A continuous metal-insulator transition driven by spin correlations.

While Mott insulators induced by Coulomb interactions are a well-recognized class of metal-insulator transitions, insulators purely driven by spin correlations are much less common, as the reduced energy scale often invites competition from other degrees of freedom. Here, we demonstrate a clean example of a spin-correlation-driven metal-insulator transition in the all-in-all-out pyrochlore antiferromagnet Cd2Os2O7, where the lattice symmetry is preserved by the antiferromagnetism. After the antisymmetric linear magnetoresistance from conductive, ferromagnetic domain walls is removed experimentally, the bulk Hall coefficient reveals four Fermi surfaces of both electron and hole types, sequentially departing the Fermi level with decreasing temperature below the Néel temperature, TN = 227 K. In Cd2Os2O7, the charge gap of a continuous metal-insulator transition opens only at T ~ 10 K << TN. The insulating mechanism parallels the Slater picture, but without a folded Brillouin zone, and contrasts sharply with Mott insulators and spin density waves, where the electronic gap opens above and at TN, respectively.

Optical Raman measurements of low frequency magnons under high pressure.

The application of giga-Pascal scale pressures has been widely used as a tool to systematically tune the properties of materials in order to access such general questions as the driving mechanisms underlying phase transitions. While there is a large and growing set of experimental tools successfully applied to high-pressure environments, the compatibility between diamond anvil cells and optical probes offers further potential for examining lattice, magnetic, and electronic states, along with their excitations. Here, we describe the construction of a highly efficient optical Raman spectrometer that enables measurements of magnetic excitations in single crystals down to energies of 9 cm-1 (1.1 meV or 13 K) at cryogenic temperatures and under pressures of tens of GPa.

Antisymmetric linear magnetoresistance and the planar Hall effect.

The phenomena of antisymmetric magnetoresistance and the planar Hall effect are deeply entwined with ferromagnetism. The intrinsic magnetization of the ordered state permits these unusual and rarely observed manifestations of Onsager's theorem when time reversal symmetry is broken at zero applied field. Here we study two classes of ferromagnetic materials, rare-earth magnets with high intrinsic coercivity and antiferromagnetic pyrochlores with strongly-pinned ferromagnetic domain walls, which both exhibit antisymmetric magnetoresistive behavior. By mapping out the peculiar angular variation of the antisymmetric galvanomagnetic response with respect to the relative alignments of the magnetization, magnetic field, and electrical current, we experimentally distinguish two distinct underlying microscopic mechanisms: namely, spin-dependent scattering of a Zeeman-shifted Fermi surface and anomalous electron velocities. Our work demonstrates that the anomalous electron velocity physics typically associated with the anomalous Hall effect is prevalent beyond the ρxy(Hz) channel, and should be understood as a part of the general galvanomagnetic behavior.

A Comparison of Food Portion Size Estimation by Older Adults, Young Adults and Nutritionists.

OBJECTIVES: To investigate the ability of older adults, younger adults and nutritionists to assess portion size using traditional methods versus a computer-based method. This was to inform the development of a novel dietary assessment method for older adults "The NANA system". DESIGN: Older and younger adults assessed the portion size of self-served portions of foods from a buffet style set up using traditional and computerised portion size assessment aids. Nutritionists assessed the portion size of foods from digital photographs using computerised portion size aids. These estimates were compared to known weights of foods using univariate analyses of covariance (ANCOVA). SETTING: The University of Sheffield, United Kingdom. SUBJECTS: Forty older adults (aged 65 years and over), 41 younger adults (aged between 18 and 40 years) and 25 nutritionists. RESULTS: There was little difference in the abilities of older and younger adults to assess portion size using both assessment aids with the exception of small pieces morphology. Even though the methods were not directly comparable among the test groups, there was less variability in portion size estimates made by the nutritionists. CONCLUSION: Older adults and younger adults are similar in their ability to assess food portion size and demonstrate wide variability of estimation compared to the ability of nutritionists to estimate portion size from photographs. The results suggest that the use of photographs of meals consumed for portion size assessment by a nutritionist may improve the accuracy of dietary assessment. Improved portion size assessment aids are required for all age groups.

Comparison of chronic physical and emotional social defeat stress effects on mesocorticolimbic circuit activation and voluntary consumption of morphine.

Chronic social defeat stress (CSDS) is a well-established rodent model of depression that induces persistent social avoidance. CSDS triggers molecular adaptations throughout the mesocorticolimbic reward circuit, including changes in the activity of dopamine neurons in the ventral tegmental area (VTA), that may also influence drug reward. One limitation of traditional, physical CSDS (PS) is that injury complicates the study of opiate drugs like morphine. Thus, we sought to characterize a variation of CSDS, termed emotional CSDS (ES), that eliminates this confound. We assessed the effect of PS and ES on mesocorticolimbic circuit activation, VTA gene expression, and morphine intake. We found that PS and ES similarly induced ΔFosB in the hippocampus, but only PS significantly increased ΔFosB expression in the prefrontal cortex and striatum. In contrast, cFos expression was similarly reduced by both PS and ES. Interestingly, we found that PS and ES similarly increased voluntary morphine consumption immediately following stress, despite differences in the magnitude of the depressive phenotype and striatal ΔFosB expression at this time point. Combined, these data suggest that both stress paradigms may be useful for investigation of stress-induced changes in drug behavior.

Comparing two deep brain stimulation leads to one in refractory tremor.

A sizable proportion of medication refractory tremor patients may not respond satisfactorily to deep brain stimulation (DBS) to the ventralis intermedialis nucleus of the thalamus (Vim). Implanting a second DBS lead ipsilaterally to the first one is thought to be beneficial based on scarce and unblinded data. This article aims to report a double-blind assessment of five patients with a second DBS lead for refractory tremor. Tremor was assessed by two blinded movement disorder specialists using a videotaped tremor rating scale (TRS) evaluation of each patient in four conditions: both leads OFF, Vim ON/2nd lead OFF, Vim OFF/2nd lead ON, and both leads ON. Paired t-test was used to determine if double stimulation was different than stimulation of Vim alone or than stimulation of the 2nd lead alone. Each hypothesis was tested with the total TRS as well as the contralateral upper limb score and the contralateral hemibody score. Tremor was secondary to multiple sclerosis in two patients and to essential tremor in three. The second lead was in the ventralis oralis anterior nucleus of the thalamus in three patients and in the prelemniscal radiations in two patients. There was improvement with the 2nd lead or double ON in four patients compared to stimulating the Vim alone. However, when taken as a group, the results were not statistically significant. These results were constant with the three different ratings used. The lack of overall statistically significant improvement might be secondary to the small size and the heterogeneity of our sample. However, four patients had 17 to 60 % tremor improvement after the implant of the 2nd lead on double-blinded evaluation. We report objective improvement after addition of a second DBS lead in patients with tremor refractory to Vim DBS. Larger studies are needed to confirm these results.

Immunological indicators of coeliac disease activity are not altered by long-term oats challenge.

Coeliac disease is a gluten-sensitive enteropathy that develops in genetically susceptible individuals. The disease exhibits many features of an autoimmune disorder. These include the production of highly specific anti-endomysial autoantibodies directed against the enzyme tissue transglutaminase. It is well accepted that wheat-, barley- and rye-based foods should be excluded in the gluten-free diet. Although several studies report that oats ingestion is safe in this diet, the potential toxicity of oats remains controversial. In the current study, 46 coeliac patients ingested oats for 1 year and were investigated for a potential immunogenic or toxic effect. Stringent clinical monitoring of these patients was performed and none experienced adverse effects, despite ingestion of a mean of 286 g of oats each week. Routine histological analysis of intestinal biopsies showed improvement or no change in 95% of the samples examined. Furthermore, tissue transglutaminase expression in biopsy samples, determined quantitatively using the IN Cell Analyzer, was unchanged. Employing immunohistochemistry, oats ingestion was not associated with changes in intraepithelial lymphocyte numbers or with enterocyte proliferation as assessed by Ki-67 staining. Finally, despite the potential for tissue transglutaminase to interact with oats, neither endomysial nor tissue transglutaminase antibodies were generated in any of the patients throughout the study. To conclude, this study reaffirms the lack of oats immunogenicity and toxicity to coeliac patients. It also suggests that the antigenic stimulus caused by wheat exposure differs fundamentally from that caused by oats.

Defining premature ejaculation for experimental and clinical investigations.

Researchers investigating premature ejaculation (PE) have employed widely diverse definitions of it, thereby limiting progress in the field. This study summarizes available research on PE, notes patterns that emerge from these studies, compares patterns across several types of studies, and suggests a common model for defining PE groups to guide future research. We surveyed two bibliographic databases, identifying 45 studies employing a definition or description of a PE group. From these, we extracted a range of information, including descriptions of the participants, recruitment procedures, if PE subtypes were identified, operational criteria for PE classification, relationship and partner information, and additional inclusion/exclusion criteria. Over 50% of studies reported no criteria, or relied on simple self-identification by participants to establish the PE group. Quantifiable behavioral criteria were used in 49% of the studies, with ejaculatory latency reported most frequently. This measure was also used as a criterion more frequently in studies focusing on assessment of sexual response, whereas the number of penile thrusts was used more frequently in studies prior to 1989. Partner information was often included but seldom used as part of the assessment procedure. Progress on research and treatment of PE will continue to be limited by the absence of commonly accepted criteria for PE group membership and by a lack of identification of relevant PE subtypes and etiologies. This paper suggests a flowchart, based on data and a rational analysis of 40 years of research, for characterizing PE in ways that could assist the development of the field.

Effects of inactivation of the anterior interpositus nucleus on the kinematic and dynamic control of multijoint movement.

We previously showed that inactivating the anterior interpositus nucleus in cats disrupts prehension; paw paths, normally straight and accurate, become curved, hypometric, and more variable. In the present study, we determined the joint kinematic and dynamic origins of this impairment. Animals were restrained in a hammock and trained to reach and grasp a cube of meat from a narrow food well at varied heights; movements were monitored using the MacReflex analysis system. The anterior interpositus nucleus was inactivated by microinjection of the GABA agonist muscimol (0.25-0.5 microgram in 0.5 microliter saline). For each joint, we computed the torque due to gravity, inertial resistance (termed self torque), interjoint interactions (termed interaction torque), and the combined effects of active muscle contraction and passive soft tissue stretch (termed generalized muscle torque). Inactivation produced significant reductions in the amplitude, velocity, and acceleration of elbow flexion. However, these movements continued to scale normally with target height. Shoulder extension was reduced by inactivation but wrist angular displacement and velocity were not. Inactivation also produced changes in the temporal coordination between elbow, shoulder, and wrist kinematics. Dynamic analysis showed that elbow flexion both before and during inactivation was produced by the combined action of muscle and interaction torque, but that the timing depended on muscle torque. Elbow interaction and muscle torques were scaled to target height both before and during inactivation. Inactivation produced significant reductions in elbow flexor interaction and muscle torques. The duration of elbow flexor muscle torque was prolonged to compensate for the reduction in flexor interaction torque. Shoulder extension was produced by extensor interaction and muscle torques both before and during inactivation. Inactivation produced a reduction in shoulder extension, primarily by reduced interaction torque, but without compensation. Wrist plantarflexion, which occurred during elbow flexion, was driven by plantarflexor interaction and gravitational torques both before and during inactivation. Muscle torque acted in the opposite direction with a phase lead to restrain the plantarflexor interaction torque. During inactivation, there was a reduction in plantarflexor interaction torque and a loss of the phase lead of the muscle torque. Our findings implicate the C1/C3 anterior interpositus zone of the cerebellum in the anticipatory control of intersegmental dynamics during reaching, which zone is required for coordinating the motions of the shoulder and wrist with those of the elbow. In contrast, this cerebellar zone does not play a role in scaling the movement to match a target.

Differential effects of deep cerebellar nuclei inactivation on reaching and adaptive control.

This study examined the effects of selective inactivation of the cerebellar nuclei in the cat on the control of multijoint trajectories and trajectory adaptation to avoid obstacles. Animals were restrained in a hammock and trained to perform a prehension task in which they reached to grasp a small cube of meat from a narrow food well. To examine trajectory adaptation, reaching was obstructed by placing a horizontal bar in the limb's path. Inactivation was produced by microinjection of the GABA agonist muscimol (0.25-1.0 microg in 1 microL saline). Fastigial nucleus inactivation produced a severe impairment in balance and in head and trunk control but no effect on reaching and grasping. Dentate inactivation slowed movements significantly and produced a significant increase in tip path curvature but did not impair reaching and grasping. Selective inactivation of the anterior and posterior interpositus nuclei did not impair grasping but severely decreased the accuracy of reaching movements and produced different biases in wrist and paw paths. Anterior interpositus inactivation produced movement slowing (wrist speed) and under-reaching to the food well. Wrist and tip paths showed anterior biases and became more curved. Also animals could no longer make anticipatory adjustments in limb kinematics to avoid obstructions but sensory-evoked corrective responses were preserved. Posterior interpositus inactivation produced a significant increase in wrist speed and overreaching. Wrist and tip paths showed a posterior bias and became more curved, although in a different way than during anterior interpositus inactivation. Posterior interpositus inactivation did not impair trajectory adaptation to reach over the obstacle. During inactivation of either interpositus nucleus, all measures of kinematic temporal and spatial variability increased with somewhat greater effects being produced by anterior interpositus inactivation. We discuss our results in relation to the hypothesis that anterior and posterior interpositus have different roles in trajectory control, related possibly to feed-forward use of cutaneous and proprioceptive inputs, respectively. The loss of adaptive reprogramming during anterior interpositus inactivation further suggests a role in motor learning. Comparison with results from our earlier motor cortical study shows that the distinctive impairments produced by inactivation of these two nuclei are similar to those produced by selective inactivation of different zones in the forelimb area of rostral motor cortex. Our findings are consistent with the hypothesis that there are separate functional output channels from the anterior and posterior interpositus nuclei to rostral motor cortex for distinct aspects of trajectory control and, from anterior interpositus alone, for trajectory adaptation.

A pilot study of dental students' esthetic perceptions of computer-generated mild dental fluorosis compared to other conditions.

OBJECTIVES: Few studies have considered people's opinions about the esthetics of dental fluorosis. Assessments of fluorosis esthetics can be confounded by differences in a number of clinical factors, including tooth shape, color, contour, and gingival status. This pilot study compared esthetic perceptions of mild fluorosis and other conditions using computer-generated images made from a base set of normal appearing teeth. METHODS: Entering dental students (n = 61) completed questionnaires about four sets of paired photographs. Three sets consisted of fluorotic teeth (very mild to mild) versus other conditions (diastema, isolated enamel opacity, "normal"/control) and the other pair compared two presentations of mild fluorosis (generalized versus limited to incisal one-third). Six questions, both qualitative and quantitative, were asked about each pair of photographs. RESULTS: Mild fluorosis was assessed less favorably than normal/control, midline diastema was less favorable than mild fluorosis, and mild fluorosis was less favorable than isolated opacity. CONCLUSIONS: This approach allows fluorosis to be better compared with other oral conditions because the images are standardized. Additional research with this method is warranted, including more variations in conditions, more comparisons, and other study populations.

A pilot study of esthetic perceptions of dental fluorosis vs. selected other dental conditions.

The prevalence of fluorosis has increased over the past fifty years, and with this increase, esthetic concerns pertaining to fluorosis should also be taken into consideration. Canadian, Australian, and British studies have explored perceptions concerning enamel fluorosis, but no studies in this area have been published from the United States. In the previous studies, esthetic concerns resulting from fluorosis generally were not compared with the esthetic perceptions of other conditions such as isolated opacities, tetracycline staining, or various types of malocclusion. In the present investigation, respondents answered written questions about paired photographs, one of fluorotic teeth and the other with one of the other conditions. Results show that not only is fluorosis noticeable, but it may be more of an esthetic concern than the other conditions.

The treatment of premature ejaculation: psychological and biological strategies.

This review provides criteria for defining premature ejaculation (PE) and identifying men with this dysfunction. Included are discussions of possible PE subtypes and causes of PE. Furthermore, two empirically supported cognitive-behavioral approaches for treating PE are described and salient issues surrounding these types of treatment are considered. Biologically based treatments available to PE men are presented, with attention to the relative effectiveness and limitations of the various alternatives. Finally, a model illustrating factors relevant to determining the best therapeutic strategy is described, concluding with a brief discussion of the value of combining biological and psychological modes of treatment.

Genital and psychoaffective response to erotic stimulation in sexually functional and dysfunctional men.

To understand the sexual response patterns of men with premature ejaculation and erectile dysfunction, the authors compared genital and affective responses of sexually functional and dysfunctional men with 3 types of sexual stimulation: an erotic video, penile vibrotactile stimulation, and a combination of both. Genital response differed across both groups and stimulus conditions, with an interactive effect indicating that groups showed different response patterns depending on the stimulation. Affective responses also differed across groups and interacted with stimulus conditions. The combination genital and affective response was superior to either alone in distinguishing men with no sexual problems from those with erectile or ejaculatory problems (or both). These factors were particularly useful in discriminating men with premature ejaculation from those with combined premature ejaculation and erectile dysfunction.

A preliminary investigation of affective and cognitive response to erotic stimulation in men before and after sex therapy.

Affective and cognitive responses to erotic stimulation were studied in sexually dysfunctional men before and after treatment in a sex therapy program. A comparison group of functional men was studied over the same time interval. A pool of 34 Likert-scaled items assessing various cognitions, affects, and perceptions was administered during baseline and following two erotic audiotapes and a self-generated sexual fantasy. To focus on global response patterns rather than individual item responses, five aggregate indices (sexual arousal, physicality, sensuality, negative affect, positive affect) were derived using a strategy that combined face-validity and reliability analysis. Cluster analysis was employed as an auxiliary technique to confirm the coherence of these groupings. All five indices differentiated dysfunctional men from controls, and further, three indices (physicality, sensuality, sexual arousal) showed significant variation across types of erotic stimulation. Correlations among the five indices, as well as with penile response, revealed two trends that differentiated dysfunctional men from controls during the pretest, but that diminished following sex therapy in the dysfunctional men. Future investigations might further rely on multiple-item indices as described here. Such measures may provide a more integrated view of sexual response in the laboratory and lead to greater understanding of affective and perceptual differences between functional and dysfunctional men.

Kinematic analysis of reaching in the cat.

The present study examines the kinematic features of forelimb movements made by cats reaching for food in horizontal target wells located at different heights and distances. Wrist paths consisted of two relatively straight segments joined at a "via-point" in front of the aperture of the food well. In the initial lift phase, the paw was raised to the via-point in front of the target. In the second, or thrust phase, the paw was directed forward into the food well. During the lift, the paw was moved toward the target primarily by elbow flexion, accompanied by a sequence of biphasic shoulder and wrist movements. Thrust was accomplished primarily by shoulder flexion while the wrist and the paw were maintained at near-constant angles. The animals varied the height of the reach primarily by varying elbow flexion with proportional changes in elbow angular velocity and angular acceleration and with corresponding variations in wrist speed. Thus, cats reached for targets at different heights by scaling a common kinematic profile. Over a relatively large range of target heights, animals maintained movement duration constant, according to a simple "pulse-height" control strategy (isochronous scaling). For reaches to a given target height, animals compensated for variability in peak acceleration by variations in movement time. We examined the coordination between the shoulder and the wrist with the elbow. Early during the lift, peak shoulder extensor and peak elbow flexor accelerations were synchronized. Late during the lift phase, wrist extensor acceleration was found to occur during the period of elbow flexor deceleration. We hypothesize that these linkages could, in part, be due to passive mechanical interactions. To determine how the angular trajectories of the different joints were organized in relation to target location, we plotted joint kinematic changes directly on the wrist and MCP joint paths. These plots revealed that for all target heights and movement speeds, wrist extensor deceleration occurred at approximately the same spatial location with respect to the target. This analysis also demonstrated that the second phase of MCP flexion occurred when the paw was below the lower lip of the food well, while the subsequent extension occurred after the tip cleared this obstacle. During thrust, wrist and MCP angles were maintained, reflecting the need to align the paw within the food well. Our findings suggest that cats plan the reaching phase of prehension as a sequence of discrete movement segments, each serving a particular goal in the task, rather than as an single unit.

Accuracy of planar reaching movements. II. Systematic extent errors resulting from inertial anisotropy.

This study examines the source of direction-dependent errors in movement extent made by human subjects in a reaching task. As in the preceding study, subjects were to move a cursor on a digitizing tablet to targets displayed on a computer monitor. Movements were made without concurrent visual feedback of cursor position, but movement paths were displayed on the monitor after the completion of each movement. We first examined horizontal hand movements made at waist level with the upper arm in a vertical orientation. Targets were located at five distances and two directions (30 degrees and 150 degrees) from one of two initial positions. Trajectory shapes were stereotyped, and movements to more distant targets had larger accelerations and velocities. Comparison of movements in the two directions showed that in the 30 degrees direction responses were hypermetric, accelerations and velocities were larger, and movement times were shorter. Since movements in the 30 degrees direction required less motion of the upper arm than movements in the 150 degrees direction, we hypothesized that the differences in accuracy and acceleration reflected a failure to take into account the difference in total limb inertia in the two directions. To test this hypothesis we simulated the initial accelerations of a two-segment limb moving in the horizontal plane with the hand at shoulder level when a constant force was applied at the hand in each of 24 directions. We compared these simulated accelerations to ones produced by our subjects with their arms in the same position when they aimed movements to targets in the 24 directions and at equal distances from an initial position. The magnitudes of both simulated and actual accelerations were greatest in the two directions perpendicular to the forearm, where inertial resistance is least, and lowest for movements directed along the axis of the forearm. In all subjects, the directional variation in peak acceleration was similar to that predicted by the model and shifted in the same way when the initial position of the hand was displaced. The pattern of direction-dependent variations in initial acceleration did not depend on the speed of movement. It was also unchanged when subjects aimed their movements toward targets presented within the workspace on the tablet instead of on the computer monitor. These findings indicate that, in programming the magnitude of the initial force that will accelerate the hand, subjects do not fully compensate for direction dependent differences in inertial resistance.(ABSTRACT TRUNCATED AT 400 WORDS)

Differential effects of local inactivation within motor cortex and red nucleus on performance of an elbow task in the cat.

This study examined changes in the performance of a single-joint, elbow task produced by reversible inactivation of local regions within the proximal forelimb representation in area 4 gamma of motor cortex (MCx) and the red nucleus (RN) of the cat. Inactivation was carried out by microinjecting lidocaine, gamma-aminobutyric acid, or muscimol into sites where microstimulation evoked contraction of elbow muscles. Reaction time, amplitude, and speed (velocity or dF/dt) of position and force responses elicited during inactivation were compared to control values obtained immediately prior to inactivation. In addition, we assessed qualitatively the effects of inactivation on reaching, placing reactions, and proprioceptive responses to imposed limb displacement. In the single-joint task, injections in MCx did not increase reaction time (simple or choice) and produced modest and inconsistent reductions in response amplitude (mean -8%) and speed (mean -19%). In contrast, injections of the same amounts of inactivating agents in the forelimb representation of RN consistently increased reaction time (34.4%), and increased the reaction time coefficient of variability (32%). There were small reductions in response amplitude (-4%) and speed (-10%) which were less than those produced by MCx inactivation. During reaching, however, these same injections in MCx and RN produced a substantial loss of accuracy. For MCx, this was due, in part, to systematic hypometria: for RN, inaccuracy resulted from increased variability in paw paths. Placing reactions and corrective responses to imposed limb displacements were also depressed by the cortical and rubral injections. Our results suggest that the forelimb representation in RN plays a role in the initiation of the single-joint, elbow tracking response examined here. The RN may mediate cerebellar regulation of response timing, a function that is likely to be important for interjoint coordination. Although neurons in the forelimb representations of MCx may contribute to force generation in single-joint movements, their contribution to multijoint control appears to be more important and is examined in the subsequent report (Martin and Ghez 1993).