Individual differences in laughter perception reveal roles for mentalizing and sensorimotor systems in the evaluation of emotional authenticity.

Humans express laughter differently depending on the context: polite titters of agreement are very different from explosions of mirth. Using functional MRI, we explored the neural responses during passive listening to authentic amusement laughter and controlled, voluntary laughter. We found greater activity in anterior medial prefrontal cortex (amPFC) to the deliberate, Emitted Laughs, suggesting an obligatory attempt to determine others' mental states when laughter is perceived as less genuine. In contrast, passive perception of authentic Evoked Laughs was associated with greater activity in bilateral superior temporal gyri. An individual differences analysis found that greater accuracy on a post hoc test of authenticity judgments of laughter predicted the magnitude of passive listening responses to laughter in amPFC, as well as several regions in sensorimotor cortex (in line with simulation accounts of emotion perception). These medial prefrontal and sensorimotor sites showed enhanced positive connectivity with cortical and subcortical regions during listening to involuntary laughter, indicating a complex set of interacting systems supporting the automatic emotional evaluation of heard vocalizations.

Approximating the stability region of a neural network with a general distribution of delays.

We investigate the linear stability of a neural network with distributed delay, where the neurons are identical. We examine the stability of a symmetrical equilibrium point via the analysis of the characteristic equation both when the connection matrix is symmetric and when it is not. We determine a mean delay and distribution independent stability region. We then illustrate a way of improving on this conservative result by approximating the true region of stability when the actual distribution is not known, but some moments or cumulants of the distribution are known. Finally, we compare the approximate stability regions with the stability regions in the case of the uniform and gamma distributions. We show that the approximations improve as more moments or cumulants are used, and that the approximations using cumulants give better results than the ones using moments.

Tillage and residue burning affects weed populations and seed banks.

An integrated weed management approach requires alternative management practices to herbicide use such as tillage, crop rotations and cultural controls to reduce soil weed seed banks. The objective of this study was to examine the value of different tillage practices and stubble burning to exhaust the seed bank of common weeds from the northern grain region of Australia. Five tillage and burning treatments were incorporated in a field experiment, at Armidale (30 degrees 30'S, 151 degrees 40'E), New South Wales, Australia in July 2004 in a randomized block design replicated four times. The trial was continued and treatments repeated in July 2005 with all the mature plants from the first year being allowed to shed seed in their respective treatment plots. The treatments were (i) no tillage (NT), (ii) chisel ploughing (CP), (iii) mould board ploughing (MBP), (iv) wheat straw burning with no tillage (SBNT) and (v) wheat straw burning with chisel ploughing (SBC). Soil samples were collected before applying treatments and before the weeds flowered to establish the seed bank status of the various weeds in the soil. Wheat was sown after the tillage treatments. Burning treatments were only initiated in the second year, one month prior to tillage treatments. The major weeds present in the seed bank before initiating the trial were Polygonum aviculare, Sonchus oleraceus and Avena fatua. Tillage promoted the germination of other weeds like Hibiscus trionum, Medicago sativa, Vicia sp. and Phalaris paradoxa later in the season in 2004 and Convolvulus erubescens emerged as a new weed in 2005. The MBP treatment in 2004 reduced the weed biomass to a significantly lower level of 55 g/m2 than the other treatments of CP (118 g/m2) and NT plots (196 g/m2) (P < 0.05). However, in 2005 SBC and MBP treatments were similar in reducing the weed biomass. In 2004, the grain yield trend of wheat was significantly different between CP and NT, and MBP and NT (P < 0.05) with maximum yield of 5898 kg/ha in CP and 5731 kg/ha in MBP. Rainfall before the start of the second trial season promoted the germination of a large numbers of weeds. SBC and MBP treatments reduced the numbers of most of the individual weed species compared with CP, SBNT and NT. SBC was able to destroy a large proportion of seeds most likely through burning and burying some in the soil and was found to be the best treatment in exhausting the seed bank followed closely by MBP which probably buried large number of seeds deep in the soil and promoted others to germinate. CP might have buried some of the seeds in the top 5-10 cm but also promoted parts of the seed bank to germinate. SBNT and NT provided an ideal medium for weeds to germinate and resulted in heavy infestations of weeds.

Differential response of chickpea genotypes to isoxaflutole.

A polyhouse experiment was conducted to determine the tolerance of twenty chickpea genotypes, ten from desi and ten from kabuli types, to isoxaflutole applied preemergence at 0, 25, 50, 100 (recommended rate), 200, 400 and 800 g ha(-1). There was a strong dose response, and injury ratings, plant height, shoot and root dry weight reduction were greater at the higher doses than at the lower doses for all genotypes. Shoot dry matter was significantly reduced for desi chickpea genotypes Jimbour, Amethyst, ICLL 87322 and 91025-3021. But the reductions were not significant for most of the kabuli types except for Kaniva and S 95425. The genotypexherbicide rate interactions were weakly significant (P = 0.07) for root dry matter but the effects of single factor were highly significant. Root dry weight reductions were significant for the desi genotypes Jimbour, Amethyst, Yorker, ICLL 87322 and 91025-3021. FLIP 94-90C, Kaniva and S 95425 only showed significant reductions in root dry matter among the kabuli types. There was less herbicide injury to the kabuli genotypes than to the desi types at both of the assessment days. The desi chickpea genotypes Yorker, Howzat, Amethyst, Gully and 91025-3021 exhibited overall mean injury ratings greater than 4.1 and can be regarded as susceptible. Among these genotypes significant shoot dry weight reductions occurred in Amethyst and 91025-3021. Amethyst, Yorker and 91025-3021 also experienced significant root dry matter reductions. Furthermore, all of the five above mentioned desi genotypes exhibited significant plant height reductions. Hence, chickpea genotypes differed in their response to isoxaflutole and desi genotypes are more susceptible than to the kabuli types.

Identifying hazards in complex ecological systems. Part 3: Hierarchical Holographic Model for herbicide tolerant oilseed rape.

This paper is the third in a series designed to demonstrate the application of rigorous, systematic hazard identification techniques to ecological systems. Here we use Hierarchical Holographic Modelling to identify the potential ecological hazards associated with the commercial release of herbicide tolerant oilseed rape. Hierarchical Holographic Models decompose complex systems into a series of sub-systems and consider interactions between the components and processes of these sub-systems in order to identify hazards. In this example we considered 1356 potential interactions between the biological, chemical and physical components and processes of the herbicide tolerant oilseed rape environment, and identified 152 potential hazards, grouped into 14 categories. The hazards were subsequently scored for degree of concern and plausibility, and then compared with an equivalent list of hazards generated independently by a checklist approach. The incidence of herbicide tolerant volunteers (and weeds) both on and off the farm had the highest average score of all the ecological hazard categories. The checklist based approach identified or implied 44% of the hazards identified in the Hierarchical Holographic Model, including nine of the ten hazards ranked most important. The checklist approach focussed almost exclusively on the phenotypic and genotypic hazards associated with herbicide tolerant oilseed rape and largely ignored the hazards associated with the circumstances surrounding its use. As a result the checklist identified only 6 out of the 79 potential hazards associated with changes to farming practice. The commercial release of herbicide tolerant oilseed rape will be associated with changes in tillage and the application of post-emergent herbicides. It may also lead to changes in spray schedules of insecticide and fungicide. Many of the environmental hazards identified with these changes are plausible and may warrant further investigation or targeted monitoring.