Spatial Hearing with Simultaneous Sound Sources: A Psychophysical Investigation

This thesis provides an overview of work conducted to investigate human spatial hearing in situations involving multiple concurrent sound sources. Much is known about spatial hearing with single sound sources, including the acoustic cues to source location and the accuracy of localisation under different conditions. However, more recently interest has grown in the behaviour of listeners in more complex environments. Concurrent sound sources pose a particularly difficult problem for the auditory system, as their identities and locations must be extracted from a common set of sensory receptors and shared computational machinery. It is clear that humans have a rich perception of their auditory world, but just how concurrent sounds are processed, and how accurately, are issues that are poorly understood. This work attempts to fill a gap in our understanding by systematically examining spatial resolution with multiple sound sources. A series of psychophysical experiments was conducted on listeners with normal hearing to measure performance in spatial localisation and discrimination tasks involving more than one source. The general approach was to present sources that overlapped in both frequency and time in order to observe performance in the most challenging of situations. Furthermore, the role of two primary sets of location cues in concurrent source listening was probed by examining performance in different spatial dimensions. The binaural cues arise due to the separation of the two ears, and provide information about the lateral position of sound sources. The spectral cues result from location-dependent filtering by the head and pinnae, and allow vertical and front-rear auditory discrimination. Two sets of experiments are described that employed relatively simple broadband noise stimuli. In the first of these, two-point discrimination thresholds were measured using simultaneous noise bursts. It was found that the pair could be resolved only if a binaural difference was present; spectral cues did not appear to be sufficient. In the second set of experiments, the two stimuli were made distinguishable on the basis of their temporal envelopes, and the localisation of a designated target source was directly examined. Remarkably robust localisation was observed, despite the simultaneous masker, and both binaural and spectral cues appeared to be of use in this case. Small but persistent errors were observed, which in the lateral dimension represented a systematic shift away from the location of the masker. The errors can be explained by interference in the processing of the different location cues. Overall these experiments demonstrated that the spatial perception of concurrent sound sources is highly dependent on stimulus characteristics and configurations. This suggests that the underlying spatial representations are limited by the accuracy with which acoustic spatial cues can be extracted from a mixed signal. Three sets of experiments are then described that examined spatial performance with speech, a complex natural sound. The first measured how well speech is localised in isolation. This work demonstrated that speech contains high-frequency energy that is essential for accurate three-dimensional localisation. In the second set of experiments, spatial resolution for concurrent monosyllabic words was examined using similar approaches to those used for the concurrent noise experiments. It was found that resolution for concurrent speech stimuli was similar to resolution for concurrent noise stimuli. Importantly, listeners were limited in their ability to concurrently process the location-dependent spectral cues associated with two brief speech sources. In the final set of experiments, the role of spatial hearing was examined in a more relevant setting containing concurrent streams of sentence speech. It has long been known that binaural differences can aid segregation and enhance selective attention in such situations. The results presented here confirmed this finding and extended it to show that the spectral cues associated with different locations can also contribute. As a whole, this work provides an in-depth examination of spatial performance in concurrent source situations and delineates some of the limitations of this process. In general, spatial accuracy with concurrent sources is poorer than with single sound sources, as both binaural and spectral cues are subject to interference. Nonetheless, binaural cues are quite robust for representing concurrent source locations, and spectral cues can enhance spatial listening in many situations. The findings also highlight the intricate relationship that exists between spatial hearing, auditory object processing, and the allocation of attention in complex environments

Fatigue in cancer survivors. From assessment to cognitive behaviour therapy.

Contains fulltext : 45169_fatiincas.pdf (publisher's version ) (Open Access)RU Radboud Universiteit Nijmegen, 17 januari 2008Promotores : Bleijenberg, G., Mulder, P.H.M. de Co-promotor : Verhagen, C.A.H.H.V.M.181 p

Interventions to reduce postcancer fatigue: a literature overview.

Contains fulltext : 69637.pdf (publisher's version ) (Closed access

Cognitive behaviour therapy for fatigued cancer survivors.

Contains fulltext : 52726.pdf (publisher's version ) (Closed access

Useful fatigue assessmant tools in research and clinical practice.

Contains fulltext : 69460.pdf (publisher's version ) (Closed access

Psychosocial interventions for reducing fatigue during cancer treatment in adults.

BACKGROUND: Fatigue is a common symptom in cancer patients receiving active treatment. There are a limited number of reviews evaluating interventions for fatigue during active treatment, and they are restricted to patients with advanced cancer, or to patients during radiotherapy. To date there is no systematic review on psychosocial interventions for fatigue during cancer treatment. OBJECTIVES: To evaluate if psychosocial interventions are effective in reducing fatigue in cancer patients receiving active treatment for cancer, and which types of psychosocial interventions are the most effective. SEARCH STRATEGY: In September 2008 we searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library), PUBMED, MEDLINE, EMBASE, CINAHL and PsycINFO, and checked the reference lists. SELECTION CRITERIA: Randomised controlled trials (RCTs) were included which evaluated psychosocial interventions in adult cancer patients during treatment, with fatigue as an outcome measure. DATA COLLECTION AND ANALYSIS: Three review authors independently extracted data from the selected studies, and assessed the methodological quality using several quality rating scales and additional criteria. MAIN RESULTS: Twenty-seven studies met the inclusion criteria with a total of 3324 participants, and seven studies reported significant effects of the psychosocial intervention on fatigue. In three studies the effect was maintained at follow-up. The quality of the studies was generally moderate. Effect sizes varied between 0.17 to 1.07.The effectiveness of interventions specific for fatigue was significantly higher (80%) compared to interventions not specific for fatigue (14%). In five studies the interventions were specifically focused on fatigue, with four being effective. The five interventions were brief, consisting of three individual sessions, provided by (oncology) nurses. In general, during these interventions participants were educated about fatigue, were taught in self-care or coping techniques, and learned activity management.Of the remaining 22 studies only three were effective in reducing fatigue, and these interventions had a more general approach. These interventions were aimed at psychological distress, mood and physical symptoms, and varied strongly in duration and content. AUTHORS' CONCLUSIONS: There is limited evidence that psychosocial interventions during cancer treatment are effective in reducing fatigue. At present, psychosocial interventions specifically for fatigue are a promising type of intervention. However, there is no solid evidence for the effectiveness of interventions not specific for fatigue. Most aspects of the included studies were heterogeneous, and therefore it could not be established which other types of interventions, or elements were essential in reducing fatigue

The relationship of fatigue in breast cancer survivors with quality of life and factors to address in psychological interventions: A systematic review

Item does not contain fulltextSevere fatigue occurs in one in four breast cancer survivors (BCS). Quality of life (QOL) and psychological factors are important in fatigue-oriented interventions for BCS, but an up-to-date overview is lacking. The aims of this review were to (i) provide a comprehensive overview of the relationship of fatigue with QOL and factors that can be addressed in psychological interventions for fatigue in BCS and (ii) determine the strength of evidence for these relationships. A systematic literature search was conducted to find studies on fatigue in BCS who had completed curative breast cancer treatment. Fatigue-related factors of 57 eligible studies were extracted and the level of evidence was determined. Factors regarding QOL (ie, general QOL, functioning, work ability, and mental health) had a negative relationship with fatigue (moderate to strong evidence). Target factors for psychological interventions were divided into the subcategories emotional problems, sleep disturbances, physical activity, pain, coping with cancer, dysfunctional cognitions, and social support. Moderate to strong evidence appeared for a relationship of fatigue with depressive symptoms, anxiety, distress, sleep disturbances, lower physical activity levels, pain, difficulties with coping with cancer, and catastrophizing about symptoms. These factors are points of attention for existing and future psychological interventions for fatigue in BCS

Effects of cognitive behavior therapy in severely fatigued disease-free cancer patients compared with patients waiting for cognitive behavior therapy: a randomized controlled trial.

Contains fulltext : 50248.pdf (publisher's version ) (Closed access)PURPOSE: Persistent fatigue is a long-term adverse effect experienced by 30% to 40% of patients cured of cancer. The main objective of this randomized controlled trial was to show the effectiveness of cognitive behavior therapy (CBT) especially designed for fatigue in cancer survivors. PATIENTS AND METHODS: A total of 112 cancer survivors with somatically unexplained fatigue were allocated randomly to immediate cognitive behavior therapy or to a waiting list condition for therapy. Both conditions were assessed two times, at baseline and 6 months later. The primary outcome variables were fatigue severity (Checklist Individual Strength) and functional impairment (Sickness Impact Profile). Data were analyzed by intention to treat. RESULTS: Analyses were based on 50 patients in the intervention condition and 48 patients in the waiting list condition. Patients in the intervention condition reported a significantly greater decrease than patients in the waiting list condition in fatigue severity (difference, 13.3; 95% CI, 8.6 to 18.1) and in functional impairment (difference, 383.2; 95% CI, 197.1 to 569.2). Clinically significant improvement for the CBT group compared with the waiting list group was seen in fatigue severity (54% v 4% of the patients, respectively) and in functional impairment (50% v 18% of the patients, respectively). CONCLUSION: Cognitive behavior therapy has a clinically relevant effect in reducing fatigue and functional impairments in cancer survivors