Biomedical subjects

S Aalto

Publications and source records attributed to S Aalto.

7 recordsLinked to original sources

PubMed2006

Voxel-based analysis of PET amyloid ligand [11C]PIB uptake in Alzheimer disease.

BACKGROUND: PET studies with N-methyl-[(11)C]2-(4':-methylaminophenyl)-6-hydroxybenzothiazole ([(11)C]PIB) have revealed an increased tracer uptake in several brain regions in Alzheimer disease (AD). OBJECTIVE: To employ voxel-based analysis method to identify brain regions with significant increases in [(11)C]PIB uptake in AD vs healthy control subjects, indicative of increased amyloid accumulation in these regions. METHODS: We studied 17 patients with AD and 11 control subjects with PET using [(11)C]PIB as tracer. Parametric images were computed by calculating a region-to-cerebellum ratio over 60 to 90 minutes in each voxel. Group differences in [(11)C]PIB uptake were analyzed with statistical parametric mapping (SPM) and automated region-of-interest (ROI) analysis. RESULTS: SPM showed increased uptake (p < 0.001) in the frontal, parietal, and lateral temporal cortices as well as in the posterior cingulate and the striatum. No significant differences in uptake were found in the primary sensory and motor cortices, primary visual cortex, thalamus, and medial temporal lobe. These results were supported by automated ROI analysis, with most prominent increases in AD subjects in the frontal cortex ([(11)C]PIB uptake 163% of the control mean) and posterior cingulate (146%) followed by the parietal (146%) and temporal (145%) cortices and striatum (133%), as well as small increases in the occipital cortex (117%) and thalamus (115%). CONCLUSIONS: Voxel-based analysis revealed widespread distribution of increased [(11)C]PIB uptake in Alzheimer disease (AD). These findings are in accordance with the distribution and phases of amyloid pathology in AD, previously documented in postmortem studies.

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PubMed2005

Correlation of EEG spectral entropy with regional cerebral blood flow during sevoflurane and propofol anaesthesia.

ENTROPY index monitoring, based on spectral entropy of the electroencephalogram, is a promising new method to measure the depth of anaesthesia. We examined the association between spectral entropy and regional cerebral blood flow in healthy subjects anaesthetised with 2%, 3% and 4% end-expiratory concentrations of sevoflurane and 7.6, 12.5 and 19.0 microg.ml(-1) plasma drug concentrations of propofol. Spectral entropy from the frequency band 0.8-32 Hz was calculated and cerebral blood flow assessed using positron emission tomography and [(15)O]-labelled water at baseline and at each anaesthesia level. Both drugs induced significant reductions in spectral entropy and cortical and global cerebral blood flow. Midfrontal-central spectral entropy was associated with individual frontal and whole brain blood flow values across all conditions, suggesting that this novel measure of anaesthetic depth can depict global changes in neuronal activity induced by the drugs. The cortical areas of the most significant associations were remarkably similar for both drugs.

Adult↗

PubMed2003

Extrastriatal dopamine D(2) receptors in Parkinson's disease: a longitudinal study.

Most antiparkinsonian drugs are known to act through central dopamine D(2) receptor agonism. A previous longitudinal positron emission tomography (PET) study has indicated that, in the striatum of Parkinson's disease (PD) patients, dopamine D(2) receptor binding declines at a relatively fast annual rate of 2-4% (compared to the rate of <1%/year in healthy individuals). In the present study, the examination of longitudinal changes in D(2) receptors was extended to extrastriatal brain regions in PD. Eight early PD patients were examined twice with PET, approximately 3 years apart, using a high-affinity extrastriatal D(2)/D(3) receptor tracer, [(11)C]FLB 457. Both the MRI-referenced region-of-interest method and the voxel-based statistical analysis method were used independently in the analysis. Regional D(2)-like availabilities (binding potentials) in the left dorsolateral prefrontal cortex, the left temporal cortex and the left and right medial thalami were significantly decreased at the second examination by 20-37% (corresponding to an annual decline of 6-11%). Thus, the annual loss of extrastriatal D(2) availability in PD is up to three times faster than the rate previously reported in the putamen. Our longitudinal study shows first evidence concerning cortical D(2) receptor loss in the progression of PD, although it is not possible to distinguish between the effects of the therapy and the disease.

Aged↗

PubMed2003

Measurement of striatal and thalamic dopamine D2 receptor binding with 11C-raclopride.

11C-Raclopride is a widely used positron emission tomography (PET) tracer for measurement of striatal D2 dopamine receptor binding characteristics. Recently, 11C-raclopride has also been used for quantification of thalamic D2 receptor binding. We studied reproducibility and validity issues on the thalamic D2 binding measurements using healthy volunteer test-retest data and simulated data. Eight healthy male volunteers received 11C-raclopride as a bolus injection in a standard test-retest design using 3-dimensional PET. The displacement of thalamic 11C-raclopride binding by the D2 receptor antagonist haloperidol was studied in two female schizophrenic patients. With regards to reproducibility and reliability, thalamic 11C-raclopride binding could be described with a simplified reference tissue model resulting in binding potentials (BPs) between 0.38 and 0.66. In comparison, the model failed to describe 11C-raclopride binding consistently in temporal cortex due to low specific signal. Measurement of thalamic 11C-raclopride BP was reproducible with a test-retest variability of 7.6+/-6.2% and reliable with an intraclass correlation coefficient (ICC) of 0.87. Comparable ICCs were observed in caudate and putamen (0.84-0.96). With regard to validity, subchronic low dose haloperidol treatment reduced specific 11C-raclopride binding equally in putamen and thalamus but a higher dose induced clearly higher D2 receptor occupancy in putamen than in thalamus. Noise simulations indicated that this can partly be explained by an over-estimation of thalamic D2 receptor BP in noisy conditions (low signal, high occupancy). The D2 receptor BP in putamen was clearly more resistant to noise. We conclude that the reproducibility and reliability of thalamic 11C-raclopride BP is good and equal to, or only slightly less than, those observed in caudate or putamen. However, the signal-to-noise ratio for quantification may become too low especially in receptor occupancy-type studies, leading to an artefactual underestimation of measured D2 receptor occupancy.

Adult↗

PubMed2002

Neuroanatomical substrata of amusement and sadness: a PET activation study using film stimuli.

The aim of the present study was to explore the neuroanatomical substrata of film-induced amusement and sadness, aiming at maximal reliability by using strict statistics. Film-induced changes in regional cerebral blood flow (rCBF) were measured using positron emission tomography and [15O]water. It appeared that many brain regions were involved similarly and symmetrically in both emotions. Activation of the occipitotemporal and anterior temporal cortex and cerebellum during both emotions agreed well with the earlier findings. Contrary to some earlier studies, the posterior cingulate gyrus and some frontal areas were deactivated in both emotions. The strict explorative analysis did not reveal activations in the limbic or subcorticai structures seen in some earlier studies. However, an additional analysis restricted to the subcortical and limbic system structures revealed bilateral activation of the amygdala in both target emotions. The outcomes of imaginal studies of emotions seem to be largely dependent on the conservativeness of the statistical analysis and very likely also on the method of emotion induction.

Adult↗

PubMed2002

Severe somatization in women is associated with altered cerebral glucose metabolism.

BACKGROUND: Somatization is a clinical phenomenon characterized by multiple, medically unexplained somatic symptoms. The pathophysiology remains unknown. We aimed to test the hypothesis of a central nervous system dysfunction in the pathophysiology of this disorder. METHOD: We studied 10 female patients diagnosed as having somatization disorder or undifferentiated somatoform disorder with no current Axis I disorders according to DSM-IV. They were compared with 17 healthy female volunteers using brain [18F]-fluorodeoxyglucose-PET with MRI reference. RESULTS: The patients had lower cerebral metabolism rates of glucose (P<0.05) in both caudate nuclei, left putamen and right precentral gyrus compared with healthy volunteers. CONCLUSIONS: This is the first study to demonstrate changes in brain metabolism in somatizing women. The regional cerebral hypometabolism is probably associated with the pathophysiology of somatization.

Adult↗

PubMed2002

Cognitive functioning in severe somatization--a pilot study.

OBJECTIVE: Somatizing patients often report cognitive complaints but neuropsychological research on somatization is scarce. We investigated somatizing patients for functioning in different cognitive domains. METHOD: Ten female patients with somatization disorder or undifferentiated somatoform disorder and 10 non-somatizing controls participated in neuropsychological examinations. RESULTS: The patients performed at a lower level than the controls in tests involving semantic memory, verbal episodic memory and visuo-spatial tasks, and were slower in attentional tasks. CONCLUSION: Somatization patients may suffer from substantial problems in cognitive performance.

Adult↗