Newer techniques in magnetic resonance imaging and their potential for neuropsychiatric research

The neural correlates of performance in adolescents at risk for schizophrenia: inefficiently increased cortico-striatal responses measured with fMRI

BACKGROUND

fMRI studies indicate that schizophrenia patients and their adult relatives require greater prefrontal activation to maintain performance at levels equal to controls, but studies have not established if this pattern of inefficiency is observed in child and adolescent offspring of schizophrenia patients (SCZ-Off).

METHODS

Using a task with visual working memory demands, we investigated activation in cortico-striatal networks and dorsal prefrontal modulation of regions underlying visual working memory in a group of SCZ-Off (n = 19) and controls with no family history of psychosis (n = 25 subjects) using an event-related design. Trials were divided based on memory performance (correct vs. incorrect) to specifically identify the neural correlates of correct working memory performance.

RESULTS

Whereas groups did not differ in terms of behavioral accuracy, SCZ-Off demonstrated significantly increased fMRI-measured activation in dorsal prefrontal cortex and the caudate nucleus during correct, relative to incorrect memory performance. Whereas activation in SCZ-Off was high and independent of performance in each region, in controls the fMRI response was related to behavioral proficiency in the caudate. Further, exploratory analyses indicated that this inefficiency in the dorsal prefrontal cortex response increased with age in SCZ-Off (but in no other regions or group). Finally, these differences were not based in differences in dorsal prefrontal modulation of other regions during successful performance.

DISCUSSION

These results are consistent with observed patterns in adult patients and first-degree relatives. Inefficient fronto-striatal responses during working memory may characterize the schizophrenia diathesis and may reflect the effects of the illness and vulnerability for the illness.

Fronto-parietal hypo-activation during working memory independent of structural abnormalities: conjoint fMRI and sMRI analyses in adolescent offspring of schizophrenia patients

Adolescent offspring of schizophrenia patients (HR-S) are an important group in whom to study impaired brain function and structure, particularly of the frontal cortices. Studies of working memory have suggested behavioral deficits and fMRI-measured hypoactivity in fronto-parietal regions in these subjects. Independent structural MRI (sMRI) studies have suggested exaggerated frontal gray matter decline. Therefore the emergent view is that fronto-parietal deficits in function and structure characterize HR-S. However, it is unknown if fronto-parietal sub-regions in which fMRI-measured hypo-activity might be observed are precisely those regions of the cortex in which gray matter deficits are also observed. To investigate this question we conducted conjoint analyses of fronto-parietal function and structure in HR-S (n=19) and controls (n=24) with no family history of psychoses using fMRI data during a continuous working memory task (2 back), and sMRI collected in the same session. HR-S demonstrated significantly reduced BOLD activation in left dorso-lateral prefrontal cortex (BA 9/46) and bilateral parietal cortex (BA 7/40). Sub-regions of interest were created from the significant fronto-parietal functional clusters. Analyses of gray matter volume from volume-modulated gray matter segments in these clusters did not reveal significant gray matter differences between groups. The results suggest that functional impairments in adolescent HR-S can be independent of impairments in structure, suggesting that the relationship between impaired function and structure is complex. Further studies will be needed to more closely assess whether impairments in function and structure provide independent or interacting pathways of vulnerability in this population.

Chronic osteoarthritis and adherence to exercise: a review of the literature

Osteoarthritis (OA) is a chronic disease that disables many aging adults. People with OA are often asked to adhere to prescribed exercise regimens that must be undertaken in the presence of pain and other disease-related symptoms. We conducted a review of literature that focused on what is known about exercise adherence and the factors that influence exercise adherence among people with OA. Results revealed multiple determinants of exercise adherence; however, these determinants have not been carefully studied in the context of exercise adherence and OA. Almost all studies of exercise adherence among people with OA are short-term and do not use validated measures of adherence. Moreover, poor adherence is the most compelling explanation for the declining impact of the benefits of exercise over time. We conclude that interventions to enhance self-efficacy, social support, and skills in long-term monitoring of progress are necessary to foster exercise adherence among people with OA.

Disease, deficit or denial? Models of poor insight in psychosis

OBJECTIVE

To examine the evidence for the three kinds of aetiological model that dominate the current literature on poor insight in psychosis: clinical models, the neuropsychological model, and the psychological denial model.

METHOD

Studies pertaining to one or more of these aetiological models were identified, reviewed and critically evaluated.

RESULTS

There is little support for clinical models, partly because they lack testable hypotheses. Several studies reveal a positive relationship between insight and executive function, which may be related to frontal lobe dysfunction. However, the extent to which this relationship is specific and independent of general cognitive impairment remains unclear. There is tentative evidence to support the psychological denial model. Recent data combining the latter two approaches suggest that multiple factors contribute to poor insight.

CONCLUSION

Integration of different aetiological models is necessary for a fuller understanding of insight in psychosis. Future research should assess multiple aetiological mechanisms in single investigations.

Approaches for adolescents with an affected family member with schizophrenia

Prospective studies of adolescents at risk for schizophrenia (high-risk studies) can shed light on the possible premorbid precursors of schizophrenia. Recent studies have provided evidence of neurobehavioral, brain structural, physiologic, and neurochemical deficits in adolescent nonpsychotic high-risk relatives that may date back to childhood or earlier. These results are collectively providing a critical window into the inter-relationships between genetic predisposition, neurodevelopment, and premorbid indicators of risk in schizophrenia. Convergent approaches are inherently powerful in mutually informing each other in enriching the knowledge of the risk factors that predict the eventual onset of schizophrenia. Defining such reliable predictors of the onset of schizophrenia may provide us with the tools to better understand the etiology and pathophysiology of the illness, and may pave the way for innovative methods of treatment and possibly prevention. The authors review the relevant literature in this promising field of inquiry and summarize recent findings from high-risk studies.