Browsing by Author "Yoon, Gihyun"

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    Alcohol withdrawal hallucinations in the general population, an epidemiological study
    (Elsevier, 2018-04) Stephane, Massoud; Arnaout, Bachaar; Yoon, Gihyun; Psychiatry, School of Medicine
    Hallucinations are sometimes encountered in the course of alcohol withdrawal; however, both the factors predisposing to alcohol withdrawal hallucinations (AWH) and the implications of AWH with respect to the mechanisms of hallucinations remain unclear. To clarify these issues, we used data from the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC) to investigate the demographic correlates, alcohol-use clinical patterns, and psychiatric comorbidities in two groups: drinkers with and without a history of AWH. We estimated the odds ratios for studied factors and used logistic regression analyses to compare the two groups. We found that over 2% of drinkers reported AWH (758 of a sample of 34,533 subjects). Alcohol tolerance and withdrawal seizures were highly associated with AWH, and exposure to alcohol during brain development was associated with a 10-fold increase in AWH compared to exposure during adulthood. African Americans, Native Americans, and unmarried subjects, as well as subjects with lower levels of education and lower levels of income were more likely to experience AWH. Furthermore, those with a history of AWH had higher odds ratios for most psychiatric illnesses than those without such history—yet of anxiety disorders, only panic was associated with AWH. These associations suggest that higher levels of education and of standard of living could protect against AWH; while social isolation, hypervigilance, exposure to alcohol during brain development, and long and severe exposure to alcohol could predispose to AWH.
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    Keeping the inner voice inside the head, a pilot fMRI study
    (Wiley, 2021-04) Stephane, Massoud; Dzemidzic, Mario; Yoon, Gihyun; Psychiatry, School of Medicine
    Introduction: The inner voice is experienced during thinking in words (inner speech) and silent reading and evokes brain activity that is highly similar to that associated with external voices. Yet while the inner voice is experienced in internal space (inside the head), external voices (one's own and those of others) are experienced in external space. In this paper, we investigate the neural basis of this differential spatial localization. Methods: We used fMRI to examine the difference in brain activity between reading silently and reading aloud. As the task involved reading aloud, data were first denoised by removing independent components related to head movement. They were subsequently processed using finite impulse response basis function to address the variations of the hemodynamic response. Final analyses were carried out using permutation-based statistics, which is appropriate for small samples. These analyses produce spatiotemporal maps of brain activity. Results: Reading silently relative to reading aloud was associated with activity of the "where" auditory pathway (Inferior parietal lobule and middle temporal gyrus), and delayed activity of the primary auditory cortex. Conclusions: These pilot data suggest that internal space localization of the inner voice depends on the same neural resources as that for external space localization of external voices-the "where" auditory pathway. We discuss the implications of these findings on the possible mechanisms of abnormal experiences of the inner voice as is the case in verbal hallucinations.