Browsing by Author "Yung, Matthew G."

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    Brain Activation Patterns during Visual Scene Encoding and Recognition fMRI Tasks in Early Phase Psychosis
    (Office of the Vice Chancellor for Research, 2015-04-17) Ayoubi, Nawead Z.; Mehdiyoun, Nicole F.; Yung, Matthew G.; Hummer, Tom; Francis, Michael M.; Breier, Alan
    Schizophrenia is a chronic and disabling illness that is associated with significant impairments in areas such as independent living, social functioning, and vocational functioning. Cognitive dysfunction is a core facet of schizophrenia with deficits occurring in areas of abstraction, attention, language, and memory. Episodic memory (EM) is a cognitive domain that has been shown to be impaired in schizophrenia. EM combines event-specific autobiographical experiences and information regarding the context in which events took place. Patients with schizophrenia may exhibit broad impairments in EM, with deficits occurring during encoding and retrieval with both visual and verbal tasks. There are a number of inconsistencies in the EM fMRI literature and indicating a need for first episode psychosis (FEP) versus chronic phase schizophrenia research. FEP have fewer and less severe medical comorbidities, shorter durations of antipsychotic treatment exposure, and lower severity of illness, all of which can impact data interpretation. In this study, brain activation patterns were assessed during performance of visual scene encoding and recognition fMRI tasks in FEP patients and healthy control subjects. It is hypothesized that FEP patients would demonstrate decreased activation during encoding and recognition in the main areas that mediate EM function, namely the hippocampus, prefrontal, and parietal cortices. Within the FEP group correlations can be determined by comparing brain activation patterns with cognition (Brief Assessment of Cognition in Schizophrenia [BACS]) and symptom (Positive and Negative Syndrome Scale [PANSS]) outcome measures. Results indicate that during the encoding task FEP exhibited significantly lower activation in the hippocampus and fusiform gyrus when compared to controls. During the recognition task FEP showed a significantly weaker cortical response in the posterior cingulate cortex, the precuneus, and the left middle temporal cortex when compared to controls. These results demonstrate a pattern of alteration in hippocampal, parietal, and temporal activity during EM processes in FEP. Altered hippocampal response in FEP may reflect dysfunctional binding mechanisms and less efficient encoding.
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    Functional network connectivity in early-stage schizophrenia
    (Elsevier, 2020-04) Hummer, Tom A.; Yung, Matthew G.; Goñi, Joaquín; Conroy, Susan K.; Francis, Michael M.; Mehdiyoun, Nicole F.; Breier, M. A. Alan; Psychiatry, School of Medicine
    Schizophrenia is a disorder of altered neural connections resulting in impaired information integration. Whole brain assessment of within- and between-network connections may determine how information processing is disrupted in schizophrenia. Patients with early-stage schizophrenia (n = 56) and a matched control sample (n = 32) underwent resting-state fMRI scans. Gray matter regions were organized into nine distinct functional networks. Functional connectivity was calculated between 278 gray matter regions for each subject. Network connectivity properties were defined by the mean and variance of correlations of all regions. Whole-brain network measures of global efficiency (reflecting overall interconnectedness) and locations of hubs (key regions for communication) were also determined. The control sample had greater connectivity between the following network pairs: somatomotor-limbic, somatomotor-default mode, dorsal attention-default mode, ventral attention-limbic, and ventral attention-default mode. The patient sample had greater variance in interactions between ventral attention network and other functional networks. Illness duration was associated with overall increases in the variability of network connections. The control group had higher global efficiency and more hubs in the cerebellum network, while patient group hubs were more common in visual, frontoparietal, or subcortical networks. Thus, reduced functional connectivity in patients was largely present between distinct networks, rather than within-networks. The implications of these findings for the pathophysiology of schizophrenia are discussed.
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    Functional neuroanatomical correlates of episodic memory impairment in early phase psychosis
    (SpringerNature, 2016-03) Francis, Michael Matthew; Hummer, Tom A.; Vohs, Jenifer L.; Yung, Matthew G.; Liffick, Emily; Mehdiyoun, Nicole F.; Radnovich, Alexander J.; McDonald, Brenna C.; Saykin, Andrew J.; Breier, Alan; Department of Psychiatry, IU School of Medicine
    Studies have demonstrated that episodic memory (EM) is often preferentially disrupted in schizophrenia. The neural substrates that mediate EM impairment in this illness are not fully understood. Several functional magnetic resonance imaging (fMRI) studies have employed EM probe tasks to elucidate the neural underpinnings of impairment, though results have been inconsistent. The majority of EM imaging studies have been conducted in chronic forms of schizophrenia with relatively few studies in early phase patients. Early phase schizophrenia studies are important because they may provide information regarding when EM deficits occur and address potential confounds more frequently observed in chronic populations. In this study, we assessed brain activation during the performance of visual scene encoding and recognition fMRI tasks in patients with earlyphase psychosis (n = 35) and age, sex, and race matched healthy control subjects (n = 20). Patients demonstrated significantly lower activation than controls in the right hippocampus and left fusiform gyrus during scene encoding and lower activation in the posterior cingulate, precuneus, and left middle temporal cortex during recognition of target scenes. Symptom levels were not related to the imaging findings, though better cognitive performance in patients was associated with greater right hippocampal activation during encoding. These results provide evidence of altered function in neuroanatomical circuitry subserving EM early in the course of psychotic illness, which may have implications for pathophysiological models of this illness.
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    Metacognition in Early Phase Psychosis: Toward Understanding Neural Substrates
    (MDPI AG (Basel, Switzerland), 2015-06-29) Vohs, Jenifer L.; Hummer, Tom A.; Yung, Matthew G.; Francis, Michael M.; Lysaker, Paul H; Breier, Alan; Department of Psychiatry, IU School of Medicine
    Individuals in the early phases of psychotic illness have disturbed metacognitive capacity, which has been linked to a number of poor outcomes. Little is known, however, about the neural systems associated with metacognition in this population. The purpose of this study was to elucidate the neuroanatomical correlates of metacognition. We anticipated that higher levels of metacognition may be dependent upon gray matter density (GMD) of regions within the prefrontal cortex. Examining whole-brain structure in 25 individuals with early phase psychosis, we found positive correlations between increased medial prefrontal cortex and ventral striatum GMD and higher metacognition. These findings represent an important step in understanding the path through which the biological correlates of psychotic illness may culminate into poor metacognition and, ultimately, disrupted functioning. Such a path will serve to validate and promote metacognition as a viable treatment target in early phase psychosis.