81 research outputs found
The Neuroscience of Visual Hallucinations
No full textEach year, some two million people in the United Kingdom experience visual hallucinations. Infrequent, fleeting visual hallucinations, often around sleep, are a usual feature of life. In contrast, consistent, frequent, persistent hallucinations during waking are strongly associated with clinical disorders; in particular delirium, eye disease, psychosis, and dementia. Research interest in these disorders has driven a rapid expansion in investigatory techniques, new evidence, and explanatory models. In parallel, a move to generative models of normal visual function has resolved the theoretical tension between veridical and hallucinatory perceptions. From initial fragmented areas of investigation, the field has become increasingly coherent over the last decade. Controversies
and gaps remain, but for the first time the shapes of possible unifying models are becoming clear, along with the techniques for testing these.
This book provides a comprehensive survey of the neuroscience of visual hallucinations and the clinical techniques for testing these. It brings together the very latest evidence from cognitive neuropsychology, neuroimaging, neuropathology, and neuropharmacology, placing this within current models of visual perception.
Leading researchers from a range of clinical and basic science areas describe visual hallucinations in their historical and scientific context, combining introductory information with up-to-date discoveries. They discuss results from the main investigatory techniques applied in a range of clinical disorders. The final section outlines future research directions investigating the potential for new understandings of veridical and hallucinatory perceptions, and for treatments of problematic hallucinations.
Fully comprehensive, this is an essential reference for clinicians in the fields of the psychology and psychiatry of hallucinations, as well as for researchers in departments, research institutes and libraries. It has strong foundations in neuroscience, cognitive science, optometry, psychiatry, psychology, clinical medicine, and philosophy. With its lucid explanation and many illustrations, it is a clear resource for educators and advanced undergraduate and graduate students
Serum 25-hydroxyvitamin D and cognitive decline in the very old: The Newcastle 85+ study
No full textBackground and purpose:
Studies investigating the association between 25-hydroxyvitamin D [25(OH)D] and cognition in the very old (85+) are lacking.
Methods:
Cross-sectional (baseline) and prospective data (up to 3 years follow-up) from 775 participants in the Newcastle 85+ Study were analysed for global (measured by the Standardized Mini-Mental State Examination) and attention-specific (measured by the attention battery of the Cognitive Drug Research test) cognitive performance in relation to season-specific 25(OH)D quartiles.
Results:
Those in the lowest and highest season-specific 25(OH)D quartiles had an increased risk of impaired prevalent (1.66, 95% confidence interval 1.06–2.60, P = 0.03; 1.62, 95% confidence interval 1.02–2.59, P = 0.04, respectively) but not incident global cognitive functioning or decline in functioning compared with those in the middle quartiles adjusted for sociodemographic, health and lifestyle confounders. Random effects models showed that participants belonging to the lowest and highest 25(OH)D quartiles, compared with those in the middle quartiles, had overall slower (log-transformed) attention reaction times for Choice Reaction Time (lowest, b = 0.023, P = 0.01; highest, b = 0.021, P = 0.02), Digit Vigilance Task (lowest, b = 0.009, P = 0.05; highest,b = 0.01, P = 0.02) and Power of Attention (lowest, b = 0.017, P = 0.02;highest, b = 0.022, P = 0.002) and greater Reaction Time Variability (lowest,b = 0.021, P = 0.02; highest, b = 0.02, P = 0.03). The increased risk of worse global cognition and attention amongst those in the highest quartile was not observed in non-users of vitamin D supplements/medication.
Conclusion:
Low and high season-specific 25(OH)D quartiles were associated with prevalent cognitive impairment and poorer overall performance in attention-specific tasks over 3 years in the very old, but not with global cognitive decline or incident impairment
Visual hallucinations
No full textResearch into visual hallucinations has accelerated over the last decade from around 350 publications per year in 2000 to over 500 in 2010. Increased recognition of the frequent occurrence of visual hallucinations in a number of common disorders, coupled with improvements in the measurement of phenomenology, and more sophisticated imaging techniques have allowed the development and initial testing of sophisticated models. However, key questions remain unanswered. Amongst these are: whether there is a satisfactory definition of hallucinations in a constructive visual system; whether there are one, two or several core varieties of hallucinations; what are the underlying brain mechanisms for hallucinations; and what, if anything, can be done to treat them when they lead to distress? Looking across research in several clinical areas suggests a tentative integrative model that allows the possibility of answering these questions, but much work remains to be done
Psychotherapy, consciousness, and brain plasticity
No full textPurely psychological treatments for emotional distress produce lasting, measureable, and reproducible changes in cognitive and emotional consciousness and brain function. How these changes come about illustrates the interplay between brain and consciousness. Studies of the effects of psychotherapy highlight the holistic nature of consciousness. Pre and post treatment functional Magnetic Resonance Imaging localises the brain changes following psychotherapy to frontal, cingulate, and limbic circuits, but emphasise that these areas support a wide range of conscious experiences. Multivoxel Pattern Analysis of distributed changes in function across these brain areas may be able to provide the ability to distinguish between different states of consciousness
Identifying specific interpretations and use of safety behaviours in people with distressing visual hallucinations: an exploratory study
No full textVisual hallucinations (VH) are a common experience and can be distressing and disabling, particularly for people suffering from psychotic illness. However, not everyone with visual hallucinations reports the experience to be distressing. Models of VH propose that appraisals of VH as a threat to wellbeing and the use of safety seeking behaviours help maintain the distress
Dreaming and hallucinations – Continuity or discontinuity? Perspectives from dementia with Lewy bodies
No full textSeeing for ourselves: Insights into the development of moral behaviour from models of visual perception and misperception
No full textAbstractParallels from visual processing support Doris's cognitive architecture underlying moral agency. Unconscious visual processes change with conscious reflection. The sparse and partial representations of vision, its illusions, and hallucinations echo biases in moral reasoning and behaviour. Traditionally, unconscious moral processes are developed by teaching and reflection. Modern neuroscience could bypass reflection and directly influence unconscious processes, creating new dangers.</jats:p
Visual complaints and visual hallucinations in Parkinson's disease
No full textBackground
Visual symptoms are common in Parkinson's disease (PD) and are frequently under-diagnosed. The detection of visual symptoms is important for differential diagnosis and patient management.
Aim
To establish the prevalence of recurrent visual complaints (RVC) and recurrent visual hallucinations (RVH) and to investigate their interaction in PD patients and controls.
Methods
This cross-sectional study included 88 PD patients and 90 controls. RVC and RVH were assessed with a visual symptom questionnaire and the North-East-Visual-Hallucinations-Interview (NEVHI).
Results
Double vision (PD vs. Controls: 18.2% vs. 1.3%; p < 0.001), misjudging objects when walking (PD vs. Controls: 12.5% vs. 1.3%; p < 0.01), words moving whilst reading (PD vs. Controls: 17.0% vs. 1.3%; p < 0.001) and freezing in narrow spaces (PD vs. Controls: 30.7% vs. 0%; p < 0.001) were almost exclusively found in PD patients. The same was true for recurrent complex visual hallucinations and illusions (PD vs. Controls: both 17.0% vs. 0%; p < 0.001). Multiple RVC (43.2% vs. 15.8%) and multiple RVH (29.5% vs. 5.6%) were also more common in PD patients (both p < 0.001). RVC did not predict recurrent complex visual hallucinations; but double vision (p = 0.018, R2 = 0.302) and misjudging objects (p = 0.002, R2 = 0.302) predicted passage hallucinations. Misjudging objects also predicted the feeling of presence (p = 0.010, R2 = 0.321).
Conclusions
Multiple and recurrent visual symptoms are common in PD. RVC emerged as risk factors predictive of the minor forms of hallucinations, but not recurrent complex visual hallucinations
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