Abnormal negative feedback processing in first episode schizophrenia: evidence from an oculomotor rule switching task

Background. Previous studies have shown that patients with schizophrenia are impaired on executive tasks, where positive and negative feedbacks are used to update task rules or switch attention. However, research to date using saccadic tasks has not revealed clear deficits in task switching in these patients. The present study used an oculomotor ‘ rule switching ’ task to investigate the use of negative feedback when switching between task rules in people with schizophrenia. Method. A total of 50 patients with first episode schizophrenia and 25 healthy controls performed a task in which the association between a centrally presented visual cue and the direction of a saccade could change from trial to trial. Rule changes were heralded by an unexpected negative feedback, indicating that the cue-response mapping had reversed. Results. Schizophrenia patients were found to make increased errors following a rule switch, but these were almost entirely the result of executing saccades away from the location at which the negative feedback had been presented on the preceding trial. This impairment in negative feedback processing was independent of IQ. Conclusions. The results not only confirm the existence of a basic deficit in stimulus–response rule switching in schizophrenia, but also suggest that this arises from aberrant processing of response outcomes, resulting in a failure to appropriately update rules. The findings are discussed in the context of neurological and pharmacological abnormalities in the conditions that may disrupt prediction error signalling in schizophrenia

Does the Southern Farmington Canyon Complex Record a Late Archean/Early Proterozoic Accretionary Complex?

The Farmington Canyon Complex, situated along the Wasatch front in northern Utah, has been the target for many studies. The FCC has been interpreted to be a passive margin sedimentary wedge. Previous studies have yielded isotopic ages that broadly support an Archean age of formation, and a prominent mid-proterozoic amphibolite grade metamorphic event. Based on this study, a new interpretation for the FCC is presented. Field relations and whole-rock geochemistry as well as recent advances in understanding Archean crustal processes have resulted in the FCC to be considered as an accretionary complex that formed along the SW margin of the Wyoming province in the early Archean. Rock assemblages such as mafic and ultramafic metavolcanics have chemistries that resemble oceanic crust and arc related volcanics. The extensive quartzo-felspathic gneiss and schist units have compositions that reflect greywacke, and are presented here as a melange matrix. The quartzites have chemistries, which may represent cherts or silicified microbial mats. The field relations and timing of these rocks indicate that the FCC may represent a continental arc synchronous with the closing of an ocean basin, forming an accretionary wedge. This culminated with the mid-proterozoic metamorphic event as this continental arc collided with the Santaquin arc, as well as the SW margin of Laurentia. This amphibolite grade metamorphic event has subsequently reset or overprinted isotopic evidence and obscured any textures that may have existed. Although much has yet to be learned about Archean processes, comparison to other recognized Archean accretionary complexes has yielded striking similarities, and it is presented here that the FCC represents an active margin, and is likely an accretionary melange

Dissecting the Urge to Create

A neuropsychiatrist reviews "The Midnight Disease: The drive to write, writer's block and the creative brain

Women, Work, and Worship in Lincoln\u27s Country: The Dumville Family Letters

Review of: Women, Work, and Worship in Lincoln\u27s Country: The Dumville Family Letters, edited by Anne M. Heinz and John P. Heinz

Equation-free modeling of evolving diseases: Coarse-grained computations with individual-based models

We demonstrate how direct simulation of stochastic, individual-based models can be combined with continuum numerical analysis techniques to study the dynamics of evolving diseases. % Sidestepping the necessity of obtaining explicit population-level models, the approach analyzes the (unavailable in closed form) `coarse' macroscopic equations, estimating the necessary quantities through appropriately initialized, short `bursts' of individual-based dynamic simulation. % We illustrate this approach by analyzing a stochastic and discrete model for the evolution of disease agents caused by point mutations within individual hosts. % Building up from classical SIR and SIRS models, our example uses a one-dimensional lattice for variant space, and assumes a finite number of individuals. % Macroscopic computational tasks enabled through this approach include stationary state computation, coarse projective integration, parametric continuation and stability analysis.Comment: 16 pages, 8 figure