Eye movement parameters and cognitive functions in Parkinson's disease patients without dementia.

BACKGROUND: Cognitive deficits and eye movement abnormalities have been demonstrated to be detectable early clinical manifestations of Parkinson's disease. Understanding the relationship between these phenotypes may yield insight into the underlying anatomical pathways, assisting in the search for simple non-invasive markers of early neurodegeneration. OBJECTIVE: To explore the correlations between eye movement parameters with multi-domain cognitive functions in patients suffering from Parkinson's disease without dementia. METHOD: This is a cross-sectional case-control study of Parkinson's disease patients without dementia. Participants underwent global and domain-specific cognitive tests and an eye-tracking visual search task to characterize eye movement parameters. RESULTS: 62 Chinese Parkinson's disease patients without dementia and 62 sex-, age- and education-matched controls were recruited. The disease group performed worse in multiple cognitive tasks and exhibited a smaller saccadic amplitude. Negative correlations between the eye fixation duration and performance in semantic verbal fluency, verbal and visual recognition memory tasks were observed, though there was no moderation effect on the correlations due to the presence of Parkinson's disease. A common cholinergic deficit in the temporal and parietal regions may account for the observed correlations. The lack of association with predominantly frontal-executive tasks may suggest specificity of these correlations. CONCLUSION: Prolonged visual fixation duration is correlated with poorer performance in semantic verbal fluency, verbal and visual recognition memory tasks in Parkinson's disease patients without dementia, although these correlations are not specific. The clinical utility of eye movement parameters as an early marker for cognitive decline in Parkinson's disease warrants further exploration in longitudinal studies.

Challenges to the uniqueness of psychotic experience in psychosis: insights on research methodology and intervention.

Paul Bebbington's recent Special Article on the value of psychosocial epidemiology as a tool for understanding the symptomatology of psychosis provides a fresh perspective on understanding the etiology of schizophrenia and related psychotic conditions. Assessment of psychotic-like experiences in non-clinical populations may help to clarify the role of non-psychotic symptoms such as anxiety and depression in the onset and course of psychotic disorders. This approach may also make it possible to expand the repertoire of interventions for preventing the onset or ameliorating the course of psychotic conditions. There is, however, a long road to travel before the mapping of the relationships between brain pathology, psychological symptoms, environmental stressors, and clinical diagnoses are sufficiently detailed to merit the creation of a new psychiatric nosology.