References of "Bahri, Mohamed Ali"
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See detailDorsomedial prefrontal metabolism and unawareness of current characteristics of personality traits in Alzheimer’s disease
Jedidi, Haroun ULg; Feyers, Dorothée ULg; Collette, Fabienne ULg et al

in Social Cognitive and Affective Neuroscience (2014), 9(10), 1458-1463

Anosognosia is a complex symptom corresponding to a lack of awareness of one’s current clinical status. Anosognosia for cognitive deficits has frequently been described in Alzheimer’s disease (AD), while ... [more ▼]

Anosognosia is a complex symptom corresponding to a lack of awareness of one’s current clinical status. Anosognosia for cognitive deficits has frequently been described in Alzheimer’s disease (AD), while unawareness of current characteristics of personality traits has rarely been considered. We used a well-established questionnaire-based method in a group of 37 AD patients and in healthy controls to probe self- and hetero-evaluation of patients’ personality and we calculated differential scores between each participant’s and his/her relative’s judgments. A brain-behavior correlation was performed using FDG-PET images. The behavioral data showed that AD patients presented with anosognosia for current characteristics of their personality and their anosognosia was primarily explained by impaired third perspective taking. The brain-behavior correlation analysis revealed a negative relationship between anosognosia for current characteristics of personality and dorsomedial prefrontal cortex (dMPFC) activity. Behavioral and neuroimaging data are consistent with the view that impairment of different functions subserved by the dMPFC (self-evaluation, inferences regarding complex enduring dispositions of self and others, confrontation of perspectives in interpersonal scripts) plays a role in anosognosia for current characteristics of personality in AD patients. [less ▲]

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See detailFunctional connectivity and recognition of familiar faces in Alzheimer’s disease
Kurth, Sophie ULg; Bahri, Mohamed Ali ULg; Moyse, Evelyne ULg et al

in Frontiers in Human Neuroscience (2014)

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See detailCognitive and neuroimaging evidence of impaired interaction between Self and memory in Alzheimer’s disease
Genon, Sarah ULg; Bahri, Mohamed Ali ULg; Collette, Fabienne ULg et al

in Cortex : A Journal Devoted to the Study of the Nervous System & Behavior (2014), 51

In human cognition, self and memory processes strongly interact, as evidenced by the memory advantage for self-referential materials (Self Reference Effect (SRE) and Self Reference Recollection Effect ... [more ▼]

In human cognition, self and memory processes strongly interact, as evidenced by the memory advantage for self-referential materials (Self Reference Effect (SRE) and Self Reference Recollection Effect (SRRE)). The current study examined this interaction at the behavioural level and its neural correlates in patients with Alzheimer’s disease (AD). Healthy older controls (HC) and AD patients performed trait-adjectives judgements either for self-relevance or for other-relevance (encoding phase). In a first experiment, the encoding and subsequent yes-no recognition phases were administrated in an MRI scanner. Brain activation as measured by fMRI was examined during self-relevance judgements and anatomical images were used to search for correlation between the memory advantage for self-related items and grey matter density (GMD). In a second experiment, participants described the retrieval experience that had driven their recognition decisions (familiarity vs. recollective experience). The behavioural results revealed that the SRE and SRRE were impaired in AD patients compared to HC participants. Furthermore, verbal reports revealed that the retrieval of self-related information was preferentially associated with the retrieval of contextual details, such as source memory in the HC participants, but less so in the AD patients. Our imaging findings revealed that both groups activated the medial prefrontal cortex (MPFC) at encoding during self-relevance judgments. However, the variable and limited memory advantage for self-related information was associated with GMD in the lateral prefrontal cortex in the AD patients, a region supporting high-order processes linking self and memory. These findings suggest that even if AD patients engage MPFC during self-referential judgments, the retrieval of self-related memories is qualitatively and quantitatively impaired in relation with altered high-order processes in the lateral PFC. [less ▲]

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See detailMetabolic cerebral correlates of conjunctive and relational memory in Alzheimer's disease
Bastin, Christine ULg; Bahri, Mohamed Ali ULg; Collette, Fabienne ULg et al

Poster (2014)

Introduction. Memory deficits are the clinical hallmark of typical Alzheimer’s disease. The precise nature of these deficits however remains to be fully characterized. In this study, we investigated ... [more ▼]

Introduction. Memory deficits are the clinical hallmark of typical Alzheimer’s disease. The precise nature of these deficits however remains to be fully characterized. In this study, we investigated binding in long-term episodic memory. Relational binding processes in memory create an associative link between independent items or between items and context into episodic memories (Cohen et al., 1999). An alternative process, conjunctive binding, allows associations to be encoded as a united representation of features into a single entity (O'Reilly and Rudy, 2001; Mayes et al., 2007). The current study (1) assessed whether Alzheimer’s disease disrupt both conjunctive and relational memory, and (2) related patients’ memory performance to cerebral metabolism. Methods. Thirty patients with mild Alzheimer’s disease and 24 healthy older adults performed a source memory task where items were associated to a background color (Diana et al., 2008, 2010). In one condition, relational binding was promoted by the instruction to associate the item with another object of the same color as the background. In the other condition, color had to be integrated as an item feature (conjunctive binding). Patients’ brain metabolic activity at rest (FDG-PET) was analysed with spatio-temporal Partial Least Squares (McIntosh et al., 1996) in order to assess the relation of behavioral performance and activity in functional cerebral networks. Results. Alzheimer’s disease patients had an impaired capacity to remember item-color associations, with deficits in both relational and conjunctive memory. However, performance in the two kinds of associative memory varied independently across patients. Partial least square analyses revealed a significant pattern of metabolic activity that correlated specifically with each condition (accounting for 76.48 % of the covariance in the data; p< .05). More specifically, poor conjunctive memory was related to hypometabolism in an anterior temporal-posterior fusiform brain network, whereas relational memory correlated with metabolism in regions of the default mode network. Conclusions. These findings support the hypothesis of distinct neural systems specialized in different types of associative memory and point to heterogeneous profiles of memory alteration in Alzheimer’s disease as a function of damage to the respective neural networks. [less ▲]

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See detailA Partial Least Squares Analysis of the self reference effect in Alzheimer's disease: A reply to Irish
Genon, Sarah ULg; Bastin, Christine ULg; Angel, Lucie et al

in Cortex : A Journal Devoted to the Study of the Nervous System & Behavior (2014), 54

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See detailPLS analysis of fMRI data on cognitive processes
Bahri, Mohamed Ali ULg; Genon, Sarah ULg; Bastin, Christine ULg et al

Conference (2013, December 12)

Cognitive processes like memory and self-referential are known to be underlined by extended neural networks. To study these complex processes, multivariate methods appear as the methods of the first ... [more ▼]

Cognitive processes like memory and self-referential are known to be underlined by extended neural networks. To study these complex processes, multivariate methods appear as the methods of the first choice since they take into account the functional integration. Partial Least Square (PLS) was used to study neural networks related to memory and self-referential processing in Alzheimer’s disease patients (AD) and two examples were presented. In the first one, we investigated the metabolic correlates of two forms of memory (conjunctive and relational memory performances) in AD. PLS identified two different brain networks highlighting correlations of the two types of memory and the glucose metabolism. In the second example, we assessed brain regions engaged during self-referential processing of information in AD patients during a task related fMRI study. PLS identified a wide brain network showing the effect of self- vs. other-referential processing. In contrast to univariate methods, PLS showed to be suitable for the study of cognitive processes. [less ▲]

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See detailPerformance evaluation and X-ray dose quantification for various scanning protocols of the GE eXplore 120 micro-CT
Bretin, Florian ULg; Warnock, Geoffrey; Luxen, André ULg et al

in IEEE Transactions on Nuclear Science (2013), 60(5), 3235-3241

The aim of this study was to evaluate the performance of the General Electric eXplore 120 micro-CT regarding image quality and delivered dose of several protocols. Image quality (resolution, linearity ... [more ▼]

The aim of this study was to evaluate the performance of the General Electric eXplore 120 micro-CT regarding image quality and delivered dose of several protocols. Image quality (resolution, linearity, uniformity and geometric accuracy) was assessed using the vmCT phantom developed for the GE eXplore Ultra, the QRM low contrast and the QRM Bar Pattern Phantom. All dose measurements were performed using a mobileMOSFET dose verification system and the CTDI100 and the MSAD were determined with a custom built PMMA phantom. Additionally, in vivo scans in sacrificed rats with different weights were acquired to assess dose, contrast and resolution variation due to X-ray absorption in surrounding tissue. The spatial resolution was determined as between 95 and 138 μm with a geometric accuracy of 0.1%. The system has a highly linear response to the iodine concentrations (0.937 to 30 mg/ml) for all protocols. The calculated CTDI100 ranged from 20.15 to 56.79 mGy and the MSAD from 27.98 to 77.45 mGy. The results were confirmed by in vivo scans in rats with different weights and no impact of body weight on delivered dose could be observed. However, body weight had a slight impact on image contrast and resolution. [less ▲]

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See detailIn vivo PET/CT in a human glioblastoma chicken chorioallantoic membrane model: A new tool for oncology and radiotracer development.
Warnock, Geoffrey; Turtoi, Andrei ULg; Blomme, Arnaud ULg et al

in Journal of Nuclear Medicine : Official Publication, Society of Nuclear Medicine (2013), 54(10), 1782-1788

For many years the laboratory mouse has been used as the standard model for in vivo oncology research, particularly in the development of novel PET tracers, but the growth of tumors on chicken ... [more ▼]

For many years the laboratory mouse has been used as the standard model for in vivo oncology research, particularly in the development of novel PET tracers, but the growth of tumors on chicken chorioallantoic membrane (CAM) provides a more rapid, low cost and ethically sustainable alternative. For the first time, we demonstrate the feasibility of in vivo PET and CT imaging in a U87 glioblastoma tumor model on chicken chorioallantoic membrane (CAM), with the aim of applying this model for screening of novel PET tracers. Methods: U87 glioblastoma cells were implanted on the CAM at day 11 post-fertilization and imaged at day 18. A small animal imaging cell was used to maintain incubation and allow anesthesia using isoflurane. Radiotracers were injected directly into the exposed CAM vasculature. Sodium [18F]fluoride was used to validate the imaging protocol, demonstrating that image-degrading motion can be removed with anesthesia. Tumor glucose metabolism was imaged using [18F]fluorodeoxyglucose and tumor protein synthesis was imaged using 2-[18F]fluoro-L-tyrosine. Anatomical images were obtained by contrast enhanced CT, facilitating clear delineation of the tumor, delineation of tracer uptake in tumor versus embryo and accurate volume measurements. Results: PET imaging of tumor glucose metabolism and protein synthesis was successfully demonstrated in the CAM U87 glioblastoma model. Catheterization of CAM blood vessels facilitated dynamic imaging of glucose metabolism with [18F]fluorodeoxyglucose and demonstrated the ability to study PET tracer uptake over time in individual tumors, while CT imaging improved the accuracy of tumor volume measurements. Conclusion: In summary, we describe the novel application of PET/CT in the CAM tumor model, with optimization of typical imaging protocols. PET imaging in this valuable tumor model could prove particularly useful for rapid, high-throughput screening of novel radiotracers. [less ▲]

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See detailBrain metabolic dysfunction in Capgras syndrome during Alzheimer’s disease: a positron emission tomography study
Jedidi, Haroun ULg; Daury, Noémy; Cappa, Rémi et al

Poster (2013, June)

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