Allen Thornton | Simon Fraser University (original) (raw)

Papers by Allen Thornton

Archives of Clinical Neuropsychology, 1992

Stroke, 2017

Background: White Matter Hyperintensities (WMH) are features of cerebral small vessel disease (cS... more Background: White Matter Hyperintensities (WMH) are features of cerebral small vessel disease (cSVD) along with lacunes, cerebral microbleeds and perivascular spaces. Vascular risk factors account for only a small proportion of the variability of the presence of WMH, and the role of additional risk factors including drug use/dependence or infections is not well defined. Objective: Examine prevalence and risk factors associated with WMH of presumed vascular origin within the HOTEL cohort, a population living in marginal housing with a high prevalence of prior homelessness, substance dependence, head trauma, mental illness and infectious diseases. Methods: Baseline imaging on 3T MRI included T1, T2-FLAIR and SWI sequences. WMH not consistent with vascular origins were excluded. Two raters assessed WMH using the Fazekas scale. Participants were divided into those with or without moderate-severe WMH (periventricular Fazekas score >2 or deep score >1). Potential cSVD risk factors w...

Brain and Behavior, 2019

This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Schizophrenia Bulletin, 2017

anterior cingulate cortex (dACC), a key region involved in perception of and reaction to stress. ... more anterior cingulate cortex (dACC), a key region involved in perception of and reaction to stress. Methods: We developed a somatic stress paradigm involving pseudorandom application of safe but painfully hot stimuli to the forearm of participants while they were undergoing serial proton magnetic resonance spectroscopy to measure changes in glutamate and glutamine levels in the dACC. This paradigm was tested in a sample of 21 healthy controls and 23 patients with schizophrenia. Results: Across groups, glutamate levels significantly decreased following exposure to thermal pain, while ratio of glutamine to glutamate significantly increased. However, schizophrenia patients exhibited an initial increase in glutamate levels during challenge that was significantly different from controls, after controlling for heat pain tolerance. Furthermore, in patients, the acute glutamate response was positively correlated with childhood trauma (r = .41, P = .050) and inversely correlated with working memory (r = −.49, P = .023). Conclusion: These results provide preliminary evidence for abnormal glutamatergic response to stress in schizophrenia patients, which may point toward novel approaches to understanding how stress contributes to the illness.

Schizophrenia Bulletin, 2017

International Congress on Schizophrenia Research S240 Posters (Monday) analyses have the potentia... more International Congress on Schizophrenia Research S240 Posters (Monday) analyses have the potential to contribute with more specific information about the underlying mechanisms that affect white matter microstructure during antipsychotic treatment.

Neuropsychology, 1997

To assess the nature and magnitude of memory impairment in multiple sclerosis (MS), the authors a... more To assess the nature and magnitude of memory impairment in multiple sclerosis (MS), the authors analyzed quantitatively 36 studies comparing the memory performance of MS participants to healthy controls. The authors studied (a) the pattern of impairment across short-term memory (STM), working memory (WM), and long-term memory (LTM); (b) the moderating influence of retrieval support on LTM impairment; (c) the

Neuropsychology, 1995

Sustained attention was assessed in 20 patients with severe closed head injury (CHI) and 20 norma... more Sustained attention was assessed in 20 patients with severe closed head injury (CHI) and 20 normal matched controls. Participants were presented with a visual continuous performance task (CPT) with 3 levels of complexity. Performance was assessed by examining response latencies and error rates. Across all levels of complexity, the CHI patients demonstrated a vigilance decrement, whereas the performance of the matched controls was stable across time. The vigilance decrement was not differentially affected by the manipulation of task complexity in the CHI patients. However, findings suggest that the overall vigilance performance of CHI patients was differentially affected by increasing the complexity of the task.

Journal of Nervous & Mental Disease, 2013

The objective of this study was to identify predictors of sustained psychotic symptoms after meth... more The objective of this study was to identify predictors of sustained psychotic symptoms after methamphetamine (MA) abuse during the course of 6 months from patterns of MA and other substance use, depressive symptoms, family history of psychosis, antisocial personality disorder, and trauma history. A total of 295 individuals with MA abuse and psychotic symptoms seeking psychiatric services were assessed at baseline and then monthly on symptoms and substance use for 6 months. Trajectory analyses revealed two trajectories of the individuals with positive symptoms, with one group presenting with persistent psychotic symptoms (30% of the sample). Those with persistent psychosis were significantly older, had more severe psychotic symptoms, misused MA for more years, had more antisocial personality traits, and had more sustained depressive symptoms. The strongest predictors of belonging to the persistent psychosis group, via logistic regressions, were more severe psychotic symptoms, longer use of MA, and sustained depressive symptoms. Our results highlight the important comorbidities, especially regarding depressive symptoms and persistent psychosis, in individuals seeking psychiatric help after MA abuse. This study also highlights the importance of identifying people with persistent psychosis within MA users to facilitate rapid and effective treatment of co-occurring psychotic disorder.

International Clinical Psychopharmacology, 2011

and their mean age was 42 ± 14 years. 3078 patients (21%) reported a treatment switch in the prev... more and their mean age was 42 ± 14 years. 3078 patients (21%) reported a treatment switch in the previous twelve weeks and constituted the Switch population. Data from 1240 patients in this group were available for the interim analysis. In this group, the diagnosis was most frequently paranoid schizophrenia (71%), with a duration of illness of over one year for 91.5% of patients. The principal reasons for antipsychotic treatment change were inadequate symptom control (76.8%), relapse on medication (33.3%), adverse events (55.0%; principally sedation 23.6%, weight gain 22.0% and extrapyramidal symptoms 19.5%), poor compliance for 25.2%, poor quality of life 32.9% and patient request (22.3%). Prior to the switch, treatment was with second generation antipsychotics in 69.3% of cases and with polytherapy associating first and second generation antipsychotics in 2.5%. After the switch, these therapies constituted 78.8% and 15.1% of treatments respectively.

American Journal of Psychiatry, 2013

The health of people living in marginal housing is not well characterized, particularly from the ... more The health of people living in marginal housing is not well characterized, particularly from the perspective of multimorbid illness. The authors investigated this population in a community sample. Method: A prospective community sample (N=293) of adults living in single-room occupancy hotels was followed for a median of 23.7 months. Assessment included psychiatric and neurological evaluation, multimodal MRI, and viral testing. Results: Previous homelessness was described in 66.6% of participants. Fifteen deaths occurred during 552 person-years of follow-up. The standardized mortality ratio was 4.83 (95% CI=2.91-8.01). Substance dependence was ubiquitous (95.2%), with

Professional Psychology: Research and Practice, 1988

Journal of Dual Diagnosis, 2013

Objective: Research suggests several possible associations among methamphetamine abuse, psychotic... more Objective: Research suggests several possible associations among methamphetamine abuse, psychotic symptoms, depression, and posttraumatic stress disorder (PTSD), but the exact nature and clinical significance of these associations is unclear. Individuals who abuse methamphetamine increasingly present in hospital emergency rooms with acute psychiatric symptoms. The aim of this study was to identify patterns of depressive symptoms and explore predictors of acute versus sustained depressive symptoms in individuals who abuse methamphetamine and who have had psychotic symptoms. Methods: This longitudinal study, conducted in Vancouver, British Columbia, included 295 participants with methamphetamine use disorder who were seeking psychiatric help for depressive or psychotic symptoms, assessed at baseline and monthly for 6 months. Measures included substance use (including frequency, quantity, and route of administration), family history of psychosis and depression, trauma exposure, and PTSD symptoms. Results: Trajectory analyses on depressive symptoms revealed two profiles of depression: one with more severe and sustained depressive symptoms and one with decreasing and lower levels of depressive symptoms. Group comparisons showed that those with more severe and persistent depressive symptoms had more family history of depression ( p < .05), more years of alcohol and cocaine abuse ( p < .01), more traumatic events ( p < .001), and more PTSD symptoms ( p < .001). Logistic regression suggested that the strongest predictors of belonging to the high depression group were more severe psychotic symptoms at baseline (odds ratio [OR] = 2.03, p < .001), followed by quantity of methamphetamine used in the month preceding baseline (OR = 1.13, p < .05), severity of PTSD symptoms at baseline (OR = 1.07, p < .001), and the frequency of drug injection (OR = 1.25, p < .05). Conclusions: Our results are similar to those of other studies suggesting that depression and psychosis often coexist and that the intensity of methamphetamine abuse is linked to the severity of the depressive symptoms. The individuals who took part in this study had many coexisting problems, such as PTSD symptoms, polysubstance abuse, depression, and psychosis. In fact, depression, psychosis, PTSD, and substance abuse appeared to be intertwined in their development and expression. A more comprehensive treatment program to help individuals with multiple coexisting psychiatric and substance misuse issues is needed.

The Iowa Gambling Task (IGT) is a widely used measure of decision making, but its value in signif... more The Iowa Gambling Task (IGT) is a widely used measure of decision making, but its value in signifying behaviors associated with adverse, “real-world” consequences has not been consistently demonstrated in persons who are precariously housed or homeless. Studies evaluating the ecological validity of the IGT have primarily relied on traditional IGT scores. However, computational modeling derives underlying component processes of the IGT, which capture specific facets of decision making that may be more closely related to engagement in behaviors associated with negative consequences. This study employed the Prospect Valence Learning (PVL) model to decompose IGT performance into component processes in 294 precariously housed community residents with substance use disorders. Results revealed a predominant focus on gains and a lack of sensitivity to losses in these vulnerable community residents. Hypothesized associations were not detected between component processes and self-reported hea...

The relationship between juvenile adjudicative competence and executive functioning was investiga... more The relationship between juvenile adjudicative competence and executive functioning was investigated in a sample of 96 middle and high school students. Measures of adjudicative competence (selected questions from the Fitness Interview Test—Revised Understanding scale) and legal decision-making were administered together with cognitive and neuropsychological testing assessing various domains of executive functioning. Adolescents ages 13-14 performed less well than older adolescents (ages 17-18) with regard to competency abilities. Significant correlations were observed between competency scores and working memory, response inhibition/impulsivity, and metacognition/insight, but not cognitive flexibility. Hierarchical regression analyses testing the incremental predictive ability of executive functions indicated that metacognition/insight remained a significant predictor of competency beyond age and intelligence.

Schizophrenia Bulletin

Methods: Twenty-two right-handed patients with schizophrenia (12 males and 10 females, mean age =... more Methods: Twenty-two right-handed patients with schizophrenia (12 males and 10 females, mean age = 45.9 years) and 20 right-handed healthy control subjects (13 males and 7 females, mean age = 42.8 years) consented to participate in this study. We measured musical ability, cognitive functions, and clinical assessments using the Montreal Battery for Evaluation of Amusia (MBEA), Brief Assessment of Cognition in Schizophrenia (BACS), and Positive and Negative Syndrome Scale (PANSS), respectively. We employed automatic probabilistic tractography DTI analysis using TRActs Constrained by UnderLying Anatomy (TRACULA) available in the Freesurfer software for the reconstruction of major tract bundles. Results: Whole-tract diffusion characteristics in patients with schizophrenia and controls were significantly different. Fractional anisotropy (FA) was lower for patients with schizophrenia compared to controls in the left superior longitudinal fasciculus-parietal endings (slfp) (p < 0.001), left cingulum-angular bundle (cab) (p < 0.001), and corpus callosum-forceps minor (fminor) (p < 0.001). We found significant correlation between musical abilities and FA alterations in slfp in both controls and patients with schizophrenia. While lower musical ability corresponds to lower FA in slfp of controls (r =-0.572, p = 0.013), it is associated with higher FA in the slfp of patients with schizophrenia (r = 0.515, p = 0.021). Discussion: This study shows that TRACULA can be used for the detection of decrements in several DTI tracts including the left slfp, left cab, and fminor in patients with schizophrenia. It revealed that while lower musical ability correlates with lower FA values in the left slfp in controls, it is associated with higher FA values in the same region in patients with schizophrenia. This contradictory finding in controls and patients with schizophrenia with regard to white matter pathology may reflect left supramarginal region malfunction resulting in cortical pathology in patients with schizophrenia. The data suggest that patients with schizophrenia may be more susceptible to changes in cortical thickness in the supramarginal region, and white matter alteration in the left slfp. Further study is needed to confirm the results. The characteristics of grey and white matter in the left parietal region which are relevant to musical ability may provide insight into pathological progression in patients with schizophrenia.

Frontiers in Public Health

Objective: Homeless and marginally housed youth are particularly vulnerable members of society, a... more Objective: Homeless and marginally housed youth are particularly vulnerable members of society, and are known to experience numerous health problems, including psychiatric illness, substance use, and viral infection. Despite the presence of these risk factors for cognitive compromise, there is limited research on the cognitive functioning of homeless and marginally housed youth. The present study examines the degree and pattern of cognitive impairment and associations with key risk factors in a sample of marginally housed young adults. Method: Participants (N = 101) aged 20-29 years old were recruited from single-room occupancy hotels, and underwent cognitive, psychiatric, neurological, and serological assessments. Results: Forty percent of participants were identified as mildly cognitively impaired across multiple domains, and 16% were moderately-severely impaired. Deficits in memory and attention were most prevalent, while impairments in inhibitory control/processing speed and cognitive flexibility were also present but tended to be less severe. Developmental and historical factors (premorbid intellectual functioning, neurological soft signs, earlier exposure to and longer duration of homelessness or marginal housing), as well as current health risks (stimulant dependence and hepatitis C exposure), were associated with cognitive impairment. Conclusions: The strikingly high rate of cognitive impairment in marginally housed young adults represents a major public health concern and is likely to pose a significant barrier to treatment and rehabilitation. These results suggest that the pathway to cognitive impairment involves both developmental vulnerability and modifiable risk factors. This study highlights the need for early interventions that address cognitive impairment and risk factors in marginalized young people.

Archives of Clinical Neuropsychology

Objective: Persons who are homeless or marginally housed exhibit significant cognitive dysfunctio... more Objective: Persons who are homeless or marginally housed exhibit significant cognitive dysfunction, with memory being the most impaired domain. Hippocampal subfield volumes have been found to differentially relate to component processes of memory. The neural correlates of memory have not been previously examined in marginalized persons who are understudied and underserved. We examined whether hippocampal subfields and entorhinal cortex volumes are uniquely related to indices of verbal episodic memory using the Hopkins Verbal Learning Test-Revised. Method: Data was used from a large sample of community dwelling homeless and marginally housed adults (N = 227). Regression analyses were conducted to examine hippocampal subfield volumes (CA1, CA3, CA4, dentate gyrus, subiculum) and entorhinal cortex, and their associations with measures of verbal immediate recall, learning slope, and verbal delayed recall. Results: Greater CA3 subfield volume was associated with better performance on an index of encoding (immediate recall), but only in older individuals. Greater CA1 and subiculum volumes were associated with better performance on immediate and delayed recall (measures that tap into retrieval processes), but not with learning slope (a more pure index of encoding). Entorhinal cortex volume was related to all components of memory beyond total hippocampal volume. Conclusions: Our results suggest common neuroanatomical correlates of memory dysfunction in large sample of marginalized persons, and these are uniquely related to different components of memory. These findings have clinical relevance for marginalized populations and theoretical relevance to the growing literature on functional specialization of the hippocampal subfields.

Archives of Clinical Neuropsychology, 1992

Stroke, 2017

Background: White Matter Hyperintensities (WMH) are features of cerebral small vessel disease (cS... more Background: White Matter Hyperintensities (WMH) are features of cerebral small vessel disease (cSVD) along with lacunes, cerebral microbleeds and perivascular spaces. Vascular risk factors account for only a small proportion of the variability of the presence of WMH, and the role of additional risk factors including drug use/dependence or infections is not well defined. Objective: Examine prevalence and risk factors associated with WMH of presumed vascular origin within the HOTEL cohort, a population living in marginal housing with a high prevalence of prior homelessness, substance dependence, head trauma, mental illness and infectious diseases. Methods: Baseline imaging on 3T MRI included T1, T2-FLAIR and SWI sequences. WMH not consistent with vascular origins were excluded. Two raters assessed WMH using the Fazekas scale. Participants were divided into those with or without moderate-severe WMH (periventricular Fazekas score >2 or deep score >1). Potential cSVD risk factors w...

Brain and Behavior, 2019

This is an open access article under the terms of the Creative Commons Attribution License, which... more This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Schizophrenia Bulletin, 2017

anterior cingulate cortex (dACC), a key region involved in perception of and reaction to stress. ... more anterior cingulate cortex (dACC), a key region involved in perception of and reaction to stress. Methods: We developed a somatic stress paradigm involving pseudorandom application of safe but painfully hot stimuli to the forearm of participants while they were undergoing serial proton magnetic resonance spectroscopy to measure changes in glutamate and glutamine levels in the dACC. This paradigm was tested in a sample of 21 healthy controls and 23 patients with schizophrenia. Results: Across groups, glutamate levels significantly decreased following exposure to thermal pain, while ratio of glutamine to glutamate significantly increased. However, schizophrenia patients exhibited an initial increase in glutamate levels during challenge that was significantly different from controls, after controlling for heat pain tolerance. Furthermore, in patients, the acute glutamate response was positively correlated with childhood trauma (r = .41, P = .050) and inversely correlated with working memory (r = −.49, P = .023). Conclusion: These results provide preliminary evidence for abnormal glutamatergic response to stress in schizophrenia patients, which may point toward novel approaches to understanding how stress contributes to the illness.

Schizophrenia Bulletin, 2017

International Congress on Schizophrenia Research S240 Posters (Monday) analyses have the potentia... more International Congress on Schizophrenia Research S240 Posters (Monday) analyses have the potential to contribute with more specific information about the underlying mechanisms that affect white matter microstructure during antipsychotic treatment.

Neuropsychology, 1997

To assess the nature and magnitude of memory impairment in multiple sclerosis (MS), the authors a... more To assess the nature and magnitude of memory impairment in multiple sclerosis (MS), the authors analyzed quantitatively 36 studies comparing the memory performance of MS participants to healthy controls. The authors studied (a) the pattern of impairment across short-term memory (STM), working memory (WM), and long-term memory (LTM); (b) the moderating influence of retrieval support on LTM impairment; (c) the

Neuropsychology, 1995

Sustained attention was assessed in 20 patients with severe closed head injury (CHI) and 20 norma... more Sustained attention was assessed in 20 patients with severe closed head injury (CHI) and 20 normal matched controls. Participants were presented with a visual continuous performance task (CPT) with 3 levels of complexity. Performance was assessed by examining response latencies and error rates. Across all levels of complexity, the CHI patients demonstrated a vigilance decrement, whereas the performance of the matched controls was stable across time. The vigilance decrement was not differentially affected by the manipulation of task complexity in the CHI patients. However, findings suggest that the overall vigilance performance of CHI patients was differentially affected by increasing the complexity of the task.

Journal of Nervous & Mental Disease, 2013

The objective of this study was to identify predictors of sustained psychotic symptoms after meth... more The objective of this study was to identify predictors of sustained psychotic symptoms after methamphetamine (MA) abuse during the course of 6 months from patterns of MA and other substance use, depressive symptoms, family history of psychosis, antisocial personality disorder, and trauma history. A total of 295 individuals with MA abuse and psychotic symptoms seeking psychiatric services were assessed at baseline and then monthly on symptoms and substance use for 6 months. Trajectory analyses revealed two trajectories of the individuals with positive symptoms, with one group presenting with persistent psychotic symptoms (30% of the sample). Those with persistent psychosis were significantly older, had more severe psychotic symptoms, misused MA for more years, had more antisocial personality traits, and had more sustained depressive symptoms. The strongest predictors of belonging to the persistent psychosis group, via logistic regressions, were more severe psychotic symptoms, longer use of MA, and sustained depressive symptoms. Our results highlight the important comorbidities, especially regarding depressive symptoms and persistent psychosis, in individuals seeking psychiatric help after MA abuse. This study also highlights the importance of identifying people with persistent psychosis within MA users to facilitate rapid and effective treatment of co-occurring psychotic disorder.

International Clinical Psychopharmacology, 2011

and their mean age was 42 ± 14 years. 3078 patients (21%) reported a treatment switch in the prev... more and their mean age was 42 ± 14 years. 3078 patients (21%) reported a treatment switch in the previous twelve weeks and constituted the Switch population. Data from 1240 patients in this group were available for the interim analysis. In this group, the diagnosis was most frequently paranoid schizophrenia (71%), with a duration of illness of over one year for 91.5% of patients. The principal reasons for antipsychotic treatment change were inadequate symptom control (76.8%), relapse on medication (33.3%), adverse events (55.0%; principally sedation 23.6%, weight gain 22.0% and extrapyramidal symptoms 19.5%), poor compliance for 25.2%, poor quality of life 32.9% and patient request (22.3%). Prior to the switch, treatment was with second generation antipsychotics in 69.3% of cases and with polytherapy associating first and second generation antipsychotics in 2.5%. After the switch, these therapies constituted 78.8% and 15.1% of treatments respectively.

American Journal of Psychiatry, 2013

The health of people living in marginal housing is not well characterized, particularly from the ... more The health of people living in marginal housing is not well characterized, particularly from the perspective of multimorbid illness. The authors investigated this population in a community sample. Method: A prospective community sample (N=293) of adults living in single-room occupancy hotels was followed for a median of 23.7 months. Assessment included psychiatric and neurological evaluation, multimodal MRI, and viral testing. Results: Previous homelessness was described in 66.6% of participants. Fifteen deaths occurred during 552 person-years of follow-up. The standardized mortality ratio was 4.83 (95% CI=2.91-8.01). Substance dependence was ubiquitous (95.2%), with

Professional Psychology: Research and Practice, 1988

Journal of Dual Diagnosis, 2013

Objective: Research suggests several possible associations among methamphetamine abuse, psychotic... more Objective: Research suggests several possible associations among methamphetamine abuse, psychotic symptoms, depression, and posttraumatic stress disorder (PTSD), but the exact nature and clinical significance of these associations is unclear. Individuals who abuse methamphetamine increasingly present in hospital emergency rooms with acute psychiatric symptoms. The aim of this study was to identify patterns of depressive symptoms and explore predictors of acute versus sustained depressive symptoms in individuals who abuse methamphetamine and who have had psychotic symptoms. Methods: This longitudinal study, conducted in Vancouver, British Columbia, included 295 participants with methamphetamine use disorder who were seeking psychiatric help for depressive or psychotic symptoms, assessed at baseline and monthly for 6 months. Measures included substance use (including frequency, quantity, and route of administration), family history of psychosis and depression, trauma exposure, and PTSD symptoms. Results: Trajectory analyses on depressive symptoms revealed two profiles of depression: one with more severe and sustained depressive symptoms and one with decreasing and lower levels of depressive symptoms. Group comparisons showed that those with more severe and persistent depressive symptoms had more family history of depression ( p < .05), more years of alcohol and cocaine abuse ( p < .01), more traumatic events ( p < .001), and more PTSD symptoms ( p < .001). Logistic regression suggested that the strongest predictors of belonging to the high depression group were more severe psychotic symptoms at baseline (odds ratio [OR] = 2.03, p < .001), followed by quantity of methamphetamine used in the month preceding baseline (OR = 1.13, p < .05), severity of PTSD symptoms at baseline (OR = 1.07, p < .001), and the frequency of drug injection (OR = 1.25, p < .05). Conclusions: Our results are similar to those of other studies suggesting that depression and psychosis often coexist and that the intensity of methamphetamine abuse is linked to the severity of the depressive symptoms. The individuals who took part in this study had many coexisting problems, such as PTSD symptoms, polysubstance abuse, depression, and psychosis. In fact, depression, psychosis, PTSD, and substance abuse appeared to be intertwined in their development and expression. A more comprehensive treatment program to help individuals with multiple coexisting psychiatric and substance misuse issues is needed.

The Iowa Gambling Task (IGT) is a widely used measure of decision making, but its value in signif... more The Iowa Gambling Task (IGT) is a widely used measure of decision making, but its value in signifying behaviors associated with adverse, “real-world” consequences has not been consistently demonstrated in persons who are precariously housed or homeless. Studies evaluating the ecological validity of the IGT have primarily relied on traditional IGT scores. However, computational modeling derives underlying component processes of the IGT, which capture specific facets of decision making that may be more closely related to engagement in behaviors associated with negative consequences. This study employed the Prospect Valence Learning (PVL) model to decompose IGT performance into component processes in 294 precariously housed community residents with substance use disorders. Results revealed a predominant focus on gains and a lack of sensitivity to losses in these vulnerable community residents. Hypothesized associations were not detected between component processes and self-reported hea...

The relationship between juvenile adjudicative competence and executive functioning was investiga... more The relationship between juvenile adjudicative competence and executive functioning was investigated in a sample of 96 middle and high school students. Measures of adjudicative competence (selected questions from the Fitness Interview Test—Revised Understanding scale) and legal decision-making were administered together with cognitive and neuropsychological testing assessing various domains of executive functioning. Adolescents ages 13-14 performed less well than older adolescents (ages 17-18) with regard to competency abilities. Significant correlations were observed between competency scores and working memory, response inhibition/impulsivity, and metacognition/insight, but not cognitive flexibility. Hierarchical regression analyses testing the incremental predictive ability of executive functions indicated that metacognition/insight remained a significant predictor of competency beyond age and intelligence.

Schizophrenia Bulletin

Methods: Twenty-two right-handed patients with schizophrenia (12 males and 10 females, mean age =... more Methods: Twenty-two right-handed patients with schizophrenia (12 males and 10 females, mean age = 45.9 years) and 20 right-handed healthy control subjects (13 males and 7 females, mean age = 42.8 years) consented to participate in this study. We measured musical ability, cognitive functions, and clinical assessments using the Montreal Battery for Evaluation of Amusia (MBEA), Brief Assessment of Cognition in Schizophrenia (BACS), and Positive and Negative Syndrome Scale (PANSS), respectively. We employed automatic probabilistic tractography DTI analysis using TRActs Constrained by UnderLying Anatomy (TRACULA) available in the Freesurfer software for the reconstruction of major tract bundles. Results: Whole-tract diffusion characteristics in patients with schizophrenia and controls were significantly different. Fractional anisotropy (FA) was lower for patients with schizophrenia compared to controls in the left superior longitudinal fasciculus-parietal endings (slfp) (p < 0.001), left cingulum-angular bundle (cab) (p < 0.001), and corpus callosum-forceps minor (fminor) (p < 0.001). We found significant correlation between musical abilities and FA alterations in slfp in both controls and patients with schizophrenia. While lower musical ability corresponds to lower FA in slfp of controls (r =-0.572, p = 0.013), it is associated with higher FA in the slfp of patients with schizophrenia (r = 0.515, p = 0.021). Discussion: This study shows that TRACULA can be used for the detection of decrements in several DTI tracts including the left slfp, left cab, and fminor in patients with schizophrenia. It revealed that while lower musical ability correlates with lower FA values in the left slfp in controls, it is associated with higher FA values in the same region in patients with schizophrenia. This contradictory finding in controls and patients with schizophrenia with regard to white matter pathology may reflect left supramarginal region malfunction resulting in cortical pathology in patients with schizophrenia. The data suggest that patients with schizophrenia may be more susceptible to changes in cortical thickness in the supramarginal region, and white matter alteration in the left slfp. Further study is needed to confirm the results. The characteristics of grey and white matter in the left parietal region which are relevant to musical ability may provide insight into pathological progression in patients with schizophrenia.

Frontiers in Public Health

Objective: Homeless and marginally housed youth are particularly vulnerable members of society, a... more Objective: Homeless and marginally housed youth are particularly vulnerable members of society, and are known to experience numerous health problems, including psychiatric illness, substance use, and viral infection. Despite the presence of these risk factors for cognitive compromise, there is limited research on the cognitive functioning of homeless and marginally housed youth. The present study examines the degree and pattern of cognitive impairment and associations with key risk factors in a sample of marginally housed young adults. Method: Participants (N = 101) aged 20-29 years old were recruited from single-room occupancy hotels, and underwent cognitive, psychiatric, neurological, and serological assessments. Results: Forty percent of participants were identified as mildly cognitively impaired across multiple domains, and 16% were moderately-severely impaired. Deficits in memory and attention were most prevalent, while impairments in inhibitory control/processing speed and cognitive flexibility were also present but tended to be less severe. Developmental and historical factors (premorbid intellectual functioning, neurological soft signs, earlier exposure to and longer duration of homelessness or marginal housing), as well as current health risks (stimulant dependence and hepatitis C exposure), were associated with cognitive impairment. Conclusions: The strikingly high rate of cognitive impairment in marginally housed young adults represents a major public health concern and is likely to pose a significant barrier to treatment and rehabilitation. These results suggest that the pathway to cognitive impairment involves both developmental vulnerability and modifiable risk factors. This study highlights the need for early interventions that address cognitive impairment and risk factors in marginalized young people.

Archives of Clinical Neuropsychology

Objective: Persons who are homeless or marginally housed exhibit significant cognitive dysfunctio... more Objective: Persons who are homeless or marginally housed exhibit significant cognitive dysfunction, with memory being the most impaired domain. Hippocampal subfield volumes have been found to differentially relate to component processes of memory. The neural correlates of memory have not been previously examined in marginalized persons who are understudied and underserved. We examined whether hippocampal subfields and entorhinal cortex volumes are uniquely related to indices of verbal episodic memory using the Hopkins Verbal Learning Test-Revised. Method: Data was used from a large sample of community dwelling homeless and marginally housed adults (N = 227). Regression analyses were conducted to examine hippocampal subfield volumes (CA1, CA3, CA4, dentate gyrus, subiculum) and entorhinal cortex, and their associations with measures of verbal immediate recall, learning slope, and verbal delayed recall. Results: Greater CA3 subfield volume was associated with better performance on an index of encoding (immediate recall), but only in older individuals. Greater CA1 and subiculum volumes were associated with better performance on immediate and delayed recall (measures that tap into retrieval processes), but not with learning slope (a more pure index of encoding). Entorhinal cortex volume was related to all components of memory beyond total hippocampal volume. Conclusions: Our results suggest common neuroanatomical correlates of memory dysfunction in large sample of marginalized persons, and these are uniquely related to different components of memory. These findings have clinical relevance for marginalized populations and theoretical relevance to the growing literature on functional specialization of the hippocampal subfields.