Measuring unconscious actions in action-blindsight: exploring the kinematics of pointing movements to targets in the blind field of two patients with cortical hemianopia

We tested two patients with posterior cerebral lesions on two pointing tasks. In the first task, the patients pointed to targets presented on a touch screen monitor and pointing accuracy was recorded. One patient (JR) demonstrated good localisation of targets presented to her blind field while the other patient (YP) did not. Movement kinematics were measured in the second task to compare the kinematics of movements made to sighted field targets with those made to blind field targets. For this version of the task both patients demonstrated above chance localisation of blind field targets although the slope of the relationship between the end of pointing movements and the target locations was significantly steeper for JR than for YP. Furthermore, JR showed a kinematic profile for movements made to blind field targets that mirrored the profile of kinematics to sighted field targets. That is, both peak velocity and time to peak velocity increased with increasing target eccentricity for movements made to blind and sighted field targets alike. Although patient YP now showed more reliable spatial localisation on this pointing task when compared with the touch screen task, his kinematics for movements made to targets in his blind field were quite different from those made to targets in his sighted field. Based on the patients' CT scans, we suggest that the superior performance of patient JR is a consequence of greater sparing of her parietal cortex in the damaged hemisphere.     

Analysis of spatial correlation between 99mTc-Sestamibi uptake and radiographic breast density

Breast scintigraphy is a technique by which the biological properties of breast lesions can be assessed using an injected radiopharmaceutical. It may be particularly useful for women with radiographically dense breasts, in whose mammograms, lesions are often obscured by breast tissue. We are evaluating a dual modality breast scanner developed at the University of Virginia for its ability to distinguish between benign and malignant lesions. The scanner obtains a digital mammogram and a gamma ray emission image in quick succession with the breast held under mild compression, resulting in a fused image in which structures in the digital mammogram can be directly correlated with those in the scintigram. Our experience has shown that radiopharmaceutical uptake by normal breast tissue can sometimes obscure uptake by small lesions. It would therefore be advantageous to correct for this background uptake if possible. One potential way of accomplishing this is to use the information from the digital mammogram to help predict the background radiopharmaceutical distribution. With this in mind, we retrospectively investigated the degree of spatial correlation between the distribution of background activity and the distribution of radiodense breast tissue in normal breasts. Using a histogram-based analysis, we have quantified the degree of correlation in 16 images obtained from a total of 8 patients. We also used the mammographic images to quantify the radiographic density of each breast. Our results suggest that spatial correlation between areas of high radiopharmaceutical uptake and parenchymal density exists in the most dense regions of the breast for either extremely dense or heterogeneously dense breasts. High correlation was also observed for some homogeneously fatty breasts. In the latter case however, variation in breast thickness appeared to be the cause of the increased correlation. Correlation properties are approximately equal in both right and left breasts for a particular patient, except in cases exhibiting focal radiotracer uptake in a lesion. Although our preliminary results suggest that correlation between radiopharmaceutical uptake and parenchymal density exists, the number of cases thus far is too small for definitive conclusions. In addition, the planar nature of the dual modality scans imposes an inherent limitation on our ability to take into account attenuation of the emitted gamma radiation, which thus constitutes an uncontrolled variable in the correlation analysis. In principle, this problem can be eliminated by 3-dimensional imaging.     

Multispectral analysis of magnetic resonance images

Magnetic resonance (MR) imaging systems produce spatial distribution estimates of proton density, relaxation time, and flow, in a two dimensional matrix form that is analogous to that of the image data obtained from multispectral imaging satellites. Advanced NASA satellite image processing offers sophisticated multispectral analysis of MR images. Spin echo and inversion recovery pulse sequence images were entered in a digital format compatible with satellite images and accurately registered pixel by pixel. Signatures of each tissue class were automatically determined using both supervised and unsupervised classification. Overall tissue classification was obtained in the form of a theme map. In MR images of the brain, for example, the classes included CSF, gray matter, white matter, subcutaneous fat, muscle, and bone. These methods provide an efficient means of identifying subtle relationships in a multi-image MR study.     

Giant duodenal ulcer

Benign giant duodenal ulcer appears to be a unique type of generalized peptic ulcer disease. Massive hemorrhage, perforation, and obstruction are frequent complications. The disorder is best diagnosed endoscopically and treated with one of the standard acid-reducing procedures.