This thesis examines information-processing in chronic pain. "Schematic" processing is investigated selective memory for pain-related information is explored in depressed and non-depressed chronic pain patients, depressed non pain-patients and controls. A memory bias for sensory adjectives is found in the non depressed chronic pain group, while a tendency to over-recall both sensory and affective compared to neutral information is found in the depressed chronic pain group. No memory bias is observed in an acute pain group, and the implications of this are discussed. A possible cognitive avoidance mechanism is identified in depression. A questionnaire assessing beliefs about pain ("conceptual" processing) is developed and validated, and shown to differentiate between chronic pain patients and controls. The impact of two interventions for chronic pain (surgery and cognitive-behavioural management) on schematic and conceptual processing is investigated prospectively. In general the endorsement of organic beliefs decreases while the emphasis on psychological beliefs increases post-intervention. Evidence is found to suggest that surgery, but not cognitive-behavioural treatment, reverses pain-related memory biases. This is discussed in relation to changes in pain intensity. Evidence is provided to suggest that beliefs are causally related to several pain-related measures including anxiety, depression, health locus of control, cognitive coping strategies and activity levels. A word completion paradigm is employed to explore further the role of schematic processing in chronic pain, and finally, a lexical decision task is used to assess the role of word frequency effects in information-processing in chronic pain. These results suggest that memory biases in chronic pain cannot be explained by frequency effects, hence addressing the validity of the memory biases described earlier in the thesis.

Thesis (M. Phil.)--University of Hong Kong, 1996. / Includes bibliographical references (leaf 112-114) and index.

In this work, I characterized a series of potential application kernels using a set of architectural and non-architectural metrics, and performed a comparison of four different alternatives for processing-in-memory cores (PIMs): ARM cores, GPGPUs, coarse-grained reconfigurable dataflow (DF-PIM), and a domain specific architecture using SIMD PIM engine consisting of a series of multiply-accumulate circuits (MACs). For each PIM alternative I investigated how performance and energy efficiency changes with respect to a series of system parameters, such as memory bandwidth and latency, number of PIM cores, DVFS states, cache architecture, etc. In addition, I compared the PIM core choices for a subset of applications and discussed how the application characteristics correlate to the achieved performance and energy efficiency. Furthermore, I compared the PIM alternatives to a host-centric solution that uses a traditional server-class CPU core or PIM-like cores acting as host-side accelerators instead of being part of 3D-stacked memories. Such insights can expose the achievable performance limits and shortcomings of certain PIM designs and show sensitivity to a series of system parameters (available memory bandwidth, application latency and bandwidth sensitivity, etc.). In addition, identifying the common application characteristics for PIM kernels provides opportunity to identify similar types of computation patterns in other applications and allows us to create a set of applications which can then be used as benchmarks for evaluating future PIM design alternatives.

No description available.

In dieser Arbeit wird in mehreren Experimenten untersucht, wie gut junge und alte Erwachsene Sätze mit unterschiedlich komplexer syntaktischer Struktur verstehen können. Zentrales Thema dabei sind die Schwierigkeiten, die ältere Erwachsene mit der Objekt-vor-Subjekt-Wortstellung haben. Untersucht wird, inwiefern diese beobachteten Altersunterschiede durch eine reduzierte verbale Arbeitsgedächtniskapazität der älteren Erwachsenen erklärt werden können. Dabei stellt sich die Frage, ob die Defizite ein generelles verbales Arbeitsgedächtnis betreffen oder ob es ein eigenes Verarbeitungs-system für syntaktische Informationen gibt, dessen Kapazität mit dem Alter abnimmt. Es wurde versucht, die postulierte reduzierte Arbeitsgedächtniskapazität der älteren Erwachsenen an jungen Erwachsenen zu simulieren, indem deren Arbeitsgedächtniska-pazität durch eine Zusatzaufgabe künstlich eingeschränkt wurde. Weiterhin wurden die Altersunterschiede bei syntaktisch komplexen zentraleingebetteten Relativsätzen mit denen bei syntaktisch einfacheren koordinierten Hauptsätzen verglichen. Um die Studienteilnehmer mit den seltenen objektinitialen Strukturen zu konfrontieren und ihre Erfahrung mit solchen Sätzen zu verändern, wurden schließlich sowohl junge als auch alte Erwachsene mit Sätzen mit Objekt-vor-Subjekt-Wortstellung trainiert. / In this paper several experiments about age differences in comprehension of sentences with different syntactical structure are reported. The main focus is on the difficulties old adults experience when a sentence starts with an object. Can the age differences be explained by differences in working memory capacity? Have old adults less working memory capacity, or does there exist a separate working memory for syntactic information which declines with age? In an age simulation, young adults working memory capacity was reduced by an additional digit load. Age differences in comprehension of syntactical complex sentences were compared with age differences in sentences with less complex syntactical structure. To change their experience with the rare object initial word order participants were trained with object initial sentences.

Despite extensive evidence documenting abnormal hypothalamic-pituitary-adrenal (HPA) axis functioning as a risk factor for the development of depression and other psychiatric disorders, and experimental evidence from acute stress manipulations, the effects of sustained cortisol alterations on clinically relevant cognitive-behavioural and neural processing remain poorly understood. The aim of this thesis was to characterise how non-acute changes in cortisol levels modify behavioural and neural biases implicated in stress-related disorders by following two complementary lines of evidence: firstly, by increasing cortisol via a direct pharmacological intervention; and secondly, by testing the ability of gut microbiota manipulations to alter cortisol reactivity. The first study found that sustained increases in cortisol following 10-day administration of hydrocortisone were associated with altered memory and emotional processing in healthy volunteers. Specifically, participants receiving hydrocortisone showed enhanced recognition of emotional words, while their neutral memory performance was unaffected despite lower parahippocampal and occipital activation during viewing and encoding of neutral pictures. Furthermore, we found that resting-state functional connectivity between limbic-temporal regions of interest (amygdala and hippocampus) and the striatum (head of the caudate), as well as frontal and prelimbic cortices was decreased. In contrast, hippocampal and visual processing during negative facial expressions, and functional connectivity between the amygdala and the brainstem at rest, were increased in the hydrocortisone versus placebo groups. Overall, these findings suggest that non-acute increases in glucocorticoids enhance processing of emotionally salient information in limbic-temporal regions, which may modulate further neural mechanisms of sensory and homeostatic relevance. Enhancements in declarative emotional memory following hydrocortisone also implicate the modulation of amygdalar-hippocampal interactions by cortisol. Conversely, neutral stimulus processing was found to be either reduced or unaffected across a number of cognitive and memory domains. A specific increase for negative processing was further supported by poorer self-reported well-being at the mid-point of the study in participants receiving hydrocortisone. In a separate study exploring the ability of prebiotic supplements to affect cortisol reactivity and emotional processing, a Bimuno-galactooligosaccharide prebiotic was found to reduce the waking cortisol response and increase positive versus negative attentional processing in healthy volunteers. While these effects were not found to be associated, they provide initial promising evidence of the ability to target the HPA axis and emotional processing via the gut microbiota in humans. Overall, this thesis supports the idea that stress-induced physiological changes after prolonged or repeated cortisol exposure are associated with neural and behavioural alterations, which in turn have been crucial in understanding neuropsychological mechanisms underlying psychiatric disease. A better stratification of the effects of sustained HPA axis alterations on psychiatrically relevant cognitive-emotional domains and neural mechanisms thus remains of high priority.

Originally presented as the author's thesis (Ph. D.)--Leiden University. / Includes bibliographical references (p. 265-280) and index.

Originally presented as the author's thesis (Ph. D.)--Leiden University. / Includes bibliographical references (p. 265-280) and index.

Originally presented as the author's Thesis (Ph. D.)--Leiden University. / Includes bibliographical references (p. 265-280) and index.

Photonic quantum information processing has emerged as a powerful platform for realising quantum-enhanced technologies. In order to be scalable, many of these technologies depend on the availability of a suitable quantum memory for the coherent storage and on-demand retrieval of photonic quantum states. In this thesis, I investigate broadband light storage in a room-temperature Raman memory, implemented both in free space and, for the first time, inside a low-finesse optical cavity designed for low-noise operation. The ability of the Raman memory to preserve phase coherence was tested by storing coherent polarisation states in two spatially separate atomic ensembles. Polarisation storage with a fidelity of up to 97 ± 1% was demonstrated by performing full process tomography on the system. The Raman memory was then interfaced for the first time with a spontaneous parametric downconversion (SPDC) source of heralded, GHz-bandwidth single photons. The memory performance was characterised by measuring the second-order autocorrelation of the retrieved fields. While the SPDC input photon statistics showed a clear influence on the statistics of the retrieved field, four-wave mixing (FWM) noise, stimulated by spontaneous Raman scattering, prevented the preservation of non-classical photon statistics during read-out. Suppressing this source of noise represents the last remaining challenge for realising a broadband single-photon Raman memory suitable for quantum information applications. To this end, I demonstrate a novel cavity implementation of the Raman memory which reduces the FWM contribution relative to the signal field by re-distributing the density of states into which the noise photons can be scattered. Cavity-enhanced memory operation was investigated using weak coherent input states, showing a significant improvement of the signal-to-noise ratio compared to the free-space memory implementation. This proof-of-principle demonstration suggests that cavity Raman memories may offer a practical route towards low-noise, high-bandwidth quantum storage at room temperature.