The ability to control electroencephalographic rhythms and to map those changes to the actuation of mechanical devices provides the basis for an assistive brain-computer interface (BCI). In this study, we investigate the ability of subjects to manipulate the sensorimotor mu rhythm (8-12-Hz oscillations recorded over the motor cortex) in the context of a rich visual representation of the feedback signal. Four subjects were trained for approximately 10 h over the course of five weeks to produce similar or differential mu activity over the two hemispheres in order to control left or right movement in a three-dimensional video game. Analysis of the data showed a steep learning curve for producing differential mu activity during the first six training sessions and leveling off during the final four sessions. In contrast, similar mu activity was easily obtained and maintained throughout all the training sessions. The results suggest that an intentional BCI based on a binary signal is possible. During a realistic, interactive, and motivationally engaging task, subjects learned to control levels of mu activity faster when it involves similar activity in both hemispheres. This suggests that while individual control of each hemisphere is possible, it requires more learning time.

No abstract

No abstract

Cross-sectional echocardiography was used to quantify volume in 21 canine left ventricles that were fixed in formalin and immersed in mineral oil. Area, length and diameter measurements were obtained from short- and long-axis cross-sectional images of the left ventricle and volume was calculated by seven mathematic models. Calculated volume was then compared, by linear regression and percent error analyses, with fluid volume of the left ventricle, obtained by filling the chamber with a known amount of fluid. Volumes ranged from 13-146 ml. Mathematic models using short-axis area and long-axis length gave higher correlation coefficients (r = 0.982 and r = 0.969) and lower mean errors (10-20%) than standard formulas previously used for M-mode echo and angiography. Thus, short-axis area analysis with cross-sectional echocardiography is well-suited for quantifying left ventricular volumes in dogs.

The velocity and attenuation of sound has been determined for freshly excised human and canine arterial tissues using a time delay spectrometer (TDS) technique. Frequency was swept from 0 to 10 MHz with data being taken in the range from 2 to 10 MHz. The velocity was determined using a comparison of the time delay for the received signal between a water path and a sample tissue of measured thickness. The velocity of sound was measured for various pathologies and related to biochemical assays of tissue. It was found to increase with increasing ultrasound attenuation of the tissue. The velocity was shown to increase with increased collagen, C, expressed as a percentage of wet weight of the tissue, [V = 17.8* C + 1561 m/s at 37 degrees C, r = 0.77] but was strongly dependent on tissue cholesterol or low levels of calcium. For highly calcified lesions, the velocity of sound was found to be approximately 2000 m/s at 37 degrees C.