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Biomedical subjects

Edmond Chiu

Publications and source records attributed to Edmond Chiu.

16 recordsLinked to original sources
PubMed2006

Proximity to clinical onset influences motor and cognitive performance in presymptomatic Huntington disease gene carriers.

BACKGROUND: Neuroimaging studies of Huntington disease (HD) gene carriers have shown that characteristic striatal atrophy begins long before symptom onset, but findings regarding the presence of preclinical functional deficits are inconsistent. OBJECTIVE: To further investigate potential motor and cognitive deficits in presymptomatic gene carriers (PSGCs), and relationships between performance and estimated proximity to HD symptom onset. METHOD: PSGCs and age-matched controls performed motor tasks involving cued sequential button presses, and cognitive tasks involving simple and complex choice responses to visuospatial stimuli. RESULTS: PSGCs demonstrated similar motor performance speed, and nonsignificantly slower cognitive reaction times, to controls. PSGCs made more errors than controls to stimuli requiring a spatially incongruent response, possibly suggesting some difficulty in inhibiting automatic responses. Movement times for motor conditions where little advance information was provided, and reaction times for low demand cognitive tasks, were positively correlated with PSGCs' estimated probability of symptom onset within 5 years. CONCLUSIONS: Response speed was slower for those PSGCs estimated to have higher probabilities of close onset. These findings suggest that to provide improved knowledge of how HD begins, knowledge that may be used in clinical trials, future research should further explore relationships between function and proximity to onset.

Adult↗
PubMed2005

Evidence for a disorder of locomotor timing in Huntington's disease.

Disturbances of walking have been described in people with Huntington's disease (HD), although the nature of the deficits have not yet been well defined. The purpose of this investigation was to determine whether people with HD have a deficit in the regulation of footstep timing during walking. The footstep patterns of 30 people with HD and 30 matched comparisons were measured at self-selected slow, preferred, and fast speeds. Subjects were also instructed to match their footsteps to auditory metronome cues set at 80 and 120 beats per minute. Gait speed, cadence, stride length, and double limb support as a percentage of the gait cycle were measured using a computerized foot-switch system. People with HD demonstrated a disorder in their ability to regulate cadence, manifest as a reduced step frequency when walking at preferred speed and when required to increase their speed. For all walking conditions, people with HD had increased variability of footstep cadence. They also had difficulty synchronizing their footstep timing to an auditory cue. For all walking conditions, people with HD had reduced stride length. Thus, in HD, there is a disorder in the regulation of footstep timing, with increased variability, a restricted cadence range, difficulty synchronizing footsteps to an auditory cue and reduced stride length. The exact neural correlates of this timing disorder are yet to be determined.

Acoustic Stimulation↗
PubMed2005

Limitations in the current classification systems for dementia.

A brief review of classification in psychiatry from Kraepelin to ICD-10 and DSM-IV reveals that the categorical paradigm inherent in these nosological systems has certain inadequacies when applied to dementia specifically and cognitive impairment in general. There are "outcasts" from these two systems that, with the rapid advances in an understanding of cognitive disorders, expose significant limitations in them. As and when they are revised, serious consideration of a different view, accepting a dimensional paradigm, would contribute to a more inclusive and clinically relevant nosology for dementia and cognitive disorders.

Cognition Disorders↗
PubMed2005

Nutrition and geriatric psychiatry: a neglected field.

PURPOSE OF REVIEW: Nutritional issues have received little attention in geriatric psychiatry research. This review focuses on literature published in 2003 and 2004 on nutritional factors in mental illness in the elderly and proposes directions for future research. RECENT FINDINGS: There has been more research on the role of micronutrients in psychiatric disorders of older adults but studies examining nutritional state in this population are lacking. The former research suggests associations between low folic acid/vitamin B12 status and depression in older adults whereas evidence for other micronutrients is still tentative. In the latter work, there is only one study that examines malnutrition in psychogeriatric patients despite the availability of well-validated screening tools for assessing nutritional state in the elderly and the known impact of undernutrition in ageing and the development of frailty. The role of obesity in ageing is also relevant especially as more people with schizophrenia live longer, although the current evidence in the non-mentally ill elderly suggests that being overweight may have protective effects in the elderly. SUMMARY: Malnutrition is likely to have considerable impact on the mental and physical state of the elderly.

Editorial↗
PubMed2004

Impaired modulation of the vestibulo-ocular reflex in Huntington's disease.

The vestibulo-ocular reflex (VOR) stabilizes gaze during movement, in conjunction with other afferent information: visual, proprioceptive, and somaesthetic. The reflex can either be augmented or suppressed, depending on visual requirements, and undergoes long-term adaptation to compensate for physical changes in the subject. Importantly, over relatively short periods of time, the VOR should function consistently under the same circumstances. This study examines VOR function in patients with Huntington's disease (HD), with a view to investigating cortical influences on the reflex. Horizontal eye movements were recorded in 9 patients with HD and 7 normal subjects, using the scleral search coil technique, in response to high frequency, unpredictable head rotations imposed manually. To establish base VOR function, recordings were made in darkness, without instruction, before and after wearing x2 magnifying lenses for a period of 2 hours to adapt the reflex. Recordings were also made before adaptation, while fixating a stationary visual target (VOR augmentation), and while fixating a target moving with the head (VOR suppression). Although results suggest that the VOR is preserved in HD, with relatively normal gain values and appropriate augmentation and suppression of the reflex with visual input, patients were unable to adapt the VOR to altered visual conditions. This represents a novel finding in HD and suggests that cortical structures compromised in HD exert influences on the long-term adaptation of the VOR.

Adult↗
PubMed2004

Epidemiology of depression in the Asia Pacific region.

OBJECTIVE: To summarise studies reporting rates of depression (for the general population and older samples) and suicide in the Asia Pacific region. METHODS: Information on local data was collected from the members of the SEBoD International Advisory Board on known epidemiological studies. Additionally, online searches were conducted using Medline and PsycInfo for the period 1994-2004. RESULTS: Across the Asia Pacific region, rates of current or 1-month major depression ranged from 1.3% to 5.5%, rates of major depression in the previous year ranged from 1.7% to 6.7%, and lifetime rates ranged from 1.1% to 19.9%, with a median of 3.7%. Rates of suicide in the Asia Pacific region are now similar to those in Europe and the Americas. The exceptions include China and South Korea. CONCLUSIONS: Epidemiological studies in Asian populations are rare and use various diagnostic criteria. However, studies indicate that rates of depression in Asia Pacific, whilst lower, are comparable to other western countries. As such, depression as a health issue in Asia Pacific demands greater recognition. It is important that Asian countries should have the human and financial resources to conduct large scale epidemiological surveys not only in the area of depression, but also in the broader field of mental disorders.

Adult↗
PubMed2003

Future directions in research with presymptomatic individuals carrying the gene for Huntington's disease.

Presymptomatic individuals carrying the gene for Huntington's disease (HD) provide researchers with a unique opportunity of learning more about the neuropathophysiology, symptom onset, behavioural functioning, and mediating factors of this fatal disease. In this review, we attempt to demonstrate that research over the last 8 years, since the isolation of the gene, has remained at large controversial. Although we are aware of some of the factors that can influence age at onset and disease progression, we are still unable to determine exactly when an individual will develop HD symptoms, and how fast these symptoms will progress. In an era rapidly advancing with respect to therapeutic intervention that could forestall the onset and progression of HD, systematic research with improved inclusion criteria is paramount. A greater understanding of the time course of the disease would be beneficial not only in monitoring the effectiveness of future treatments, but also in determining the most appropriate time to administer them. Finally, we present various ethical considerations, as well as put forward various recommendations that could assist in better diagnosing preclinical deficits in presymptomatic individuals.

Age of Onset↗
PubMed2003

Teaching and training in old age psychiatry: a general survey of the World Psychiatric Association member societies.

OBJECTIVE: One of the main goals of the World Psychiatric Association (WPA) section on old age psychiatry is to promote its discipline and consequently to help member societies to promote and develop locally specific medical education programmes in old age psychiatry. In order to target its support to the needs expressed by the member societies, the section conducted a survey within the WPA during the year 2001. METHOD: A questionnaire was sent to each of the 116 WPA member societies in 93 countries. It assessed the level of development of medical education in old age psychiatry in each country, as well as the perceived needs in educational material. RESULTS: Answers were obtained from 50 WPA member societies (response rate 54%) from 48 countries (response rate 52%). The existence of specific old age psychiatry services was reported in 40 (83%) countries, but the discipline is recognized as a subspecialty in only 13 (27%). Formal teaching in old age psychiatry was reported at the undergraduate level in 44 (92%) countries. Specific learning objectives for postgraduate training were reported in 30 (86%) of the countries where the discipline is not yet recognized as a subspecialty. Specific Continuing Medical Education (CME) programs were however reported in only 50% of the countries. Support for the development of educational material was mostly thought to be useful at the postgraduate level. Depression, dementia, psychopharmacology and psychotherapy were among the most frequently cited areas in which educational material might be usefully provided. CONCLUSION: Support for the development of postgraduate training is seen as the most pressing need by WPA member societies. Such support could help to increase the level of recognition of the discipline locally and hence provide more effective support to older people with mental disorders.

Aged↗
PubMed2003

Vascular burden and BPSD: a reconceptualization.

With increasing understanding of BPSD, the question of whether there are differences between BPSD of AD and VaD may be raised. The available evidence from the Cache County Study, the role of vascular risk factors in late-life depression, and vascular pathology in AD and VaD all converge to explore the impact of vascular burden on cerebral function and BPSD. This article argues that there may be domain differences in BPSD between AD and VaD and suggests that BPSVaD may be a concept to be pursued with possible useful clinical implications.

Aged↗
PubMed2002

Effect of an attentional strategy on movement-related potentials recorded from subjects with Huntington's disease.

Huntington's disease patients perform automatic movements in a bradykinetic manner, somewhat similar to patients with Parkinson's disease. Cortical activity relating to the preparation of movement in Parkinson's disease is significantly improved when a cognitive strategy is used. It is unknown whether patients with Huntington's disease can utilise an attentional strategy, and what effect this strategy would have on the premovement cortical activity. Movement-related potentials were recorded from 12 Huntington's disease patients and controls performing externally cued finger tapping movement, allowing an examination of cortical activity related to movement performance and bradykinesia in this disease. All subjects were tested in two conditions, which differed only by the presence or absence of the cognitive strategy. The Huntington's disease group, unlike controls, did not produce a rising premovement potential in the absence of the strategy. The Huntington's disease group did produce a rising premovement potential for the strategy condition, but the early slope of the potential was significantly reduced compared with the control group's early slope. These results are similar to those found previously with Parkinson's disease patients. The strategy may have put the task, which previously might have been under deficient automatic control, under attentional control.

Adult↗
PubMed2002

Alzheimer disease. Current treatment options.

BACKGROUND: In the past Alzheimer disease (AD) has been presented to elderly people and their families as a very frightening condition, based on media representation of the worst possible case scenarios. OBJECTIVE: The current status of pharmacological and psychosocial Intervention in Alzheimer disease is reviewed from the recent literature. DISCUSSION: In the last decade, the picture of AD has turned to one of hope and optimism as a result of advances in developing pharmacological and psychological management.

Aged↗
PubMed2002

Reorientation of attention in Huntington disease.

OBJECTIVES AND BACKGROUND: This experiment sought to quantify the extent to which patients with Huntington disease (HD) have difficulties in orienting attention, via a vibrotactile version of a Posner-type cost-benefit paradigm. METHOD: Participants were required to push a button in response to a vibration delivered to the index finger of either hand. Prior to each stimulus vibration, a precue (valid, neutral, or invalid) was delivered to the finger. Benefits and costs were calculated from valid and invalid precues. RESULTS: Although patients with HD were overall slower than the controls, their performance was no different; both patients and controls demonstrated increased benefits from valid compared with invalid and neutral cues. Of interest was the finding that patients, unlike controls, performed significantly slower with the cue presented to the left compared with the right side. The crossed arm configuration proved to be too difficult for the patients with HD, and thus an analysis on these data was not permitted. CONCLUSIONS: Patients may experience difficulties in allocating attentional resources toward their left nonpreferred hand. Overall, findings demonstrate that patients with HD, with minimal caudate damage at early stages of disease onset, may not experience problems in their ability to orient attention.

Adult↗