Multilayer depressive symptom networks in adults with bodily pain living in precarious housing or homelessness.

Housing insecurity is associated with co-occurring depression and pain interfering with daily activities. Network analysis of depressive symptoms along with associated risk or protective exposures may identify potential targets for intervention in patients with co-occurring bodily pain. In a community-based sample of adults (n = 408) living in precarious housing or homelessness in Vancouver, Canada, depressive symptoms were measured by the Beck Depression Inventory; bodily pain and impact were assessed with the 36-item Short Form Health Survey. Network and bootstrap permutation analyses were used to compare depressive symptoms endorsed by Low versus Moderate-to-Severe (Mod + Pain) groups. Multilayer networks estimated the effects of risk and protective factors. The overall sample was comprised of 78% men, mean age 40.7 years, with 53% opioid use disorder and 14% major depressive disorder. The Mod + Pain group was characterized by multiple types of pain, more persistent pain, more severe depressive symptoms and a higher rate of suicidal ideation. Global network connectivity did not differ between the two pain groups. Suicidal ideation was a network hub only in the Mod + Pain group, with high centrality and a direct association with exposure to lifetime trauma. Antidepressant medications had limited impact on suicidal ideation. Guilt and increased feelings of failure represented symptoms from two other communities of network nodes, and completed the shortest pathway from trauma exposure through suicidal ideation, to the non-prescribed opioid exposure node. Interventions targeting these risk factors and symptoms could affect the progression of depression among precariously housed patients.

Risk factors for hippocampal cavities in a marginally housed population.

Cavities in the hippocampus are morphological variants of uncertain significance. Aberrant neurodevelopment along with vascular and inflammatory etiologies have been proposed. We sought to characterize these cavities and their potential risk factors in a marginally housed population, with high rates of viral infection, addiction, and mental illness. (1) The volume of hippocampal cavities (HCavs) is greater in this highly multimorbid population compared to the general population. (2) Conventional vascular risk factors such as greater age and systolic blood pressure are associated with higher HCav volume. (3) Nonprescribed substance-related risk factors such as stimulant use or dependence, and smoking are associated with increased HCav volume independent of vascular risk factors. This is a retrospective analysis of an ongoing prospective study. We analyzed baseline data, including medical history, physical exam, psychiatric diagnosis, and MRI from a total of 375 participants. Hippocampal cavities were defined as spaces isointense to CSF on T1 MRI sequences, bounded on all sides by hippocampal tissue, with a volume of at least 1 mm3 . Risk factors were evaluated using negative binomial multiple regression. Stimulant use was reported by 87.3% of participants, with stimulant dependence diagnosed in 83.3% of participants. Prevalence of cavities was 71.6%, with a mean total bilateral HCav volume of 13.89 mm3 . On average, a 1 mmHg greater systolic blood pressure was associated with a 2.17% greater total HCav volume (95% CI = [0.57%, 3.79%], p = .0076), while each cigarette smoked per day trended toward a 2.69% greater total HCav volume (95% CI = [-0.87%, 5.54%], p = .058). A diagnosis of stimulant dependence was associated with a 95.6% greater total HCav volume (95% CI = [5.39%, 263.19%], p = .0335). Hypertension and diagnosis of stimulant dependence were associated with a greater total volume of HCav.

Characterizing Traumatic Brain Injury and Its Association with Losing Stable Housing in a Community-based Sample.

OBJECTIVE: Traumatic brain injury (TBI) is increasingly recognized as a common and impactful health determinant in homeless and precariously housed populations. We sought to describe the history of TBI in a precariously housed sample and evaluate how TBI was associated with the initial loss and lifetime duration of homelessness and precarious housing. METHOD: We characterized the prevalence, mechanisms, and sex difference of lifetime TBI in a precariously housed sample. We also examined the impact of TBI severity and timing on becoming and staying homeless or precariously housed; 285 precariously housed participants completed the Brain Injury Screening Questionnaire in addition to other health assessments. RESULTS: A history of TBI was reported in 82.1% of the sample, with 64.6% reporting > 1 TBI, and 21.4% reporting a moderate or severe TBI. Assault was the most common mechanism of injury overall, and females reported significantly more traumatic brain injuries due to physical abuse than males (adjusted OR = 1.26, 95% CI = 1.14 to 1.39, P < 0.0001). The first moderate or severe TBI was significantly closer to the first experience of homelessness (b = 2.79, P = 0.003) and precarious housing (b = 2.69, P < 0.0001) than was the first mild TBI. In participants who received their first TBI prior to becoming homeless or precariously housed, traumatic brain injuries more proximal to the initial loss of stable housing were associated with a longer lifetime duration of homelessness (RR = 1.04, 95% CI = 1.02 to 1.06, P < 0.0001) and precarious housing (RR = 1.03, 95% CI = 1.01 to 1.04, P < 0.0001). CONCLUSIONS: These findings demonstrate the high prevalence of TBI in this vulnerable population, and that aspects of TBI severity and timing are associated with the loss and lifetime duration of stable housing.

History of Functional Somatic Syndromes and Persistent Symptoms After Mild Traumatic Brain Injury.

OBJECTIVE: Somatization is thought to underlie functional somatic syndromes (FSSs) and may also contribute to prolonged symptoms after mild traumatic brain injury (mTBI). The investigators evaluated the prevalence of FSSs in patients seeking specialty care after mTBI and whether a history of FSSs was associated with symptom persistence. METHODS: A total of 142 patients with mTBI completed questionnaires regarding demographic information, injury characteristics, and medical history, including history of diagnosed FSSs at clinic intake (mean=41 days postinjury [SD=22.41]). Postconcussion symptoms were assessed at clinic intake and again 1 and 3 months later. A linear mixed-effects model was used to determine whether history of FSSs was related to persistent mTBI symptoms over time. RESULTS: A history of at least one FSS was reported by 20.4% of patients. In the linear mixed model, postconcussion symptom scores were not significantly different over time among patients with a history of one or more FSSs or two or more FSSs from those with no FSSs. A history of one or more FSSs or two or more FSSs (versus no FSS) was not associated with increased odds of severe postconcussion symptoms at clinic intake (one or more FSSs: odds ratio=0.88, 95% CI=0.38-2.03; two or more FSSs: odds ratio=1.78, 95% CI=0.45-7.03), at the 1-month follow-up visit (one or more FSSs: odds ratio=0.57, 95% CI=0.22-1.45; two or more FSSs: odds ratio=0.57, 95% CI=0.14-2.37), or at the 3-month follow-up visit (one or more FSSs: odds ratio=0.97, 95% CI=0.36-2.63; two or more FSSs: odds ratio=1.27, 95% CI=0.29-5.65). CONCLUSIONS: In this sample, the prevalence rates of FSSs were higher than rates previously reported for the general population. However, FSS history did not predict higher postconcussion symptom burden at clinic intake or persistence over the following 3 months. Further research is needed to clarify the potential role of somatization in poor mTBI outcome.

Characterization of Bodily Pain and Use of Both Prescription and Non-Prescription Opioids in Tenants of Precarious Housing.

BACKGROUND: opioid use, which includes both prescribed and non-prescribed drugs, is relatively common amongst marginalized populations. Past research has shown that among those who use non-prescribed or diverted opioids recreationally, many were first exposed to the drug as prescribed pain medication. Objective: to better understand the relationship between pain and opioid use in tenants of precarious housing. Methods: in the present study, 440 individuals from a cohort living in homeless or precariously housed conditions in a neighborhood with high rates of poverty and drug use were interviewed for their bodily pain and opioid use. We examined the relationship between bodily pain levels, assessed using the Maudsley Addiction Profile questionnaire, and prescribed, non-prescribed and combined self-reported opioid use in the prior 28 days assessed using the Timeline Followback and Doctor-Prescribed Medication Timeline Followback questionnaires. Results: Analysis of the results indicated that sex (female), age (younger) and early exposure to opioids (≤ age 18) predicted current opioid use, but there was no association between current bodily pain levels and opioid use. Conclusions: these unexpected findings indicate the complex nature of the relationship between pain and opioid use in this population.

The effects of enhanced attention and working memory on smooth pursuit eye movement.

It has long been suggested that increasing attentional demands can alter smooth pursuit eye movements, but the precise nature of the changes generated is not clear. Our goal was to examine smooth pursuit with a task that enhanced attention to the target and that increased demands on working memory, without distracting from the target. 15 subjects tracked a target moving around a predictable circular trajectory at a constant tangential velocity. An n-back task with two levels of additional working memory load was integrated into the pursuit target to increase cognitive demands. In the single-task conditions, subjects either performed pursuit alone or the n-back task with a stationary target. In the dual-task conditions, pursuit and the n-back task were performed together. Performance of the n-back tasks was not impaired by simultaneous smooth pursuit. The n-back tasks had negligible effects on horizontal or vertical pursuit gain, but generated increased phase lag and reduced the variability of position error during pursuit. Increasing the difficulty of the n-back task further reduced the variability of position errors. We conclude that enhanced attention does not alter the velocity gain of smooth pursuit but rather improves its consistency. As long as attention remains focused on the target, increased attentional demands further reduce pursuit variability. Increases in phase lag may serve to improve attentional processing of the target.

Music perception in acquired prosopagnosia.

BACKGROUND: Acquired prosopagnosia is often associated with other deficits such as dyschromatopsia and topographagnosia, from damage to adjacent perceptual networks. A recent study showed that some subjects with developmental prosopagnosia also have congenital amusia, but problems with music perception have not been described with the acquired variant. OBJECTIVE: Our goal was to determine if music perception was also impaired in subjects with acquired prosopagnosia, and if so, its anatomic correlate. METHOD: We studied eight subjects with acquired prosopagnosia, all of whom had extensive neuropsychological and neuroimaging testing. They performed a battery of tests evaluating pitch and rhythm processing, including the Montréal Battery for the Evaluation of Amusia. RESULTS: At the group level, subjects with anterior temporal lesions were impaired in pitch perception relative to the control group, but not those with occipitotemporal lesions. Three of eight subjects with acquired prosopagnosia had impaired musical pitch perception while rhythm perception was spared. Two of the three also showed reduced musical memory. These three reported alterations in their emotional experience of music: one reported music anhedonia and aversion, while the remaining two had changes consistent with musicophilia. The lesions of these three subjects affected the right or bilateral temporal poles as well as the right amygdala and insula. None of the three prosopagnosic subjects with lesions limited to the inferior occipitotemporal cortex exhibited impaired pitch perception or musical memory, or reported changes in music appreciation. CONCLUSION: Together with the results of our previous studies of voice recognition, these findings indicate an anterior ventral syndrome that can include the amnestic variant of prosopagnosia, phonagnosia, and various alterations in music perception, including acquired amusia, reduced musical memory, and subjective reports of altered emotional experience of music.

Post-Concussion Symptoms and Disability in Adults With Mild Traumatic Brain Injury: A Systematic Review and Meta-Analysis.

Studies investigating long-term symptoms and disability after mild traumatic brain injury (mTBI) have yielded mixed results. This systematic review and meta-analysis aimed to determine the prevalence of self-reported post-concussion symptoms (PCS) and disability following mTBI. We systematically searched MEDLINE, Embase, CINAHL, CENTRAL, and PsycInfo to identify inception cohort studies of adults with mTBI. Paired reviewers independently extracted data and assessed risk of bias with the Scottish Intercollegiate Guidelines Network criteria. We identified 43 eligible studies for the systematic review; 41 were rated as high risk of bias, primarily due to high attrition (> 20%). Twenty-one studies (49%) were included in the meta-analyses (five studies were narratively synthesized; 17 studies were duplicate reports). At 3-6 months post-injury, the estimated prevalence of PCS from random-effects meta-analyses was 31.3% (95% confidence interval [CI] = 25.4-38.4) using a lenient definition of PCS (2-4 mild severity PCS) and 18.3% (95% CI = 13.6-24.0) using a more stringent definition. The estimated prevalence of disability was 54.0% (95% CI = 49.4-58.6) and 29.6% (95% CI = 27.8-31.5) when defined as Glasgow Outcome Scale-Extended <8 and <7, respectively. The prevalence of symptoms similar to PCS was higher in adults with mTBI versus orthopedic injury (prevalence ratio = 1.57, 95% CI = 1.22-2.02). In a meta-regression, attrition rate was the only study-related factor significantly associated with higher estimated prevalence of PCS. Setting attrition to 0%, the estimated prevalence of PCS (lenient definition) was 16.1%. We conclude that nearly one in three adults who present to an emergency department or trauma center with mTBI report at least mild severity PCS 3-6 months later, but controlling for attrition bias, the true prevalence may be one in six. Studies with representative samples and high retention rates are needed.

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.

Movement disorders associated with substance use in adults living in precarious housing or homelessness.

OBJECTIVE: Many individuals living in precarious housing or homelessness have multimorbid illnesses, including substance use, psychiatric, and neurological disorders. Movement disorders (MDs) associated substance use are amongst the poorly studied subtopics of drug-induced MDs. The aim of the present study was, therefore, to determine the proportion affected and severity of different signs of MDs, as well as their associations with substance use in a community-based sample of precariously housed and homeless individuals. METHODS: Participants were recruited from an impoverished urban neighborhood and were assessed for substance dependence and self-reported substance use (alcohol, cannabis, cocaine, methamphetamine, nicotine, and opioids), as well as for the severity of signs of MDs (akathisia, dyskinesia, dystonia, and parkinsonism). Adjusted regression models were used to estimate the associations of the severity of signs with the frequency of substance use over the past 4 weeks and with the baseline diagnosis of substance dependence. RESULTS: The proportion of the sample with clinically relevant signs of MDs in any of the four categories was 18.6% (n = 401), and these participants demonstrated lower levels of functioning than those without signs. Of the different types of substance use, only methamphetamine (its frequency of use and dependence) was significantly associated with greater severity of overall signs of MDs. Frequency of methamphetamine use significantly interacted with age and sex, whereby older female participants exhibited the greatest overall severity with increased methamphetamine use. Of the different signs of MDs, methamphetamine use frequency was positively associated with the severity of trunk/limb dyskinesia and hypokinetic parkinsonism. Relative to no use, concurrent use of antipsychotics demonstrated lower severity of trunk/limb dyskinesia and greater severity of hypokinetic parkinsonism with methamphetamine use, and greater severity of dystonia with cocaine use. CONCLUSIONS: Our study found a high proportion of MDs in a relatively young sample, and their severity was consistently associated with methamphetamine use, moderated by participant demographics and antipsychotic use. These disabling sequelae represent an important and understudied neurological condition that may affect quality of life and will require further study.

Differential age-associated brain atrophy and white matter changes among homeless and precariously housed individuals compared with the general population.

Background: Homeless or precariously housed individuals live with poor health and experience premature mortality compared with the general population, yet little is known about age-related brain changes among these individuals. We evaluated whether MRI measures of brain structure are differentially associated with age and selected risk factors among individuals who are homeless or precariously housed compared with a general population sample. Methods: We compared T1-weighted and diffusion tensor imaging measures of brain macrostructure and white matter microstructure in a well-characterised sample of 312 precariously housed participants with a publicly available dataset of 382 participants recruited from the general population. We used piecewise and multiple linear regression to examine differential associations between MRI measures and between the samples, and to explore associations with risk factors in the precariously housed sample. Results: Compared with the general population sample, older age in the precariously housed sample was associated with more whole-brain atrophy (ß=-0.20, p=0.0029), lower whole-brain fractional anisotropy (ß=-0.32, p<0.0001) and higher whole-brain mean diffusivity (ß=0.69, p<0.0001). Several MRI measures had non-linear associations with age, with further adverse changes after age 35-40 in the precariously housed sample. History of traumatic brain injury, stimulant dependence and heroin dependence was associated with more atrophy or alterations in white matter diffusivity in the precariously housed sample. Conclusions: Older age is associated with adverse MRI measures of brain structure among homeless and precariously housed individuals compared with the general population. Education, improvements in care provision and policy may help to reduce the health disparities experienced by these individuals.

Traumatic brain injury in precariously housed persons: Incidence and risks.

BACKGROUND: Homeless and precarious housed persons are particularly prone to traumatic brain injuries (TBIs), but existent incidence rates are hampered by poor case acquisition. We rigorously documented TBIs in precariously housed persons transitioning in and out of homelessness. METHODS: Between December 2016 and May 2018, 326 precariously housed participants enrolled in a longitudinal study in Vancouver, Canada were assessed monthly for TBI occurrences after education on sequelae. Over one participant-year, 2433 TBI screenings were acquired for 326 person-years and variables associated with odds of incident TBI were evaluated. FINDINGS: One hundred participants acquired 175 TBIs, yielding an observed incidence proportion of 30·7% and event proportion of 53·7%. Of the injured, 61% reported one TBI and 39% reported multiple injuries. Acute intoxication was present for more than half of the TBI events assessed. Additionally, 9·7% of TBI events occurred in the context of a drug overdose. Common injury mechanisms were falls (45·1%), assaults (25·1%), and hitting one's head on an object (13·1%). In this community-based but non-randomly recruited sample, exploratory analyses identified factors associated with odds of an incident TBI over one year of follow-up, including: schizophrenia disorders (odds ratio (OR) = 0·43, 95% confidence interval (CI) 0·19, 0·94), role functioning (OR = 0·69, 95% CI 0·52, 0·91), opioid dependence (OR = 2·17, 95% CI 1·27, 3·72) and those reporting past TBIs (OR = 1·99, 95% CI 1·13, 3·52). INTERPRETATION: Given the ubiquity of TBIs revealed in this precariously housed sample, we identify an underappreciated and urgent healthcare priority. Several factors modified the odds of incident TBI, which can facilitate investigations into targeted prevention efforts. FUNDING: Canadian Institutes of Health Research, Natural Sciences and Engineering Research Council of Canada, William and Ada Isabelle Steel Research Fund, Simon Fraser University Vice-President Research Undergraduate Student Research Award and Simon Fraser University Psychology Department Research Grant.

Differential effects of cannabis exposure during early versus later adolescence on the expression of psychosis in homeless and precariously housed adults.

Longitudinal studies of cannabis exposure during early adolescence in the general population frequently report an increased risk of subsequently developing psychotic symptoms or a psychotic illness. However, there is a dearth of knowledge about the effects of early cannabis exposure on psychosis in homeless and precariously housed adults, who represent a population afflicted with high rates of psychosis. The aim of the present study was to examine how early cannabis exposure (by age 15) compared to later first use (after age 15) affected the expression of adult psychosis in this population. Secondary measures of psychopathology, drug use, cognition and brain structure were also collected. 437 subjects were recruited from single room occupancy hotels in the urban setting of the Downtown Eastside of Vancouver, Canada. Psychiatric diagnoses were determined, and psychotic symptom severity was measured with the 5-factor PANSS. Participants completed a battery of neurocognitive tests, and brain structure was assessed using structural and diffusion tensor imaging MRI scans. Results indicated that early cannabis exposure was associated with an increased risk (OR = 1.09, p < .05) of developing substance induced psychosis, whereas later first use increased risk (OR = 2.19, p < .01) of developing schizophrenia or schizoaffective disorder. There was no group difference in neurocognitive function, although differences were observed in the lateral orbitofrontal cortex and white matter tract diffusivity. These findings indicate that early cannabis exposure in this population may increase the risk of developing drug associated psychoses, which could potentially be mediated in part through altered neurodevelopmental brain changes.

Traumatic brain injury in homeless and marginally housed individuals: a systematic review and meta-analysis.

BACKGROUND: Homelessness is a global public health concern, and traumatic brain injury (TBI) could represent an underappreciated factor in the health trajectories of homeless and marginally housed individuals. We aimed to evaluate the lifetime prevalence of TBI in this population, and to summarise findings on TBI incidence and the association between TBI and health-related or functioning-related outcomes. METHODS: For this systematic review and meta-analysis, we searched without date restrictions for original research studies in English that reported data on the prevalence or incidence of TBI, or the association between TBI and one or more health-related or function-related outcome measures. Studies were included if they had a group or clearly identifiable subgroup of individuals who were homeless, marginally housed, or seeking services for homeless people. With use of random-effects models, we calculated pooled estimates of the lifetime prevalence of any severity of TBI and the lifetime prevalence of moderate or severe TBI. We used meta-regression and subgroup analysis to evaluate potential moderators of prevalence estimates and the leave-one-out method for sensitivity analyses. We then summarised findings from all studies that evaluated TBI incidence and the association between TBI and health-related or functioning-related outcomes. All statistical analyses were done using R version 3.5.1. The study is registered with PROSPERO, number CRD42019119678. FINDINGS: Of 463 potentially eligible studies identified by the search, 38 studies were included in the systematic review and 22 studies were included in the meta-analysis. The lifetime prevalence of any severity of TBI in homeless and marginally housed individuals (18 studies, n=9702 individuals) was 53·1% (95% CI 46·4-59·7; I2=97%) and the lifetime prevalence of moderate or severe TBI (nine studies, n=5787) was 22·5% (13·5-35·0; I2=99%). The method used to ascertain TBI history, the age of the sample, and the sample size significantly moderated estimated lifetime prevalence of any severity of TBI. TBI was consistently associated with poorer self-reported physical and mental health, higher suicidality and suicide risk, memory concerns, and increased health service use and criminal justice system involvement. INTERPRETATION: The lifetime prevalence of TBI is high among homeless and marginally housed individuals, and a history of TBI is associated with poorer health and general functioning. Health-care providers and public health officials should have an increased awareness of the burden of TBI in this population. Prospective and longitudinal studies are needed to better understand how the health of this population is affected by TBI. FUNDING: Canadian Institutes of Health Research.

Atypical Somatic Symptoms in Adults With Prolonged Recovery From Mild Traumatic Brain Injury.

Somatization may contribute to persistent symptoms after mild traumatic brain injury (mTBI). In two independently-recruited study samples, we characterized the extent to which symptoms atypical of mTBI but typical for patients suffering from somatization (e.g., gastrointestinal upset, musculoskeletal, and cardiorespiratory complaints) were present in adult patients with prolonged recovery following mTBI. The first sample was cross-sectional and consisted of mTBI patients recruited from the community who reported ongoing symptoms attributable to a previous mTBI (n = 16) along with a healthy control group (n = 15). The second sample consisted of patients with mTBI prospectively recruited from a Level 1 trauma center who had either good recovery (GOSE = 8; n = 32) or poor recovery (GOSE < 8; n = 29). In all participants, we evaluated atypical somatic symptoms using the Patient Health Questionnaire-15 and typical post-concussion symptoms with the Rivermead Post-Concussion Symptom Questionnaire. Participants with poor recovery from mTBI had significantly higher "atypical" somatic symptoms as compared to the healthy control group in Sample 1 (b = 4.308, p < 0.001) and to mTBI patients with good recovery in Sample 2 (b = 3.169, p < 0.001). As would be expected, participants with poor outcome in Sample 2 had a higher burden of typical rather than atypical symptoms [t (28) = 4.750, p < 0.001, d = 0.88]. However, participants with poor recovery still reported atypical somatic symptoms that were significantly higher (1.4 standard deviations, on average) than those with good recovery. Our results suggest that although "typical" post-concussion symptoms predominate after mTBI, a broad range of somatic symptoms also frequently accompanies mTBI, and that somatization may represent an important, modifiable factor in mTBI recovery.

Perception of musical pitch in developmental prosopagnosia.

Studies of developmental prosopagnosia have often shown that developmental prosopagnosia differentially affects human face processing over non-face object processing. However, little consideration has been given to whether this condition is associated with perceptual or sensorimotor impairments in other modalities. Comorbidities have played a role in theories of other developmental disorders such as dyslexia, but studies of developmental prosopagnosia have often focused on the nature of the visual recognition impairment despite evidence for widespread neural anomalies that might affect other sensorimotor systems. We studied 12 subjects with developmental prosopagnosia with a battery of auditory tests evaluating pitch and rhythm processing as well as voice perception and recognition. Overall, three subjects were impaired in fine pitch discrimination, a prevalence of 25% that is higher than the estimated 4% prevalence of congenital amusia in the general population. This was a selective deficit, as rhythm perception was unaffected in all 12 subjects. Furthermore, two of the three prosopagnosic subjects who were impaired in pitch discrimination had intact voice perception and recognition, while two of the remaining nine subjects had impaired voice recognition but intact pitch perception. These results indicate that, in some subjects with developmental prosopagnosia, the face recognition deficit is not an isolated impairment but is associated with deficits in other domains, such as auditory perception. These deficits may form part of a broader syndrome which could be due to distributed microstructural anomalies in various brain networks, possibly with a common theme of right hemispheric predominance.

Dopamine replacement remediates risk aversion in Parkinson's disease in a value-independent manner.

INTRODUCTION: Clinical evidence suggests that Parkinson's Disease (PD) patients are risk averse. Dopaminergic therapy has been reported to increase risk tolerance, but the underlying mechanisms are unclear. Some studies have suggested an amplification of subjective reward value, consistent with the role of dopamine in reward value coding. Others have reported value-independent risk enhancement. We evaluated the value-dependence of the effects of PD and its therapy on risk using tasks designed to sensitively measure risk over a wide range of expected values. METHOD: 36 patients with idiopathic PD receiving levodopa monotherapy and 36 healthy matched controls performed two behavioural economic tasks aimed at quantifying 1) risk tolerance/aversion in the gain frame and 2) valuation of potential gains relative to losses. PD patients performed the tasks on and off their usual dose of levodopa in randomized order; controls performed the same tasks twice. RESULTS: Relative to the controls, unmedicated PD patients showed significant value-independent risk aversion in the gain frame, which was normalized by levodopa. PD patients did not differ from controls in their valuation of gains relative to losses. However, across both tasks and regardless of medication, choices of the patients were more determined by expected values of the prospects than those of controls. CONCLUSION: Dopamine deficiency in PD was associated with risk aversion, and levodopa promoted riskier choice in a value-independent manner. PD patients also showed an increased sensitivity to expected value, which was independent of levodopa and does not appear to result directly from dopamine deficiency.

Working memory load improves diagnostic performance of smooth pursuit eye movement in mild traumatic brain injury patients with protracted recovery.

Smooth pursuit eye movements have been investigated as a diagnostic tool for mild traumatic brain injury (mTBI). However, the degree to which smooth pursuit differentiates mTBI patients from healthy controls (i.e. its diagnostic performance) is only moderate. Our goal was to establish if simultaneous performance of smooth pursuit and a working memory task increased the diagnostic performance of pursuit metrics following mTBI. We integrated an n-back task with two levels of working memory load into a pursuit target, and tested single- and dual-task pursuit in mTBI patients and healthy controls. We assessed pursuit using measures of velocity accuracy, positional accuracy and positional variability. The mTBI group had higher pursuit variability than the control group in all conditions. Performing a concurrent 1-back task decreased pursuit variability for both the mTBI and control groups. Performing a concurrent 2-back task produced differential effects between the groups: Pursuit variability was significantly decreased in the control group, but not in the mTBI group. Diagnostic indices were improved when pursuit was combined with the 2-back task, and increased by 20% for the most sensitive variable. Smooth pursuit with simultaneous working memory load may be a superior diagnostic tool for mTBI than measuring smooth pursuit alone.