Publications by authors named "Alexandre Rosa Franco"

16 Publications

  • Page 1 of 1

Neuroanatomical Correlates of Macrolinguistic Aspects in Narrative Discourse in Unilateral Left and Right Hemisphere Stroke: A Voxel-Based Morphometry Study.

J Speech Lang Hear Res 2021 Apr 12:1-16. Epub 2021 Apr 12.

Linguistics Department, School of Humanities, Pontifical Catholic University of Rio Grande do Sul, Porto Alegre, Brazil.

Background A growing body of literature has demonstrated the importance of discourse assessment in patients who suffered from brain injury, both in the left and right hemispheres, as discourse represents a key component of functional communication. However, little is known about the relationship between gray matter density and macrolinguistic processing. Purpose This study aimed to investigate this relationship in a group of participants with middle-low to low socioeconomic status. Method Twenty adults with unilateral left hemisphere ( = 10) or right hemisphere ( = 10) chronic ischemic stroke and 10 matched (age, education, and socioeconomic status) healthy controls produced three oral narratives based on sequential scenes. Voxel-based morphometry analysis was conducted using structural magnetic resonance imaging. Results Compared to healthy controls, the left hemisphere group showed cohesion impairments, whereas the right hemisphere group showed impairments in coherence and in producing macropropositions. Cohesion positively correlated with gray matter density in the right primary sensory area (PSA)/precentral gyrus and the pars opercularis. Coherence, narrativity, and index of lexical informativeness were positively associated with the left PSA/insula and the superior temporal gyrus. Macropropositions were mostly related to the left PSA/insula and superior temporal gyrus, left cingulate, and right primary motor area/insula. Discussion Overall, the present results suggest that both hemispheres are implicated in macrolinguistic processes in narrative discourse. Further studies including larger samples and with various socioeconomic status should be conducted. Supplemental Material https://doi.org/10.23641/asha.14347550.
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http://dx.doi.org/10.1044/2020_JSLHR-20-00500DOI Listing
April 2021

Cortical thickness and subcortical volume abnormalities in male crack-cocaine users.

Psychiatry Res Neuroimaging 2021 Apr 23;310:111232. Epub 2020 Nov 23.

Department of Neuroscience, Pontifical Catholic University of Rio Grande do Sul, 90619900, Porto Alegre, Brasil.

Crack-cocaine offers a higher risk of abuse than intranasal and intravenous use of cocaine. Yet, current treatments remain disappointing and our understanding of the mechanism of crack-cocaine neurotoxicity is still incomplete. Magnetic resonance images studies on brain changes of crack-cocaine addicts show divergent data. The present study investigated gray matter (GM) abnormalities in crack-cocaine dependents (n = 18) compared to healthy controls (n = 17). MRI data was analysed using FreeSurfer and voxel-based morphometry (VBM). FreeSurfer analysis showed that CD had decreased cortical thickness (CT) in the left inferior temporal cortex (lTC), left orbitofrontal cortex (lOFC) and left rostro frontal cortex (lRFC), enlargement in left inferior lateral ventricle, and smaller GM volume in right hippocampus and right ventral diencephalon. VBM analysis showed that CD had significantly decreased GM volume in left Putamen and left nucleus accumbens. Furthermore, we found a negative correlation between duration of crack-cocaine use and lTC CT. These results provide compelling evidence for GM abnormalities in CD and also suggest that duration of crack-cocaine use may be associated with CT alterations.
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http://dx.doi.org/10.1016/j.pscychresns.2020.111232DOI Listing
April 2021

An fMRI study of inhibitory control and the effects of exposure to violence in Latin-American early adolescents: alterations in frontoparietal activation and performance.

Soc Cogn Affect Neurosci 2019 10;14(10):1097-1107

School of Medicine, PUCRS-Pontifícia Universidade Catolica do Rio Grande do Sul, Porto Alegre, RS, Brazil, 90619-900.

We used functional magnetic resonance to investigate the effects of exposure to violence on early adolescent brain function in an inhibitory control task. We investigated the association among scores on self-reported exposure to violence, performance and brain activation. Thirty-seven early adolescents (ages 10-14) from a Latin-American urban region participated in the study. Results showed that recent and chronic exposure to violence was associated with less activation of a network of frontal regions, including the anterior cingulate gyrus and the superior frontal cortex; recent exposure to violence was also associated with less activation of the superior parietal lobe. Results also showed that less activation correlated with more prominent deterioration in the performance in the inhibitory control task (increased latency with time). The findings suggest that early adolescence exposure to violence is associated with differences in activation of a neural network commonly associated with executive function and control. The results underscore the urgency of addressing exposure to violence in adolescence, a period of high susceptibility to the environment, and are discussed in the light of the evidence of the effects of violence on adolescent brain function. Executive function training may be a candidate for targeted cognitive interventions aimed at mitigating these effects.
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http://dx.doi.org/10.1093/scan/nsz092DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7036087PMC
October 2019

Evaluating fMRI-Based Estimation of Eye Gaze During Naturalistic Viewing.

Cereb Cortex 2020 03;30(3):1171-1184

Center for the Developing Brain, Child Mind Institute, New York, NY, USA.

The collection of eye gaze information during functional magnetic resonance imaging (fMRI) is important for monitoring variations in attention and task compliance, particularly for naturalistic viewing paradigms (e.g., movies). However, the complexity and setup requirements of current in-scanner eye tracking solutions can preclude many researchers from accessing such information. Predictive eye estimation regression (PEER) is a previously developed support vector regression-based method for retrospectively estimating eye gaze from the fMRI signal in the eye's orbit using a 1.5-min calibration scan. Here, we provide confirmatory validation of the PEER method's ability to infer eye gaze on a TR-by-TR basis during movie viewing, using simultaneously acquired eye tracking data in five individuals (median angular deviation < 2°). Then, we examine variations in the predictive validity of PEER models across individuals in a subset of data (n = 448) from the Child Mind Institute Healthy Brain Network Biobank, identifying head motion as a primary determinant. Finally, we accurately classify which of the two movies is being watched based on the predicted eye gaze patterns (area under the curve = 0.90 ± 0.02) and map the neural correlates of eye movements derived from PEER. PEER is a freely available and easy-to-use tool for determining eye fixations during naturalistic viewing.
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http://dx.doi.org/10.1093/cercor/bhz157DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7132907PMC
March 2020

Effects of computerized cognitive training as add-on treatment to stimulants in ADHD: a pilot fMRI study.

Brain Imaging Behav 2020 Oct;14(5):1933-1944

ADHD Outpatient Program, Hospital de Clinicas de Porto Alegre, Department of Psychiatry, Federal University of Rio Grande do Sul, Serviço de Psiquiatria. Ramiro Barcelos, 2350. Bairro Santa Cecília, Porto Alegre, RS, CEP: 90035-903, Brazil.

The neurofunctional effects of Cognitive training (CT) are poorly understood. Our main objective was to assess fMRI brain activation patterns in children with ADHD who received CT as an add-on treatment to stimulant medication. We included twenty children with ADHD from a clinical trial of stimulant medication and CT (10 in medication + CT and 10 in medication + non-active training). Between-group differences were assessed in performance and in brain activation during 3 fMRI paradigms of working memory (N-back: 0-back, 1-back, 2-back, 3-back), sustained attention (Sustained Attention Task - SAT: 2 s, 5 s and 8 s delays) and inhibitory control (Go/No-Go). We found significant group x time x condition interactions in working memory (WM) and sustained attention on brain activation. In N-back, decreases were observed in the BOLD signal change from baseline to endpoint with increasing WM load in the right insula, right putamen, left thalamus and left pallidum in the CT compared to the non-active group; in SAT - increases in the BOLD signal change from baseline to endpoint with increasing delays were observed in bilateral precuneus, right insula, bilateral associative visual cortex and angular gyrus, right middle temporal, precentral, postcentral, superior frontal and middle frontal gyri in the CT compared to the non-active group. CT in ADHD was associated with changes in activation in task-relevant parietal and striato-limbic regions of sustained attention and working memory. Changes in brain activity may precede behavioral performance modifications in working memory and sustained attention, but not in inhibitory control.
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http://dx.doi.org/10.1007/s11682-019-00137-0DOI Listing
October 2020

Violence and Latin-American preadolescents: A study of social brain function and cortisol levels.

Dev Sci 2019 09 20;22(5):e12799. Epub 2019 Feb 20.

PUCRS, Brain Institute of Rio Grande do Sul (BraIns), Porto Alegre, Brazil.

The present study investigated exposure to violence and its association with brain function and hair cortisol concentrations in Latin-American preadolescents. Self-reported victimization scores (JVQ-R2), brain imaging (fMRI) indices for a social cognition task (the 'eyes test'), and hair cortisol concentrations were investigated, for the first time, in this population. The eyes test is based on two conditions: attributing mental state or sex to pictures of pairs of eyes (Baron-Cohen, Wheelwright, Hill, Raste, & Plumb, 2001). The results showed an association among higher victimization scores and (a) less activation of posterior temporoparietal right-hemisphere areas, in the mental state condition only (including right temporal sulcus and fusiform gyrus); (b) higher functional connectivity indices for the Amygdala and Right Fusiform Gyrus (RFFG) pair of brain regions, also in the mental state condition only; (c) higher hair cortisol concentrations. The results suggest more exposure to violence is associated with significant differences in brain function and connectivity. A putative mechanism of less activation in posterior right-hemisphere regions and of synchronized Amygdala: RFFG time series was identified in the mental state condition only. The results also suggest measurable effects of exposure to violence in hair cortisol concentrations, which contribute to the reliability of self-reported scores by young adolescents. The findings are discussed in light of the effects of exposure to violence on brain function and on social-cognitive development in the adolescent brain. A video abstract of this article can be viewed at https://www.youtube.com/watch?v=qHcXq7Y9PBk.
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http://dx.doi.org/10.1111/desc.12799DOI Listing
September 2019

Atlas selection for hippocampus segmentation: Relevance evaluation of three meta-information parameters.

Comput Biol Med 2018 04 9;95:90-98. Epub 2018 Feb 9.

School of Technology, PUCRS, Porto Alegre, Brazil. Electronic address:

Current state-of-the-art methods for whole and subfield hippocampus segmentation use pre-segmented templates, also known as atlases, in the pre-processing stages. Typically, the input image is registered to the template, which provides prior information for the segmentation process. Using a single standard atlas increases the difficulty in dealing with individuals who have a brain anatomy that is morphologically different from the atlas, especially in older brains. To increase the segmentation precision in these cases, without any manual intervention, multiple atlases can be used. However, registration to many templates leads to a high computational cost. Researchers have proposed to use an atlas pre-selection technique based on meta-information followed by the selection of an atlas based on image similarity. Unfortunately, this method also presents a high computational cost due to the image-similarity process. Thus, it is desirable to pre-select a smaller number of atlases as long as this does not impact on the segmentation quality. To pick out an atlas that provides the best registration, we evaluate the use of three meta-information parameters (medical condition, age range, and gender) to choose the atlas. In this work, 24 atlases were defined and each is based on the combination of the three meta-information parameters. These atlases were used to segment 352 vol from the Alzheimer's Disease Neuroimaging Initiative (ADNI) database. Hippocampus segmentation with each of these atlases was evaluated and compared to reference segmentations of the hippocampus, which are available from ADNI. The use of atlas selection by meta-information led to a significant gain in the Dice similarity coefficient, which reached 0.68 ± 0.11, compared to 0.62 ± 0.12 when using only the standard MNI152 atlas. Statistical analysis showed that the three meta-information parameters provided a significant improvement in the segmentation accuracy.
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http://dx.doi.org/10.1016/j.compbiomed.2018.02.005DOI Listing
April 2018

Decoupling of the Occipitotemporal Cortex and the Brain's Default-Mode Network in Dyslexia and a Role for the Cingulate Cortex in Good Readers: A Brain Imaging Study of Brazilian Children.

Dev Neuropsychol 2019 Jan-Feb;44(1):146-157. Epub 2018 Feb 7.

e School of Engineering, Brain Institute of Rio Grande do Sul (BRAINS) , Pontifical Catholic University of Rio Grande do Sul (PUCRS), Porto Alegre , Brazil.

The goal of the present study was to investigate intrinsic and reading-related brain function associated with dyslexia and typical readers in monolingual Brazilian children. Two fMRI studies were carried out: a resting-state and a word-reading study. The results show (a) underconnectivity between the occipitotemporal region (visual word form area) and the brain's default-mode network in dyslexic readers and (b) more activation of the anterior cingulate cortex for typical readers relative to dyslexic readers. The findings provide evidence for brain connectivity and function differences in an underrepresented population in fMRI studies of dyslexia; the results suggest atypical intrinsic function, and differences in directed attention processes in dyslexia.
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http://dx.doi.org/10.1080/87565641.2017.1292516DOI Listing
April 2019

Identification of autism spectrum disorder using deep learning and the ABIDE dataset.

Neuroimage Clin 2018 30;17:16-23. Epub 2017 Aug 30.

PUCRS, School of Computer Science, Porto Alegre 90619, Rio Grande do Sul, Brazil; PUCRS, Brain Institute of Rio Grande do Sul (BraIns), Porto Alegre 90619, Rio Grande do Sul, Brazil. Electronic address:

The goal of the present study was to apply deep learning algorithms to identify autism spectrum disorder (ASD) patients from large brain imaging dataset, based solely on the patients brain activation patterns. We investigated ASD patients brain imaging data from a world-wide multi-site database known as ABIDE (Autism Brain Imaging Data Exchange). ASD is a brain-based disorder characterized by social deficits and repetitive behaviors. According to recent Centers for Disease Control data, ASD affects one in 68 children in the United States. We investigated patterns of functional connectivity that objectively identify ASD participants from functional brain imaging data, and attempted to unveil the neural patterns that emerged from the classification. The results improved the state-of-the-art by achieving 70% accuracy in identification of ASD versus control patients in the dataset. The patterns that emerged from the classification show an anticorrelation of brain function between anterior and posterior areas of the brain; the anticorrelation corroborates current empirical evidence of anterior-posterior disruption in brain connectivity in ASD. We present the results and identify the areas of the brain that contributed most to differentiating ASD from typically developing controls as per our deep learning model.
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http://dx.doi.org/10.1016/j.nicl.2017.08.017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5635344PMC
June 2018

Decreased comfort food intake and allostatic load in adolescents carrying the A3669G variant of the glucocorticoid receptor gene.

Appetite 2017 09 8;116:21-28. Epub 2017 Apr 8.

Graduate Program in Neuroscience, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil; Department of Psychiatry, McGill University, Montreal, QC, Canada.

Background: The A3669G single nucleotide polymorphism (SNP) of the glucocorticoid receptor (GR) gene NR3C1 is associated with altered tissue sensitivity to glucocorticoids (GCs). GCs modulate the food reward circuitry and are implicated in increased intake of palatable foods, which can lead to the metabolic syndrome and obesity. We hypothesized that presence of the G variant of the A3669G SNP would affect preferences for palatable foods and alter metabolic, behavioural, and neural outcomes.

Methods: One hundred thirty-one adolescents were genotyped for the A3669G polymorphism, underwent anthropometric assessment and nutritional evaluations, and completed behavioural measures. A subsample of 74 subjects was followed for 5 years and performed a brain functional magnetic resonance imaging (fMRI) paradigm to verify brain activity in response to food cues.

Results: Sugar and total energy consumption were lower in A3669G G allele variant carriers. On follow-up, this group also had reduced serum insulin concentrations, increased insulin sensitivity, and lower anxiety scores. Because of our unbalanced sample sizes (31/37 participants non-G allele carriers/total), our imaging data analysis failed to find whole brain-corrected significant results in between-group t-tests.

Conclusion: These results highlight that a genetic variation in the GR gene is associated, at the cellular level, with significant reduction in GC sensitivity, which, at cognitive and behavioural levels, translates to altered food intake and emotional stress response. This genetic variant might play a major role in decreasing risk for metabolic and psychiatric diseases.
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http://dx.doi.org/10.1016/j.appet.2017.04.004DOI Listing
September 2017

Amygdala-based intrinsic functional connectivity and anxiety disorders in adolescents and young adults.

Psychiatry Res Neuroimaging 2016 Nov 22;257:11-16. Epub 2016 Sep 22.

Anxiety Disorders Program for Child and Adolescent Psychiatry (PROTAIA), Hospital de Clínicas de Porto Alegre (HCPA), Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil; Postgraduate Program in Neuroscience, Institute of Basic Sciences/Health (ICBS), Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil; Postgraduate Program in Medical Sciences: Psychiatry, Hospital de Clínicas de Porto Alegre (HCPA), Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS, Brazil.

Anxiety disorders (AD) are the most prevalent group of psychiatric disorders in adolescents and young adults. Nevertheless, the pathophysiology of anxiety disorders is still poorly understood. This study investigated differences in the functional connectivity of intrinsic amygdala-based networks of participants with and without AD. Resting state fMRI data were obtained from 18 participants with an AD and 19 healthy comparison individuals. Psychiatric diagnosis was assessed using standardized structured interviews. The comparison between groups was carried out using functional connectivity maps from six seed regions defined using probabilistic maps bilaterally within the amygdala (basolateral, superficial and centromedial amygdala). We found significant between-group differences in five clusters, which showed aberrant functional connectivity with the left basolateral amygdala: right precentral gyrus, right cingulate gyrus, bilateral precuneus, and right superior frontal gyrus in subjects with AD as compared with the comparison subjects. For the comparison subjects, the correlations between the amygdala and the five clusters were either non-significant, or negative. The present study suggests there is an intrinsic disruption in the communication between left basolateral amygdala and a network of brain regions involved with emotion regulation, and with the default mode network in adolescents and young adults with anxiety disorders.
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http://dx.doi.org/10.1016/j.pscychresns.2016.09.010DOI Listing
November 2016

Interaction between perceived maternal care, anxiety symptoms, and the neurobehavioral response to palatable foods in adolescents.

Stress 2016 05;19(3):287-94

a Programa de Pós-Graduação em Saúde da Criança e do Adolescente, Faculdade de Medicina, Hospital de Clínicas de Porto Alegre , Universidade Federal do Rio Grande do Sul , Porto Alegre , Brazil ;

Studies in rodents have shown that early life trauma leads to anxiety, increased stress responses to threatening situations, and modifies food intake in a new environment. However, these associations are still to be tested in humans. This study aimed to verify complex interactions among anxiety diagnosis, maternal care, and baseline cortisol on food intake in a new environment in humans. A community sample of 32 adolescents and young adults was evaluated for: psychiatric diagnosis using standardized interviews, maternal care using the Parental Bonding Inventory (PBI), caloric consumption in a new environment (meal choice at a snack bar), and salivary cortisol. They also performed a brain fMRI task including the visualization of palatable foods vs. neutral items. The study found a three-way interaction between anxiety diagnosis, maternal care, and baseline cortisol levels on the total calories consumed (snacks) in a new environment. This interaction means that for those with high maternal care, there were no significant associations between cortisol levels and food intake in a new environment. However, for those with low maternal care and who have an anxiety disorder (affected), cortisol was associated with higher food intake; whereas for those with low maternal care and who did not have an anxiety disorder (resilient), cortisol was negatively associated with lower food intake. In addition, higher anxiety symptoms were associated with decreased activation in the superior and middle frontal gyrus when visualizing palatable vs. neutral items in those reporting high maternal care. These results in humans mimic experimental research findings and demonstrate that a combination of anxiety diagnosis and maternal care moderate the relationship between the HPA axis functioning, anxiety, and feeding behavior in adolescents and young adults.
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http://dx.doi.org/10.1080/10253890.2016.1191464DOI Listing
May 2016

Intrinsic Brain Connectivity Following Long-Term Treatment with Methylphenidate in Children with Attention-Deficit/Hyperactivity Disorder.

J Child Adolesc Psychopharmacol 2016 08 30;26(6):555-61. Epub 2016 Mar 30.

2 Brain Institute (InsCer) , PUCRS, Porto Alegre, Brazil .

Introduction: Although widely used for the treatment of attention-deficit/hyperactivity disorder (ADHD) across the life span, the effects of methylphenidate (MPH) on the brain are not completely understood. Functional neuroimaging techniques may help increase knowledge about the mechanisms of MPH action.

Objective: To evaluate changes in functional connectivity patterns of the default mode network (DMN) in children with ADHD following long-term treatment with MPH.

Methods: Twenty-three right-handed treatment-naïve boys with ADHD underwent a protocol of intrinsic functional connectivity before and after 6 months of treatment with MPH. Functional connectivity was analyzed using a region of interest (ROI) approach and independent component analysis (ICA).

Results: ROI analyses showed no significant changes in connectivity between regions of the DMN following treatment, with a relatively small increase in the anterior-posterior connectivity of the network. ICA revealed a significant increase in connectivity between the left putamen and the DMN (p < 0.001, corrected). There was a correlation between the reduction of symptoms and the increased connectivity between the putamen and the DMN after treatment (rho = -0.65, p = 0.017).

Conclusion: Dysfunctions in cortical-subcortical circuits have often been associated with the pathophysiology of ADHD. Our findings suggest that effective treatment with MPH in children with ADHD may affect brain functioning by increasing connectivity between the DMN and subcortical nuclei.
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http://dx.doi.org/10.1089/cap.2015.0221DOI Listing
August 2016

Decreasing ADHD phenotypic heterogeneity: searching for neurobiological underpinnings of the restrictive inattentive phenotype.

Eur Child Adolesc Psychiatry 2016 Mar 10;25(3):273-82. Epub 2015 Jun 10.

Department of Psychiatry, ADHD Outpatient Program, Hospital de Clinicas de Porto Alegre, Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.

During the process of developing the DSM-5, a new phenotype of ADHD was proposed-the ADHD restrictive inattentive presentation (ADHD-RI), describing subjects with high endorsement of inattentive symptoms and a low level of hyperactivity. However, this phenotype was not included in the DSM-5 because of the lack of robust neurobiological data. We aimed to assess the specific neurobiological underpinnings of individuals presenting ADHD-RI. We compared a sample of 301 subjects (101 ADHD-Combined; 50 ADHD-RI; 50 ADHD predominantly inattentive type and 100 typically developing subjects) aged 8-15 years, using a complete neuropsychological battery, molecular genetic data (DRD4 and DAT1 most studied polymorphisms) and functional MRI during a Go-No/Go task. Subjects with ADHD-RI had a significantly different neuropsychological profile compared with the other groups, including lower psychomotor speeds, longer reaction times and the worst overall performance in the global neurocognitive index. The proportion of subjects with the presence of DRD4-7 repeat allele was significantly higher in ADHD-RI. The fMRI data suggested that more attention-related posterior brain regions (especially temporo-occipital areas) are activated in ADHD-RI during both Go and No-Go cues compared to TD controls and ADHD predominantly inattentive type. ADHD-RI may represent a different phenotype than other types of ADHD. In addition, our results suggest that reducing the phenotypic heterogeneity may aid in the search for the neurobiological underpinnings of ADHD.
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http://dx.doi.org/10.1007/s00787-015-0731-3DOI Listing
March 2016

Automated methods for hippocampus segmentation: the evolution and a review of the state of the art.

Neuroinformatics 2015 Apr;13(2):133-50

School of Computer Science, PUCRS - Pontifícia Universidade Católica do Rio Grande do Sul, Building 32, Office 607, Av. Ipiranga 6681, 90619-000, Porto Alegre, RS, Brazil,

The segmentation of the hippocampus in Magnetic Resonance Imaging (MRI) has been an important procedure to diagnose and monitor several clinical situations. The precise delineation of the borders of this brain structure makes it possible to obtain a measure of the volume and estimate its shape, which can be used to diagnose some diseases, such as Alzheimer's disease, schizophrenia and epilepsy. As the manual segmentation procedure in three-dimensional images is highly time consuming and the reproducibility is low, automated methods introduce substantial gains. On the other hand, the implementation of those methods is a challenge because of the low contrast of this structure in relation to the neighboring areas of the brain. Within this context, this research presents a review of the evolution of automatized methods for the segmentation of the hippocampus in MRI. Many proposed methods for segmentation of the hippocampus have been published in leading journals in the medical image processing area. This paper describes these methods presenting the techniques used and quantitatively comparing the methods based on Dice Similarity Coefficient. Finally, we present an evaluation of those methods considering the degree of user intervention, computational cost, segmentation accuracy and feasibility of application in a clinical routine.
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http://dx.doi.org/10.1007/s12021-014-9243-4DOI Listing
April 2015

Whole cortical and default mode network mean functional connectivity as potential biomarkers for mild Alzheimer's disease.

Psychiatry Res 2014 Jan 11;221(1):37-42. Epub 2013 Nov 11.

Department of Neurology, University of Campinas (Unicamp), Sao Paulo 13083-970, Brazil.

The search for an Alzheimer's disease (AD) biomarker is one of the most relevant contemporary research topics due to the high prevalence and social costs of the disease. Functional connectivity (FC) of the default mode network (DMN) is a plausible candidate for such a biomarker. We evaluated 22 patients with mild AD and 26 age- and gender-matched healthy controls. All subjects underwent resting functional magnetic resonance imaging (fMRI) in a 3.0 T scanner. To identify the DMN, seed-based FC of the posterior cingulate was calculated. We also measured the sensitivity/specificity of the method, and verified a correlation with cognitive performance. We found a significant difference between patients with mild AD and controls in average z-scores: DMN, whole cortical positive (WCP) and absolute values. DMN individual values showed a sensitivity of 77.3% and specificity of 70%. DMN and WCP values were correlated to global cognition and episodic memory performance. We showed that individual measures of DMN connectivity could be considered a promising method to differentiate AD, even at an early phase, from normal aging. Further studies with larger numbers of participants, as well as validation of normal values, are needed for more definitive conclusions.
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http://dx.doi.org/10.1016/j.pscychresns.2013.10.010DOI Listing
January 2014