Researcher: Karamürsel, Sacit
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Karamürsel, Sacit
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Publication Metadata only Effectiveness of anodal otDCS following with anodal tDCS rather than tDCS alone for increasing of relative power of intrinsic matched EEG bands in rat brains(Multidisciplinary Digital Publishing Institute (MDPI), 2023) Al-Tawarah, Nafe M.; Kaptan, Zulal; Abu-Harirah, Hashem A.; Nofal, Mohammad; Almajali, Belal; Jarrar, Sultan; Bayraktaroğlu, Zübeyir; Qaralleh, Haitham; Khleifat, Khaled M.; Ziylan, Ziya Y.; Al dmour, Rawand H.; Alqaraleh, Moath; Karamürsel, Sacit; Faculty Member; School of Medicine; 19597Background: This study sought to determine whether (1) evidence is available of interactions between anodal tDCS and oscillated tDCS stimulation patterns to increase the power of endogenous brain oscillations and (2) the frequency matching the applied anodal otDCS’s frequency and the brain’s dominant intrinsic frequency influence power shifting during stimulation pattern sessions by both anodal DCS and anodal oscillated DCS. Method: Rats received different anodal tDCS and otDCS stimulation patterns using 8.5 Hz and 13 Hz state-related dominant intrinsic frequencies of anodal otDCS. The rats were divided into groups with specific stimulation patterns: group A: tDCS–otDCS (8.5 Hz)–otDCS (13 Hz); group B: otDCS (8.5 Hz)–tDCS–otDCS (13 Hz); group C: otDCS (13 Hz)–tDCS–otDCS (8.5 Hz). Acute relative power changes (i.e., following 10 min stimulation sessions) in six frequency bands—delta (1.5–4 Hz), theta (4–7 Hz), alpha-1 (7–10 Hz), alpha-2 (10–12 Hz), beta-1 (12–15 Hz) and beta-2 (15–20 Hz)—were compared using three factors and repeated ANOVA measurement. Results: For each stimulation, tDCS increased theta power band and, above bands alpha and beta, a drop in delta power was observed. Anodal otDCS had a mild increasing power effect in both matched intrinsic and delta bands. In group pattern stimulations, increased power of endogenous frequencies matched exogenous otDCS frequencies—8.5 Hz or 13 Hz—with more potent effects in upper bands. The power was markedly more potent with the otDCS–tDCS stimulation pattern than the tDCS–otDCS pattern. Significance: The findings suggest that the otDCS–tDCS pattern stimulation increased the power in matched intrinsic oscillations and, significantly, in the above bands in an ascending order. We provide evidence for the successful corporation between otDCS (as frequency-matched guidance) and tDCS (as a power generator) rather than tDCS alone when stimulating a desired brain intrinsic band (herein, tES specificity).Publication Metadata only Effect of prefrontal transcranial direct current stimulation on interoception in healthy individuals(Wiley, 2022) Aksu, Serkan; N/A; Karamürsel, Sacit; Faculty Member; School of Medicine; 19597N/APublication Metadata only Elimination of pseudo-HFOs in iEEG using sparse representation and random forest classifier(Verasonics, 2022) Besheli, Behrang Fazli; Sha, Zhiyi; Henry, Thomas; Gavvala, Jay R; Ince, Nuri F.; N/A; Karamürsel, Sacit; Gürses, Rabia Candan; Faculty Member; Faculty Member; School of Medicine; School of Medicine; 19597; 110149High-Frequency Oscillation (HFO) is a promising biomarker of the epileptogenic zone. However, sharp artifacts might easily pass the conventional HFO detectors as real HFOs and reduce the seizure onset zone (SOZ) localization. We hypothesize that, unlike pseudo-HFOs, which originates from artifacts with sharp changes or arbitrary waveform characteristic, real HFOs could be represented by a limited number of oscillatory waveforms. Accordingly, to distinguish true ones from pseudo-HFOs, we established a new classification method based on sparse representation of candidate events that passed an initial detector with high sensitivity but low specificity. Specifically, using the Orthogonal Matching Pursuit (OMP) and a redundant Gabor dictionary, each event was represented sparsely in an iterative fashion. The approximation error was estimated over 30 iterations which were concatenated to form a 30-dimensional feature vector and fed to a random forest classifier. Based on the selected dictionary elements, our method can further classify HFOs into Ripples (R) and Fast Ripples (FR). In this scheme, two experts visually inspected 2075 events captured in iEEG recordings from 5 different subjects and labeled them as true-HFO or Pseudo-HFO. We reached 90.22% classification accuracy in labeled events and a 21.16% SOZ localization improvement compared to the conventional amplitude-threshold-based detector. Our sparse representation framework also classified the detected HFOs into R and FR subcategories. We reached 91.24% SOZ accuracy with the detected R+FR events. Clinical Relevance---This sparse representation framework establishes a new approach to distinguish real from pseudo-HFOs in prolonged iEEG recordings. It also provides reliable SOZ identification without the selection of artifact-free segments.Publication Metadata only Effects of transcranial direct current stimulation on cgrp and pacap-38 levels in menstrual migraine(Wiley, 2022) Bayir, B. Hasirci; Aksu, S.; Gezegen, H.; Karaaslan, Z.; Yuceer, H.; Sirin, T. Cerrahoglu; Kucukali, C.; Kurt, A.; Baykan, B.; N/A; Karamürsel, Sacit; Faculty Member; School of Medicine; 19597N/APublication Metadata only Is allodynia a determinant factor in the effectiveness of transcranial direct current stimulation in the prophylaxis of migraine?(Wiley, 2021) Cerrahoglu Sirin, Tuba; Aksu, Serkan; Hasirci Bayir, Buse Rahime; Ulukan, Cagri; Kurt, Adnan; Baykan, Betul; N/A; Karamürsel, Sacit; Faculty Member; School of Medicine; 19597Objectives Allodynia, the clinical marker of central sensitization, affects even simple daily living activities and increases the tendency for migraine to be more resistant to treatment and have a chronic course. Migraine that impairs quality of life can often be treated with variable pharmaceutical agents, but with various side effects. Transcranial direct current stimulation (tDCS) is a potential alternative treatment for migraine prophylaxis. Materials and Methods Seventy-seven patients diagnosed with migraine (48 with allodynia and 29 without allodynia) were included in the study. Randomly, 41 of the 77 patients received sham stimulation and 36 patients underwent three sessions of anodal left primary motor cortex stimulation for 2 mA, 20 min. Migraine attack characteristics (frequency, severity, and duration) and analgesic drug use were followed with headache diaries for one month after the stimulation. Results After tDCS, migraine attack frequency (p = 0.021), the number of headache days (p = 0.005), duration of attacks (p = 0.008), and symptomatic analgesic drug use (p = 0.007) decreased in patients receiving active tDCS, compared to the sham group. The therapeutic gain of tDCS was calculated as 44% (95% confidence interval [CI]: 22-60%) for headache days and 76% (95% CI: 55-86) for headache duration. Response to tDCS treatment was higher in patients without allodynia (60% vs. 24%; p = 0.028) and allodynia came out as an independent predictor of response to tDCS with logistic regression analysis. Side effects were rare and similar to the sham group. Conclusions tDCS is a safe, efficacious, and fast method for migraine prophylaxis. However, the administration of tDCS before allodynia occurs, that is, before central sensitization develops, will provide increased responsiveness to the treatment. Significance tDCS is more effective before the development of allodynia, but it also improves the quality of life even after the development of allodynia.Publication Metadata only A sparse representation strategy to eliminate pseudo-HFO events from intracranial EEG for seizure onset zone localization(Institute of Physics (IOP) Publishing, 2022) Besheli, Behrang Fazli; Sha, Zhiyi; Gavvala, Jay R.; Quach, Michael M.; Curry, Daniel J.; Sheth, Sameer A.; Francis, David J.; Henry, Thomas R.; Ince, Nuri F.; N/A; Karamürsel, Sacit; Gürses, Rabia Candan; Faculty Member; Faculty Member; School of Medicine; School of Medicine; 19597; 110149Objective. High-frequency oscillations (HFOs) are considered a biomarker of the epileptogenic zone in intracranial EEG recordings. However, automated HFO detectors confound true oscillations with spurious events caused by the presence of artifacts. Approach. We hypothesized that, unlike pseudo-HFOs with sharp transients or arbitrary shapes, real HFOs have a signal characteristic that can be represented using a small number of oscillatory bases. Based on this hypothesis using a sparse representation framework, this study introduces a new classification approach to distinguish true HFOs from the pseudo-events that mislead seizure onset zone (SOZ) localization. Moreover, we further classified the HFOs into ripples and fast ripples by introducing an adaptive reconstruction scheme using sparse representation. By visualizing the raw waveforms and time-frequency representation of events recorded from 16 patients, three experts labeled 6400 candidate events that passed an initial amplitude-threshold-based HFO detector. We formed a redundant analytical multiscale dictionary built from smooth oscillatory Gabor atoms and represented each event with orthogonal matching pursuit by using a small number of dictionary elements. We used the approximation error and residual signal at each iteration to extract features that can distinguish the HFOs from any type of artifact regardless of their corresponding source. We validated our model on sixteen subjects with thirty minutes of continuous interictal intracranial EEG recording from each. Main results. We showed that the accuracy of SOZ detection after applying our method was significantly improved. In particular, we achieved a 96.65% classification accuracy in labeled events and a 17.57% improvement in SOZ detection on continuous data. Our sparse representation framework can also distinguish between ripples and fast ripples. Significance. We show that by using a sparse representation approach we can remove the pseudo-HFOs from the pool of events and improve the reliability of detected HFOs in large data sets and minimize manual artifact elimination.Publication Metadata only Single session anodal transcranial direct current stimulation on different cortical areas effects on pain modulation in healthy subjects(Hogrefe Publishing Group) Kucuk, Zeynep; Eskikurt, Gokcer; Kurt, Adnan; Ermutlu, Numan; Erdoğan, Ezgi Tuna; Karamürsel, Sacit; Faculty Member; Faculty Member; School of Medicine; School of Medicine; 168716; 19597Transcranial 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.Publication Metadata only Working memory improvement after transcranial direct current stimulation paired with working memory training in diabetic peripheral neuropathy(Taylor & Francis, 2023) Aksu, Serkan; Bayir, Buse Rahime Hasirci; Sayman, Ceyhun; Soyata, Ahmet Zihni; Boz, Gokalp; N/A; Karamürsel, Sacit; Faculty Member; School of Medicine; 19597Association of cognitive deficits and diabetic peripheral neuropathy (DPN) is frequent. Working memory (WM) deficits result in impairment of daily activities, diminished functionality, and treatment compliance. Mounting evidence suggests that transcranial Direct Current Stimulation (tDCS) with concurrent working memory training (WMT) ameliorates cognitive deficits. Emboldening results of tDCS were shown in DPN. The study aimed to evaluate the efficacy of anodal tDCS over the left dorsolateral prefrontal cortex (DLPFC) coupled with cathodal right DLPFC with concurrent WMT in DPN for the first time. The present randomized triple-blind parallel-group sham-controlled study evaluated the efficacy of 5 sessions of tDCS over the DLPFC concurrent with WMT in 28 individuals with painful DPN on cognitive (primary) and pain-related, psychiatric outcome measures before, immediately after, and 1-month after treatment protocol. tDCS enhanced the efficacy of WMT on working memory and yielded lower anxiety levels than sham tDCS but efficacy was not superior to sham on other cognitive domains, pain severity, quality of life, and depression. tDCS with concurrent WMT enhanced WM and ameliorated anxiety in DPN without affecting other cognitive and pain-related outcomes. Further research scrutinizing the short/long-term efficacy with larger samples is accredited.Publication Metadata only Effect of transcranial direct current stimulation on pain and physical functions in individuals with lumbar spinal stenosis: a double-blind randomized sham-controlled study(Wiley, 2023) Is, Enes Efe; Aksu, Serkan; Ketenci, Aysegul; Sindel, Dilsad; N/A; Karamürsel, Sacit; Faculty Member; School of Medicine; 19597N/APublication Metadata only Transcranial electrical stimulation for neuromodulation of somatosensory processing(Elsevier, 2021) Erdoğan, Ezgi Tuna; Karamürsel, Sacit; Faculty Member; Faculty Member; School of Medicine; School of Medicine; 168716; 19597Transcranial electrical stimulation is a promising neuromodulation technique that has gained interest in the last 20 years after Nitsche and Paulus showed the polarity-specific cortical modulation effect of the weak direct current stimulation over the scalp in 2000. In the following years, new electrical stimulation techniques were introduced, such as alternative current stimulation, random noise stimulation, and pulse current stimulation. According to the literature, transcranial electrical stimulation may be a potential tool to modulate inhibitory circuits to improve the sensory discrimination function and reduce the perception threshold. Furthermore, studies investigating the modulation of multisensory integration support that modulation of sensory networks may increase the perception of body ownership and sensory perception in patients with the prosthesis. Based on the current findings, the electrical modulation of somatosensory processing should be further investigated regarding the type of stimulation, target cortical areas, and optimal parameters of the application.