Neuropsychological functioning in depressed versus nondepressed participants with Alzheimer's disease.

Differences in cognitive functioning between participants with Alzheimer's Disease (AD) reporting depressive symptomatology (AD-Dep; n = 37) and a control group of nondepressed participants with AD (AD-Con; n = 98) were investigated based on hypothesized impairments of attention/concentration, psychomotor speed, and simple motor speed. Groups did not differ in age, education, overall severity of dementia, auditory comprehension, or use of psychotropic medications. AD-Dep participants performed significantly more poorly than AD-Con participants on 3 of the 13 measures on which they were hypothesized to exhibit greater impairment (WAIS-R Block Design, WAIS-R Digit Symbol, and speeded motor programming); and there were trends toward poorer performance on four additional measures (WAIS-R Object Assembly, WAIS-R Picture Arrangement, WAIS-R Digit Span-backward, and letter fluency). There was only one significant effect for the 13 measures on which no group differences were hypothesized; the AD-Dep participants unexpectedly obtained better WMS-R Logical Memory delayed recall scores than the AD-Con participants. Finally, AD-Dep participants exhibited an unexpected pattern of greater right hand advantage on the Finger Tapping Test.

Assessment of regional myocardial perfusion with myocardial contrast echocardiography in a canine model of varying degrees of coronary stenosis.

Previous studies showed that myocardial contrast echocardiography can be used to detect relative regional underperfusion in a canine model of critical coronary stenoses. The aim of this study was to determine if myocardial contrast echocardiography performed with a sterile sonicated human serum albumin preparation (Albunex, Molecular Biosystems, San Diego, Calif.) could detect the presence of coronary stenoses of variable degrees of severity. The results were compared with myocardial blood flow as assessed by radiolabeled microspheres in 16 open-chest dogs during baseline, following the creation of a coronary stenosis of variable severity and at the peak of dipyridamole-induced hyperemia. When flow ratios (that is, flow in the control area/ischemic area) were examined, a good correlation was observed between the area under the time-intensity curve and radioactive microsphere blood flow (r = 0.94, p < 0.0001), which allowed distinction of mild from severe stenosis. However, a consistent underestimation of the dipyridamole-induced hyperemia by myocardial contrast echo was seen in the control zone. This could be partially explained by a simultaneous increase in coronary blood flow and blood volume with dipyridamole and by attenuation of the ultrasound signal because of the high concentration of microbubbles at high flows. Myocardial contrast echocardiography can quantitate the amount of jeopardized myocardium during various degrees of coronary stenoses.

A model of the phonatory response time of stutterers and fluent speakers to frequency-modulated tones.

Stutterers and fluent speakers tracked frequency-modulated tones by humming. The response time (RT) to the first corrective change in fundamental frequency in response to linear ramps of increasing and decreasing frequency was measured. The results demonstrate that RT is a function of the stimulus ramp velocity. A model of this dependency is provided which consists of parameters of threshold frequency and a fixed time delay. The estimated threshold frequency for the fluent speakers is 2.029 Hz with 95% confidence interval: (1.70 Hz, 2.35 Hz) whereas that of the stutterers is 3.937 Hz (3.28 Hz, 4.60 Hz). These threshold frequencies are significantly different (p < 0.0001). This implies that stutterers are slower to respond to changes in frequency than are fluent speakers. The fixed time delays for the two groups are not significantly different. This means that it is possible for the stutterers to respond as fast as the fluent speakers (i.e., their basic "reflexes" are the same); however, they spend more time in the detection of the change in a tracking signal. This supports the model of the stuttered event as being triggered by an instability in a multiloop speech motor control system.

Contrast opacification of left ventricular myocardium following intravenous administration of sonicated albumin microspheres.

Albunex is a new echocardiographic (2-D echo) contrast agent that traverses the pulmonary vasculature when injected intravenously in humans. We examined whether intravenous Albunex resulted in changes in myocardial intensity of sufficient magnitude to produce time intensity curves (TICs). Thirty mildly hypertensive patients were divided into three groups of 10. Each patient received three injections of intravenous Albunex (group I dosages: 0.01, 0.02, and 0.04 cm3/kg; group II: 0.04, 0.06, and 0.08 cm3/kg; group III: 0.08, 0.1, and 0.12 cm3/kg) and two control injections of 5% human serum albumin while imaging with 2-D echo (phased-array; apical four-chamber). Fourty-three injections showed complete opacification of the left ventricle. Videointensity analysis of digitized end-diastolic frames produced myocardial TICs (total as well as background-subtracted intensity curves) in 20 of 43 injections. By visual inspection, a myocardial contrast effect was seen in 10 of 43 injections. Detection of myocardial TICs was dose-related (0 of 7 in group I, 9 of 18 in group II, 11 of 18 in group III) and always paralleled the degree of left ventricular opacification. No myocardial contrast effect was observed in any patient during control injections of albumin or in any patient in whom the injection of Albunex did not result in left ventricular opacification. Thus myocardial opacification with intravenous Albunex can be detected simultaneously with good left ventricular opacification. The potential significance of the myocardial opacification observed is discussed.

Assessment of regional myocardial perfusion by contrast echocardiography. II. Detection of changes in transmural and subendocardial perfusion during dipyridamole-induced hyperemia in a model of critical coronary stenosis.

Measurements of myocardial contrast (sonicated meglumine diatrizoate) intensity were compared with myocardial flow by radioactive microspheres before and after administration of dipyridamole (0.5 mg/kg body weight intravenously) in 10 open chest dogs with a critical stenosis in the left circumflex coronary artery. Computer measurements of contrast time-intensity curves corrected for background myocardial intensity were made along 12 transmural segments of the left ventricle at mid-papillary level and for the subendocardial and subepicardial half of each segment. After administration of dipyridamole, transmural flow in the control region increased significantly (p less than 0.001), resulting in a dipyridamole/baseline flow ratio (i.e., coronary reserve ratio) of 2.54 +/- 0.95. Similar changes (p less than 0.001) were seen by contrast echocardiography; the coronary reserve ratio was 2.10 +/- 0.60 with use of peak intensity and 3.48 +/- 1.58 with use of area under the time-intensity curve. In contrast, no significant changes were observed in myocardial flow, peak contrast intensity or area under the curve in the ischemic region after dipyridamole. In the control region the ratio of subendocardial to subepicardial flow was similar at baseline and after dipyridamole administration as assessed by microspheres (1.08 +/- 0.24 versus 1.17 +/- 0.25) or by area under the time-intensity curve (1.11 +/- 0.45 versus 1.11 +/- 0.56). In the ischemic region, the subendocardial/subepicardial flow ratio decreased significantly after dipyridamole administration as measured by microspheres (1.15 +/- 0.19 to 0.82 +/- 0.25; p less than 0.001) or by area under the curve (1.10 +/- 0.28 to 0.70 +/- 0.47; p less than 0.01). Thus, myocardial contrast echocardiography appears to be a sensitive technique with which to detect changes in myocardial flow induced by dipyridamole in the various myocardial layers of normal segments as well as of segments supplied by a critically stenotic coronary artery.

Comments on "Two-mass models of the vocal cords for natural sounding voice synthesis".

Koizumi et al. [J. Acoust. Soc. Am. 82, 1179-1192 (1987)] have proposed a way to incorporate mucosal waves into previous two-mass mechanical models of the vocal folds. This was accomplished by allowing the mass of the masses to vary with time. The equations of motion Koizumi et al. used to mathematically describe this model neglected terms from the time rate of change of momentum of Newton's second law. In this letter, approximations of the magnitude of this term indicate that it must not be neglected.