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Öğe Cortisol response to stress in schizophrenia: associations with oxytocin, social support and social functioning(Elsevier Ireland Ltd, 2018) Taş, Cumhur; Brown, Elliot C.; Eskikurt, Gökçer; Irmak, Sezen; Aydın, Orkun; Esen-Danacı, Aysen; Bruene, MartinPrevious studies reported attenuated cortisol reactivity as one explanation for poor social functioning in schizophrenia. Recent research has demonstrated that both glucocorticoid and oxytocin systems are central to stress regulation. Here, we studied the associations between basal oxytocin, stress-induced cortisol levels, and social functioning and social support in schizophrenia. A mock job interview was used as an ecologically-valid social stressor in 32 schizophrenia patients. Blood samples were taken before and after stress induction to assess basal oxytocin and cortisol levels. In addition social functioning and social support scales were collected. Patients were divided into cortisol responders and non-responders according to percentage change following stress induction. Our findings revealed a possible subgroup of patients who did not exhibit attenuated cortisol responses. Importantly, cortisol responders had generally better social functioning, but perceived social support was not different between groups. There was also no evidence of a relationship between cortisol and oxytocin. This study highlights the heterogeneity of cortisol responses to stress in a schizophrenia population, and the importance of the relationship between social functioning and cortisol reactivity. These findings could be relevant when considering therapeutic interventions that manipulate endocrinology in order to improve real-world functioning.Öğe Dancers and fastball sports athletes have different spatial visual attention styles(Springer, 2018) İşoğlu-Alkaç, Ümmühan; Ermutlu, M. Numan; Eskikurt, Gökçer; Yücesir, İlker; Temel, Sernaz Demirel; Temel, TanPhysical exercise and the training effects of repeated practice of skills over an extended period of time may have additive effects on brain networks and functions. Various motor skills and attentional styles can be developed by athletes engaged in different sports. In this study, the effects of fast ball sports and dance training on attention were investigated by event related potentials (ERP). ERP were recorded in auditory and visual tasks in professional dancer, professional fast ball sports athlete (FBSA) and healthy control volunteer groups consisting of twelve subjects each. In the auditory task both dancer and FBSA groups have faster N200 (N2) and P300 (P3) latencies than the controls. In the visual task FBSA have faster latencies of P3 than the dancers and controls. They also have higher P100 (P1) amplitudes to non-target stimuli than the dancers and controls. On the other hand, dancers have faster latencies of P1 and higher N100 (N1) amplitude to non-target stimuli and they also have higher P3 amplitudes than the FBSA and controls. Overall exercise has positive effects on cognitive processing speed as reflected on the faster auditory N2 and P3 latencies. However, FBSA and dancers differed on attentional styles in the visual task. Dancers displayed predominantly endogenous/top down features reflected by increased N1 and P3 amplitudes, decreased P1 amplitude and shorter P1 latency. On the other hand, FBSA showed predominantly exogenous/bottom up processes revealed by increased P1 amplitude. The controls were in between the two groups.Öğe The effect of cerebellar transcranial direct current stimulation on balance tests in healthy young(Science Direct, 2019) Erdoğan, Ezgi; Kır, Can; Beycan, Esin; Karakaya, Esin; Altınçınar, Sanem; Bayramoğlu, Türkü; Eskikurt, Gökçer; Karamürsel, SacitTranscranial direct current stimulation (tDCS) studies showed positive results about postural control and motor adaptation especially in patients and older adults. We aimed to investigate the effect of cerebellar anodal stimulation on balance tests. Besides, errors and reaction time (RT) were also measured by continuous performance test. Eleven young healthy volunteers participated in the study.Öğe Investigation of the effects of transcranial direct current stimulation and neurofeedback by continuous performance test(Elsevier Ireland Ltd, 2020) Güleken, Zozan; Eskikurt, Gökçer; Karamürsel, SacitTranscranial direct current stimulation (tDCS) is a noninvasive neuromodulation technique based on weak direct current stimulation through the scalp. Neurofeedback (NFB) is a learning strategy that may help alter to brain wave parameters, by monitoring electroencephalography (EEG) feedback via special programs. We aimed to investigate the supportive effects of tDCS in addition to NFB training. 16 healthy volunteers were divided equally into two groups. One of the groups was trained by NFB with the sensorimotor rhythm (SMR) protocol; 2 days per week, 10 sessions of 30 min, the other group received 10 min of tDCS before each NFB sessions. Continuous Performance Test (CPT) was used to measure, response time and suppression and to determine selective attention condition. Also, Beck Depression and Anxiety Inventories were used to exclude people with depression and anxiety. Depression scores of NFB + tDCS group were decreased significantly. CPT scores were better at last sessions for both groups compared to the first sessions. Sessions were analyzed by comparing 1st, 2nd, 5th and 10th sessions. While the NFB + tDCS group had statistically significant changes at theta/beta ratios with SMR and alpha band amplitudes, NFB group statistics had changed at theta/SMR ratios. NFB training shows its effects at the end of 10 sessions. Despite an increase in the latencies of correct and commission responses on the task of CPT, additional use of tDCS improves cognitive performance. Also, tDCS has a supportive effect on the healthy participants who have mild anxiety and depression; also inhibition deficits of subjects were clear.Öğe Neural underpinnings of negative emotional expressions evoked by audiovisual stimuli(SAGE PUBLICATIONS LTD, 2021) Türk, Dilara D.; Eskikurt, Gökçer; Taşlıyurt, Şule; Yıldırım, Funda[No Abstract Available]Öğe Neuromodulation of the left auditory cortex with transcranial direct current stimulation (tDCS) has no effect on the categorical perception of speech sounds(Elsevier, 2023) Işık, Mevlüde; Eskikurt, Gökçer; Erdoğan, Ezgi TunaTemporal cue analysis in auditory stimulus is essential in the perception of speech sounds. The effect of transcranial direct current stimulation (tDCS) on auditory temporal processing remains unclear. In this study, we examined whether tDCS applied over the left auditory cortex (AC) has a polarity-specific behavioral effect on the categorical perception of speech sounds whose temporal features are modulated. Sixteen healthy volunteers in each group were received anodal, cathodal, or sham tDCS. A phonetic categorization task including auditory stimuli with varying voice onset time was performed before and during tDCS, and responses were analyzed. No statistically significant difference was observed between groups (anode, cathode, sham) and within the groups (pre-tDCS, during tDCS) in comparisons of the slope parameter of the identification function obtained from the phonetic categorization task data. Our results show that a single-session application of tDCS over the left AC does not significantly affect the categorical perception of speech sounds. © 2022 Elsevier LtdÖğe Single session anodal transcranial direct current stimulation on different cortical areas effects on pain modulation in healthy subjects(HOGREFE PUBLISHING CORP, 2022) Erdoğan, Ezgi Tuna; Küçük, Zeynep; Eskikurt, Gökçer; Kurt, Adnan; Ermutlu, Numan; Karamürsel, SacitTranscranial direct current stimulation (tDCS) studies in healthy volunteers have shown conflicting results in terms of modulation in pain thresholds. The aim of this study was to investigate how single session anodal tDCS and modulated tDCS (mtDCS) of distinct cortical areas affected pain and perception thresholds in healthy participants. Five different stimulation conditions were applied at different cortical sites to 20 healthy volunteers to investigate the effects of tDCS and mtDCS (20 Hz) on pain and perception thresholds. TDCS over the motor cortex (M1), mtDCS over the motor cortex, tDCS over the dorsolateral prefrontal cortex (DLPFC), mtDCS of the DLPFC, and mtDCS over the occipital cortex were the stimulation conditions. All of the stimulations were anodal. The stimulations were given in a randomized order at 20-minute intervals. For comparison, electrical pain and perception thresholds were obtained from the right middle finger before and during the tDCS. After each measurement, participants were asked to give a score to their pain. In repeated measures analysis of variance (RM-ANOVA) test, the Condition x Time interaction showed no significant influence on changes in pain, perception thresholds, and pain scores (p = .48, p = .89, and p = .50, respectively). However, regardless of the condition types, there was a significant difference in pain and perceptual thresholds during tDCS (p = .01, p = .025, respectively). Our findings did not support difference in pain and perception modulation by a single session anodal tDCS over M1 and DLPFC compared to the occipital cortex in healthy volunteers. The increase in all thresholds during tDCS, irrespective of conditions, and peripheral sensations, including an active control group, taken together, suggest a placebo effect of active tDCS. Future studies about pain and perception in healthy subjects should consider the level of experimental pain and a strong placebo effect.
