Cognitive and neural mechanisms underlying auditory verbal hallucinations in a non-clinical sample

Auditory verbal hallucinations (AVHs) are the experience of hearing a voice in the absence of any speaker. Cognitive models of AVHs have suggested that they may occur when an internal mental event, such as inner speech, is misattributed to an external source. This has variously been explained by reference to biases in self-monitoring, source monitoring, or reality discrimination processes. Evidence suggests that, mechanistically, this may be related to atypical functioning of a forward model system which usually predicts the outcome of self-generated actions, attenuating activity in sensory cortices to the resulting perceptual input. At a higher level, excessive vividness and low cognitive effort associated with internal mental events may be associated with external misattributions of inner speech. Chapter 1 reviews inner speech models of AVH, as well as recent attempts to reduce the frequency of AVHs using neurostimulation. Chapter 2 then provides a methodological overview of techniques used in this thesis. The first two empirical studies presented in this thesis, in Chapters 3 and 4, explore the cognitive mechanisms underlying AVHs by investigating the associations between self-reported hallucination-proneness and phenomenology of inner speech, and performance on source monitoring and self-monitoring tasks, in a non-clinical, student sample. The results indicated that hallucination-prone participants were more likely to misattribute self-generated auditory verbal imagery, both when instructed to generate imagery and when they retrospectively reported using imagery. Regression analysis also indicated that a tendency to use dialogic inner speech, biased performance on reality discrimination and self-monitoring tasks, and a tendency to perceive meaning in jumbled speech independently predicted hallucination-proneness. The studies presented in Chapters 5 and 6 investigated the neural basis of performance on auditory signal detection and source monitoring tasks using transcranial direct current stimulation (tDCS). Results indicated that modulating activity in the superior temporal gyrus/temporoparietal junction (STG/TPJ) affected the number of false perceptions on the signal detection task. However, stimulation to the left STG or medial prefrontal cortex did not affect performance on a source monitoring task. These results indicate that different cortical regions may be involved in the two tasks, and hence that they may reflect different aspects of how self-generated actions are experienced as such. Together, the four experimental chapters 1) provide evidence for inner speech accounts of AVH, 2) indicate the need for a more complex account of self-monitoring and reality discrimination in which both are seen as independent predictors of AVHs, and 3) suggest that the left STG plays a key role in reality discrimination, but less so in source monitoring tasks (at least in the encoding stage). The thesis concludes with a general discussion of these issues, and recommendations for future research

The Poetry of Rafael Alberto Arrieta

It is with the Post-Modernist group that we are concerned in this study, for it is in this direction that the poetry of Rafael Alberto Arrieta leads. The poetic expression of Arrieta is not, however, a conscious, deliberate rebellion against Modernism. Arrieta was born in the 1889; he therefore grew up under the influence of Modernism. The most formative years of his life were spent while Modernism dominated the world of poetry. Yet Arrieta had the literary integrity to express his own personality in spite of the prevailing influences

Airborne 20-65 micron spectrophotometry of Comet Halley

Observations of Comet Halley with a grating spectrometer on board the Kuiper Airborne Observatory on four nights in Dec. 1985 to Apr. 1986 are reported. Low resolution 20 to 65 micrometer spectra of the nucleus with a 40 arcsec FWHM beam was obtained on 17 Dec. 1985, and on 15 and 17 Apr. 1986. On 20 Dec. 1985, only a 20 to 35 micrometer spectrum was obtained. Most of the data have been discussed in a paper where the continuum was dealt with. In that paper, models were fit to the continuum that showed that more micron sized particles of grain similar to amorphous carbon were needed to fit the spectrum than were allowed by the Vega SP-2 mass distribution, or that a fraction of the grains had to be made out of a material whose absorption efficiency fell steeper than lambda sup -1 for lambda greater than 20 micrometers. Spectra was also presented taken at several points on the coma on 15 Apr. which showed that the overall shape to the spectrum is the same in the coma. Tabulated values of the data and calibration curves are available. The spectral features are discussed

Conclusion: Hanging by a Thread: The Future of Cotton in Africa

Several broad themes emerge from the chapters in this volume. While declining world prices are a serious issue, the ability of farmers to weather declines in prices is often determined by national and local issues. These include government policy, institutions that provide marketing and supply services, access to resources such as land, labor, and agricultural inputs, and individual decision making. Despite declining world prices, some cotton growing economies have had success with cotton production while others have not fared well. In particular, the failure of cotton institutions in many countries is striking.Whether it comes to managing input distribution, new technologies, or marketing, cotton institutions are failing African farmers. Prices offered to farmers in West Africa declined from 2003 to 2007 at the same time that input prices increased in many countries, making cotton production precarious for local producers. Problems with corruption, particularly in the marketing and transportation of cotton, have made cotton difficult for poorer farmers, who are cash constrained. Late payments, a theme of many chapters in this book, have put farmers in a bind, constraining them to sell food crops (which must often be repurchased later in the season for a higher price) in order to settle debts. One of the results of this squeeze has been high levels of indebtedness. Cotton farmers must borrow large amounts of money for inputs, sometimes equaling almost half of what they expect to gain at the end of the season. The risks of crop failure are high, for many reasons, from household labor shortages to late pickup, to unforeseen natural disaster. These risks become less and less justifiable as cotton prices decline