Biomedical subjects

Tuomo Hänninen

Publications and source records attributed to Tuomo Hänninen.

13 recordsLinked to original sources

PubMed2006

MRI of hippocampus and entorhinal cortex in mild cognitive impairment: a follow-up study.

The concept of mild cognitive impairment (MCI) has been proposed to represent a transitional stage between normal aging and dementia. We studied the predictive value of the MRI-derived volumes of medial temporal lobe (MTL) structures, white matter lesions (WML), neuropsychological tests, and Apolipoprotein E (APOE) genotype on conversion of MCI to dementia and AD. The study included 60 subjects with MCI identified from population cohorts. During the mean follow-up period of 34 months, 13 patients had progressed to dementia (9 to Alzheimer's disease (AD)). In Cox regression analysis the baseline volumes of the right hippocampus, the right entorhinal cortex and CDR sum of boxes predicted the progression of MCI to dementia during the follow-up. In a bivariate analysis, only the baseline volumes of entorhinal cortex predicted conversion of MCI to AD. The Mini-Mental State Examination (MMSE) score at baseline, WML load, or APOE genotype were not significant predictors of progression. The MTL volumetry helps in identifying among the MCI subjects a group, which is at high risk for developing AD.

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PubMed2006

Increased fMRI responses during encoding in mild cognitive impairment.

Structural and functional magnetic resonance imaging (fMRI) was performed on 21 healthy elderly controls, 14 subjects with mild cognitive impairment (MCI) and 15 patients with mild Alzheimer's disease (AD) to investigate changes in fMRI activation in relation to underlying structural atrophy. The fMRI paradigm consisted of associative encoding of novel picture-word pairs. Structural analysis of the brain was performed using voxel-based morphometry (VBM) and hippocampal volumetry. Compared to controls, the MCI subjects exhibited increased fMRI responses in the posterior hippocampal, parahippocampal and fusiform regions, while VBM revealed more atrophy in MCI in the anterior parts of the left hippocampus. Furthermore, the hippocampal volume and parahippocampal activation were negatively correlated in MCI, but not in controls or in AD. We suggest that the increased fMRI activation in MCI in the posterior medial temporal and closely connected fusiform regions is compensatory due to the incipient atrophy in the anterior medial temporal lobe.

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PubMed2006

The effect of apolipoprotein polymorphism on brain in mild cognitive impairment: a voxel-based morphometric study.

We investigated the effect of apolipoprotein E (ApoE) on the whole brain in 51 individuals with mild cognitive impairment using voxel-based morphometry. Between cases heterozygous for the ApoE epsilon4 (n = 15) and those who were ApoE epsilon4 noncarriers (n = 28), only the right parahippocampal gyrus, with the entorhinal cortex included, reached the level of statistical significance. In cases homozygous for the epsilon4 allele (n = 8) versus noncarriers, the greatest atrophy was located in the right amygdala followed by the right parahippocampal gyrus, the left amygdala and the left medial dorsal thalamic nucleus.

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PubMed2005

Genetic analysis of BDNF and TrkB gene polymorphisms in Alzheimer's disease.

According to previous biochemical and genetic findings, brain-derived neurotrophic factor (BDNF), via activation of its tyrosine kinase receptor B (TrkB), is considered as a plausible candidate for contributing to Alzheimer's disease (AD). To examine the genetic association of BDNF and TrkB genes with AD, we genotyped multiple single nucleotide polymorphisms (SNPs) within these genes among 375 Finnish AD patients and 460 control subjects. Single locus and multi-loci haplotype association analyses of BDNF and TrkB gene SNPs did not reveal significant differences between unstratified AD and control groups. In the case of BDNF SNPs, different allele and haplotype frequencies were observed when 160 sporadic AD cases were compared with 460 control subjects. However, these differences did not remain statistically significant after multiple corrections. We conclude that BDNF and TrkB genes are not contributing significant risk effect among Finnish AD patients.

Adult↗

PubMed2005

Estrogen receptor beta gene variants are associated with increased risk of Alzheimer's disease in women.

We investigated the association of five intronic single-nucleotide polymorphism (SNP) at the estrogen receptor beta (ESR2) gene locus and the susceptibility of developing Alzheimer's disease (AD) in 387 subjects with clinically diagnosed probable AD and 467 cognitively normal individuals derived from eastern Finland. According to our results, variation in the ESR2 gene is associated with an increased risk of AD in women, whereas it does not contribute to the disease susceptibility in men. More specifically, in women, the allele T and the genotype T/T of two of the studied ESR2 gene SNPs (SNP2 and SNP3) were more frequent in AD women than in cognitively normal control women (P=0.012 and P=0.016, respectively). The ESR2 SNP2 T/T genotype and the SNP3 T/T genotype were associated with a significant, nearly two-fold increase in the risk of AD in women (OR=1.87, 95% CI=1.21-2.90), and remained significant after adjustment with the APOE genotype and age (OR=1.63, 95% CI, 1.00-1.68). The combined effect of the ESR2 SNP2 T/T or SNP3 T/T genotype and female gender increases the risk of the disease (OR=3.2, 95% CI=1.3-7.7). Consistent with these results, also the frequency of the haplotype containing the two above ESR2 gene risk alleles was elevated in AD women (P=0.027, OR=1.3, 95% CI=1.02-1.65). Results show that variation in ESR2 gene may be linked with increased AD susceptibility and furthermore, this association is gender specific.

Age of Onset↗

PubMed2005

Distinct and overlapping fMRI activation networks for processing of novel identities and locations of objects.

The ventral visual stream processes information about the identity of objects ('what'), whereas the dorsal stream processes the spatial locations of objects ('where'). There is a corresponding, although disputed, distinction for the ventrolateral and dorsolateral prefrontal areas. Furthermore, there seems to be a distinction between the anterior and posterior medial temporal lobe (MTL) structures in the processing of novel items and new spatial arrangements, respectively. Functional differentiation of the intermediary mid-line cortical and temporal neocortical structures that communicate with the occipitotemporal, occipitoparietal, prefrontal, and MTL structures, however, is unclear. Therefore, in the present functional magnetic resonance imaging (fMRI) study, we examined whether the distinction among the MTL structures extends to these closely connected cortical areas. The most striking difference in the fMRI responses during visual presentation of changes in either items or their locations was the bilateral activation of the temporal lobe and ventrolateral prefrontal cortical areas for novel object identification in contrast to wide parietal and dorsolateral prefrontal activation for the novel locations of objects. An anterior-posterior distinction of fMRI responses similar to the MTL was observed in the cingulate/retrosplenial, and superior and middle temporal cortices. In addition to the distinct areas of activation, certain frontal, parietal, and temporo-occipital areas responded to both object and spatial novelty, suggesting a common attentional network for both types of changes in the visual environment. These findings offer new insights to the functional roles and intrinsic specialization of the cingulate/retrosplenial, and lateral temporal cortical areas in visuospatial cognition.

Adult↗

PubMed2004

Incidence and risk factors for mild cognitive impairment: a population-based three-year follow-up study of cognitively healthy elderly subjects.

BACKGROUND: Mild cognitive impairment (MCI) has attracted considerable interest as a potential predictor of Alzheimer's disease (AD). Both the apolipoprotein E (ApoE) epsilon4 allele and vascular factors have been associated with a higher risk for AD, recently they have also been linked to the risk of MCI. OBJECTIVES: To estimate the incidence of MCI among cognitively healthy elderly subjects during a 3-year follow-up, and to evaluate the impact of demographic and vascular factors as well as the ApoE epsilon4 allele on the conversion to MCI. METHODS: At baseline, the cognitive abilities of 806 out of 1,150 eligible subjects (aged 60-76 years) from a population-based sample were examined. Cognitively intact subjects (n = 747) were followed for an average of 3 years. RESULTS: 66 subjects (8.8%) had converted to MCI. The global incidence rate of MCI was 25.94/1,000 person-years. Persons with higher age (OR 1.08, 95% CI 1.01-1.16), ApoE epsilon4 allele carriers (OR 2.04, 95% CI 1.15-3.64) and persons with medicated hypertension (OR 1.86, 95% CI 1.05-3.29) were more likely to convert to MCI than those individuals of lower age and without an ApoE epsilon4 allele or medicated hypertension. Persons with high education (OR 0.79, 95% CI 0.70-0.89) were less likely to convert to MCI than persons with low or no education. In subjects with both the ApoE epsilon4 allele and medicated hypertension, the crude OR for conversion was 3.92 (95% CI 1.81-8.49). In subjects with cardiovascular disease, the crude OR for conversion was 2.13 (95% CI 1.26-3.60). Gender, elevated blood pressure, diabetes or cerebrovascular disease had no significant effect on the conversion to MCI. CONCLUSION: Higher age, the presence of at least one ApoE epsilon4 allele and medicated hypertension are independent risk factors, but high education is a protective factor for MCI. The results suggest that vascular factors may have an important role in the pathogenesis of MCI.

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PubMed2004

Hippocampus and entorhinal cortex in mild cognitive impairment and early AD.

Magnetic resonance imaging (MRI) has been suggested as a useful tool in early diagnosis of Alzheimer's disease (AD). Based on MRI-derived volumes, we studied the hippocampus and entorhinal cortex (ERC) in 59 controls, 65 individuals with mild cognitive impairment (MCI) and 48 patients with AD. The controls and individuals with MCI were derived from population-based cohorts. Volumes of the hippocampus and ERC were significantly reduced in the following order: control > MCI > AD. Stepwise discriminant function analysis showed that the most efficient overall classification between controls and individuals with MCI subjects was achieved with ERC measurements (65.9%). However, the best overall classification between controls and AD patients (90.7%), and between individuals with MCI and AD patients (82.3%) was achieved with hippocampal volumes. Our results suggest that the ERC atrophy precedes hippocampal atrophy in AD. The ERC volume loss is dominant over the hippocampal volume loss in MCI, whereas more pronounced hippocampal volume loss appears in mild AD.

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PubMed2004

Visual presentation of novel objects and new spatial arrangements of objects differentially activates the medial temporal lobe subareas in humans.

A number of studies in rodents and monkeys report a distinction between the contributions of the hippocampus and perirhinal cortex to memory, such that the hippocampus is crucial for spatial memory whereas the perirhinal cortex has a pivotal role in perception and memory for visual objects. To determine if there is such a distinction in humans, we conducted a functional magnetic resonance imaging study to compare the medial temporal lobe responses to changes in object identity and spatial configurations of objects. We found evidence for the predicted distinction between hippocampal and perirhinal cortical activations, although part of the hippocampus was also activated by identification of novel objects. Additionally, an anterior-posterior activation gradient emerged inside the hippocampus and parahippocampal cortex. The anterior hippocampus, perirhinal cortex and anterior parahippocampal cortex are involved in perception of contextually novel objects, whereas the posterior hippocampus and posterior parahippocampal cortex are involved in processing of novel arrangements of familiar objects. These results demonstrate that there is a functional dissociation between processing of novel object identities and new spatial locations of objects among the subregions of medial temporal lobe structures in humans also.

Adult↗

PubMed2003

Encoding of novel picture pairs activates the perirhinal cortex: an fMRI study.

It is well established in nonhuman primates that the medial temporal lobe (MTL) structures, the hippocampus and the entorhinal and perirhinal cortices, are necessary for declarative memory encoding. In humans, the neuropathological and neuropsychological changes in early Alzheimer's disease (AD) further support a role for the rhinal cortex in the consolidation of new events into long-term memory. Little is known, however, regarding the function of the rhinal cortex in humans in vivo. To examine the participation of the interconnected MTL structures as well as the whole-brain network of activated brain areas in visual associative long-term memory, functional magnetic resonance imaging (fMRI) was used to determine the brain regions that are activated during encoding and retrieval of paired pictures in 12 young control subjects. The most striking finding in the MTL activation pattern was the consistent activation of the perirhinal cortex in the encoding-baseline and encoding-retrieval comparisons with a strict statistical threshold (P < 0.00001). In contrast, no perirhinal cortex activation was detected in the retrieval-baseline or retrieval-encoding comparisons even with a low statistical threshold (P < 0.05). The location of the perirhinal activation area was in the transentorhinal part of the perirhinal cortex, in the medial bank of the collateral sulcus. The hippocampus and the more posterior parahippocampal gyrus were activated in both encoding and retrieval conditions. During the encoding processing, MTL activations were more consistent and the hippocampal activation area located more anteriorly than during retrieval. The frontal, parietal, temporal, and occipital association cortices were also activated in the encoding-baseline and retrieval-baseline comparisons. The data suggest that encoding, but not retrieval, of novel picture pairs activates the perirhinal cortex. To our knowledge, this is the first fMRI study reporting encoding activation in this transentorhinal part of the perirhinal cortex, the site of the very earliest neuropathological changes in AD.

Adult↗

PubMed2003

Assessment of executive function in clinical trials.

Cerebrovascular disease and stroke are related to high risk of cognitive impairment. One of the main neuropsychological features in vascular cognitive impairment and vascular dementia is executive dysfunction. Definition of the essential subcomponents and concepts of executive function is important before determining the methodology in clinical trials. The scientific research and new methods on this topic are rapidly growing. We present some most commonly used neuropsychological tests and discuss the methodological aspects in light of clinical trials.

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PubMed2002

Apolipoprotein E epsilon4 allele, elevated midlife total cholesterol level, and high midlife systolic blood pressure are independent risk factors for late-life Alzheimer disease.

BACKGROUND: Presence of the apolipoprotein E (apoE) epsilon4 allele, which is involved in cholesterol metabolism, is the most important genetic risk factor for Alzheimer disease. Elevated midlife values for total cholesterol level and blood pressure have been implicated recently as risk factors for Alzheimer disease. OBJECTIVE: To study the relative importance and the putative relationship among the apoE epsilon4 allele, midlife total cholesterol level, and midlife blood pressure as risk factors for late-life Alzheimer disease. DESIGN: Prospective population-based study. SETTING: Kuopio and Joensuu, eastern Finland. PARTICIPANTS: Participants were derived from random population surveys from 1972, 1977, 1982, and 1987. A total of 1449 persons (73%), 65 to 79 years of age, participated in the reexamination in 1998 (mean follow-up, 21 years). MEASUREMENTS: Midlife blood pressure and total cholesterol level, apoE genotype, and development of Alzheimer disease during follow-up. RESULTS: The apoE epsilon4 allele was an independent risk factor for Alzheimer disease, even after adjustment for midlife vascular risk factors and other confounders (odds ratio, 2.1 [95% CI, 1.1 to 4.1]). Similarly, elevated midlife values for serum total cholesterol level (odds ratio, 2.8 [CI, 1.2 to 6.7]) and systolic blood pressure (odds ratio, 2.6 [CI, 1.1 to 6.6]) were independent risk factors for Alzheimer disease, even after adjustment for apoE genotype and other confounding factors. CONCLUSIONS: The association between the apoE epsilon4 allele and Alzheimer disease does not seem to be mediated by vascular factors. The apoE epsilon4 allele, elevated midlife total cholesterol level, and high midlife systolic blood pressure are independent risk factors for Alzheimer disease. The risk for Alzheimer disease from treatable factors--elevated total cholesterol level and blood pressure--appears to be greater than that from the apoE epsilon4 allele.

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PubMedDate not supplied

Interleukin-6 promoter polymorphism and late-onset Alzheimer's disease in the Finnish population.

Recently, the involvement of the inflammatory response in Alzheimer's disease (AD) has received considerable attention. The gene encoding for interleukin-6 (IL-6) is interesting since IL-6 has been reported not only to be involved in immune functions but also in AD. We investigated whether the IL-6-174 G/C polymorphism is associated with late onset AD (LOAD) in the Finnish subjects. The G allele was over-represented in ApoE4-LOAD patients but remained unimportant in all and in the ApoE E4 carriers. Interestingly, the G allele frequency was lower in our population in both AD patients and in controls compared to Southern European populations.

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