Functional magnetic resonance imaging (fMRI) was used to identify and map the representation of the visual field in seven areas of human cerebral cortex and to identify at least two additional visually responsive regions.The cortical locations of neurons responding to stimulation along the vertical or horizontal visual field meridia were charted on three-dimensional models of the cortex and on unfolded maps of the cortical surface. These maps were used to identify the borders among areas that would be topographically homologous to areas Vl, V2, V3, VP, and parts of V3A and V4 of the macaque monkey. Visually responsive areas homologous to the middle temporal/medial superior temporal area complex and unidentified parietal visual areas were also observed. The topography of the visual areas identified thus far is consistent with the organization in macaque monkeys. However, these and other findings suggest that human and simian cortical organization may begin to differ in extrastriate cortex at, or beyond, V3A and V4.In contrast to our extensive knowledge of cortical organization in nonhuman primates, far less is known about the identity and topography of functional subdivisions in human cerebral cortex. In the macaque monkey cortex, 30 or more distinct visual areas have been tentatively identified (1). In the human brain, a strong case has been made for only two or three areas (Vi, V2, and middle temporal) (2, 4-6), though several additional areas have been proposed (6-11). Brain images produced by functional magnetic resonance imaging (fMRI) show signals that are thought to represent local changes in blood oxygenation. These changes can be elicited by sensory-evoked neural activity though other factors such as alterations in blood volume and proton movement may also contribute [for review, see DeYoe et al. (12)]. We have used this technology to chart several functionally distinct visual areas in the human. Preliminary reports of this work have appeared (13,14). MATERIALS AND METHODSTo map angular positions within the visual field, four male and two female subjects (ages 24-40 years old) viewed a flickering black-and-white-checkered hemifield that rotated slowly about a central fixation point during a fMRI scan. To map visual field eccentricity (distance from the center of gaze), subjects viewed an expanding checkered annulus. In this manner, neurons responding to stimulation at different locations in the visual field were activated at different times during the stimulus sequence. Corresponding differences in the temporal phase of the fMRI response thus identified the retinotopic locationThe publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact. 2382represented by each active site in the brain (12). A similar technique has been described by Engel et al. (15).To enhance activation of extrastriate cortex (12) and to help maintain attention and arousal, the subj...

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Canine neutrophils can be induced to adhere in vitro to isolated adult cardiac myocytes by stimulation of the neutrophils with chemotactic factors such as zymosan-activated serum (ZAS) only if the myocytes have been previously exposed to cytokines such as interleukin 1 (IL-1) or tumor necrosis factor-a. These cytokines induce synthesis and surface expression ofintercellular adhesion molecule-i (ICAM-1) on the myocyte, and neutrophil adhesion is almost entirely CD18 and ICAM-1 dependent. The present study examines cardiac-specific lymph collected from awake dogs during i-h coronary occlusion and 3 d of reperfusion for its ability to induce both ICAM-1 expression in cardiac myocytes, and neutrophil-myocyte adherence. Reperfusion lymph induced ICAM-1 expression in isolated myocytes, and myocyte adherence to ZAS-stimulated neutrophils that was completely inhibited by anti-CD18 and anti-ICAM-i monoclonal antibodies. This activity peaked at 90 min of reperfusion and persisted for up to 72 h. Preischemic lymph was not stimulatory. IL-1 appeared not to be a stimulating factor in lymph in that dilutions of lymph were found to inhibit the stimulatory effects of recombinant IL-1it. However, investigation of interleukin 6 (IL-6) revealed that recombinant IL-6 stimulated myocyte adhesiveness for ZAS-stimulated neutrophils (ED90 = 0.002 U/ml) and expression of ICAM-1 by isolated myocytes. IL-6 neutralizing antibody markedly reduced the ability of reperfusion lymph to stimulate adhesion and ICAM-1 expression, and estimates of levels of IL-6 in reperfusion lymph ranged from 0.035 to 0.14 U/ml. These results indicate that cytokines capable of promoting neutrophil-myocyte adhesion occur in extracellular fluid during reperfusion of ischemic myocardium, and that one of these cytokines is IL-6. Neutrophilmyocyte adhesion may be of pathogenic significance because it may enhance the cytotoxic activity of the neutrophil. (J. Clin. Invest. 1992. 89:602-609.) Key words: cardiac lymph * cytokine induction * intercellular adhesion molecule-i * interleukin 6 * ischemia-reperfusion injury Introduction Numerous studies indicate that neutrophils contribute to myocardial cell injury after ischemia particularly under conditions

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As shape memory alloys (SMAs) gain popularity as high energy density actuators, one characteristic that becomes particularly important is the thermomechanical transformation fatigue life, in addition to maximum transformation strain and stability of actuation cycles. In this paper, a novel test frame design and testing protocol are discussed, for investigating the thermally activated transformation fatigue characteristics of SMAs under various applied loads for both complete and partial phase transformation. A Ni50Ti40Cu10 (at.%) SMA was chosen for this investigation and the effects of various heat treatments on the transformation temperatures and the transformation fatigue lives of actuators were studied. For selected heat treatments, the evolution of recoverable and irrecoverable strains up to failure under different applied stress levels was studied in detail. The influence of complete and partial transformation on the fatigue life is also presented. The irrecoverable strain accumulation as a function of the number of cycles to failure for different stress levels is presented by a relationship similar to the Manson–Coffin law for both partial and complete transformations.

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The focus of this study is the thermomechanical characterization and comparison between two different shape memory alloys (SMAs) quantifying the effect of plastic strain on the transformation characteristics of SMA actuators. In this study, the thermomechanical response and transformation characteristics of a NiTiCu and a NiTi SMA are studied as a function of the induced plastic strain for four different loading paths: 1) an elastic-plastic loading of the austenitic phase, 2) a stress-induced martensitic phase transformation, 3) an elastic-detwinningplastic loading of the martensitic phase and 4) thermally-induced phase transformation under a constant applied stress. Each loading path is repeated multiple times, with an incremental change of the total applied strain, to determine the effect of accumulated plastic strain on the phase transformation characteristics of the two SMA material systems. The effects of plastic strain are quantified by measurements of recoverable strain during a thermal cycle under zero applied stress, measurements of heat of transformation from a differential scanning calorimeter and microstructural evaluations.