The Tokophobia Severity Scale (TSS): measurement model, power and sample size considerations.

OBJECTIVE: To examine the measurement model of the Tokophobia Severity Scale and consider issues of statistical power and sample size from the original instrument development study. BACKGROUND: Fear of childbirth (FoC) and tokophobia represents an area of increasing concern within perinatal mental health research and clinical practice. Existing measures of the FoC have been criticised due to either measurement inconsistencies, difficulties in scoring or practical clinical application. Attempting to address these limitations, researchers developed the Tokophobia Severity Scale (TSS). A fundamental assumption underpinning the use of the TSS is unidimensionality, however this assertion may have been based on sub-optimal sample size and approach taken to factor structure determination. METHOD: Parallel analysis (PA), principal components analysis (PCA), exploratory factor analysis (EFA), power analysis and sample size calculation using a reconstruction of the original dataset from published summary data. RESULTS: Following replication of the original PCA, a three-factor model was found to offer a significantly better fit to data than a unidimensional model. Power analysis suggested the original study was underpowered. CONCLUSION: The TSS remains a promising tool but assumptions regarding its measurement model are based on an inadequate sample size. Sample sizes for a sufficiently powered study indicated.

Sleep patterns in Parkinson's disease patients with visual hallucinations.

Visual hallucinations (VHs) in Parkinson's disease (PD) can be a frequent and disturbing complication of the disease with 33% of PD patients undergoing long-term treatment experiencing VHs during the course of their illness. One line of evidence that is emerging as a possible risk factor in the occurrence of VHs is the sleep-wake cycle and sleep behavior in patients with PD. This study compared sleep patterns in a group of visually hallucinating Parkinson's patients with a group of nonhallucinating PD patients and an age-matched control group. Nocturnal sleep was assessed by actigraphy and diaries, while daytime sleepiness and function were assessed by a battery of self-rating sleep questionnaires. Compared with the control group both patient groups had more sleep-related problems and significantly altered sleep patterns, as measured by both actigraphy and sleep questionnaires. Patients who hallucinated however slept less than nonhallucinating patients and also had increased awakenings after sleep onset, reduced sleep efficiency, and increased daytime sleepiness. We propose that VHs in some PD patients may be a symptom of poor sleep and prolonged daytime sleepiness, suggesting that arousal may play a role in the genesis of the hallucination phenomenon.

Visual memory transformations in dyslexia.

Representational Momentum refers to observers' distortion of recognition memory for pictures that imply motion because of an automatic mental process which extrapolates along the implied trajectory of the picture. Neuroimaging evidence suggests that activity in the magnocellular visual pathway is necessary for representational momentum to occur. It has been proposed that individuals with dyslexia have a magnocellular deficit, so it was hypothesised that these individuals would show reduced or absent representational momentum. In this study, 30 adults with dyslexia and 30 age-matched controls were compared on two tasks, one linear and one rotation, which had previously elicited the representational momentum effect. Analysis indicated significant differences in the performance of the two groups, with the dyslexia group having a reduced susceptibility to representational momentum in both linear and rotational directions. The findings highlight that deficits in temporal spatial processing may contribute to the perceptual profile of dyslexia.

Behavioural coping patterns in Parkinson's patients with visual hallucinations.

Visual Hallucinations are considered to affect about 20%-40% of patients with Parkinson's disease. They are generally seen as a side effect of this long-term illness and can severely affect the daily quality of life of patients. The aim of this study was to determine the coping patterns or strategies used by patients and establish whether the phenomenology and behaviours used by patients enabled control of the phenomenon. Demographic and clinical variables were recorded, including motor measures, cognitive status, and depressive symptoms. Patient with hallucinations were at a more advance stage of the disease and displayed more depressive symptoms than their non-hallucinating counterparts. Most patients used more than one constructive coping strategy, the most common were simple behavioural strategies based around motor action or cognitive approaches resulting in visual modification. In addition, humour was a common technique used by the patients to deal with the phenomenon. Emotional responses varied between patients, but it was found that the actual content of the hallucination was not directly associated with whether it caused trouble to the patient, but perceived stress was strongly correlated with the subjective disturbing nature of visual hallucinations (VHs). This study gives insight into the role of cognitive-behavioural approaches when dealing with VHs and opens up avenues for future studies in helping patient to deal with hallucinations.