A study of the reliability and validity of the Chinese version of the Dementia Rating Scale

Author name used in this publication: Andrew M. H. Siu2004-2005 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Computational study on subdural cortical stimulation - the influence of the head geometry, anisotropic conductivity, and electrode configuration.

Subdural cortical stimulation (SuCS) is a method used to inject electrical current through electrodes beneath the dura mater, and is known to be useful in treating brain disorders. However, precisely how SuCS must be applied to yield the most effective results has rarely been investigated. For this purpose, we developed a three-dimensional computational model that represents an anatomically realistic brain model including an upper chest. With this computational model, we investigated the influence of stimulation amplitudes, electrode configurations (single or paddle-array), and white matter conductivities (isotropy or anisotropy). Further, the effects of stimulation were compared with two other computational models, including an anatomically realistic brain-only model and the simplified extruded slab model representing the precentral gyrus area. The results of voltage stimulation suggested that there was a synergistic effect with the paddle-array due to the use of multiple electrodes; however, a single electrode was more efficient with current stimulation. The conventional model (simplified extruded slab) far overestimated the effects of stimulation with both voltage and current by comparison to our proposed realistic upper body model. However, the realistic upper body and full brain-only models demonstrated similar stimulation effects. In our investigation of the influence of anisotropic conductivity, model with a fixed ratio (1∶10) anisotropic conductivity yielded deeper penetration depths and larger extents of stimulation than others. However, isotropic and anisotropic models with fixed ratios (1∶2, 1∶5) yielded similar stimulation effects. Lastly, whether the reference electrode was located on the right or left chest had no substantial effects on stimulation

Effects of arm weight support training to promote recovery of upper limb function for subacute patients after stroke with different levels of arm impairments

2015-2016 > Academic research: refereed > Publication in refereed journalVersion of RecordSelf-fundedPublishe

The influence of the geometry of the brain model on the effective depth and effective volume with stimulation voltage (V) and current (mA).

<p>Anisotropic conductivity in the white matter and a single electrode configuration were applied.</p

The spatial distribution of current density of 1V using right and left reference electrode model.

<p>The results in the brain are the same with the reference electrode on the right (left) and the left (right). However, the distribution of current density is flipped horizontally only under the neck.</p

Impedance and output current of each model.

<p>Impedance and output current of each model.</p

Geometric structure of the brain model.

<p>A realistic upper body model (a), realistic full brain-only model (b), and simplified extruded slab model (c).</p

Current density distribution in the brain.

<p>A 3D visualization of the brain with implanted paddle-array (left). The red line is the tangential slice of the right top and right bottom electrodes. The current density map is of the tangential slice (log scale) in the brain. We visualized only over the motor cortex threshold (2.5 A/m²); the thin black line is the edge of the threshold.</p

Current density distribution and flow in the brain.

<p>Realistic upper head (a) and simplified extruded slab model (b). The anisotropic conductivity in the white matter and a single electrode configuration were applied.</p

The coronal slice of the fractional anisotropy (FA) map and current direction for the isotropic and anisotropic models.

<p>A realistic upper body model and single electrode configuration were applied. Dotted area encircles the corpus callosum.</p