Search PubMed⌕ Search

Biomedical subjects

Peter W Halligan

Publications and source records attributed to Peter W Halligan.

At least 19 recordsLinked to original sources
PubMed2007

Hypnotic depth and response to suggestion under standardized conditions and during FMRI scanning.

Hypnosis is a potentially valuable cognitive tool for neuroimaging studies. However, understandable concern that Magnetic Resonance Imaging (MRI) in particular may adversely affect hypnotic procedures remains. Measurements of hypnotic depth and responsiveness to suggestions were taken using a standardized procedure that met all the requirements for functional MRI (fMRI). Testing outside the scanning environment showed reliable and stable changes in subjective hypnotic depth, with no carryover once the hypnosis had been terminated. Within-subject comparisons showed that the magnitude and pattern of these changes and the degree of responsiveness to hypnotic suggestion were not discernibly affected by the fMRI environment. It is concluded that hypnosis can be employed as a discrete and reliable cognitive tool within fMRI neuroimaging settings.

Adolescent↗
PubMed2006

Diagnosing delusions: a review of inter-rater reliability.

Although several studies have examined the reliability of diagnosing delusions there is no comprehensive review of the literature. Therefore, the reliability of diagnosing 'delusions in general' and the subcategory of 'bizarre delusions' was reviewed, including both structured interview and standardized instrument methods. The literature suggests that delusions in general can be diagnosed reliably with both structured interview and standardized instruments. However, bizarre delusions are not reliably diagnosed by either, suggesting that this concept may have little clinical validity. Nevertheless, many of the studies reviewed are poorly designed or subject to significant confounds. Criteria are suggested for adequate future studies.

Delusions↗
PubMed2006

Explaining delusions: a cognitive perspective.

There is now considerable evidence for reasoning, attention, metacognition and attribution biases in delusional patients. Recently, these findings have been incorporated into a number of cognitive models that aim to explain delusion formation, maintenance and content. Although delusions are commonly conceptualized as beliefs, not all models make reference to models of normal belief formation. This review considers those models that explain delusions as a breakdown of normal belief formation (belief-positive models), approaches that explain the pathology only (belief-negative models) and approaches that view delusions as one end of a distribution of anomalous mental phenomena (the continuum view). A cognitive theory that includes the 'pragmatic pathology' of delusions will be able to address both the phenomenology and the treatment of delusion-related distress.

Attention↗
PubMed2006

Awareness and knowing: implications for rehabilitation.

It has been known for well over a century that brain-damaged patients are often unaware of the very deficits that impair performance in everyday life. Pathologies of awareness have been described for many neurological, psychiatric and neuropsychological deficits and the construct of "awareness" or "insight" understandably now receives attention from many researchers within the clinical and cognitive neurosciences. This paper does not attempt to explain the nature of consciousness or its impairment but rather considers four aspects of consciousness/awareness that health care professionals interested in understanding, measuring and improving deficits of awareness should consider.

Awareness↗
PubMed2005

The Cardiff Anomalous Perceptions Scale (CAPS): a new validated measure of anomalous perceptual experience.

The study describes the Cardiff Anomalous Perceptions Scale (CAPS), a new validated measure of perceptual anomalies. The 32-item CAPS measure is a reliable, self-report scale, which uses neutral language, demonstrates high content validity, and includes subscales that measure distress, intrusiveness, and frequency of anomalous experience. The CAPS was completed by a general population sample of 336 participants and 20 psychotic inpatients. Approximately 11% of the general population sample scored above the mean of the psychotic patient sample, although, as a group, psychotic inpatients scored significantly more than the general population on all CAPS subscales. A principal components analysis of the general population data revealed 3 components: "clinical psychosis" (largely Schneiderian first-rank symptoms), "temporal lobe disturbance" (largely related to temporal lobe epilepsy and related seizure-like disturbances) and "chemosensation" (largely olfactory and gustatory experiences), suggesting that there are multiple contributory factors underlying anomalous perceptual experience and the "psychosis continuum."

Adolescent↗
PubMed2005

'Internet delusions': a case series and theoretical integration.

BACKGROUND: Delusions involving the internet have been reported as examples of the influence of cultural innovations on delusion formation, although there has been some debate as to whether such innovations simply affect surface content, or whether they have more substantial clinical or psychopathological implications. SAMPLING AND METHODS: Four cases of patients with delusions involving the internet were identified following a general request to local consultant psychiatrists for referrals. RESULTS: The internet had a specific effect on aetiology in one case, and knowledge of the internet seemed to constrain the type of delusion formed in two others. The presence of an internet-related delusion in the final case was used to frame a successful clinical intervention based on the 'collaborative empiricism' method, using cognitive behavioural therapy and collaborative use of the internet to resolve the delusional belief. CONCLUSIONS: Cultural technical innovations may have specific influences on the form, origin and content of delusional beliefs. For some patients the presence of internet-themed delusions may be a good prognostic indicator since, given the rich sources of information available, they may be well suited to treatment with cognitive behavioural therapy.

Adult↗
PubMed2003

Stimulus symmetry affects the bisection of figures but not lines: evidence from event-related fMRI.

Many geometric shapes retain their symmetry when bisected, but appear asymmetrical when misbisected. We have previously shown that this correspondence can guide the accuracy and speed of perceptual bisection (Landmark) judgments. Using event-related fMRI, here we examined whether the behavioural effects of symmetry are also evident at the neural level. The data showed that the presence/absence of symmetry modulates the activity of right anterior cingulate gyrus, an area associated with a variety of higher level attentional functions. A previous visual half-field study also showed that bisected lines are apprehended more quickly and accurately than misbisected lines in right, but not left, visual field. We were able to localise this advantage to right superior temporal gyrus. Significantly, we found no evidence that symmetry played a role in apprehending the midpoint of the line stimuli traditionally used to assess visual neglect. The data clarify the effects of visual symmetry on bisection behaviour, and highlight novel dissociations within the neural systems thought to underline Landmark performance.

Adult↗
PubMed2003

Simulating unilateral neglect in normals using prism adaptation: implications for theory.

Rightward deviation on line bisection is considered one of the most classic clinical signs of unilateral visual neglect--a cognitive disorder of spatial processing that commonly follows right brain damage. Recently, short-term adaptation to wedge prisms has been shown to significantly reduce neglect on this and other conventional diagnostic tasks. Our previous study has shown that visuomotor adaptation in normals produces a similar pattern of directional bias on a line bisection task. Based on the good working knowledge of how neglect patients perform on different versions of the standard diagnostic task, we showed here that using leftward-deviating prisms in normals, it is possible to produce: (1) a reliable bias on line bisection, (2) a rightward specific deviation, (3) a modulation of rightward deviation, which depends on the relative spatial location of the target lines and (4) a line length effect. A final experiment confirmed that these after-effects are specific to prism adaptation rather than passive prism exposure. Collectively, these findings confirm that adaptation to left-deviating prisms in normals produces a reliable right-sided bias and as shown by a previous visuospatial judgement task, these findings cannot be adequately explained by the symmetric sensori-motor effects of prism adaptation. Taken together with the improvement of spatial neglect shown by right-deviating prisms only, the present study suggests that low level sensori-motor adaptations play a greater role in right hemisphere organisation for spatial cognition than previously thought.

Adaptation, Physiological↗
PubMed2003

Relative contribution of footwear to the efficacy of ankle-foot orthoses.

OBJECTIVE: To examine the relative effects of footwear and an ankle-foot orthosis (AFO) on hemiplegic gait. DESIGN: A case series with three contrasting conditions: walking without footwear, with footwear alone, and with footwear and an AFO. Spatio-temporal parameters reflecting walking performance were analysed using an analysis of variance (ANOVA). PATIENTS: Five patients with hemiplegia and reduced mobility following stroke. SETTING: A specialist rehabilitation centre. INTERVENTION: Wearing either footwear alone, or footwear with an AFO. MEASURES: Video recordings of gait were subjected to a kinematic analysis to determine spatio-temporal parameters. RESULTS: Stride length was increased by an average of 5 cm when wearing footwear. An additional 5-cm increase was also observed when wearing an AFO. Swing velocity was also affected by the manipulation. CONCLUSIONS: The appropriate comparative baseline for assessing the efficacy of an AFO is subjects walking with existing footwear and not barefoot.

Adult↗
PubMed2002

The effects of interdistracter similarity on search processes in superior parietal cortex.

The superior parietal lobe has been associated with the spatial integration of visual features, an important step in the detection of particular form conjunctions. However, behavioral research has indicated that when target items can be segmented from neighboring distracters via similarity grouping, detection may not rely on spatial integration. The question therefore arises as to whether the superior parietal cortex is an integral component of conjunction search or only important in the absence of certain grouping relations. Here, we acquired measures of reaction time and event-related fMRI, while subjects searched for conjunction targets in displays containing either homogeneous or heterogeneous distracters. We confirm that under conditions of low distracter similarity, search involves parietal-motor areas associated with spatial selection. However, we also demonstrate that under conditions of high distracter similarity, search is instead associated with activation of right temporal-parietal cortex. These results suggest that the superior parietal cortex is not a necessary component of visual conjunction search and highlight a new role for the right temporal-parietal cortex in perceptual grouping.

Adult↗
PubMed2002

The effects of stimulus symmetry on landmark judgments in left and right visual fields.

Line bisection impairment is greater following right compared to left hemisphere damage, suggesting that some of the underlying visuo-spatial mechanisms may be lateralised. One important perceptual component of line bisection is estimating stimulus midpoint. Here, we used a modified version of the perceptual landmark task to examine, in healthy individuals, how the midpoint of a stimulus is apprehended, and if the cerebral hemispheres are equally as efficient in performing such a task. We show that the right, relative to the left, hemisphere is both faster and more accurate at apprehending prebisected lines, but no better at apprehending misbisected lines. We then demonstrate that the right hemisphere advantage stems from a specialisation in detecting stimulus symmetry; by associating prebisected lines with the presence of display symmetry, transect location can be inferred without having to explicitly calculate the midpoint of lines. The findings provide a further reason why right hemisphere damage is so deterimental to perceptual line bisection. In addition, the data indicate that the detection of visual symmetry is preferentially lateralised to the right hemisphere.

Adult↗
PubMed2002

RIVCAM: a simple video-based kinematic analysis for clinical disorders of gait.

This paper describes the development of and reports on the accuracy of the Rivermead video-based clinical gait analysis method (RIVCAM), a simple and comparatively inexpensive movement recording system, which operates at 50 Hz. The system comprises five basic steps; firstly subjects are recorded using a PAL video camera with white markers affixed to the leg. Second, the video footage is digitised onto a computer. Thirdly, a program analyses each frame of footage to locate the position of white markers located on the subject's leg. Fourth, the data are calibrated (turned into real world co-ordinates) and the markers on the legs are identified (such as, heel, toe, etc.). Finally, a kinematic analysis is performed on the data, which not only produces a range of relevant spatio-temporal parameters (such as gait velocity, cadence and stride length), but also determines the joint angles at the hip, knee and ankle during the gait cycle. Overall the system has a reasonable constant and variable error; in a recorded scene measuring 2.6 x 1.6 m and divided into a 3 x 3 grid, a 400 mm bar was recorded, on average, as being 401.1 mm with a standard deviation (S.D.) of 2.97 mm. Although not without shortcomings when compared with more expensive and complicated systems, the RIVCAM system represents a valid, reliable and affordable way of collecting objective measures of gait in a busy therapy setting.

Adult↗
PubMed2002

Phantom limbs: The body in mind.

INTRODUCTION: Advances in our knowledge of corporeal awareness is not limited to patients with amputations, however, until recently, the study of ''phantom limbs'' was neglected by comparison with less common disorders of body perception. METHOD: Reasons for the neglect of this potentially informative and common condition are conspicuous by their absence in previous reviews. Over the past decade, however, experimental investigations of phantom limbs have revealed the dynamic neural processes that provide for both phantom and normal corporeal embodiment. Moreover, these findings helped to overturn widely held scientific assumptions regarding the extent of neural plasticity in the adult brain. RESULTS: It is suggested that throughout medical history, the construct of ''phantom limbs'' posed a challenge to fundamental folk assumptions regarding the assumed relationship between body and mind. CONCLUSION: Reluctance to entertain the counter-intuitive phenomenon of a ''limbless perception'' contributed to the comparative neglect of this fascinating phenomenon until the late 20th century.

Journal Article↗
PubMed2002

Hypnotic imagery as a treatment for phantom limb pain: two case reports and a review.

OBJECTIVE: To provide a theoretical background, to review existing literature and to present new case material relevant to the treatment of phantom limb pain using hypnotic imagery. METHOD: This paper presents two new case reports involving the use of hypnotic imagery procedures in the alleviation of phantom limb pain and reviews 10 previous clinical studies which have involved a similar approach. The earlier studies were identified by electronic and manual searches of the relevant literature. RESULTS: Two main treatment strategies can be identified: (1) ipsative/imagery-based approaches and (2) movement/imagery-based approaches. A common finding is the need to treat the phantom limb as a 'real' body part, to accept its existence as a valid mental representation and to avoid treating the amputation stump as the sole source of the phantom pain sensations. CONCLUSION: Hypnotic procedures appear to be a useful adjunct to established strategies for the treatment of phantom limb pain and would repay further, more systematic, investigation. Suggestions are provided as to the factors which should be considered for a more systematic research programme.

Aged↗