| 1. |
- Anders, Silke, et al.
(författare)
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When seeing outweighs feeling : a role for prefrontal cortex in passive control of negative affect in blindsight
- 2009
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Ingår i: Brain. - Oxford : Oxford University Press. - 0006-8950 .- 1460-2156. ; 132:11, s. 3021-3031
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Tidskriftsartikel (refereegranskat)abstract
- Affective neuroscience has been strongly influenced by the viewthat a ‘feeling’ is the perception of somatic changesand has consequently often neglected the neural mechanisms thatunderlie the integration of somatic and other information inaffective experience. Here, we investigate affective processingby means of functional magnetic resonance imaging in nine corticallyblind patients. In these patients, unilateral postgeniculatelesions prevent primary cortical visual processing in part ofthe visual field which, as a result, becomes subjectively blind.Residual subcortical processing of visual information, however,is assumed to occur in the entire visual field. As we have reportedearlier, these patients show significant startle reflex potentiationwhen a threat-related visual stimulus is shown in their blindvisual field. Critically, this was associated with an increaseof brain activity in somatosensory-related areas, and an increasein experienced negative affect. Here, we investigated the patients’response when the visual stimulus was shown in the sighted visualfield, that is, when it was visible and cortically processed.Despite the fact that startle reflex potentiation was similarin the blind and sighted visual field, patients reported significantlyless negative affect during stimulation of the sighted visualfield. In other words, when the visual stimulus was visibleand received full cortical processing, the patients’ phenomenalexperience of affect did not closely reflect somatic changes.This decoupling of phenomenal affective experience and somaticchanges was associated with an increase of activity in the leftventrolateral prefrontal cortex and a decrease of affect-relatedsomatosensory activity. Moreover, patients who showed strongerleft ventrolateral prefrontal cortex activity tended to showa stronger decrease of affect-related somatosensory activity.Our findings show that similar affective somatic changes canbe associated with different phenomenal experiences of affect,depending on the depth of cortical processing. They are in linewith a model in which the left ventrolateral prefrontal cortexis a relay station that integrates information about subcorticallytriggered somatic responses and information resulting from in-depthcortical stimulus processing. Tentatively, we suggest that theobserved decoupling of somatic responses and experienced affect,and the reduction of negative phenomenal experience, can beexplained by a left ventrolateral prefrontal cortex-mediatedinhibition of affect-related somatosensory activity.
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| 2. |
- Engler, Henry, et al.
(författare)
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Two-year follow-up of amyloid deposition in patients with Alzheimer's disease
- 2006
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Ingår i: Brain. - : Oxford University Press (OUP). - 0006-8950 .- 1460-2156. ; 129:Pt 11, s. 2856-2866
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Tidskriftsartikel (refereegranskat)abstract
- Beta amyloid is one of the major histopathological hallmarks of Alzheimer's disease. We recently reported in vivo imaging of amyloid in 16 Alzheimer patients, using the PET ligand N-methyl[11C]2-(4'-methylaminophenyl)-6-hydroxy-benzothiazole (PIB). In the present study we rescanned these 16 Alzheimer patients after 2.0 +/- 0.5 years and have described the interval change in amyloid deposition and regional cerebral metabolic rate for glucose (rCMRGlc) at follow-up. Sixteen patients with Alzheimer's disease were re-examined by means of PET, using PIB and 2-[18F]fluoro-2-deoxy-d-glucose (FDG) after 2.0 +/- 0.5 years. The patients were all on cholinesterase inhibitor treatment and five also on treatment with the N-methyl-d-aspartate (NMDA) antagonist memantine. In order to estimate the accuracy of the PET PIB measurements, four additional Alzheimer patients underwent repeated examinations with PIB within 20 days (test-retest). Relative PIB retention in cortical regions differed by 3-7% in the test-retest study. No significant difference in PIB retention was observed between baseline and follow-up while a significant (P < 0.01) 20% decrease in rCMRGlc was observed in cortical brain regions. A significant negative correlation between rCMRGlc and PIB retention was observed in the parietal cortex in the Alzheimer patients at follow-up (r = 0.67, P = 0.009). A non-significant decline in Mini-Mental State Examination (MMSE) score from 24.3 +/- 3.7 (mean +/- standard deviation) to 22.7 +/- 6.1 was measured at follow-up. Five of the Alzheimer patients showed a significant decline in MMSE score of >3 (21.4 +/- 3.5 to 15.6 +/- 3.9, P < 0.01) (AD-progressive) while the rest of the patients were cognitively more stable (MMSE score = 25.6 +/- 3.1 to 25.9 +/- 3.7) (AD-stable) compared with baseline. A positive correlation (P = 0.001) was observed in the parietal cortex between Rey Auditory Verbal Learning (RAVL) test score and rCMRGlc at follow-up while a negative correlation (P = 0.018) was observed between RAVL test and PIB retention in the parietal at follow-up. Relatively stable PIB retention after 2 years of follow-up in patients with mild Alzheimer's disease suggests that amyloid deposition in the brain reaches a plateau by the early clinical stages of Alzheimer's disease and therefore may precede a decline in rCMRGlc and cognition. It appears that anti-amyloid therapies will need to induce a significant decrease in amyloid load in order for PIB PET images to detect a drug effect in Alzheimer patients. FDG imaging may be able to detect a stabilization of cerebral metabolism caused by therapy administered to patients with a clinical diagnosis of Alzheimer's disease.
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| 3. |
- Hooshmand, Babak, et al.
(författare)
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Plasma homocysteine, Alzheimer and cerebrovascular pathology : a population-based autopsy study
- 2013
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Ingår i: Brain. - : Oxford University Press (OUP). - 0006-8950 .- 1460-2156. ; 136, s. 2707-2716
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Tidskriftsartikel (refereegranskat)abstract
- Elevated plasma total homocysteine is associated with increased risk of dementia/Alzheimer's disease, but underlying pathophysiological mechanisms are not fully understood. This study investigated possible links between baseline homocysteine, and post-mortem neuropathological and magnetic resonance imaging findings up to 10 years later in the Vantaa 85+ population including people aged epsilon 85 years. Two hundred and sixty-five individuals had homocysteine and autopsy data, of which 103 had post-mortem brain magnetic resonance imaging scans. Methenamine silver staining was used for amyloid-beta and modified Bielschowsky method for neurofibrillary tangles and neuritic plaques. Macroscopic infarcts were identified from cerebral hemispheres, brainstem and cerebellum slices. Standardized methods were used to determine microscopic infarcts, cerebral amyoloid angiopathy, and alpha-synuclein pathology. Magnetic resonance imaging was used for visual ratings of the degree of medial temporal lobe atrophy, and periventricular and deep white matter hyperintensities. Elevated baseline homocysteine was associated with increased neurofibrillary tangles count at the time of death: for the highest homocysteine quartile, odds ratio (95% confidence interval) was 2.60 (1.28-5.28). The association was observed particularly in people with dementia, in the presence of cerebral infarcts, and with longer time between the baseline homocysteine assessment and death. Also, elevated homocysteine tended to relate to amyloid-beta accumulation, but this was seen only with longer baseline-death interval: odds ratio (95% confidence interval) was 2.52 (0.88-7.19) for the highest homocysteine quartile. On post-mortem magnetic resonance imaging, for the highest homocysteine quartile odds ratio (95% confidence interval) was 3.78 (1.12-12.79) for more severe medial temporal atrophy and 4.69 (1.14-19.33) for more severe periventricular white matter hyperintensities. All associations were independent of several potential confounders, including common vascular risk factors. No relationships between homocysteine and cerebral macro- or microinfarcts, cerebral amyoloid angiopathy or alpha-synuclein pathology were detected. These results suggest that elevated homocysteine in adults aged epsilon 85 years may contribute to increased Alzheimer-type pathology, particularly neurofibrillary tangles burden. This effect seems to be more pronounced in the presence of cerebrovascular pathology. Randomized controlled trials are needed to determine the impact of homocysteine-lowering treatments on dementia-related pathology.
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| 4. |
- Kadir, Ahmadul, et al.
(författare)
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Positron emission tomography imaging and clinical progression in relation to molecular pathology in the first Pittsburgh Compound B positron emission tomography patient with Alzheimer’s disease
- 2011
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Ingår i: Brain. - : Oxford University Press (OUP). - 0006-8950 .- 1460-2156. ; 134:1, s. 301-317
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Tidskriftsartikel (refereegranskat)abstract
- The accumulation of β-amyloid in the brain is an early event in Alzheimer’s disease. This study presents the first patient with Alzheimer’s disease who underwent positron emission tomography imaging with the amyloid tracer, Pittsburgh Compound B to visualize fibrillar β-amyloid in the brain. Here we relate the clinical progression, amyloid and functional brain positron emission tomography imaging with molecular neuropathological alterations at autopsy to gain new insight into the relationship between β-amyloid accumulation, inflammatory processes and the cholinergic neurotransmitter system in Alzheimer’s disease brain. The patient underwent positron emission tomography studies with 18F-fluorodeoxyglucose three times (at ages 53, 56 and 58 years) and twice with Pittsburgh Compound B (at ages 56 and 58 years), prior to death at 61 years of age. The patient showed a pronounced decline in cerebral glucose metabolism and cognition during disease progression, while Pittsburgh Compound B retention remained high and stable at follow-up. Neuropathological examination of the brain at autopsy confirmed the clinical diagnosis of pure Alzheimer’s disease. A comprehensive neuropathological investigation was performed in nine brain regions to measure the regional distribution of β-amyloid, neurofibrillary tangles and the levels of binding of 3H-nicotine and 125I-α-bungarotoxin to neuronal nicotinic acetylcholine receptor subtypes, 3H-L-deprenyl to activated astrocytes and 3H-PK11195 to microglia, as well as butyrylcholinesterase activity. Regional in vivo 11C-Pittsburgh Compound B-positron emission tomography retention positively correlated with 3H-Pittsburgh Compound B binding, total insoluble β-amyloid, and β-amyloid plaque distribution, but not with the number of neurofibrillary tangles measured at autopsy. There was a negative correlation between regional fibrillar β-amyloid and levels of 3H-nicotine binding. In addition, a positive correlation was found between regional 11C-Pittsburgh Compound B positron emission tomography retention and 3H-Pittsburgh Compound B binding with the number of glial fibrillary acidic protein immunoreactive cells, but not with 3H-L-deprenyl and 3H-PK-11195 binding. In summary, high 11C-Pittsburgh Compound B positron emission tomography retention significantly correlates with both fibrillar β-amyloid and losses of neuronal nicotinic acetylcholine receptor subtypes at autopsy, suggesting a closer involvement of β-amyloid pathology with neuronal nicotinic acetylcholine receptor subtypes than with inflammatory processes.
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| 5. |
- Lind, Johanna, et al.
(författare)
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Reduced functional brain activity response in cognitively intact apolipoprotein E ε4 carriers
- 2006
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Ingår i: Brain. - : Oxford University Press. - 0006-8950 .- 1460-2156. ; 129:5, s. 1240-1248
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Tidskriftsartikel (refereegranskat)abstract
- The apolipoprotein E epsilon4 (APOE epsilon4) is the main known genetic risk factor for Alzheimer's disease. Genetic assessments in combination with other diagnostic tools, such as neuroimaging, have the potential to facilitate early diagnosis. In this large-scale functional MRI (fMRI) study, we have contrasted 30 APOE epsilon4 carriers (age range: 49-74 years; 19 females), of which 10 were homozygous for the epsilon4 allele, and 30 non-carriers with regard to brain activity during a semantic categorization task. Test groups were closely matched for sex, age and education. Critically, both groups were cognitively intact and thus symptom-free of Alzheimer's disease. APOE epsilon4 carriers showed reduced task-related responses in the left inferior parietal cortex, and bilaterally in the anterior cingulate region. A dose-related response was observed in the parietal area such that diminution was most pronounced in homozygous compared with heterozygous carriers. In addition, contrasts of processing novel versus familiar items revealed an abnormal response in the right hippocampus in the APOE epsilon4 group, mainly expressed as diminished sensitivity to the relative novelty of stimuli. Collectively, these findings indicate that genetic risk translates into reduced functional brain activity, in regions pertinent to Alzheimer's disease, well before alterations can be detected at the behavioural level.
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| 6. |
- Marklund, Petter, 1968-, et al.
(författare)
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Temporal dynamics of basal ganglia under-recruitment in Parkinson's disease : transient caudate abnormalities during updating of working memory
- 2009
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Ingår i: Brain. - : Oxford University Press (OUP). - 0006-8950 .- 1460-2156. ; 132:2, s. 336-346
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Tidskriftsartikel (refereegranskat)abstract
- Using hybrid-blocked/event-related fMRI and the 2-back taskwe aimed to decompose tonic and phasic temporal dynamics ofbasal ganglia response abnormalities in working memory associatedwith early untreated Parkinson's disease. In view of the tonic/phasicdopamine hypothesis, which posits a functional division betweenphasic D2-dependent striatal updating processes and tonic D1-dependentprefrontal context-maintenance processes, we predicted thatnewly diagnosed, drug-naïve Parkinson's disease patients,with selective striatal dopamine deprivation, would demonstratetransient rather than sustained activation changes in the basalganglia during 2-back performance. Task-related activation patternswithin discrete basal ganglia structures were directly comparedbetween patients and healthy elderly controls. The obtainedresults yielded uniquely transient underactivation foci in caudatenuclei, putamen and globus pallidus in Parkinson's disease patients,which indicates suboptimal phasic implementation of striatalD2-dependent gating mechanisms during updating. Sustained underactivationwas only seen in the anterior putamen, which may reflect initialsigns of tonic control impairment. No significant changes wereexhibited in prefrontal cortex. The present findings resonatewell with the tonic/phasic dopamine account and suggest thatbasal ganglia under-recruitment associated with executive dysfunctionin early Parkinson's disease might predominantly stem from deficienciesin phasic executive components subserved by striatum.
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| 7. |
- Olofsson, Jonas K., et al.
(författare)
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A cortical pathway to olfactory naming : evidence from primary progressive aphasia
- 2013
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Ingår i: Brain. - : Oxford University Press (OUP). - 0006-8950 .- 1460-2156. ; 136, s. 1245-1259
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Tidskriftsartikel (refereegranskat)abstract
- It is notoriously difficult to name odours. Without the benefit of non-olfactory information, even common household smells elude our ability to name them. The neuroscientific basis for this olfactory language 'deficit' is poorly understood, and even basic models to explain how odour inputs gain access to transmodal representations required for naming have not been put forward. This study used patients with primary progressive aphasia, a clinical dementia syndrome characterized by primary deficits in language, to investigate the interactions between olfactory inputs and lexical access by assessing behavioural performance of olfactory knowledge and its relationship to brain atrophy. We specifically hypothesized that the temporal pole would play a key role in linking odour object representations to transmodal networks, given its anatomical proximity to olfactory and visual object processing areas. Behaviourally, patients with primary progressive aphasia with non-semantic subtypes were severely impaired on an odour naming task, in comparison with an age-matched control group. However, with the availability of picture cues or word cues, odour matching performance approached control levels, demonstrating an inability to retrieve but not to recognize the name and nature of the odorant. The magnitude of cortical thinning in the temporal pole was found to correlate with reductions in odour familiarity and odour matching to visual cues, whereas the inferior frontal gyrus correlated with both odour naming and matching. Volumetric changes in the mediodorsal thalamus correlated with the proportion of categorical mismatch errors, indicating a possible role of this region in error-signal monitoring to optimize recognition of associations linked to the odour. A complementary analysis of patients with the semantic subtype of primary progressive aphasia, which is associated with marked temporopolar atrophy, revealed much more pronounced impairments of odour naming and matching. In identifying the critical role of the temporal pole and inferior frontal gyrus in transmodal linking and verbalization of olfactory objects, our findings provide a new neurobiological foundation for understanding why even common odours are hard to name.
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| 8. |
- Rodriguez-Vieitez, Elena, et al.
(författare)
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Diverging longitudinal changes in astrocytosis and amyloid PET in autosomal dominant Alzheimer's disease
- 2016
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Ingår i: Brain. - : Oxford University Press (OUP). - 0006-8950 .- 1460-2156. ; 139:3, s. 922-936
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Tidskriftsartikel (refereegranskat)abstract
- The relationships between pathophysiological processes in Alzheimer's disease remain largely unclear. In a longitudinal, multitracer PET study, Rodriguez-Vieitez et al. reveal that progression of autosomal dominant Alzheimer's disease is accompanied by prominent early and then declining astrocytosis, increasing amyloid plaque deposition and decreasing glucose metabolism. Astrocyte activation may initiate Alzheimer pathology.See Schott and Fox (doi: 10.1093/brain/awv405) for a scientific commentary on this article. The relationships between pathophysiological processes in Alzheimer's disease remain largely unclear. In a longitudinal, multitracer PET study, Rodriguez-Vieitez et al. reveal that progression of autosomal dominant Alzheimer's disease is accompanied by prominent early and then declining astrocytosis, increasing amyloid plaque deposition and decreasing glucose metabolism. Astrocyte activation may initiate Alzheimer pathology.Alzheimer's disease is a multifactorial dementia disorder characterized by early amyloid-beta, tau deposition, glial activation and neurodegeneration, where the interrelationships between the different pathophysiological events are not yet well characterized. In this study, longitudinal multitracer positron emission tomography imaging of individuals with autosomal dominant or sporadic Alzheimer's disease was used to quantify the changes in regional distribution of brain astrocytosis (tracer C-11-deuterium-L-deprenyl), fibrillar amyloid-beta plaque deposition (C-11-Pittsburgh compound B), and glucose metabolism (F-18-fluorodeoxyglucose) from early presymptomatic stages over an extended period to clinical symptoms. The 52 baseline participants comprised autosomal dominant Alzheimer's disease mutation carriers (n = 11; 49.6 +/- 10.3 years old) and non-carriers (n = 16; 51.1 +/- 14.2 years old; 10 male), and patients with sporadic mild cognitive impairment (n = 17; 61.9 +/- 6.4 years old; nine male) and sporadic Alzheimer's disease (n = 8; 63.0 +/- 6.5 years old; five male); for confidentiality reasons, the gender of mutation carriers is not revealed. The autosomal dominant Alzheimer's disease participants belonged to families with known mutations in either presenilin 1 (PSEN1) or amyloid precursor protein (APPswe or APParc) genes. Sporadic mild cognitive impairment patients were further divided into C-11-Pittsburgh compound B-positive (n = 13; 62.0 +/- 6.4; seven male) and C-11-Pittsburgh compound B-negative (n = 4; 61.8 +/- 7.5 years old; two male) groups using a neocortical standardized uptake value ratio cut-off value of 1.41, which was calculated with respect to the cerebellar grey matter. All baseline participants underwent multitracer positron emission tomography scans, cerebrospinal fluid biomarker analysis and neuropsychological assessment. Twenty-six of the participants underwent clinical and imaging follow-up examinations after 2.8 +/- 0.6 years. By using linear mixed-effects models, fibrillar amyloid-beta plaque deposition was first observed in the striatum of presymptomatic autosomal dominant Alzheimer's disease carriers from 17 years before expected symptom onset; at about the same time, astrocytosis was significantly elevated and then steadily declined. Diverging from the astrocytosis pattern, amyloid-beta plaque deposition increased with disease progression. Glucose metabolism steadily declined from 10 years after initial amyloid-beta plaque deposition. Patients with sporadic mild cognitive impairment who were C-11-Pittsburgh compound B-positive at baseline showed increasing amyloid-beta plaque deposition and decreasing glucose metabolism but, in contrast to autosomal dominant Alzheimer's disease carriers, there was no significant longitudinal decline in astrocytosis over time. The prominent initially high and then declining astrocytosis in autosomal dominant Alzheimer's disease carriers, contrasting with the increasing amyloid-beta plaque load during disease progression, suggests astrocyte activation is implicated in the early stages of Alzheimer's disease pathology.
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| 9. |
- Skouras, Stavros, et al.
(författare)
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Earliest amyloid and tau deposition modulate the influence of limbic networks during closed-loop hippocampal downregulation
- 2020
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Ingår i: Brain. - : Oxford University Press (OUP). - 0006-8950 .- 1460-2156. ; 143, s. 976-992
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Tidskriftsartikel (refereegranskat)abstract
- Research into hippocampal self-regulation abilities may help determine the clinical significance of hippocampal hyperactivity throughout the pathophysiological continuum of Alzheimer's disease. In this study, we aimed to identify the effects of amyloid-ii peptide 42 (amyloid-beta(42)) and phosphorylated tau on the patterns of functional connectomics involved in hippocampal downregulation. We identified 48 cognitively unimpaired participants (22 with elevated CSF amyloid-beta peptide 42 levels, 15 with elevated CSF phosphorylated tau levels, mean age of 62.705 +/- 4.628 years), from the population-based 'Alzheimer's and Families' study, with baseline MRI, CSF biomarkers, APOE genotyping and neuropsychological evaluation. We developed a closed-loop, real-time functional MRI neurofeedback task with virtual reality and tailored it for training downregulation of hippocampal subfield cornu ammonis 1 (CA1). Neurofeedback performance score, cognitive reserve score, hippocampal volume, number of apolipoprotein epsilon 4 alleles and sex were controlled for as confounds in all cross-sectional analyses. First, using voxel-wise multiple regression analysis and controlling for CSF biomarkers, we identified the effect of healthy ageing on eigenvector centrality, a measure of each voxel's overall influence based on iterative whole-brain connectomics, during hippocampal CAl downregulation. Then, controlling for age, we identified the effects of abnormal CSF amyloid-beta(42) and phosphorylated tau levels on eigenvector centrality during hippocampal CAl downregulation. Across subjects, our main findings during hippocampal downregulation were: (i) in the absence of abnormal biomarkers, age correlated with eigenvector centrality negatively in the insula and midcingulate cortex, and positively in the inferior temporal gyrus; (ii) abnormal CSF amyloid-beta(42) (<1098) correlated negatively with eigenvector centrality in the anterior cingulate cortex and primary motor cortex; and (iii) abnormal CSF phosphorylated tau levels (>19.2) correlated with eigenvector centrality positively in the ventral striatum, anterior cingulate and somatosensory cortex, and negatively in the precuneus and orbitofrontal cortex. During resting state functional MRI, similar eigenvector centrality patterns in the cingulate had previously been associated to CSF biomarkers in mild cognitive impairment and dementia patients. Using the developed closed-loop paradigm, we observed such patterns, which are characteristic of advanced disease stages, during a much earlier presymptomatic phase. In the absence of CSF biomarkers, our non-invasive, interactive, adaptive and gamified neuroimaging procedure may provide important information for clinical prognosis and monitoring of therapeutic efficacy. We have released the developed paradigm and analysis pipeline as open-source software to facilitate replication studies.
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