Differential sensitivity of intraindividual variability dispersion and global cognition in the prediction of functional outcomes and mortality in precariously housed and homeless adults.

OBJECTIVE: To examine cognitive intraindividual variability (IIV) dispersion as a predictor of everyday functioning and mortality in persons who are homeless or precariously housed. METHOD: Participants were 407 community-dwelling adults, followed for up to 13 years. Neurocognition was assessed at baseline and IIV dispersion was derived using a battery of standardized tests. Functional outcomes (social, physical) were obtained at baseline and last follow-up. Mortality was confirmed with Coroner's reports and hospital records (N = 103 deaths). Linear regressions were used to predict current social and physical functioning from IIV dispersion. Repeated measures Analysis of Covariance were used to predict long-term change in functioning. Cox regression models examined the relation between IIV dispersion and mortality. Covariates included global cognition (i.e. mean-level performance), age, education, and physical comorbidities. RESULTS: Higher IIV dispersion predicted poorer current physical functioning (B = -0.46 p = .010), while higher global cognition predicted better current (B = 0.21, p = .015) and change in social functioning over a period of up to 13 years (F = 4.23, p = .040). Global cognition, but not IIV dispersion, predicted mortality in individuals under 55 years old (HR = 0.50, p = .013). CONCLUSIONS: Our findings suggest that indices of neurocognitive functioning (i.e. IIV dispersion and global cognition) may be differentially related to discrete dimensions of functional outcomes in an at-risk population. IIV dispersion may be a complimentary marker of emergent physical health dysfunction in precariously housed adults and may be best used in conjunction with traditional neuropsychological indices.

Relationship between drug-induced movement disorders and psychosis in adults living in precarious housing or homelessness.

BACKGROUND: Studies have reported positive associations between drug-induced movement disorders (DIMDs) and symptoms of psychosis in patients with schizophrenia. However, it is not clear which subtypes of symptoms are related to each other, and whether one symptom precedes another. The current report assessed both concurrent and temporal associations between DIMDs and symptoms of psychosis in a community-based sample of homeless individuals. METHODS: Participants were recruited in Vancouver, Canada. Severity of DIMDs and psychosis was rated annually, allowing for the analysis of concurrent associations between DIMDs and Positive and Negative Syndrome Scale (PANSS) five factors. A brief version of the PANSS was rated monthly using five psychotic symptoms, allowing for the analysis of their temporal associations with DIMDs. Mixed-effects linear and logistic regression models were used to assess the associations. RESULTS: 401 participants were included, mean age of 40.7 years (SD = 11.2) and 77.4% male. DIMDs and symptoms of psychosis were differentially associated with each other, in which the presence of parkinsonism was associated with greater negative symptoms, dyskinesia with disorganized symptoms, and akathisia with excited symptoms. The presence of DIMDs of any type was not associated with depressive symptoms. Regarding temporal associations, preceding delusions and unusual thought content were associated with parkinsonism, whereas dyskinesia was associated with subsequent conceptual disorganization. CONCLUSIONS: The current study found significant associations between DIMDs and symptoms of psychosis in individuals living in precarious housing or homelessness. Moreover, there were temporal associations between parkinsonism and psychotic symptoms (delusions or unusual thought content), and the presence of dyskinesia was temporally associated with higher odds of clinically relevant conceptual disorganization.

Using serial position effects to investigate memory dysfunction in homeless and precariously housed persons.

Background: Homeless and precariously housed persons exhibit significant memory impairment, but the component processes underlying memory dysfunction have not been explored. We examined the serial position profile (i.e., primacy and recency effects) of verbal memory and its neuroanatomical correlates to identify the nature of memory difficulties in a large cohort of homeless and precariously housed adults. Method: The sample included 227 community-dwelling homeless and precariously housed adults. Serial position scores (primacy, middle, recency) were computed using the Hopkins Verbal Learning Test-Revised. Paired sample t-tests were used to compare percent recall from each word list region. Age-adjusted correlations assessed associations between serial position scores and other cognitive domains (attention, processing speed, executive functioning). Regression analyses were conducted to examine regional brain volumes of interest (hippocampus, entorhinal cortex, dorsolateral prefrontal cortex [DLPFC]) and their differential associations with serial position scores. Results: The serial position profile was characterized by a diminished recency effect in relation to the primacy effect. Serial position scores positively correlated with sustained attention and cognitive control. Larger hippocampal volume was associated with better primacy item recall. DLPFC volume was not associated with serial position recall after adjustment for false discovery rate. There were no associations between regional brain volumes and recency item recall. Conclusion: Our results suggest that commonly reported memory difficulties in homeless and precariously housed adults are likely secondary to a core deficit in executive control due to compromised frontal lobe functioning. These findings have implications for cognitive rehabilitation in this complex and vulnerable group.

Examining the Role of Attention and Sensory Stimulation in the Attentional Repulsion Effect.

It has been suggested that visual attention warps space, such that stimuli appearing near its locus are perceived as farther away than they actually are. This is known as the attentional repulsion effect (ARE). Recent data challenge the role of attention as the sole factor responsible for the ARE, suggesting instead that the ARE is, at least in part, a product of low level sensory interactions between a peripheral orienting cue and the Vernier target stimulus used to measure the effect. Here, we directly test whether attentional orienting, without a cue in peripheral vision to guide attention, is sufficient for generating an ARE. In Experiment 1, attention was guided to the visual periphery by a central symbolic cue that reliably indicated the locations of to-be-identified targets in peripheral vision. On a subset of trials, we probed for an ARE with Vernier targets. Reaction time (RT) data revealed that the cue guided attention but there was no trace of an ARE. In Experiment 2, we ensured that the Vernier targets were sensitive to the ARE by using the standard spatially uninformative peripheral cue to guide attention instead of the central symbolic cue. RT data again revealed that the cue guided attention, while the Vernier targets revealed an ARE. Collectively, these data suggest that attentional orienting without peripheral sensory stimulation is not sufficient for generating an ARE.