Clinical Psychology -- Schizophrenia
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Research of Undergraduate Honors Students in the Psychological Sciences at Vanderbilt University.
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Item The Relationship Between Felt Presence and Psychosis-Proneness(Vanderbilt University, 2022-03-28) Rast, CatherineFelt presence (FP) is the perception that somebody (or something) is nearby without corresponding sensory stimuli. This phenomenon is relatively common within the general population. However, it is under-researched and mostly appears in publications as case reports. Additionally, FP has not extensively been studied in relation to schizophrenia-spectrum despite anomalous bodily self-experiences being central to this disorder. In order to address this gap, we conducted an online survey of the general population (N = 202) about their possible FP experiences using a previously validated scale for FP (Barnby & Bell, 2017), with the addition of 25 qualitative questions regarding these experiences. In addition, we examined FP in relation to psychosis risk by administering the Prodromal-Questionnaire-16 (Ising et al., 2012). In study 2, we conducted a qualitative study with individuals diagnosed with schizophrenia regarding their FP experiences. Results from Study 1 demonstrate that FP is more common in a psychosis-prone, prodromal population than those at low-risk for schizophrenia. Additionally, some characteristics of FP differed between these two groups. The psychosis-prone group tended to experience FP touch them. In addition, the two groups differed in their perception of time while experiencing FP. However, location of FP did not differ between groups. Interviews with the three patients in Study 2 showed that the presentation of FP is incredibly varied both between and within patients, regarding general emotion accompanying FP, duration, and form. In conclusion, FP is accompanied by a wide variation of sensations, perceptions, and understandings. Given the increased presence of FP in those at risk for psychosis, it might be a candidate marker for schizophrenia.Item Multisensory Processing and Anomalous Self Experiences in Schizophrenia(Vanderbilt University, 2014) Michael, Jamie; Park, Sohee; Saylor, MeganAbnormal multisensory integration is thought to play an important role in anomalous dissociative experiences of the body and self, including out-of-body experiences (OBEs) and feelings-of-presence. Aspects of OBEs including malleable self-boundaries and impaired judgments about self-location overlap with the phenomenology of schizophrenia. We sought to examine the performance of patients with schizophrenia (SZ) and healthy participants on a battery of visuo-tactile tasks designed to tap the underlying multisensory processes that may be abnormal in the schizophrenia spectrum. Methods: 7 patients with schizophrenia and 9 healthy controls participated in a battery of tasks that were designed to probe aspects of self and body integrity. The Mental Rotation Task assessed participants’ abilities to perform mental transformations (perspective taking). The Graphesthesia Task measured participants’ abilities to transform tactile stimuli to visuospatial representation. The Hand Reversal Task measured participants’ abilities to integrate conflicting visuospatial and proprioceptive information. The Pinocchio Illusion task gauged susceptibility to perceive loosened self-boundaries and ambiguous spatial location of the body. The Shape After Effect Illusion measured the tendency to experience tactile illusion. The Two Point Discrimination Task measured the tactile sensitivity and discriminability of the participants. In addition to these behavioral tasks we developed and administered a new self-report questionnaire designed to probe anomalous bodily experiences (BODI). In patients, symptoms were assessed with clinical interviews. In healthy controls, schizotypal personality questionnaire was given to assess schizotypal traits. Results: We found that reported incidence of anomalous phenomenological experience was associated with decreased tactile sensitivity and that SZs were more likely to have reduced tactile sensitivity. Furthermore, higher schizotypal traits in controls were associated with susceptibility to abnormal self-experiences. Discussion: Although there were no statistical differences between patients and controls on most of the illusion tasks, there were trends showing reduced tactile sensitivity in SZ. SZ had preserved perspective-taking abilities in the mental rotation task, which suggests that they are able to perform self-other transformations. Future research should recruit larger, age-matched participant pools and examine neural underpinnings of anomalous self-experiences in schizophrenia.Item Effects of Transcranial Direct Current Stimulation (tDCS) on Performance Monitoring and Learning Rate in Schizophrenia(Vanderbilt University, 2014-04-15) Zhu, Julia; Park, Sohee; Woodman, Geoffrey F.A reliable and valid neurophysiological index of error-monitoring ability is an eventrelated potential (ERP) known as “error-related negativity” (ERN), which is evoked following an error response. Individuals with schizophrenia show error monitoring deficits accompanied by reduced ERN. Error monitoring is mediated in part by the medial-frontal cortex, which has been shown to be abnormal in schizophrenia. Transcranial direct current stimulation (tDCS) is a noninvasive tool for transient modulation of cortical function, which delivers low current to brain areas through small electrodes. In this study, we sought to improve performance monitoring in schizophrenia by delivering tDCS to the medial-frontal area. Ten patients and 10 demographically matched controls participated in a difficult choice target color discrimination task with stop trials that were designed to elicit errors while ERPs were recorded. TDCS was delivered before the cognitive task. After anodal tDCS stimulation, performance monitoring and learning rates were improved in the patients and ERN was increased to measures comparable to healthy controls during the sham condition. These results suggest that tDCS could be used to treat cognitive deficits in schizophrenia, and other neuropsychiatric illnesses with widespread cognitive impairments.