Decreased efficiency of task-positive and task-negative networks during working memory in schizophrenia

Working memory (WM) is one of the most impaired cognitive processes in schizophrenia. Functional magnetic resonance imaging (fMRI) studies in this area have typically found a reduction in information processing efficiency but have focused on the dorsolateral prefrontal cortex. In the current study using the Sternberg Item Recognition Test, we consider networks of regions supporting WM and measure the activation of functionally connected neural networks over different WM load conditions. We used constrained principal component analysis with a finite impulse response basis set to compare the estimated hemodynamic response associated with different WM load condition for 15 healthy control subjects and 15 schizophrenia patients. Three components emerged, reflecting activated (task-positive) and deactivated (task-negative or default-mode) neural networks. Two of the components (with both task-positive and task-negative aspects) were load dependent, were involved in encoding and delay phases (one exclusively encoding and the other both encoding and delay), and both showed evidence for decreased efficiency in patients. The results suggest that WM capacity is reached sooner for schizophrenia patients as the overt levels of WM load increase, to the point that further increases in overt memory load do not increase fMRI activation, and lead to performance impairments. These results are consistent with an account holding that patients show reduced efficiency in task-positive and task-negative networks during WM and also partially support the shifted inverted-U-shaped curve theory of the relationship between WM load and fMRI activation in schizophrenia.

Origin of spin-orbit splitting for monolayers of au and ag on w(110) and mo(110)

Spin-orbit coupling can give rise to spin-split electronic states without a ferromagnet or an external magnetic field. We create large spin-orbit splittings in a Au and Ag monolayer on W(110) and show that the size of the splitting does not depend on the atomic number of the Au or Ag overlayer but of the W substrate. Spin- and angle-resolved photoemission and Fermi-surface scans reveal that the overlayer states acquire spin polarization through spin-dependent overlayer-substrate hybridization.

Are international medical graduates a factor in residency program selection? A survey of fourth-year medical students

PURPOSE

To examine whether the proportions of international medical graduates (IMGs) enrolled in certain residency programs would affect students' selection of those programs during the match, and to determine the importance of this factor relative to other established program-selection factors.

METHOD

A sample of 702 fourth-year students at 18 geographically diverse U.S. medical schools during March and April of 1994 were mailed a confidential survey asking them to rank and rate hypothetical programs and to rate the importance of selected characteristics in their rankings of programs during the match. The students were asked to rank five hypothetical programs described by nine characteristics. One-third of the students received additional information about the programs' reputations; another third, information about the percentages of IMGs in the programs. The control group received no information about these two characteristics. Comparisons of the mean rankings and ratings of the five programs between the control and intervention groups were made using the Mann-Wilcoxon rank-comparison statistical test.

RESULTS

The response rate was 44%, with 291 survey forms returned completed (45 were returned due to no forwarding address). When the rankings and ratings of the control and intervention groups were compared, the programs with higher numbers of IMGs worsened significantly in rank and rating (p < .001 for both), whereas the programs with better reputations improved in rank (p < .001) and rating (p < .005).

CONCLUSION

The results suggest that the proportion of IMGs in a residency program is a significant factor in program selection and is as important as previously established factors such as program reputation. Students, however, do not acknowledge the importance of this factor. Program directors and governing bodies may want to consider these findings when evaluating the impact and distribution of IMGs in U.S. training programs.

Leg cramps: differential diagnosis and management

Leg cramps are a common problem, especially in the elderly. The differential diagnosis is extensive and includes the following conditions: true cramps, such as those related to heat, hemodialysis and electrolyte disturbances, as well as idiopathic cramps (the most common type); contractures occurring in conditions such as metabolic myopathies and thyroid disease; tetany, which is usually related to electrolyte disturbances, and dystonias, such as occupational cramps and those related to antipsychotic medications. Other leg problems that are not cramps, such as restless legs syndrome and periodic leg movements, also must be distinguished. The etiology of idiopathic leg cramps is not clear. Treatments for leg cramps include stretching exercises, quinine sulfate and vitamin E, but no treatment is conclusively effective. Nonetheless, in many patients relief of symptoms is achieved with one or more of these treatments.

Anaphylaxis-induced diabetic ketoacidosis

Allergic reactions and complications of diabetes mellitus are commonly seen in emergency departments and primary care settings. Although stress is a known contributor to the development of diabetic ketoacidosis (DKA), anaphylaxis-induced DKA has not previously been described. The case of a type 1 diabetic woman who presented with anaphylaxis secondary to seafood ingestion and subsequently developed DKA is reported. It was concluded that stress and counter-regulatory hormones released during anaphylaxis, as well as the treatment with epinephrine and glucocorticoids, precipitated DKA in this patient despite ongoing insulin and fluid therapy. Type 1 diabetic patients experiencing anaphylaxis may require prolonged periods of observation and measurement of serial blood glucose and urine ketones.