Maite Garolera

Alterations of the salience network in obesity: A resting‐state fMRI study

Obesity is a major health problem in modern societies. It has been related to abnormal functional organization of brain networks believed to process homeostatic (internal) and/or salience (external) information. This study used resting‐state functional magnetic resonance imaging analysis to delineate possible functional changes in brain networks related to obesity. A group of 18 healthy adult participants with obesity were compared with a group of 16 lean participants while performing a resting‐state task, with the data being evaluated by independent component analysis. Participants also completed a neuropsychological assessment. Results showed that the functional connectivity strength of the putamen nucleus in the salience network was increased in the obese group. We speculate that this abnormal activation may contribute to overeating through an imbalance between autonomic processing and reward processing of food stimuli. A correlation was also observed in obesity between activation of the putamen nucleus in the salience network and mental slowness, which is consistent with the notion that basal ganglia circuits modulate rapid processing of information. Hum Brain Mapp 34:2786–2797, 2013.

Neural Responses to Visual Food Cues: Insights from Functional Magnetic Resonance Imaging

The aim of this paper is to describe the patterns of functional magnetic resonance imaging activation produced by visual food stimuli in healthy participants, as well as in those with anorexia nervosa, bulimia nervosa, binge eating disorder and obesity. We conducted a systematic review of studies published in the last decade on normal and abnormal eating. This review suggested the existence of neural differences in response to the sight of food between healthy individuals, those with an eating disorder and obese subjects. Differences were identified in two brain circuits: (i) limbic and paralimbic areas associated with salience and reward processes and (ii) prefrontal areas supporting cognitive control processes.

Nadir CD4 cell count predicts neurocognitive impairment in HIV-infected patients.

Though antiretroviral therapy attenuates neurocognitive disruption, impairment is still observed. We studied the nadir CD4 cell count as a predictor of neurocognitive changes. This cross-sectional study assessed 64 HIV-infected patients in two groups: G1 (n = 26, nadir CD4 < or =200 cells/ml) and G2 (n = 38, nadir CD4 >200 cells/ml). Percentages of patients showing neurocognitive impairment were compared according to different nadir CD4 cutoffs (200, 250, 300, and 350 cells/ml). From G2, we also took the subgroup of patients receiving treatment (G3) and compared this group with G1, in which all patients were being treated. Demographic and clinical variables were evaluated, as were differences in neurocognitive function. Neurocognitive impairment tended to be more prevalent in G1 [19 patients (73.1%)] than in G2 [20 (52.6%), p = 0.123]. When nadir CD4 cutoffs were compared, there was a trend toward more impaired subjects as the CD4 nadir decreased. Significantly different functioning was found in attention/working memory (digit span backward, p = 0.032) and executive functions (trail making test, part B, p = 0.020), with better performance in G2. Comparison between G1 and G3 confirmed those findings. We found differences in neurocognitive functioning in relation to nadir CD4 count in HIV-infected patients. Attention should be given to this value in the management of neurocognitive protection in HIV infection.

Reward processing in obesity, substance addiction and non-substance addiction

Similarities and differences between obesity and addiction are a prominent topic of ongoing research. We conducted an activation likelihood estimation meta‐analysis on 87 studies in order to map the functional magnetic resonance imaging (fMRI) response to reward in participants with obesity, substance addiction and non‐substance (or behavioural) addiction, and to identify commonalities and differences between them. Our study confirms the existence of alterations during reward processing in obesity, non‐substance addiction and substance addiction. Specifically, participants with obesity or with addictions differed from controls in several brain regions including prefrontal areas, subcortical structures and sensory areas. Additionally, participants with obesity and substance addictions exhibited similar blood‐oxygen‐level‐dependent fMRI hyperactivity in the amygdala and striatum when processing either general rewarding stimuli or the problematic stimuli (food and drug‐related stimuli, respectively). We propose that these similarities may be associated with an enhanced focus on reward – especially with regard to food or drug‐related stimuli – in obesity and substance addiction. Ultimately, this enhancement of reward processes may facilitate the presence of compulsive‐like behaviour in some individuals or under some specific circumstances. We hope that increasing knowledge about the neurobehavioural correlates of obesity and addictions will lead to practical strategies that target the high prevalence of these central public health challenges.

Frontal cortical thinning and subcortical volume reductions in early adulthood obesity

Obesity depends on homeostatic and hedonic food intake behavior, mediated by brain plasticity changes in cortical and subcortical structures. The aim of this study was to investigate cortical thickness and subcortical volumes of regions related to food intake behavior in a healthy young adult sample with obesity. Thirty-seven volunteers, 19 with obesity (age=33.7±5.7 (20-39) years body-mass index (BMI)=36.08±5.92 (30.10-49.69)kg/m(2)) and 18 controls (age=32.3±5.9 (21-40) years; BMI=22.54±1.94 (19.53-24.97)kg/m(2)) participated in the study. Patients with neuropsychiatric or biomedical disorders were excluded. We used FreeSurfer software to analyze structural magnetic resonance images (MRI) and obtain global brain measures, cortical thickness and subcortical volume estimations. Finally, correlation analyses were performed for brain structure data and obesity measures. There were no between-group differences in age, gender, intelligence or education. Results showed cortical thickness reductions in obesity in the left superior frontal and right medial orbitofrontal cortex. In addition, the obesity group had lower ventral diencephalon and brainstem volumes than controls, while there were no differences in any other subcortical structure. There were no statistically significant correlations between brain structure and obesity measures. Overall, our work provides evidence of the structural brain characteristics associated with metabolically normal obesity. We found reductions in cortical thickness, ventral diencephalon and brainstem volumes in areas that have been implicated in food intake behavior.

Dopamine Genes (DRD2/ANKK1-TaqA1 and DRD4-7R) and Executive Function: Their Interaction with Obesity

Obesity is a multifactorial disease caused by the interaction between genotype and environment, and it is considered to be a type of addictive alteration. The A1 allele of the DRD2/ANKK1-TaqIA gene has been associated with addictive disorders, with obesity and with the performance in executive functions. The 7 repeat allele of the DRD4 gene has likewise been associated with the performance in executive functions, as well as with addictive behaviors and impulsivity. Participants were included in the obesity group (N = 42) if their body mass index (BMI) was equal to or above 30, and in the lean group (N = 42) if their BMI was below 25. The DRD2/ANKK1-TaqIA and DRD4 VNTR polymorphisms were obtained. All subjects underwent neuropsychological assessment. Eating behavior traits were evaluated. The ‘DRD2/ANKK1-TaqIA A1-allele status’ had a significant effect on almost all the executive variables, but no significant ‘DRD4 7R-allele status’ effects were observed for any of the executive variables analyzed. There was a significant ‘group’ x ‘DRD2/ANKK1-TaqIA A1-allele status’ interaction effect on LN and ‘group’ x ‘DRD4 7R-allele status’ interaction effect on TMT B-A score. Being obese and a carrier of the A1 allele of DRD2/ANKK1-TaqIA or the 7R allele of DRD4 VNTR polymorphisms could confer a weakness as regards the performance of executive functions.

Functional connectivity in obesity during reward processing

Obesity is a health problem that has become a major focus of attention in recent years. There is growing evidence of an association between obesity and differences in reward processing. However, it is not known at present whether these differences are linked exclusively to food, or whether they can be detected in other rewarding stimuli. We compared responses to food, rewarding non-food and neutral pictures in 18 young adults with obesity and 19 normal-weight subjects using independent component analysis. Both groups modulated task-related activity in a plausible way. However, in response to both food and non-food rewarding stimuli, participants with obesity showed weaker connectivity in a network involving activation of frontal and occipital areas and deactivation of the posterior part of the default mode network. In addition, obesity was related with weaker activation of the default mode network and deactivation of frontal and occipital areas while viewing neutral stimuli. Together, our findings suggest that obesity is related to a different allocation of cognitive resources in a fronto-occipital network and in the default mode network.

Efficacy of an adjunctive computer-based cognitive training program in amnestic mild cognitive impairment and Alzheimer's disease: a single-blind, randomized clinical trial

This study evaluates the efficacy at 12 months of a computer‐based cognitive training (CBCT) program, adjunctive to traditional cognitive training (TCT), on the basis of pen‐and‐paper exercises.

Research with spanish-speaking populations in the United States: lost in the translation. A commentary and a plea.

Verbal material used to assess the cognitive abilities of Spanish-speakers in the the United States is frequently of linguistically unacceptable quality. The use of these materials in research settings is thought to pose a serious threat to test validity and hence to the validity of claimed results or conclusions. The authors explain how and why incorrect language finds its way into cognitive tests used in research and other settings and suggest solutions to this serious problem.

Functional network centrality in obesity: A resting-state and task fMRI study

Obesity is associated with structural and functional alterations in brain areas that are often functionally distinct and anatomically distant. This suggests that obesity is associated with differences in functional connectivity of regions distributed across the brain. However, studies addressing whole brain functional connectivity in obesity remain scarce. Here, we compared voxel-wise degree centrality and eigenvector centrality between participants with obesity (n=20) and normal-weight controls (n=21). We analyzed resting state and task-related fMRI data acquired from the same individuals. Relative to normal-weight controls, participants with obesity exhibited reduced degree centrality in the right middle frontal gyrus in the resting-state condition. During the task fMRI condition, obese participants exhibited less degree centrality in the left middle frontal gyrus and the lateral occipital cortex along with reduced eigenvector centrality in the lateral occipital cortex and occipital pole. Our results highlight the central role of the middle frontal gyrus in the pathophysiology of obesity, a structure involved in several brain circuits signaling attention, executive functions and motor functions. Additionally, our analysis suggests the existence of task-dependent reduced centrality in occipital areas; regions with a role in perceptual processes and that are profoundly modulated by attention.