Dissociation of affective modulation of recollective and perceptual experience following amygdala damage

It has been suggested that similar neural mechanisms may underlie the affective modulation of both recollective and perceptual experience. A case is reported of a patient who has bilateral amygdala damage and marked impairment in the perception of emotion, particularly fear. The patient DR and 10 healthy control subjects (matched for school leaving age, intelligence quotient, and non-emotional memory performance) were shown a series of slides accompanied by an emotionally arousing narrative. One week later DR and the controls were given a surprise memory test for this material. In addition, they completed a verbal memory test using emotionally arousing stimuli. Both DR and the healthy control subjects showed a normative pattern of enhanced memory for emotional material. On the basis of these results and the previously demonstrated impairment of perception of emotion in this patient, it is concluded that different neural mechanisms may underlie affective modulation of recollective and perceptual experience

Controlling the polarisation correlation of photon pairs from a charge-tuneable quantum dot

Correlation between the rectilinear polarisations of the photons emitted from the biexciton decay in a single quantum dot is investigated in a device which allows the charge-state of the dot to be controlled. Optimising emission from the neutral exciton states maximises the operating efficiency of the biexciton decay. This is important for single dot applications such as a triggered source of entangled photons. As the bias on the device is reduced correlation between the two photons is found to fall dramatically as emission from the negatively charged exciton becomes significant. Lifetime measurements demonstrate that electronic spin-scattering is the likely cause.Comment: 3 figure

The distribution of the dwarf succulent genus Conophytum N.E.Br. (Aizoaceae) in southern Africa.

Background: The dwarf succulent genus Conophytum N.E.Br. is one of the most speciose in the Aizoceae. The genus is most closely associated with a region of high floral endemism and biodiversity, namely the Succulent Karoo biome in Southwestern Africa. Objectives: To examine the distribution of Conophytum in Southwestern Namibia and in the Northern and Western Capes of South Africa. Method: A database consisting of 2,798 locality records representing all known species and subspecies of the genus Conophytum has been constructed. Results: The genus is primarily restricted to the arid winter rainfall region of the Northern and Western Cape of South Africa and southwestern Namibia within the Greater Cape Floristic Region. Whilst taxa are found across all the main biomes in the region (the Succulent Karoo, Nama Karoo, Desert and Fynbos biomes), 94% of Conophytum taxa are found only in the Succulent Karoo biome, and predominantly (88% of taxa) within South Africa. Endemism within specific bioregions is a feature of the genus and ~60% of taxa are endemic to the Succulent Karoo alone. Approximately 28% of all taxa could be considered point endemics. Whilst the genus has a relatively wide geographical range a pronounced centre for endemism has been identified in the southern Richtersveld. Conclusion: That the genus Conophytum can be used as a good floral model for studying patterns of diversity and speciation in the Succulent Karoo biome; the effects of climate change on dwarf succulents; as well as informing conservation planning efforts

The dwarf succulent genus Conophytum N.E.Br.: distribution, habitat and conservation.

The dwarf succulent genus Conophytum N.E.Br. is one of the most species rich in the Aizoaceae. Primarily restricted to the arid winter-rainfall region of the Northern and Western Cape Provinces of South Africa and southwestern Namibia, the genus is most closely associated with the Succulent Karoo biome, a region of high floral endemism and biodiversity. Many taxa are niche-specialists and almost a third of all Conophytum are severely range-restricted and can be considered to be pointendemics. The genus as a whole is vulnerable to anthropogenic impacts and many species are threatened by activities such as mining, agriculture and climate change

Population genetic structure and direct observations reveal sex-reversed patterns of dispersal in a cooperative bird

Sex-biased dispersal is pervasive and has diverse evolutionary implications, but the fundamental drivers of dispersal sex biases remain unresolved. This is due in part to limited diversity within taxonomic groups in the direction of dispersal sex biases, which leaves hypothesis testing critically dependent upon identifying rare reversals of taxonomic norms. Here, we use a combination of observational and genetic data to demonstrate a rare reversal of the avian sex bias in dispersal in the cooperatively breeding white-browed sparrow weaver (Plocepasser mahali). Direct observations revealed that (i) natal philopatry was rare, with both sexes typically dispersing locally to breed, and (ii), unusually for birds, males bred at significantly greater distances from their natal group than females. Population genetic analyses confirmed these patterns, as (i) corrected Assignment index (AIc), FST tests and isolation-by-distance metrics were all indicative of longer dispersal distances among males than females, and (ii) spatial autocorrelation analysis indicated stronger within-group genetic structure among females than males. Examining the spatial scale of extra-group mating highlighted that the resulting ‘sperm dispersal’ could have acted in concert with individual dispersal to generate these genetic patterns, but gamete dispersal alone cannot account entirely for the sex differences in genetic structure observed. That leading hypotheses for the evolution of dispersal sex biases cannot readily account for these sex-reversed patterns of dispersal in white-browed sparrow weavers highlights the continued need for attention to alternative explanations for this enigmatic phenomenon. We highlight the potential importance of sex differences in the distances over which dispersal opportunities can be detected

Testing the stability of behavioural coping style across stress contexts in the Trinidadian guppy

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this record.1. Within-populations, individuals can vary in stress response, a multivariate phenomenon comprising neuroendocrine, physiological and behavioural traits. 2. Verbal models of individual stress ‘coping style’ have proposed that the behavioural component of this variation can be described as a single axis, with each individual’s coping style being consistent across time and stress contexts. 3. Focusing on this behavioural component of stress response, and combining repeated measures of multiple traits with a novel multivariate modelling framework, we test for the existence of coping style variation and assess its stability across contexts in the Trinidadian guppy (Poecilia reticulata). 4. Specifically, we test the following hypotheses: (i) there exists repeatable among-individual behavioural (co)variation (‘personality’) within a mild stress context consistent with a risk-averse—risk-prone continuum of behavioural coping style, (ii) there is population-level plasticity in behaviour as a function of stressor severity, (iii) there is among-individual variation in plasticity (i.e., IxE), and (iv) the presence of IxE reduces cross-context stability of behavioural coping style. 5. We found significant repeatable among-individual behavioural (co)variation in the mild stress context (open field trial), represented as an I matrix. However, I was not readily described by a simple risk-averse—risk-prone continuum as posited by the original coping style model. We also found strong evidence for population-level changes in mean behaviour with increasing stressor severity (simulated avian and piscine predation risks). 6. Single-trait analyses did show the presence of individual-by-environment interactions (IxE), as among-individual cross-context correlations were significantly less than +1. However, multi-trait analysis revealed the consequences of this plasticity variation were minimal. Specifically, we found little evidence for changes in the structure of I between mild and moderate stress contexts overall, and only minor changes between the two moderate contexts (avian versus piscine predator). 7. We show that a multivariate approach to assessing changes in among individual (co)variance across contexts can prevent the over-interpretation of statistically significant, but small, individual-by-environment effects. While behavioural flexibility enables populations (and individuals) to respond rapidly to changes in the environment, multivariate personality structure can be conserved strongly across such contexts.Funding was provided by a grant from the Biotechnology and Biological Sciences Research Council (BBSRC, grant BB/L022656/1). A.J.Y. is supported by a BBSRC David Phillips Fellowship

Structure of Titan's mid-range magnetic tail: Cassini magnetometer observations during the T9 flyby

We analyze the magnetic structure of Titan's mid-range magnetic tail (5-6 Titan radii downstream from the moon) during Cassini's T9 flyby. Cassini magnetometer (MAG) measurements reveal a well-defined, induced magnetic tail consisting of two lobes and a distinct central current sheet. MAG observations also indicate that Saturn's background magnetic field is close to the moon's orbital plane and that the magnetospheric flow has a significant component in the Saturn-Titan direction. The analysis of MAG data in a coordinate system based on the orientation of the background magnetic field and an estimation of the incoming flow direction suggests that Titan's magnetic tail is extremely asymmetric. An important source of these asymmetries is the connection of the inbound tail lobe and the outbound tail lobe to the dayside and nightside hemispheres of Titan, respectively. Another source could be the perturbations generated by changes in the upstream conditions

Dominance-related contributions to collective territory defence are adjusted according to the threat

Across diverse societies, group members benefit from the cooperative maintenance of a shared territory (a public good). How such public goods are maintained has received extensive interest, yet individual contributions to cooperative territory defence remain poorly understood. Recent theory predicts that, in groups with social hierarchies, privileged individuals will contribute most to competition with rival groups as they benefit most from defence of the territory. Here, we investigate whether dominant individuals contribute more to territory defence in a group-territorial bird in which dominants monopolise within-group reproduction; the white-browed sparrow weaver (Plocepasser mahali). Using simulated territorial intrusions, we demonstrate that dominants contribute significantly more than subordinates to territory defence. We also demonstrate that individual contributions are adjusted according to threat: males of both social classes significantly and similarly increased their contributions to defence in response to a high threat (playback of an unfamiliar pair’s duet, rather than that of a neighbouring pair), which was associated with a stronger collective response by the group. Thus, while dominants contribute most as predicted by the asymmetry in benefits, subordinates do increase contributions when they are needed most (in small groups and under greater threat). Contributions by subordinates when needed most also highlights that dominants could still benefit substantially from tolerating the presence of subordinates despite their overall lower contributions. Our results show that public goods can be maintained despite unequal contributions, and highlight the potential importance of context-dependent behavioural flexibility in mitigating collective action problems

Cassini detection of Enceladus' cold water-group plume ionosphere

This study reports direct detection by the Cassini plasma spectrometer of freshly-produced water-group ions (O+, OH+, H2O+, H3O+) and heavier water dimer ions (HxO(2))(+) very close to Enceladus where the plasma begins to emerge from the plume. The data were obtained during two close ( 52 and 25 km) flybys of Enceladus in 2008 and are similar to ion data in cometary comas. The ions are observed in detectors looking in the Cassini ram direction exhibiting energies consistent with the Cassini speed, indicative of a nearly stagnant plasma flow in the plume. North of Enceladus the plasma slowing commences about 4 to 6 Enceladus radii away, while south of Enceladus signatures of the plasma interaction with the plume are detected 22 Enceladus radii away. Citation: Tokar, R. L., R. E. Johnson, M. F. Thomsen, R. J. Wilson, D. T. Young, F. J. Crary, A. J. Coates, G. H. Jones, and C. S. Paty ( 2009), Cassini detection of Enceladus' cold water-group plume ionosphere, Geophys. Res. Lett., 36, L13203, doi:10.1029/2009GL038923