks and visuoperceptual regions. b i Conclusion: /i /b We found a specific functional profile in the switching between task and resting state conditions in DLB patients. This result could help better characterize functional impairments in DLB and their contribution to several core symptoms of this pathology such as visual hallucinations and cognitive fluctuations.
Publisher: Mary Ann Liebert Inc
Date: 10-2017
Publisher: Springer Science and Business Media LLC
Date: 12-07-2016
DOI: 10.1186/S13195-016-0196-8
Abstract: We aimed to describe specific changes in brain perfusion in patients with dementia with Lewy bodies (DLB) at both the prodromal (also called mild cognitive impairment) and mild dementia stages, relative to patients with Alzheimer’s disease (AD) and controls. Altogether, 96 participants in five groups (prodromal DLB, prodromal AD, DLB with mild dementia, AD with mild dementia, and healthy elderly controls) took part in an arterial spin labeling MRI study. Three analyses were performed: a global perfusion value comparison, a voxel-wise analysis of both absolute and relative perfusion, and a linear discriminant analysis. These were used to assess the global decrease in perfusion, regional changes, and the sensitivity and specificity of these changes. Patterns of perfusion in DLB differed from AD and controls in both the prodromal stage and dementia, DLB having more deficits in frontal, insular, and temporal cortices whereas AD showed reduced perfusion in parietal and parietotemporal cortices. Decreases but also increases of perfusion in DLB relative to controls were observed in both absolute and relative measurements. All these regional changes of perfusion classified DLB patients with respect to either healthy controls or AD with sensitivity from 87 to 100 % and specificity from 90 to 96 % depending on the stage of the disease. Our results are consistent with previous studies. We extend the scope of those studies by integrating prodromal DLB patients and by describing both hypo- and hyperperfusion in DLB. While decreases in perfusion may relate to functional impairments, increases might suggest a functional compensation of some brain areas.
Publisher: Informa UK Limited
Date: 09-10-2016
DOI: 10.1080/09602011.2016.1240697
Abstract: While the efficacy of mental visual imagery (MVI) to alleviate autobiographical memory (AM) impairment in multiple sclerosis (MS) patients has been documented, nothing is known about the brain changes sustaining that improvement. To explore this issue, 20 relapsing-remitting MS patients showing AM impairment were randomly assigned to two groups, experimental (n = 10), who underwent the MVI programme, and control (n = 10), who followed a sham verbal programme. Besides the stringent AM assessment, the patients underwent structural and functional MRI sessions, consisting in retrieving personal memories, within a pre- ost-facilitation study design. Only the experimental group showed a significant AM improvement in post-facilitation, accompanied by changes in brain activation (medial and lateral frontal regions), functional connectivity (posterior brain regions), and grey matter volume (parahippoc al gyrus). Minor activations and functional connectivity changes were observed in the control group. The MVI programme improved AM in MS patients leading to functional and structural changes reflecting (1) an increase reliance on brain regions sustaining a self-referential process (2) a decrease of those reflecting an effortful research process and (3) better use of neural resources in brain regions sustaining MVI. Functional changes reported in the control group likely reflected ineffective attempts to use the sham strategy in AM.
Publisher: Wiley
Date: 18-07-2011
DOI: 10.1002/JMRI.22678
Abstract: To take into account the echo time (TE) influence on arterial spin labeling (ASL) signal when converting it in regional cerebral blood flow (rCBF). Gray matter ASL signal decrease with increasing TE as a consequence of the difference in the apparent transverse relaxation rates between labeled water in capillaries and nonlabeled water in the tissue (δR 2*). We aimed to measure ASL/rCBF changes in different parts of the brain and correct them. Fifteen participants underwent ASL measurements at TEs of 9.7-30 ms. Decreases in ASL values were localized by statistical parametric mapping. The corrections assessed were a subject-per-subject adjustment, an average δR 2* value adjustment, and a two-compartment model adjustment. rCBF decreases associated with increasing TEs were found for gray matter and were corrected using an average δR 2* value of 20 s(-1) . Conversely, for white matter, rCBF values increased with increasing TEs (δR 2* = -23 s(-1)). Our correction was as good as using a two-compartment model. However, it must be done separately for the gray and white matter rCBF values because the capillary R 2* values are, respectively, larger and smaller than those of surrounding tissues.
No related grants have been discovered for Daniel Roquet.