The influence of actions on auditory perception: cognitive and neural mechanisms

It is well known that self-generated stimuli are processed differently from externally generated stimuli. For example, many people have noticed since childhood that it is very difficult to make a self-tickling. In the auditory domain, self-generated sounds elicit smaller brain responses as compared to externally generated sounds, known as the sensory attenuation (SA) effect. SA is manifested in reduced amplitudes of evoked responses as measured through MEEG, decreased firing rates of neurons and a lower level of perceived loudness for self-generated sounds. The predominant explanation for SA is based on the idea that self-generated stimuli are predicted (e.g., the forward model account). It is the nature of their predictability that is crucial for SA. On the contrary, the sensory gating account emphasizes a general suppressive effect of actions on sensory processing, regardless of the predictability of the stimuli. Both accounts have received empirical support, which suggests that both mechanisms may exist. In chapter 2, three behavioural studies concerning the influence of motor activation on auditory perception were presented. Study 1 compared the effect of SA and attention in an auditory detection task and showed that SA was present even when substantial attention was paid to unpredictable stimuli. Study 2 compared the loudness perception of tones generated by others between Chinese and British participants. Compared to externally generated tones, a decrease in perceived loudness for others generated tones was found among Chinese but not among the British. In study 3, partial evidence was found that even when reading words that are related to action, auditory detection performance was impaired. In chapter 3, the classic SA effect of M100 suppression was replicated with MEG in study 4. With time-frequency analysis, a potential neural information processing sequence was found in auditory cortex. Prior to the onset of self-generated tones, there was an increase of oscillatory power in the alpha band. After the stimulus onset, reduced gamma power and alpha/beta phase locking were found. The three temporally segregated oscillatory events correlated with each other and with SA effect, which may be the underlying neural implementation of SA. In chapter 4, a TMS-MEG study was presented investigating the role of the cerebellum in adapting to delayed presentation of self-generated tones (study 5). It demonstrated that in sham stimulation condition, the brain can adapt to the delay (about 100 ms) within 300 trials of learning by showing a significant increase of SA effect in the suppression of M100, but not M200 component. Whereas after stimulating the cerebellum with a suppressive TMS protocol, the adaptation in M100 suppression disappeared and the pattern of M200 suppression reversed to M200 enhancement. These data support the idea that the suppressive effect of actions on auditory processing is a consequence of both motor driven sensory predictions and general sensory gating. The results also demonstrate the importance of neural oscillations in implementing SA effect and the critical role of the cerebellum in learning sensory predictions under sensory perturbation.

Caregivers' experiences and coping strategies relating to patient's subjective treatment-related cognitive impairment following Haematopoietic Stem Cell Transplant (HSCT)

The treatments involved in cancers of the blood and bone marrow can be physically and psychologically challenging and be associated with adverse secondary effects, including cognitive impairment. The incidence and severity of treatment-related cognitive impairment varies widely, however it can significantly impact quality of life by interfering with patients’ activities of daily living, relationships and future plans. It can also pose challenges for the patients’ caregivers, an area which has received comparatively less research attention. The aim of this study was to investigate caregivers’ experiences of treatment-related cognitive impairment in patients who have undergone Haematopoietic Stem Cell Transplant (HSCT); how they coped, both practically and emotionally, and what supports they believe could help them. Participants were caregivers to individuals who had undergone HSCT within the past 20 years and who had reported cognitive changes at the HSCT Late Effects Clinic, Beatson West of Scotland Cancer Centre. Five participants completed a single semi-structured interview. The data was then analysed using Interpretative Phenomenological Analysis (IPA). Results of this analysis illustrated four super-ordinate themes: noticing change; managing expectations, managing personal feelings and commitment. Findings from the current study highlighted the importance of caregiver education regarding post HSCT cognitive and behavioural changes and providing caregiver emotional support. Future research should explore the mutual needs of both care recipient and caregiver.

The use of Acceptance and Commitment Therapy to address psychological distress experienced by caregivers: a randomised controlled feasibility trial

Background: An extensive research literature has documented the impact of caring for an individual with acquired brain injury (ABI) on caregivers and family members, including role adjustment, psychological distress, social isolation, family tension and coping with the cognitive and behavioural difficulties of the injured person. Given these findings it is important this population have access to services and supports. Acceptance and Commitment Therapy (ACT) is an intervention that helps individuals to accept difficult experiences and commit to behaviour that is consistent with their values. Research into the effectiveness of ACT to support caregivers is at a preliminary stage. Aim: To investigate the feasibility of using ACT to reduce psychological distress and increase psychological flexibility in ABI caregivers. A secondary aim was to gain an understanding of the experience of caregivers in this context and how this can inform the development and delivery of interventions for this population. Method: Phase one was a randomised controlled feasibility trial of an ACT intervention for use with ABI caregivers. The parameters of this study were formulated around the PICO (population, intervention, control, and outcome) framework. Eighteen carers were recruited and randomised to ACT or an enhanced treatment as usual (ETAU) group. ACT was implemented over 3 sessions; and ETAU was implemented over 2 sessions. The General Health Questionnaire, Valuing Questionnaire, Acceptance and Action Questionnaire, Experiential Avoidance of Caregiving Questionnaire and the Flexibility of Responses to Self-Critical Thoughts Scale were administered to both groups at baseline and following the final session. Phase two used a retrospective qualitative design that involved conducting semi-structured interviews with four participants from phase one. Results: ACT and control participants were successfully recruited. Positive feedback was obtained from ACT participants suggesting that the intervention was acceptable. There were no significant differences between the ACT and ETAU groups on outcome measures. However, there were challenges retaining participants and the overall attrition rate was high (44.44%). Therefore a number of participants did not complete the full complement of sessions, which may have impacted on this result. Qualitative results illustrated the challenges this population face including significant adjustments in their life, the emotional impact of having a loved one with a brain injury and trying to adapt to the changes in the injured person. In addition, findings elucidated the types of support that this population would find helpful and the barriers to accessing same. Conclusions: Findings from this study highlight factors that will help the development of this intervention further for a caring population. Recommendations for future implementation include completing some preparatory work with carers before beginning the intervention, consideration of a larger sample and wider recruitment strategy from local services, barriers to attending interventions and the possibility of holding groups in local venues.

Investigating assistive technology to support memory for people with cognitive impairments

Technologies such as automobiles or mobile phones allow us to perform beyond our physical capabilities and travel faster or communicate over long distances. Technologies such as computers and calculators can also help us perform beyond our mental capabilities by storing and manipulating information that we would be unable to process or remember. In recent years there has been a growing interest in assistive technology for cognition (ATC) which can help people compensate for cognitive impairments. The aim of this thesis was to investigate ATC for memory to help people with memory difficulties which impacts independent functioning during everyday life. Chapter one argues that using both neuropsychological and human computing interaction theory and approaches is crucial when developing and researching ATC. Chapter two describes a systematic review and meta-analysis of studies which tested technology to aid memory for groups with ABI, stroke or degenerative disease. Good evidence was found supporting the efficacy of prompting devices which remind the user about a future intention at a set time. Chapter three looks at the prevalence of technologies and memory aids in current use by people with ABI and dementia and the factors that predicted this use. Pre-morbid use of technology, current use of non-tech aids and strategies and age (ABI group only) were the best predictors of this use. Based on the results, chapter four focuses on mobile phone based reminders for people with ABI. Focus groups were held with people with memory impairments after ABI and ABI caregivers (N=12) which discussed the barriers to uptake of mobile phone based reminding. Thematic analysis revealed six key themes that impact uptake of reminder apps; Perceived Need, Social Acceptability, Experience/Expectation, Desired Content and Functions, Cognitive Accessibility and Sensory/Motor Accessibility. The Perceived need theme described the difficulties with insight, motivation and memory which can prevent people from initially setting reminders on a smartphone. Chapter five investigates the efficacy and acceptability of unsolicited prompts (UPs) from a smartphone app (ForgetMeNot) to encourage people with ABI to set reminders. A single-case experimental design study evaluated use of the app over four weeks by three people with severe ABI living in a post-acute rehabilitation hospital. When six UPs were presented through the day from ForgetMeNot, daily reminder-setting and daily memory task completion increased compared to when using the app without the UPs. Chapter six investigates another barrier from chapter 4 – cognitive and sensory accessibility. A study is reported which shows that an app with ‘decision tree’ interface design (ApplTree) leads to more accurate reminder setting performance with no compromise of speed or independence (amount of guidance required) for people with ABI (n=14) compared to a calendar based interface. Chapter seven investigates the efficacy of a wearable reminding device (smartwatch) as a tool for delivering reminders set on a smartphone. Four community dwelling participants with memory difficulties following ABI were included in an ABA single case experimental design study. Three of the participants successfully used the smartwatch throughout the intervention weeks and these participants gave positive usability ratings. Two participants showed improved memory performance when using the smartwatch and all participants had marked decline in memory performance when the technology was removed. Chapter eight is a discussion which highlights the implications of these results for clinicians, researchers and designers.