RESUMO
In this study, we aimed to understand the contributions of hippocampal anteroposterior subregions (head, body, tail) and subfields (cornu ammonis 1-3 [CA1-3], dentate gyrus [DG], and subiculum [Sub]) and encoding strategies to the age-related verbal memory decline. Healthy participants were administered the California Verbal Learning Test-II to evaluate verbal memory performance and encoding strategies and underwent 4.7 T magnetic resonance imaging brain scan with subsequent hippocampal subregions and subfields manual segmentation. While total hippocampal volume was not associated with verbal memory performance, we found the volumes of the posterior hippocampus (body) and Sub showed significant effects on verbal memory performance. Additionally, the age-related volume decline in hippocampal body volume contributed to lower use of semantic clustering, resulting in lower verbal memory performance. The effect of Sub on verbal memory was statistically independent of encoding strategies. While total CA1-3 and DG volumes did not show direct or indirect effects on verbal memory, exploratory analyses with DG and CA1-3 volumes within the hippocampal body subregion suggested an indirect effect of age-related volumetric reduction on verbal memory performance through semantic clustering. As semantic clustering is sensitive to age-related hippocampal volumetric decline but not to the direct effect of age, further investigation of mechanisms supporting semantic clustering can have implications for early detection of cognitive impairments and decline.
Assuntos
Envelhecimento Saudável , Longevidade , Adulto , Humanos , Hipocampo/diagnóstico por imagem , Hipocampo/patologia , Memória , Região CA3 Hipocampal , Imageamento por Ressonância Magnética/métodosRESUMO
The ability to recognize others' emotions is vital to everyday life. The goal of this study was to assess which emotions show age-related decline in recognition accuracy of facial emotional expressions across the entire adult lifespan and how this process is related to cognitive empathy (Theory of Mind [ToM]), alexithymia traits, and amygdala subnuclei volumes in a large cohort of healthy individuals. We recruited 140 healthy participants 18-85 years old. Facial affect processing was assessed with the Penn Emotion Recognition task (ER40) that contains images of the five basic emotions: Neutral, Happy, Sad, Angry, and Fearful. Structural magnetic resonance imaging (MRI) datasets were acquired on a 4.7T MRI system. Structural equation modeling was used to test the relationship between studied variables. We found that while both sexes demonstrated age-related reduction in recognition of happy emotions and preserved recognition of sadness, male participants showed age-related reduction in recognition of fear, while in female participants, age-related decline was linked to recognition of neutral and angry facial expressions. In both sexes, accurate recognition of sadness negatively correlated with alexithymia traits. On the other hand, better ToM capabilities in male participants were associated with improvement in recognition of positive and neutral emotions. Finally, none of the observed age-related reductions in emotional recognition were related to amygdala and its subnuclei volumes. In contrast, both global volume of amygdala and its cortical and centromedial subnuclei had significant direct effects on recognition of sad images.
Assuntos
Sintomas Afetivos , Empatia , Adulto , Masculino , Humanos , Feminino , Adolescente , Adulto Jovem , Pessoa de Meia-Idade , Idoso , Idoso de 80 Anos ou mais , Sintomas Afetivos/diagnóstico por imagem , Longevidade , Emoções , Cognição , Tonsila do Cerebelo/diagnóstico por imagem , Expressão Facial , Imageamento por Ressonância MagnéticaRESUMO
Background: Reductions in total hippocampus volume have frequently been reported in MRI studies in major depressive disorder (MDD), but reports of differences in total amygdala volume have been inconsistent. Childhood maltreatment is an important risk factor for MDD in adulthood and may affect the volume of the hippocampus and amygdala. In the present study, we examined associations between the volumes of the amygdala subnuclei and hippocampal subfields and history of childhood maltreatment in participants with MDD. Methods: We recruited 35 patients who met the DSM-IV criteria for MDD and 35 healthy controls. We acquired MRI data sets on a 4.7 T Varian Inova scanner. We manually delineated the amygdala subnuclei (lateral, basal and accessory basal nuclei, and the cortical and centromedial groups) and hippocampal subfields (cornu ammonis, subiculum and dentate gyrus) using reliable volumetric methods. We assessed childhood maltreatment using the Childhood Trauma Questionnaire in participants with MDD. Results: In participants with MDD, a history of childhood maltreatment had significant negative associations with volume in the right amygdala, anterior hippocampus and total cornu ammonis subfield bilaterally. For volumes of the amygdala subnuclei, such effects were limited to the basal, accessory basal and cortical subnuclei in the right hemisphere, but they did not survive correction for multiple comparisons. We did not find significant effects of MDD or antidepressant treatment on volumes of the amygdala subnuclei. Limitations: Our study was a cross-sectional study. Conclusion: Our results provide evidence of negative associations between history of childhood maltreatment and volumes of medial temporal lobe structures in participants with MDD. This may help to identify potential mechanisms by which maltreatment leads to clinical impacts.
Assuntos
Experiências Adversas da Infância , Tonsila do Cerebelo/patologia , Transtorno Depressivo Maior/patologia , Hipocampo/patologia , Adolescente , Adulto , Adultos Sobreviventes de Eventos Adversos na Infância , Tonsila do Cerebelo/diagnóstico por imagem , Transtorno Depressivo Maior/diagnóstico por imagem , Feminino , Hipocampo/diagnóstico por imagem , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Adulto JovemRESUMO
Previous diffusion tensor imaging (DTI) studies confirmed the vulnerability of corpus callosum (CC) fibers to aging. However, most studies employed lower order regressions to study the relationship between age and white matter microstructure. The present study investigated whether higher order polynomial regression modelling can better describe the relationship between age and CC DTI metrics compared to lower order models in 140 healthy participants (ages 18-85). The CC was found to be non-uniformly affected by aging, with accelerated and earlier degradation occurring in anterior portion; callosal volume, fiber count, fiber length, mean fibers per voxel, and FA decreased with age while mean, axial, and radial diffusivities increased. Half of the parameters studied also displayed significant age-sex interaction or intracranial volume effects. Higher order models were chosen as the best fit, based on Bayesian Information Criterion minimization, in 16 out of 23 significant cases when describing the relationship between DTI measurements and age. Higher order model fits provided different estimations of aging trajectory peaks and decline onsets than lower order models; however, a likelihood ratio test found that higher order regressions generally did not fit the data significantly better than lower order polynomial or linear models. The results contrast the modelling approaches and highlight the importance of using higher order polynomial regression modelling when investigating associations between age and CC white matter microstructure.
Assuntos
Corpo Caloso/diagnóstico por imagem , Imagem de Tensor de Difusão/métodos , Envelhecimento Saudável/patologia , Processamento de Imagem Assistida por Computador/métodos , Análise de Regressão , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Corpo Caloso/patologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Adulto JovemRESUMO
In this study, we explored the associations between the brain derived neurotrophic factor (BDNF) and the apolipoprotein E (APOE) polymorphisms and hippocampal subfields in 127 healthy participants (18-85 years). MRI datasets were collected on a 4.7 T system. Participants were administered the Wechsler Memory Scale to evaluate episodic memory function. Significant associations of both polymorphisms were present only in older adults (≥50 years). BDNF polymorphism was associated with larger dentate gyrus volumes within the anterior hippocampus (head) in Met-carriers compared to Val/Val homozygotes. We found that in Met-carriers total hippocampal volume predicted performance on visuospatial memory tasks. APOE polymorphism was associated with larger total hippocampal volume, especially in cornu ammonis 1-3 and subiculum in APOE É2 carriers compared to both É4 and É3 carriers, while APOE É3 and É4 carriers did not differ from each other. APOE polymorphism was associated with better performance on visuospatial memory tasks in APOE ε2 carriers in comparison to ε4 carriers.
Assuntos
Apolipoproteínas E/genética , Fator Neurotrófico Derivado do Encéfalo/genética , Hipocampo/fisiologia , Longevidade/fisiologia , Memória Episódica , Polimorfismo de Nucleotídeo Único/genética , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Estudos Transversais , Feminino , Envelhecimento Saudável/genética , Hipocampo/diagnóstico por imagem , Humanos , Masculino , Memória , Pessoa de Meia-Idade , Tamanho do Órgão/fisiologia , Desempenho Psicomotor/fisiologia , Adulto JovemRESUMO
The functional role of the hippocampal formation in episodic memory has been studied using functional magnetic resonance imaging (fMRI) for many years. The hippocampus can be segmented into three major anteroposterior sections, called head, body and tail, and into the Cornu Ammonis (CA), dentate gyrus (DG), and subiculum (Sub) subfields based on its transverse axis. However, the exact role of these subregions and subfields in memory processes is less understood. In the present study we combined ultra-high-resolution structural Magnetic Resonance Imaging (MRI) at 4.7â¯T with an event-related high-resolution fMRI paradigm based on the 'Designs' subtest of the Wechsler Memory Scale to investigate how the hippocampal subfields and longitudinal subregions are involved in encoding and retrieval of item, spatial, and associative memories. Our results showed that during memory encoding, regardless of the type of memory being learned, all subregions and all subfields were active. During the retrieval phase, on the other hand, we observed an anterior to posterior gradient in hippocampal activity for all subfields and all types of memory. Our findings also confirmed presence of an anterior to posterior gradient in hippocampal activity during spatial learning. Comparing subfield activities to each other revealed that the DG was more active than the CA1-3 and Sub during both encoding and retrieval. Finally, our results showed that for every subfield, encoding vs. retrieval activity differences were larger in the hippocampal head than in the hippocampal body and tail. Furthermore, these encoding vs. retrieval activity differences were similar in all subfields, highlighting the importance of studying both the longitudinal and transverse axis specialization simultaneously. Current findings further elucidate the structure-function relationship between the human hippocampus and episodic memory.
Assuntos
Hipocampo/fisiologia , Memória/fisiologia , Adulto , Mapeamento Encefálico/métodos , Feminino , Humanos , Imageamento por Ressonância Magnética/métodos , Masculino , Adulto JovemRESUMO
Amygdala is a group of nuclei involved in the neural circuits of fear, reward learning, and stress. The main goal of this magnetic resonance imaging (MRI) study was to investigate the relationship between age and the amygdala subnuclei volumes in a large cohort of healthy individuals. Our second goal was to determine effects of the apolipoprotein E (APOE) and brain-derived neurotrophic factor (BDNF) polymorphisms on the amygdala structure. One hundred and twenty-six healthy participants (18-85 years old) were recruited for this study. MRI datasets were acquired on a 4.7 T system. Amygdala was manually segmented into five major subdivisions (lateral, basal, accessory basal nuclei, and cortical, and centromedial groups). The BDNF (methionine and homozygous valine) and APOE genotypes (ε2, homozygous ε3, and ε4) were obtained using single nucleotide polymorphisms. We found significant nonlinear negative associations between age and the total amygdala and its lateral, basal, and accessory basal nuclei volumes, while the cortical amygdala showed a trend. These age-related associations were found only in males but not in females. Centromedial amygdala did not show any relationship with age. We did not observe any statistically significant effects of APOE and BDNF polymorphisms on the amygdala subnuclei volumes. In contrast to APOE ε2 allele carriers, both older APOE ε4 and ε3 allele carriers had smaller lateral, basal, accessory basal nuclei volumes compared to their younger counterparts. This study indicates that amygdala subnuclei might be nonuniformly affected by aging and that age-related association might be gender specific.
Assuntos
Tonsila do Cerebelo/anatomia & histologia , Envelhecimento Cognitivo/fisiologia , Envelhecimento Saudável/fisiologia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Tonsila do Cerebelo/diagnóstico por imagem , Apolipoproteínas E/genética , Fator Neurotrófico Derivado do Encéfalo/genética , Feminino , Envelhecimento Saudável/genética , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Polimorfismo de Nucleotídeo Único , Fatores Sexuais , Adulto JovemRESUMO
The amygdala (AG) is an almond-shaped heterogeneous structure located in the medial temporal lobe. The majority of previous structural Magnetic Resonance Imaging (MRI) volumetric methods for AG measurement have so far only been able to examine this region as a whole. In order to understand the role of the AG in different neuropsychiatric disorders, it is necessary to understand the functional role of its subnuclei. The main goal of the present study was to develop a reliable volumetric method to delineate major AG subnuclei groups using ultra-high resolution high field MRI. 38 healthy volunteers (15 males and 23 females, 21-60 years of age) without any history of medical or neuropsychiatric disorders were recruited for this study. Structural MRI datasets were acquired at 4.7 T Varian Inova MRI system using a fast spin echo (FSE) sequence. The AG was manually segmented into its five major anatomical subdivisions: lateral (La), basal (B), accessory basal (AB) nuclei, and cortical (Co) and centromedial (CeM) groups. Inter-(intra-) rater reliability of our novel volumetric method was assessed using intra-class correlation coefficient (ICC) and Dice's Kappa. Our results suggest that reliable measurements of the AG subnuclei can be obtained by image analysts with experience in AG anatomy. We provided a step-by-step segmentation protocol and reported absolute and relative volumes for the AG subnuclei. Our results showed that the basolateral (BLA) complex occupies seventy-eight percent of the total AG volume, while CeM and Co groups occupy twenty-two percent of the total AG volume. Finally, we observed no hemispheric effects and no gender differences in the total AG volume and the volumes of its subnuclei. Future applications of this method will help to understand the selective vulnerability of the AG subnuclei in neurological and psychiatric disorders.
Assuntos
Tonsila do Cerebelo/anatomia & histologia , Tonsila do Cerebelo/diagnóstico por imagem , Processamento de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Neuroimagem/métodos , Adulto , Complexo Nuclear Basolateral da Amígdala/anatomia & histologia , Complexo Nuclear Basolateral da Amígdala/diagnóstico por imagem , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Adulto JovemRESUMO
BACKGROUND: Recent findings have demonstrated that hippocampal subfields can be selectively affected in different disease states, which has led to efforts to segment the human hippocampus with in vivo magnetic resonance imaging (MRI). However, no studies have examined the histological accuracy of subfield segmentation protocols. The presence of MRI-visible anatomical landmarks with known correspondence to histology represents a fundamental prerequisite for in vivo hippocampal subfield segmentation. In the present study, we aimed to: 1) develop a novel method for hippocampal body segmentation, based on two MRI-visible anatomical landmarks (stratum lacunosum moleculare [SLM] & dentate gyrus [DG]), and assess its accuracy in comparison to the gold standard direct histological measurements; 2) quantify the accuracy of two published segmentation strategies in comparison to the histological gold standard; and 3) apply the novel method to ex vivo MRI and correlate the results with histology. METHODS: Ultra-high resolution ex vivo MRI was performed on six whole cadaveric hippocampal specimens, which were then divided into 22 blocks and histologically processed. The hippocampal bodies were segmented into subfields based on histological criteria and subfield boundaries and areas were directly measured. A novel method was developed using mean percentage of the total SLM distance to define subfield boundaries. Boundary distances and subfield areas on histology were then determined using the novel method and compared to the gold standard histological measurements. The novel method was then used to determine ex vivo MRI measures of subfield boundaries and areas, which were compared to histological measurements. RESULTS: For direct histological measurements, the mean percentages of total SLM distance were: Subiculum/CA1 = 9.7%, CA1/CA2 = 78.4%, CA2/CA3 = 97.5%. When applied to histology, the novel method provided accurate measures for CA1/CA2 (ICC = 0.93) and CA2/CA3 (ICC = 0.97) boundaries, but not for the Subiculum/CA1 (ICC = -0.04) boundary. Accuracy was poorer using previous techniques for CA1/CA2 (maximum ICC = 0.85) and CA2/CA3 (maximum ICC = 0.88), with the previously reported techniques also performing poorly in defining the Subiculum/CA1 boundary (maximum ICC = 0.00). Ex vivo MRI measurements using the novel method were linearly related to direct measurements of SLM length (r2 = 0.58), CA1/CA2 boundary (r2 = 0.39) and CA2/CA3 boundary (r2 = 0.47), but not for Subiculum/CA1 boundary (r2 = 0.01). Subfield areas measured with the novel method on histology and ex vivo MRI were linearly related to gold standard histological measures for CA1, CA2, and CA3/CA4/DG. CONCLUSIONS: In this initial proof of concept study, we used ex vivo MRI and histology of cadaveric hippocampi to develop a novel segmentation protocol for the hippocampal body. The novel method utilized two anatomical landmarks, SLM & DG, and provided accurate measurements of CA1, CA2, and CA3/CA4/DG subfields in comparison to the gold standard histological measurements. The relationships demonstrated between histology and ex vivo MRI supports the potential feasibility of applying this method to in vivo MRI studies.
Assuntos
Hipocampo/anatomia & histologia , Técnicas Histológicas/métodos , Imageamento por Ressonância Magnética/métodos , Idoso , Idoso de 80 Anos ou mais , Protocolos Clínicos , Hipocampo/diagnóstico por imagem , Hipocampo/patologia , Humanos , Pessoa de Meia-Idade , Reprodutibilidade dos TestesRESUMO
The involvement of the human amygdala in emotion-related processing has been studied using functional magnetic resonance imaging (fMRI) for many years. However, despite the amygdala being comprised of several subnuclei, most studies investigated the role of the entire amygdala in processing of emotions. Here we combined a novel anatomical tracing protocol with event-related high-resolution fMRI acquisition to study the responsiveness of the amygdala subnuclei to negative emotional stimuli and to examine intra-amygdala functional connectivity. The greatest sensitivity to the negative emotional stimuli was observed in the centromedial amygdala, where the hemodynamic response amplitude elicited by the negative emotional stimuli was greater and peaked later than for neutral stimuli. Connectivity patterns converge with extant findings in animals, such that the centromedial amygdala was more connected with the nuclei of the basal amygdala than with the lateral amygdala. Current findings provide evidence of functional specialization within the human amygdala.
Assuntos
Complexo Nuclear Basolateral da Amígdala/fisiologia , Cognição/fisiologia , Emoções/fisiologia , Rede Nervosa/fisiologia , Vias Neurais/fisiologia , Adulto , Mapeamento Encefálico , Conectoma/métodos , Feminino , Humanos , Imageamento por Ressonância Magnética/métodos , Masculino , Pessoa de Meia-Idade , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
OBJECTIVE: An increasing number of human in vivo magnetic resonance imaging (MRI) studies have focused on examining the structure and function of the subfields of the hippocampal formation (the dentate gyrus, CA fields 1-3, and the subiculum) and subregions of the parahippocampal gyrus (entorhinal, perirhinal, and parahippocampal cortices). The ability to interpret the results of such studies and to relate them to each other would be improved if a common standard existed for labeling hippocampal subfields and parahippocampal subregions. Currently, research groups label different subsets of structures and use different rules, landmarks, and cues to define their anatomical extents. This paper characterizes, both qualitatively and quantitatively, the variability in the existing manual segmentation protocols for labeling hippocampal and parahippocampal substructures in MRI, with the goal of guiding subsequent work on developing a harmonized substructure segmentation protocol. METHOD: MRI scans of a single healthy adult human subject were acquired both at 3 T and 7 T. Representatives from 21 research groups applied their respective manual segmentation protocols to the MRI modalities of their choice. The resulting set of 21 segmentations was analyzed in a common anatomical space to quantify similarity and identify areas of agreement. RESULTS: The differences between the 21 protocols include the region within which segmentation is performed, the set of anatomical labels used, and the extents of specific anatomical labels. The greatest overall disagreement among the protocols is at the CA1/subiculum boundary, and disagreement across all structures is greatest in the anterior portion of the hippocampal formation relative to the body and tail. CONCLUSIONS: The combined examination of the 21 protocols in the same dataset suggests possible strategies towards developing a harmonized subfield segmentation protocol and facilitates comparison between published studies.
Assuntos
Protocolos Clínicos , Hipocampo/anatomia & histologia , Processamento de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Giro Para-Hipocampal/anatomia & histologia , Adulto , Protocolos Clínicos/normas , Humanos , Processamento de Imagem Assistida por Computador/normas , Imageamento por Ressonância Magnética/normasRESUMO
BACKGROUND: This study aimed to have international experts converge on a harmonized definition of whole hippocampus boundaries and segmentation procedures, to define standard operating procedures for magnetic resonance (MR)-based manual hippocampal segmentation. METHODS: The panel received a questionnaire regarding whole hippocampus boundaries and segmentation procedures. Quantitative information was supplied to allow evidence-based answers. A recursive and anonymous Delphi procedure was used to achieve convergence. Significance of agreement among panelists was assessed by exact probability on Fisher's and binomial tests. RESULTS: Agreement was significant on the inclusion of alveus/fimbria (P = .021), whole hippocampal tail (P = .013), medial border of the body according to visible morphology (P = .0006), and on this combined set of features (P = .001). This definition captures 100% of hippocampal tissue, 100% of Alzheimer's disease-related atrophy, and demonstrated good reliability on preliminary intrarater (0.98) and inter-rater (0.94) estimates. DISCUSSION: Consensus was achieved among international experts with respect to hippocampal segmentation using MR resulting in a harmonized segmentation protocol.
Assuntos
Hipocampo/patologia , Processamento de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Neuroimagem/métodos , Doença de Alzheimer/patologia , Atrofia , Consenso , Técnica Delphi , Hipocampo/anatomia & histologia , Humanos , Imageamento Tridimensional/métodos , InternacionalidadeRESUMO
BACKGROUND: An international Delphi panel has defined a harmonized protocol (HarP) for the manual segmentation of the hippocampus on MR. The aim of this study is to study the concurrent validity of the HarP toward local protocols, and its major sources of variance. METHODS: Fourteen tracers segmented 10 Alzheimer's Disease Neuroimaging Initiative (ADNI) cases scanned at 1.5 T and 3T following local protocols, qualified for segmentation based on the HarP through a standard web-platform and resegmented following the HarP. The five most accurate tracers followed the HarP to segment 15 ADNI cases acquired at three time points on both 1.5 T and 3T. RESULTS: The agreement among tracers was relatively low with the local protocols (absolute left/right ICC 0.44/0.43) and much higher with the HarP (absolute left/right ICC 0.88/0.89). On the larger set of 15 cases, the HarP agreement within (left/right ICC range: 0.94/0.95 to 0.99/0.99) and among tracers (left/right ICC range: 0.89/0.90) was very high. The volume variance due to different tracers was 0.9% of the total, comparing favorably to variance due to scanner manufacturer (1.2), atrophy rates (3.5), hemispheric asymmetry (3.7), field strength (4.4), and significantly smaller than the variance due to atrophy (33.5%, P < .001), and physiological variability (49.2%, P < .001). CONCLUSIONS: The HarP has high measurement stability compared with local segmentation protocols, and good reproducibility within and among human tracers. Hippocampi segmented with the HarP can be used as a reference for the qualification of human tracers and automated segmentation algorithms.
Assuntos
Hipocampo/patologia , Processamento de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Neuroimagem/métodos , Idoso , Doença de Alzheimer/genética , Doença de Alzheimer/patologia , Atrofia , Feminino , Lateralidade Funcional , Humanos , Imageamento Tridimensional/métodos , Internet , Imageamento por Ressonância Magnética/instrumentação , Masculino , Pessoa de Meia-Idade , Tamanho do Órgão , Reprodutibilidade dos TestesRESUMO
The cingulate cortex is a limbic structure involved in multiple functions, including emotional processing, pain, cognition, memory, and spatial orientation. The main goal of this structural Magnetic Resonance Imaging (MRI) study was to investigate whether age affects the cingulate cortex uniformly across its anteroposterior dimensions and determine if the effects of age differ based on sex, hemisphere, and regional cingulate anatomy, in a large cohort of healthy individuals across the adult lifespan. The second objective aimed to explore whether the decline in emotional recognition accuracy and Theory of Mind (ToM) is linked to the potential age-related reductions in the pregenual anterior cingulate (ACC) and anterior midcingulate (MCC) cortices. We recruited 126 healthy participants (18-85 years) for this study. MRI datasets were acquired on a 4.7 T system. The cingulate cortex was manually segmented into the pregenual ACC, anterior MCC, posterior MCC, and posterior cingulate cortex (PCC). We observed negative relationships between the presence and length of the superior cingulate gyrus and bilateral volumes of pregenual ACC and anterior MCC. Age showed negative effects on the volume of all cingulate cortical subregions bilaterally except for the right anterior MCC. Most of the associations between age and the cingulate subregional volumes were linear. We did not find a significant effect of sex on cingulate cortical volumes. However, stronger effects of age were observed in men compared to women. This study also demonstrated that performance on an emotional recognition task was linked to pregenual ACC volume, whist the ToM capabilities were related to the size of pregenual ACC and anterior MCC. These results suggest that the cingulate cortex contributes to emotional recognition ability and ToM across the adult lifespan.
Assuntos
Giro do Cíngulo , Teoria da Mente , Masculino , Adulto , Humanos , Feminino , Giro do Cíngulo/diagnóstico por imagem , Giro do Cíngulo/anatomia & histologia , Cognição , Imageamento por Ressonância Magnética/métodos , EnvelhecimentoRESUMO
In the present study we investigated whether hippocampal subfield (cornu ammonis 1-3, dentate gyrus, and subiculum) and anteroposterior hippocampal subregion (head,body, and tail) volumes can predict episodic memory function using high-field high resolution structural magnetic resonance imaging (MRI). We recruited 126 healthy participants (18-85 years). MRI datasets were collected on a 4.7 T system. Participants were administered the Wechsler Memory Scale (WMS-IV) to evaluate episodic memory function. Structural equation modeling was used to test the relationship between studied variables. We found that the volume of the dentate gyrus subfield and posterior hippocampus (body) showed a significant direct effect on visuospatial memory performance; additionally, an indirect effect of age on visuospatial memory mediated through these hippocampal subfield/subregion was significant. Logical and verbal memory were not significantly associated with hippocampal subfield or subregion volumes.
Assuntos
Envelhecimento Cognitivo , Memória Episódica , Humanos , Hipocampo/diagnóstico por imagem , Hipocampo/patologia , Região CA3 Hipocampal , Região CA1 Hipocampal , Imageamento por Ressonância Magnética/métodosRESUMO
The prefrontal cortex (PFC) is a heterogenous structure that is highly susceptible to the effects of aging. Few studies have investigated age effects on the superficial white matter (WM) contained within the PFC using in-vivo magnetic resonance imaging (MRI). This study used diffusion tensor imaging (DTI) tractography to examine the effects of age, sex, and intracranial volume (ICV) on superficial WM within specific PFC subregions, and to model the relationships with age using higher order polynomial regression modelling. PFC WM of 140 healthy individuals, aged 18-85, was segmented into medial and lateral orbitofrontal, medial prefrontal, and dorsolateral prefrontal subregions. Differences due to age in microstructural parameters such as fractional anisotropy (FA), axial and radial diffusivities, and macrostructural measures of tract volumes, fiber counts, average fiber lengths, and average number of fibers per voxel were examined. We found that most prefrontal subregions demonstrated age effects, with decreases in FA, tract volume, and fiber counts, and increases in all diffusivity measures. Age relationships were mostly non-linear, with higher order regressions chosen in most cases. Declines in PFC FA began at the onset of adulthood while the greatest changes in diffusivity and volume did not occur until middle age. The effects of age were most prominent in medial tracts while the lateral orbitofrontal tracts were less affected. Significant effects of sex and ICV were also observed in certain parameters. The patterns mostly followed myelination order, with late-myelinating prefrontal subregions experiencing earlier and more pronounced age effects, further supporting the frontal theory of aging.
Assuntos
Envelhecimento Saudável , Substância Branca , Pessoa de Meia-Idade , Humanos , Adulto , Substância Branca/diagnóstico por imagem , Substância Branca/patologia , Imagem de Tensor de Difusão/métodos , Envelhecimento/patologia , Imagem de Difusão por Ressonância Magnética/métodos , AnisotropiaRESUMO
Introduction: The cingulum bundle and uncinate fasciculus are major limbic white matter tracts involved in emotion, memory, and cognition. The main goal of the present study was to investigate the relationship between age and structural properties of the uncinate fasciculus and the cingulum bundle using diffusion tensor imaging (DTI) tractography in a large cohort of healthy individuals. The second goal was to determine the effects of the catechol-O-methyl transferase (COMT) gene polymorphism on the DTI measurements of these white matter tracts. Methods: We recruited 140 healthy participants (18-85 years old). DTI data sets were acquired on a 1.5T magnetic resonance imaging system. The rostral, dorsal, and parahippocampal cingulum, as well as uncinate fasciculus, were delineated using deterministic tractography. Fractional anisotropy (FA), mean (MD), radial (RD), and axial (AD) diffusivities, tract volume, linear (Cl), planar (Cp), and spherical (Cs) tensor shapes were calculated. The COMT polymorphism (methionine homozygous vs. valine carriers) was determined using single nucleotide polymorphism. Results: We found that age was negatively associated with FA, but positively associated with MD and RD for the rostral cingulum, dorsal cingulum, and the uncinate fasciculus but not for the parahippocampal cingulum. Furthermore, individuals with the COMT methionine homozygous had higher FA and lower MD, RD, AD, and Cs values in the right rostral cingulum compared with the valine carriers across the entire adult life span. Discussion: This study indicates that limbic tracts might be nonuniformly affected by healthy aging, and the methionine homozygous genotype might be associated with micro/macro white matter properties of the right rostral cingulum.
Assuntos
Envelhecimento Cognitivo , Envelhecimento Saudável , Substância Branca , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Encéfalo/patologia , Catecol O-Metiltransferase/genética , Catecóis , Imagem de Tensor de Difusão , Humanos , Metionina , Pessoa de Meia-Idade , Polimorfismo Genético , Valina , Substância Branca/diagnóstico por imagem , Substância Branca/patologia , Adulto JovemRESUMO
Functional changes in the aging human brain have been previously reported using functional magnetic resonance imaging (fMRI). Earlier resting-state fMRI studies revealed an age-associated weakening of intra-system functional connectivity (FC) and age-associated strengthening of inter-system FC. However, the majority of such FC studies did not investigate the relationship between age and network amplitude, without which correlation-based measures of FC can be challenging to interpret. Consequently, the main aim of this study was to investigate how three primary measures of resting-state fMRI signal-network amplitude, network topography, and inter-network FC-are affected by healthy cognitive aging. We acquired resting-state fMRI data on a 4.7 T scanner for 105 healthy participants representing the entire adult lifespan (18-85 years of age). To study age differences in network structure, we combined ICA-based network decomposition with sparse graphical models. Older adults displayed lower blood-oxygen-level-dependent (BOLD) signal amplitude in all functional systems, with sensorimotor networks showing the largest age differences. Our age comparisons of network topography and inter-network FC demonstrated a substantial amount of age invariance in the brain's functional architecture. Despite architecture similarities, old adults displayed a loss of communication efficiency in our inter-network FC comparisons, driven primarily by the FC reduction in frontal and parietal association cortices. Together, our results provide a comprehensive overview of age effects on fMRI-based FC.
Assuntos
Encéfalo , Envelhecimento Cognitivo , Idoso , Encéfalo/diagnóstico por imagem , Mapeamento Encefálico , Humanos , Imageamento por Ressonância Magnética , Vias Neurais/diagnóstico por imagemRESUMO
We examined age-related changes in the cerebral white matter. Structural magnetic resonance images (MRIs) and diffusion tensor images (DTIs) were acquired from 69 healthy subjects aged 22-84 years. Quantitative DTI tractography was performed for nine different white matter tracts to determine tract volume, fractional anisotropy (FA), mean diffusivity (MD), axial, and radial diffusivities. We used automated and manual segmentation to determine volumes of gray matter (GM), white mater (WM), cerebrospinal fluid (CSF), and intracranial space. The results showed significant effects of aging on WM, GM, CSF volumes, and selective effects of aging on structural integrity of different white matter tracts. WM of the prefrontal region was the most vulnerable to aging, while temporal lobe connections, cingulum, and parieto-occipital commissural connections showed relative preservation with age. This study was cross-sectional, and therefore, additional longitudinal studies are needed to confirm our findings.
Assuntos
Envelhecimento/patologia , Encéfalo/patologia , Imagem de Tensor de Difusão/métodos , Fibras Nervosas Mielinizadas/ultraestrutura , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
BACKGROUND: Previous magnetic resonance imaging (MRI) studies of patients with major depressive disorder (MDD) have consistently shown bilateral and unilateral reductions in hippocampal volume relative to healthy controls. Recent structural MRI studies have addressed the question of whether changes in the volume of hippocampal subregions may be associated with MDD. METHODS: We used a comprehensive and reliable 3-dimensional tracing protocol that enables delineation of hippocampal subregions (head, body, tail) to study changes in the hippocampus of patients with MDD. We recruited 39 MDD patients (16 medicated, 23 unmedicated) and 34 healthy age- and sex-matched controls. We acquired images using a magnetization-prepared rapid acquisition gradient echo sequence on a 1.5-T scanner with a spatial resolution of 1.5 mm x 0.5 mm x 0.5 mm. We performed volumetric analyses, blinded to diagnosis, using the interactive software package Display. All volumes were adjusted for intracranial volume. RESULTS: We found a significant reduction in the volume of the hippocampal tail bilaterally, right hippocampal head and right total hippocampus in MDD patients. Medicated MDD patients showed increased hippocampal body volume compared with both healthy controls and unmedicated patients. LIMITATIONS: This study was cross-sectional. Further prospective studies are needed to determine the direct effect of antidepressant treatment. CONCLUSION: Our results suggest that decreased hippocampal tail and hippocampal head volumes could be trait changes, whereas hippocampal body changes may be dependent on treatment. We showed that long-term antidepressant treatment may affect hippocampal volume in patients with MDD.