Superior Parietal Lobule: A Role in Relative Localization of Multiple Different Elements.

Simultanagnosia is an impairment in processing multiple visual elements simultaneously consecutive to bilateral posterior parietal damage, and neuroimaging data have specifically implicated the superior parietal lobule (SPL) in multiple element processing. We previously reported that a patient with focal and bilateral lesions of the SPL performed slower than controls in visual search but only for stimuli consisting of separable lines. Here, we further explored this patient's visual processing of plain object (colored disk) versus object consisting of separable lines (letter), presented in isolation (single object) versus in triplets. Identification of objects was normal in isolation but dropped to chance level when surrounded by distracters, irrespective of eccentricity and spacing. We speculate that this poor performance reflects a deficit in processing objects' relative locations within the triplet (for colored disks), aggravated by a deficit in processing the relative location of each separable line (for letters). Confirming this, performance improved when the patient just had to detect the presence of a specific colored disk within the triplets (visual search instruction), while the inability to identify the middle letter was alleviated when the distracters were identical letters that could be grouped, thereby reducing the number of ways individual lines could be bound.

Strontium hexaferrite nanomagnets suspended in a cosmetic preparation: a convenient tool to evaluate the biological effects of surface magnetism on human skin.

BACKGROUND/PURPOSE: Magnetic therapy has been popular for ages, but its therapeutic abilities remain to be demonstrated. We aimed to develop a homogeneous, stable dispersion of magnetic nanoparticles in a skin-care preparation, as a tool to analyze the biological and physiological effects of superficial magnetism in skin. METHODS: SrFe(12)O(19) nanoparticles were generated by ultrasound, dispersed in glycerol, stabilized in Dermud cream and permanently magnetized. The magnetic cream was applied on the epidermis of human skin organ cultures. The effects on UV-induced cell toxicity, apoptosis and inflammatory cytokine expression were analyzed. A clinical test was performed to check skin moisturization. RESULTS: Nanomagnets were found to be homogenously and stably dispersed. After magnetization, the preparation generated a magnetic field of 1-2 G. Upon cream application, no cytotoxicity and no impairment of cellular vitality were found after 24 and 48 h, respectively. The anti-apoptotic and anti-inflammatory properties of Dermud were not modified, but its long-term effect on moisturization in vivo was slightly increased. CONCLUSION: Nanomagnetic Dermud cream can be used as a tool to analyze the biological effects of nanomagnets dispersed on the skin surface at the cellular and molecular levels, thus allowing to explore the possible therapeutic uses of superficial magnetism for skin care.

Design and testing of a system for measuring high-frequency AC losses in superconducting wires and coils carrying DC and AC currents.

Development of high-power superconducting applications requires the accurate estimation of AC losses in the superconductor. In applications such as superconducting magnetic energy storage, the charge/discharge/persistent switching frequency of the coil, resulting from pulse width modulation control algorithms, is usually in the kilohertz regime. Therefore, a thorough investigation of the losses in the kilohertz regime of AC currents superimposed on large DC currents is essential in order to ensure the device stable operation at a predefined temperature. We describe here a unique experimental setup designed and built for characterizing AC losses in superconducting wires and coils under such special conditions. To minimize the eddy currents induced in the apparatus, a cryostat vacuum vessel was made of Delrin, an insulating synthetic polymer. The measurement setup allows driving DC currents up to 150 A and superimposed AC currents with amplitudes up to 10 Arms and frequencies up to 18 kHz. The system utilizes conduction cooling to reach a wide range of temperatures between 6 and 100 K and allows measurements of 10 cm long superconducting wires and coils with a diameter of 40 cm. The loss is measured by the electrical method, i.e., by direct voltage and current waveform measurement, achieving a resolution better than 100 nW. The system described here will assist in developing superconducting wires and coils for high-power applications.

The locus of attentional effects in texture segmentation.

Cuing covert spatial attention can increase spatial resolution. Here we pinpointed the specific locus of this effect using texture segmentation. At the level of visual cortex, texture segmentation theoretically involves passage of visual input through two layers of spatial linear filters separated by a pointwise nonlinearity. By manipulating the textures to differentially stimulate first- or second-order filters of various scales, we showed that the attentional effect consistently varied with the latter. These psychophysical results further support the hypothesis that attention increases resolution at the attended location and are consistent with an effect of attention at stages as early as the primary visual cortex.

Arthrodesis of the tarsometatarsal joint, using type II ESF with acrylic connecting bars in four dogs.

Hyperextension injury of the tarsometatarsal joint (TMTJ) is a debilitating injury and arthrodesis of this joint is often the only procedure that can result in full return to function. Most surgical procedures described for arthrodesis of the tarsometatarsal joint necessitate the use of external, splint or cast, to protect the implants used from fatigue failure. This report describes the successful use of type II external fixator that spans the tarsometatarsal joint in four dogs with hyperextension injury of the tarsometatarsal joint. This technique enables the patient to bear weight on the limb immediately after surgery until bony fusion is achieved, without the need for an additional protecting splint.

Transient vortex states in Bi2Sr2CaCu2O(8+delta) crystals

A high temporal resolution magneto-optical system is employed to observe the time evolution of the vortex structure in Bi(2)Sr(2)CaCu(2)O(8+delta) crystals after a sudden application of a magnetic field. The magneto-optical images reveal dynamic coexistence of two vortex phases: a quasiordered phase in the sample interior and a transient disordered phase near the sample edges. The border between these two phases, marked by an abrupt change in the gradient of the local induction, moves with time. This motion enables tracing the decay of the transient state and the concurrent growth of the thermodynamic vortex phases. The growth rate is sensitive to the location in the field-temperature phase diagram.

Functional organization of the medial geniculate body's subdivisions of the awake squirrel monkey.

The response properties of 138 cells in the medial geniculate body (MGB), of the awake squirrel monkey (Saimiri sciureus), to 7 species-specific vocalizations were studied. Cells were divided into 4 subgroups: 26 in the ventral, 24 in the medial and 46 in the lateral subdivision. Forty-two cells located on the borders between the subdivisions represent the fourth group. No significant differences were found between the subdivisions with respect to their selectivity, nor did cells in any subdivision respond preferentially to any particular vocalization. On the other hand, the response patterns of the ventral and the lateral subdivisions showed significant differences (P less than 0.001, chi 2-test) from those of the medial subdivision. Most of the cells in the medial subdivision (87.5%) responded with similar response pattern to the 7 vocalizations (mainly 'on' or 'sustain'), while most of the cells in the ventral and the lateral subdivisions (61.5% and 69.6% respectively) responded with complex, time-locked and different patterns to the various vocalizations. Cells that exhibited a response characterized as an intermediate between the two types were accumulated mainly on or close to the borders between the medial and the other subdivisions of the MGB. The possible role of each response patterns is discussed with respect to the projection of the subdivisions to the cortex.

The contribution of covert attention to the set-size and eccentricity effects in visual search.

To reexamine the role of covert attention in visual search, the authors directly manipulated attention by peripherally cueing the target location and analyzed its effects on the set-size and the eccentricity effects. Observers participated in feature and conjunction tasks. Experiment 1 used precues, and Experiment 2 used postcues in a yes-no task under valid-, invalid-, and neutral-cueing conditions. Experiments 3 and 4 used a 2-interval alternative forced-choice visual-search task under cued and neutral conditions. Precueing the target location improved performance in feature and conjunction searches; postcueing did not. For the cued targets, the eccentricity effect for features and conjunctions was diminished, suggesting that the attentional mechanism improves the quality of the sensory representation of the attended location. The conjunction set-size effect was reduced but not eliminated. This questions serial-search models that attribute a major role to covert attention in visual search.

Spatial attention improves performance in spatial resolution tasks.

This study used peripheral precueing to explore the effect of covert transient attention on performance in spatial resolution tasks. Experiments 1 (Landolt-square) and 2 ('broken-line') measured gap resolution and Experiment 3 measured vernier resolution. In all three tasks the target was presented alone in a large number of possible locations, ranging from 1.5-6 degrees of eccentricity in the vertical or horizontal axes. The precue indicated the target location but did not convey information regarding the correct response. Performance decreased as the gap size or the vernier offset size decreased and as target eccentricity increased. Precueing improved performance in terms of RT and accuracy in all three tasks; the eccentricity effect decreased in the cued trials of the gap resolution tasks. These findings support the idea that the performance improvement at attended locations results, to some extent, from an enhanced spatial resolution at the cued location, and not just from distractor exclusion, diminished uncertainty, or decisional factors.

Magneto-optical system for high speed real time imaging.

A new magneto-optical system has been developed to expand the range of high speed real time magneto-optical imaging. A special source for the external magnetic field has also been designed, using a pump solenoid to rapidly excite the field coil. Together with careful modifications of the cryostat, to reduce eddy currents, ramping rates reaching 3000 T/s have been achieved. Using a powerful laser as the light source, a custom designed optical assembly, and a high speed digital camera, real time imaging rates up to 30 000 frames per seconds have been demonstrated.

Magnetic stimulation intensity modulates motor inhibition.

Repetitive transcranial magnetic stimulation (rTMS) is a standard tool in neuroscience research and therapy. Here we study one rTMS property that has not received adequate attention, the interaction of subthreshold intensity stimulation and low frequencies. We applied 1Hz rTMS over the motor cortex at three intensities, 40%, 80% and 100% of the resting motor threshold (rMT), and measured cortical excitability before and after the stimulation sessions. When comparing motor evoked potential (MEP) measured from the abductor pollicis brevis (APB) muscle before and after rTMS stimulation, we found that low intensity (40% MT) stimulation significantly decreased MEP magnitude, some smaller (non-significant) inhibition was found for the 80% MT intensity and increased MEP was found for the high intensity (100% MT) stimulation. Our results indicate that when explaining the input-output relationship of motor cortex induced activation as an intensity-dependent function, there might be a need to split it into separate functions associated with separate processes mediated by different cell types such as interneurons, pyramidal neurons and others.