Showing papers by "Anders H. Andersen published in 1999"
TL;DR: A generalized linear systems framework for PCA based on the singular value decomposition (SVD) model for representation of spatio-temporal fMRI data sets is presented and illustrated in the setting of dynamic time-series response data from fMRI experiments involving pharmacological stimulation of the dopaminergic nigro-striatal system in primates.
255 citations
TL;DR: Cognitively normal individuals at high risk for AD demonstrate decreased brain activation in key areas engaged during naming and fluency tasks, which may be a consequence of the presence of subclinical neuropathology in the inferotemporal region or in the inputs to that region.
Abstract: Objective: To determine whether brain function is altered in cognitively normal individuals at high risk for AD several years before the typical age at onset for this illness. Background: Neuropathologic alterations in AD precede cognitive impairment by several years. It is unknown whether functional alterations in neural circuitry accompany these neuropathologic changes, and if so, whether they may be detectable before onset of symptoms. Methods: We used functional MRI to compare cortical activation between two groups of cognitively normal women differing only in their risk for developing AD. Visual naming and letter fluency tasks were used to activate brain areas subserving object and face recognition, previously described sites of hypometabolism and neuropathologic alteration in AD. The risk groups differed in family history of AD and apolipoprotein E allele status, but were matched in age, education, and measures of cognitive performance. Average age of the study participants was 52 years. Results: The regional patterns of brain activation were similar between groups. However, the high risk group showed areas of significantly reduced activation in the mid- and posterior inferotemporal regions bilaterally during both tasks despite identical naming and letter fluency performance. Conclusions: Cognitively normal individuals at high risk for AD demonstrate decreased brain activation in key areas engaged during naming and fluency tasks. Decreased activation in the high risk group may be a consequence of the presence of subclinical neuropathology in the inferotemporal region or in the inputs to that region. If so, these findings provide evidence of a window of opportunity for disease-modifying treatment before the onset of symptomatic AD.
197 citations
TL;DR: Comparison of these age-associated changes in rhesus brain with those in humans suggest that the brain aging in Rhesus is a good model of human brain aging, but occurs approximately 3-fold faster.
60 citations
TL;DR: Results suggest that fMRI can detect changes in dopamine receptor-mediated neuronal sensitivity to dopaminergic agents and reduce behavioral responsiveness to levodopa and abolish the fMRI response.
36 citations
TL;DR: Functional magnetic resonance imaging was performed on a 36‐year‐old woman with muscular dystrophy, intractable epilepsy, and bilateral temporo‐occipital lissencephaly and observed islands of task‐specific activation in lissencesphalic cortex homologous to visual association regions activated in normal subjects on the same visual confrontation naming task.
Abstract: Functional magnetic resonance imaging was performed on a 36-year-old woman with muscular dystrophy, intractable epilepsy, and bilateral temporo-occipital lissencephaly. We observed islands of task-specific activation in lissencephalic cortex homologous to visual association regions activated in normal subjects on the same visual confrontation naming task. This result suggests lissencephalic cortex may develop specific functional connections with other brain regions.
8 citations