Suboptimality in human categorization and identification.

Categorization and identification decision processes were examined and compared in 4 separate experiments. In all tasks, the critical stimulus component was a line that varied across trials in length and orientation, and the optimal decision rules were always complex piecewise quadratic functions. Evidence was found that identification is mediated by separate explicit and implicit systems. In addition, a common type suboptimality was found in both categorization and identification. In particular, observers apparently approximated the piecewise quadratic functions of the optimal decision rules with simpler piecewise linear functions. A computational model, which was motivated by a recent neuropsychological theory of category learning, successfully accounted for this suboptimal performance in both categorization and identification. The model assigns a key role to the striatum and assumes the observed suboptimality was largely due to massive convergence of visual cortical cells onto single striatal units. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cerebral arteriovenous malformations in children: neuroimaging findings

Cerebral arteriovenous malformations (CAVMs) are uncommon in children. CAVMs represent the most frequent intracranial vascular pathology at pediatric ages. This report concerns 13 children below the age of 16; all were identified between September 1995 and December 1996 with 14 CAVMs among them. All were proved by conventional cerebral angiography (CCA). Thirteen computed tomography (CT), 7 magnetic resonance images (MRI), 2 magnetic resonance angiography (MRA) and 13 conventional cerebral angiography (CCA) were analyzed. Most CAVMs nidus were located in cerebral hemispheres. Four in the temporal lobe, two in the parietal lobe, three in the frontal lobe, two in the occipital lobe, and three in the corpus callosum. One of them was of a mixed type with two nidi. The major clinical features of CAVMs were intracranial hemorrhage and seizures. Experience here was that MRI is superior to CT in showing the exact anatomic relationships of the nidus and in demonstrating the extent of CAVMs nidus obliteration after treatment. MRA provided a noninvasive means of studying blood vessels and vascular pathology in relationship to the CAVMs nidus. Standard angiography is still necessary to characterize in-flow and out-flow of vessels in CAVMs when definitive treatment is considered.     

Carbohydrate sulfotransferases: mediators of extracellular communication

Sulfated carbohydrates mediate diverse extracellular recognition events in both normal and pathological processes. The sulfotransferases that generate specific carbohydrate 'sulfoforms' have recently been recognized as key modulators of these processes and therefore represent potential therapeutic targets.     

Linkage of proximal myotonic myopathy to chromosome 3q

We performed genetic linkage analysis in nine German proximal myotonic myopathy (PROMM) families using DNA-markers D3S1541 and D3S1589 from the region of the recently discovered gene locus of myotonic dystrophy type 2 (DM2) on chromosome 3q. Two-point analysis supplied an lod score of 5.9. We conclude that a gene causing PROMM is located on chromosome 3q. PROMM and DM2 may be allelic disorders or may be caused by closely linked genes.     

Laparoscopic vesicopsoas hitch for infiltrative ureteral endometriosis

Type-specific serologic assays for herpes simplex virus (HSV) types 1 and 2 based on glycoprotein G-1 (gG-1) (HSV-1) and gG-2 (HSV-2) discriminate between antibodies against HSV-1 and HSV-2. We previously developed a Western blot assay using gG-1 and gG-2 expressed in baculovirus, performed extensive validation studies, and determined that it was both sensitive and specific for type-specific detection of HSV antibody. Here we report that, among a cohort of Thai military recruits, the serostatus of some individuals changed from positive to negative over time (6.6% among those ever positive for HSV-1, and 14.9% among those ever positive for HSV-2). We tested a subset of these specimens in three other gG-based assays: an enzyme-linked immunosorbent assay, an immunoblot strip assay, and a Western blot assay. Positive-to-negative shifts occurred in every assay; the frequency of the shifts ranged from 6. 1% to 21.2% of the specimen sets tested. There was only limited agreement among the assays concerning which individuals lost reactivity. This inaccuracy, exhibited by all of the assay protocols, was not predicted by validation studies employing specimens from cross-sectional studies and was most pronounced in HSV-2 testing. This argues for the inclusion of serial blood specimens in serologic assay validation procedures.