Biomedical subjects

Eileen Lüders

Publications and source records attributed to Eileen Lüders.

3 recordsLinked to original sources

PubMed2004

Quantitative comparison of four brain extraction algorithms.

In a companion paper (Rehm et al., 2004), we introduced Minneapolis Consensus Strip (McStrip), a hybrid algorithm for brain/non-brain segmentation. In this paper, we compare the performance of McStrip and three brain extraction algorithms (BEAs) in widespread use within the neuroimaging community--Statistical Parametric Mapping v.2 (SPM2), Brain Extraction Tool (BET), and Brain Surface Extractor (BSE)--to the "gold standard" of manually stripped T1-weighted MRI brain volumes. Our comparison was based on quantitative boundary and volume metrics, reproducibility across repeat scans of a single subject, and assessments of performance consistency across datasets acquired on different scanners at different institutions. McStrip, a hybrid method incorporating warping to a template, intensity thresholding, and edge detection, consistently outperformed SPM2, BET, and BSE, all of which rely on a single algorithmic strategy.

Algorithms↗

PubMed2002

Brain size and grey matter volume in the healthy human brain.

Magnetic resonance imaging was used to evaluate the influence of sex and brain size on compartmental brain volumes (grey matter, white matter, CSF) in a large and well-matched sample of neurologically normal women (n = 50) and men (n = 50). As expected, we found a significant sex difference for the absolute volumes of total brain, grey matter, white matter and CSF, with greater volumes for men. Relating these compartmental volume measures to brain volume resulting in proportional volume measures revealed a higher proportion of grey matter in women. No significant sex differences were found for white matter and CSF proportions. However, when the influence of sex was partialized out by regression analyses, brain volume explained 40-81% of the variance of the absolute grey matter, white matter and CSF volumes. Performing these regression analyses for the proportional volume measures revealed that brain volume explained approximately 16% of the variance in grey matter proportion. Sex or the interaction between sex and brain volume revealed no additional predicitve values. Interestingly, the correlation between brain volume and grey matter proportion was negative, with larger brains exhibiting relatively smaller proportions of grey matter. Thus, sex is not the main variable explaining the variability in grey matter volume. Rather, we suggest that brain size is the main variable determining the proportion of grey matter.

Adult↗

PubMed2002

Intermanual transfer in a simple motor task.

The present study examines the effects of a four-week training session in a pegboard task on uni- and bimanual performance. Of particular interest was whether practice transfer from the trained to the untrained hand takes place. Twenty-five consistently right-handed subjects were trained to perform the task with the dominant hand, or the subdominant hand, or with both hands. After this training, the learning effects for the trained and untrained hands were analysed. To summarise, we obtained the following findings: (1) After training, movement times were considerably reduced for all hands and for all training conditions (practice effects); (2) practice effects were found for the hand trained and also for the untrained hand; (3) there was not a great difference in the size of the practice effects for the right hand after left hand training or for the left hand after right hand training; (4) task difficulty had no clear influence on the practice effect; (5) and finally, we discovered that bimanual movements not only profit from bimanual training but also from unimanual training and conversely unimanual movements benefit from bimanual training. These findings are discussed in the context of different motor control models and in the light of recent brain imaging findings.

Adolescent↗