Visual Feedback Dominates the Sense of Agency for Brain-Machine Actions

Recent advances in neuroscience and engineering have led to the development of technologies that permit the control of external devices through real-time decoding of brain activity (brain-machine interfaces; BMI). Though the feeling of controlling bodily movements (sense of agency; SOA) has been well studied and a number of well-defined sensorimotor and cognitive mechanisms have been put forth, very little is known about the SOA for BMI-actions. Using an on-line BMI, and verifying that our subjects achieved a reasonable level of control, we sought to describe the SOA for BMI-mediated actions. Our results demonstrate that discrepancies between decoded neural activity and its resultant real-time sensory feedback are associated with a decrease in the SOA, similar to SOA mechanisms proposed for bodily actions. However, if the feedback discrepancy serves to correct a poorly controlled BMI-action, then the SOA can be high and can increase with increasing discrepancy, demonstrating the dominance of visual feedback on the SOA. Taken together, our results suggest that bodily and BMI-actions rely on common mechanisms of sensorimotor integration for agency judgments, but that visual feedback dominates the SOA in the absence of overt bodily movements or proprioceptive feedback, however erroneous the visual feedback may be.     

Inter-chromophore interactions in pigment-modified and dimer-less bacterial photosynthetic reaction centers

The magnitudes of inter-chromophore interactions in bacterial photosynthetic reaction centers are investigated by measuring absorption and Stark spectra of reaction centers in which monomeric chromophores are modified and in a novel triplet mutant which lacks the special pair. The circular dichroism spectrum of the triple mutant reaction center was also measured. Only small changes in the spectroscopic properties are observed, as has also been found for several types of reaction centers in which the absorption or chemical properties of a chromophore are altered by site-specific mutations. We conclude that the electronic absorption, circular dichroism and Stark features of the special pair and the monomeric chromophores in the reaction center are relatively insensitive to inter-chromophore interactions.     

The synthesis and spectroscopic analysis of the neurotoxic prion peptide 106-126: Comparative use of manual Boc and Fmoc chemistry

A peptide corresponding to residues 106-126 of the human prion protein (PrP) possesses the neurotoxic and amyloidogenic properties of the infectious form of the parental protein. This peptide is now identified as a 'difficult sequence' and synthesis using conventional manual Fmoc chemistry was unsuccessful with acylation terminating at a central core of hydrophobic amino acids. The use of tetramethylfluoroformamidinium hexafluorophosphate and 1-methyl-2- pyrrolidone as anti-aggregatory agents in the coupling steps improved the synthesis but still resulted in an incomplete peptide. The incorporation of N-(2-hydroxy-4-methoxybenzyl) protection at glycine residues 119 and 124 enabled synthesis of the full length peptide in low yield. Synthesis using Boc chemistry with in situ neutralisation gave the full length peptide in high yield.     

Estimating the Risk of Chronic Pain: Development and Validation of a Prognostic Model (PICKUP) for Patients with Acute Low Back Pain

BackgroundLow back pain (LBP) is a major health problem. Globally it is responsible for the most years lived with disability. The most problematic type of LBP is chronic LBP (pain lasting longer than 3 mo); it has a poor prognosis and is costly, and interventions are only moderately effective. Targeting interventions according to risk profile is a promising approach to prevent the onset of chronic LBP. Developing accurate prognostic models is the first step. No validated prognostic models are available to accurately predict the onset of chronic LBP. The primary aim of this study was to develop and validate a prognostic model to estimate the risk of chronic LBP.ConclusionsBased on its performance in these cohorts, this five-item prognostic model for patients with acute LBP may be a useful tool for estimating risk of chronic LBP. Further validation is required to determine whether screening with this model leads to a net reduction in unnecessary interventions provided to low-risk patients.     

Ontogeny and the evolution of adult body size dimorphism in apes

This analysis investigates the ontogeny of body size dimorphism in apes. The processes that lead to adult body size dimorphism are illustrated and described. Potential covariation between ontogenetic processes and socioecological variables is evaluated. Mixed-longitudinal growth data from 395 captive individuals (representing Hylobates lar [gibbon], Hylobates syndactylus [siamang], Pongo pygmaeus [orangutan], Gorilla gorilla [gorilla], Pan paniscus [pygmy chimpanzee], and Pan troglodytes [“common” chimpanzee]) form the basis of this study. Results illustrate heterogeneity in the growth processes that produce ape dimorphism. Hylobatids show no sexual differentiation in body weight growth. Adult body size dimorphism in Pongo can be largely attributed to indeterminate male growth. Dimorphism in African apes is produced by two different ontogenetic processes. Both pygmy chimpanzees (Pan paniscus) and gorillas (Gorilla gorilla) become dimorphic primarily through bimaturism (sex differences in duration of growth). In contrast, sex differences in rate of growth account for the majority of dimorphism in common chimpanzees (Pan troglodytes). Diversity in the ontogenetic pathways that produce adult body size dimorphism may be related to multiple evolutionary causes of dimorphism. The lack of sex differences in hylobatid growth is consistent with a monogamous social organization. Adult dimorphism in Pongo can be attributed to sexual selection for indeterminate male growth. Interpretation of dimorphism in African apes is complicated because factors that influence female ontogeny have a substantial effect on the resultant adult dimorphism. Sexual selection for prolonged male growth in gorillas may also increase bimaturism relative to common chimpanzees. Variation in female growth is hypothesized to covary with foraging adaptations and with differences in female competition that result from these foraging adaptations. Variation in male growth probably corresponds to variation in level of sexual selection. © 1995 Wiley-Liss, Inc.     

Long-term changes in a Wisconsin Fagus-Acer forest in relation to glaze storm disturbance

Changes in the composition of a Fagus-Acer (Beech-Sugar maple) forest in southeastern Wisconsin over a 16-yr period from 1971 to 1987 are analyzed in relation to a severe glaze (ice) storm disturbance occurring within the census period. Landscape topography created ‘windward’ and ‘leeward’ forest aspects with respect to storm severity, which resulted in greater canopy opening on the windward aspect. In the tree stratum, most species remained stable in density and most of the common species increased in basal area into larger size classes. However, Fagus grandifolia, Ulmus rubra, and the small tree Ostrya virginiana suffered net losses that suggest synergistic effects between glaze storm disturbance and other factors upon tree mortality. In the sapling stratum, canopy opening strongly promoted release of shade-to levant Acer sac-charum. On the windward forest aspect, sapling densities of less shade-tolerant species also increased, in contrast to the absence of such increases on the leeward forest aspect. In the shrub (regeneration) stratum, species responses were heterogeneous. Regeneration of most species increased over the 16-yr period, and some less shade-tolerant species showed increased regeneration differentially on the windward forest aspect. Overall, disturbance appears to have accelerated forest succession toward increased dominance by A. saccharum and persistence of both Fagus and Tilia americana through their capacities for root sprouting. However, forest succession was retarded somewhat on the windward aspect through increased recruitment of less-shade tolerant species. These results parallel those of other studies of glaze storm disturbance, and they illustrate how spatially heterogeneous disturbance intensity may contribute to maintenance of forest diversity.     

Effects of diethyldithiocarbamate (ddtc) on the plasma biotransformations of tetrachloro(d,i-trans)-1,2-diaminocyclohexaneplatinum(iv) (tetraplatin) in fischer 344 rats

We have studied the effects of diethyldithiocarbamate (DDTC) on the biotransformations of toxic doses of tetrachloro (d,l-trans)1,2-diaminocyclohexaneplatinum(IV) (tetraplatin) in Fischer 344 rats. In animals not treated with DDTC, tetraplatin was rapidly converted to dichloro(d,I-trans)1,2-diaminocyclohexaneplatinum(II) [PtCl₂(dach]. Subsequent biotransformations included the transient formation of the (d,I-trans)1,2-diaminocyclohexane-aquachloroplatinum(II) [Pt(H₂O)(Cl)(dach)]+ complex, followed by formation of the platinum (Pt)-methionine and either Pt-cysteine or Pt-ornithine complexes. Significant amounts of free (d,I-trans) 1,2-diaminocyclohexane (dach) were observed in plasma as a result of intracellular trans-labilization reactions. DDTC caused a marked decrease in both total and protein-bound platinum in the circulation. A significant increase in the plasma concentration of free dach was also observed as a result of formation of the Pt(DDTC)₂ complex. Some of the free dach could have arisen from intracellular reactions with DDTC, but the displacement of platinum from plasma proteins was more than sufficient to account for the increase in free dach in the circulation. DDTC treatment also decreased plasma concentrations of tetraplatin, PtCl₂(dach), [Pt(H₂O)(Cl)(dach)]⁺, the Pt-methionine complex, and one unidentified biotransformation product, but had no effect on the Pt-cysteine (or Pt-ornithine) complex. These effects of DDTC on protein-bound platinum and low-molecular-weight biotransformation products in plasma may contribute to the decrease in tetraplatin toxicity seen in DDTC-treated rats.