Biomedical subjects

Ansgar Quiske

Publications and source records attributed to Ansgar Quiske.

3 recordsLinked to original sources

PubMed2006

Precuneus is involved in allocentric spatial location encoding and recognition.

Using a declarative memory paradigm, the anatomical correlates of spatial location encoding and retrieval in the healthy human brain as reflected by BOLD fMRI were investigated. During encoding, subjects were instructed to view and keep in mind different locations of an object on a platform seen from different viewpoints in virtual 3D. In retrieval trials, subjects had to recognize previously learned object locations. Comparing activation patterns associated with encoding and recognition on a voxel-by-voxel basis, we found regions in the precuneus bilaterally activated by both processes. To our knowledge, this is the first study that directly compared human brain activation patterns associated with allocentric encoding and retrieval of spatial locations in virtual 3D. Our results provide further information concerning the role of the precuneus in declarative memory processes, pointing to precuneus involvement in encoding and retrieval of spatial locations.

Adult↗

PubMed2006

Cognitive functions in juvenile and adult patients with gelastic epilepsy due to hypothalamic hamartoma.

PURPOSE: To describe extend and severity of cognitive deficits in juvenile and adult patients with gelastic seizures and hypothalamic hamartoma (HH) and to analyze the impact of epilepsy-related variables on cognitive performance. METHODS: Thirteen juvenile and adult patients (mean age, 25 years; seven men) underwent comprehensive neuropsychological testing assessing intellectual performance, attention and executive functions, verbal and visual memory, and visuospatial abilities. RESULTS: Intellectual abilities ranged from moderate mental retardation to good average performance; 54% of the patients displayed below-average global intellectual abilities. Attentional and executive functions were impaired in 23% to 46% of the patients. Below-average visuospatial capabilities were observed in 39% of the cases. Memory functions were impaired regarding both visual (77%) and verbal learning (62%). Nonparametric correlation analysis revealed a significant relation between monthly partial seizure frequency and reduced cognitive flexibility and reduced performance in mental rotation. In addition, HH volume was significantly negatively correlated with cognitive flexibility, whereas age at onset and duration of epilepsy did not show significant correlation to cognitive performance. CONCLUSIONS: More than half of the adult patients with gelastic seizures and HH displayed deficits in a broad range of cognitive functions, expressed mostly in visual and verbal learning and memory. Some of the deficits could be shown to correlate with disease-related characteristics representing the severity of the epilepsy or the size of the underlying lesion. These findings prompt for a longitudinal investigation of the development of these cognitive deficits to analyze further the relevant factors contributing to this wide spectrum of cognitive impairments.

Adolescent↗

PubMed2005

The reliability of fMRI activations in the medial temporal lobes in a verbal episodic memory task.

The test-retest reliability of activation patterns elicited by encoding and recognition of word-pair associates within the whole brain and a predefined medial temporal region of interest (ROI) was investigated. Twenty healthy right-handed subjects were studied within two sessions, either on the same day or 210-308 days later. Three quantitative measures of reliability were calculated for the contrasts encoding and recognition versus a control condition within the ROI and also for the whole brain: A group correlational analysis between the lateralization indices of the first and second session, correlations of the individual SPM(t) maps of the first and the second run, and overlap ratios between both sessions. For the ROI, correlational analysis of lateralization indices during both encoding trials was significant. Eighty percent of the individual positive correlation coefficients of SPM(t) maps during encoding, and 75% during recognition reached significance. The mean percentage of overlapping voxels was 18% during encoding and 19% during recognition. The reproducibility measures evaluated for the whole brain demonstrated significantly higher values compared to the ROI. For the group that stayed inside the scanner, better whole brain test-retest reliability was observed, and no influence of the memory process (encoding or recognition) on reproducibility was found.

Adult↗