Researcher: Topkara, Betilay
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Topkara, Betilay
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Publication Metadata only A stimulus rate that is not influenced by homosynaptic post-activation depression in chronic stroke(Taylor & Francis Ltd, 2020) Yurttutmus, Zeynep; Ekici Zincirci, Dilara; Bardak, Ayşe Nur; Aydın, Tuğba; Karacan, İlhan; N/A; N/A; Topkara, Betilay; Türker, Kemal Sıtkı; PhD Student; Faculty Member; Graduate School of Health Sciences; School of Medicine; 353320; 6741Purpose: To determine a stimulus rate that is not influenced by homosynaptic post-activation depression for H-reflex studies in patients with chronic spasticity. Materials and Methods: A cohort of 15 chronic stroke patients with soleus spasticity who received inpatient treatment at our rehabilitation centre participated in this study. The effect of stimulus frequency related depression on H-reflex size was tested using four different stimulus rates (0.1, 0.2, 0.3 and 1 Hz). The affected sides stibial nerve was stimulated by a bipolar electrode. The H-reflex was recorded from the affected sideed sidee sidehe affected smine stimulus frequency related depression of H-reflex size, amplitude of the first H-reflex response (H-1) was used as control and amplitude of the second H-reflex response (H-2) as test. Results: H(2)amplitude for frequency of 1 Hz, 0.3 Hz, 0.2 Hz and 0.1 Hz were 74.3, 84.1, 85.5 and 92.7% of H-1, respectively. Depression of H(2)amplitude was statistically significant for 1 Hz, 0.3 Hz and 0.2 Hz (p < 0.001,p = 0.002,p = 0.024, respectively). Conclusions: Higher frequency stimulation of Ia afferents than 0.1 Hz induced a stimulus frequency-related depression of H-reflex size in patients with chronic spasticity. The optimal stimulus rate for H-reflex was found to be 0.1 Hz.Publication Metadata only Exploring the receptor origin of vibration-induced reflexes(Nature Publishing Group, 2020) Yıldırım, Mustafa A.; Aydın, Tuğba; Paker, Nurdan; Soy, Derya; Coşkun, Evrim; Ones, Kadriye; Bardak, Ayşenur; Kesiktaş, Nur; Çelik, Berna; Önder, Burcu; Kılıc, Ayşeguü; Küçük, Habib C.; Karacan, İlhan; N/A; N/A; N/A; Topkara, Betilay; Özyurt, Mustafa Görkem; Türker, Kemal Sıtkı; PhD Student; PhD Student; Faculty Member; Graduate School of Health Sciences; Graduate School of Sciences and Engineering; School of Medicine; 353320; N/A; 6741Study Design: An experimental design. Objectives: The aim of this study was to determine the latencies of vibration-induced reflexes in individuals with and without spinal cord injury (SCI), and to compare these latencies to identify differences in reflex circuitries. Setting: A tertiary rehabilitation center in Istanbul. Methods: Seventeen individuals with chronic SCI (SCI group) and 23 participants without SCI (Control group) were included in this study. Latency of tonic vibration reflex (TVR) and whole-body vibration-induced muscular reflex (WBV-IMR) of the left soleus muscle was tested for estimating the reflex origins. The local tendon vibration was applied at six different vibration frequencies (50, 85, 140, 185, 235, and 265 Hz), each lasting for 15 s with 3-s rest intervals. The WBV was applied at six different vibration frequencies (35, 37, 39, 41, 43, and 45 Hz), each lasting for 15 s with 3-s rest intervals. Results: Mean (SD) TVR latency was 39.7 (5.3) ms in the SCI group and 35.9 (2.7) ms in the Control group with a mean (95% CI) difference of -3.8 (-6.7 to -0.9) ms. Mean (SD) WBV-IMR latency was 45.8 (7.4) ms in the SCI group and 43.3 (3.0) ms in the Control group with a mean (95% CI) difference of -2.5 (-6.5 to 1.4) ms. There were significant differences between TVR latency and WBV-IMR latency in both the groups (mean (95% CI) difference; -6.2 (-9.3 to -3.0) ms, p = 0.0001 for the SCI group and -7.4 (-9.3 to -5.6) ms, p = 0.011 for Control group). Conclusions: The results suggest that the receptor of origin of TVR and WBV-IMR may be different.Publication Metadata only The effect of oral administration of monosodium glutamate on epileptogenesis in infant rats(John Libbey Eurotext Ltd, 2020) Demirkapu, Mahluga Jafarova; Yananli, Hasan Raci; Akşahin, Elif; Karabiber, Ceren; Gunay, Pinar; Kekilli, Arda; N/A; N/A; Topkara, Betilay; PhD Student; Graduate School of Health Sciences; 353320Aim: Glutamate is an excitatory neurotransmitter that is widely distributed throughout the brain. An increase in glutamate concentration or sensitivity of glutamate receptors triggers neurodegenerative diseases, epilepsy in particular. Monosodium glutamate is a substance added to foods to enhance flavour. We investigated the effect of monosodium glutamate on epileptogenesis, as well asheight and weight, in rats that were just weaned. Methods: Twenty-four male and female 21-day-old Wistar Albino rats were divided into two groups: one with monosodium glutamate added to the drinking water, and a control in which NaCl was added to the drinking water. The electrical stimulation threshold values were determined in animals to which the hippocampal kindling process was applied, and the stimulations at these threshold values were invariably applied to the animals until they were kindled. Results: The electrical stimulation threshold values of the monosodium glutamate group did not statistically change, whereas the number of required stimulations for kindled rats was significantly lower compared with the control group. Conclusion: These results reveal that long-term oral administration of glutamate salts causes an increase in excitability in the central nervous system during ontogenetic development.Publication Metadata only Facial muscle activity contaminates EEG signal at rest: evidence from frontalis and temporalis motor units(Iop Publishing Ltd, 2019) N/A; N/A; N/A; N/A; N/A; Yılmaz, Gizem; Budan, Abdullah Salih; Ungan, Pekcan; Topkara, Betilay; Türker, Kemal Sıtkı; PhD Student; Undergraduate Student; Faculty Member; PhD Student; Faculty Member; Graduate School of Health Sciences; School of Medicine; School of Medicine; Graduate School of Health Sciences; School of Medicine; N/A; N/A; N/A; 353320; 6741Objective: In order to reach electroencephalography (EEG) electrodes on the scalp, synchronized activity of neurons needs to pass thorough several tissue layers, including the skull and muscles covering the scalp. the contamination of EEG signal by temporalis and frontalis muscles has been well documented for voluntary muscle contraction even at low contraction levels. the extent of myogenic contamination during postural and/or rest activity of the temporalis and frontalis remains an impediment for EEG research. Approach: In this study, we first aimed to observe involuntary, continuous motor unit activity of the frontalis muscle at rest and evaluate motor unit level frontalis interference on the EEG electrodes. Second, we compared motor unit interference from the frontalis before and after artefact pruning via an independent component analysis (ICa) algorithm. Main Results: We demonstrated that motor unit activity of the frontalis muscle produces interference potentials on the frontal electrodes at rest and the interference was significantly reduced after ICa on the frontal electrodes, but not completely eliminated. Likewise, the temporalis interference at rest was significantly smaller after ICa on the fronto-temporal electrodes, but not completely removed. Significance: We documented the existence of resting involuntary activity of the temporalis and frontalis muscles underneath EEG electrodes and the removal of the EEG signal from their contiguous interference is not possible even after the use of ICa technology. We recommend that EEG researchers readdress the definition of 'rest' for EEG recordings and the ICa experts should extend their electromyography removal strategies to motor unit level interference.Publication Metadata only Effect of aging on H-reflex response to fatigue(Springer, 2020) Lavender, Andrew Philip; Balkozak, Sadik; Karacan, Ilhan; Bilici, Idil; Hill, Anne-Marie; N/A; Özyurt, Mustafa Görkem; Topkara, Betilay; Türker, Kemal Sıtkı; PhD Student; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; School of Medicine; Graduate School of Health Sciences; School of Medicine; N/A; 353320; 6741Injury as a result of tripping is relatively common among older people. The risk of falling increases with fatigue and of importance is the ability to dorsiflex the foot through timely activation of the tibialis anterior (TA) muscle to ensure the foot clears the ground, or an obstacle, during the swing phase of walking. We, therefore, questioned whether the muscle spindle input to the motoneurons alters with ongoing fatigue in older people. We electrically stimulated the common peroneal nerve to assess the TA primary afferent efficacy using H-reflex before, immediately following and after a fatiguing maximal isometric contraction. M-response was kept unchanged throughout the experiment to ensure a similar stimulus intensity was delivered across time points. H-reflex increased significantly while the TA muscle was in a state of fatigue for the younger participants but tended to decrease with increasing age. The main contributor to the tonicity of TA muscle, i.e., excitatory synapses of spindle primary endings of motoneurons that innervate TA muscle, tend to lose their efficacy during fatigue in the older individuals but increased efficiency in the majority of the younger people. Since TA muscle is the main dorsiflexor of the foot and it needs to be active during the swing phase of stepping to prevent tripping, older individuals become more susceptible to falling when their muscles are fatigued. This finding may help improve devices/treatments to overcome the problem of tripping among older individuals.Publication Metadata only The effects of l-name and agmatine in the nucleus accumbens core region on morphine withdrawal syndrome(Namık Kemal Üniversitesi, 2020) Demirkapu, Mahluga Jafarova; Yanancı, Hasan Raci; Mammadov, Elmar; Dervishi, Ina; Yaşar, Şafak Recep; Sali, Tzemal; Kurbanoğlu, Mansur; Çağlar, Merve; Sakallı, Halil Eren; N/A; Topkara, Betilay; PhD Student; Graduate School of Health Sciences; 353320Aim: The mesocorticolimbic dopaminergic system, especially the nucleus accumbens, is an important region in opioid dependence and withdrawal. Studies have shown that nitric oxide synthase inhibitors modulate the development of tolerance to opioids, opioid dependence, and withdrawal. In this study, we aimed to investigate the effects of local injections of L-NAME and agmatine into the nucleus accumbens core (NAcc), one of the nucleus accumbens subregions on withdrawal signs and locomotor activity behavior during naloxone-induced withdrawal in morphine-dependent rats. Materials and Methods: Twenty-four adult Sprague-Dawley rats were used in the study. Morphine dependence was developed in all animals after guide cannula implantation into the NAcc region. On the last day of experiment, following bilateral L-NAME, agmatine or artificial cerebrospinal fluid (aCSF, control group) microinjections morphine withdrawal was induced by naloxone. Results: Local administration of agmatine and L-NAME into the NAcc significantly suppressed the jumping number during naloxone induced withdrawal. Local agmatine treatment significantly suppressed the score of teeth chattering, although the L-NAME did not change. No significant difference was observed in withdrawal symptoms such as wet dog shakes and defecation after local agmatine and L-NAME treatment. Agmatine increased stereotypic movements, but did not change locomotor activity behaviors such as ambulatory activity and total covered distance. Local administration of L-NAME into the NAcc did not increase stereotypic and ambulatory movements, and total covered distance during naloxone-induced withdrawal. Conclusion: These results suggest that inhibition of nitric oxide synthesis in NAcc plays a role in morphine withdrawal symptoms, but it is not responsible alone. / Amaç: Mezokortikolimbik dopaminerjik sistem, özellikle de nukleus akumbens bölgesi opioid bağımlılığı ve yoksunluğunda önemli bölgelerdendir. Yapılan çalışmalara göre nitrik oksit sentaz inhibitörleri opioidlere karşı tolerans gelişimini, opioid bağımlılığı ve yoksunluğunu değiştirmektedir. Biz bu çalışmada L-NAME ve agmatinin nukleus akumbens alt-bölgelerinden biri olan nukleus akumbens çekirdek (NAcc) bölgesine lokal enjeksiyonlarının morfin bağımlısı sıçanlarda naloksonla tetiklenen yoksunluk sırasında yoksunluk bulguları ve lokomotor aktivite davranışı üzerine etkilerini araştırmayı amaçladık. Materyal ve Metot: Çalışmada yirmi dört yetişkin Sprague-Dawley sıçanı kullanıldı. Tüm hayvanlarda morfin bağımlılığı NAcc bölgelerine kılavuz kanüller yerleştirildikten sonra geliştirildi. Deneyin son gününde bilateral L-NAME, agmatin veya aCSF (yapay beyin omurilik sıvısı; kontrol grubu) mikroenjeksiyonlarını takiben nalokson uygulanarak morfin yoksunluğu tetiklendi. Bulgular: NAcc bölgesine lokal uygulanan agmatin ve L-NAME morfin bağımlısı hayvanlarda nalokson sonrası sıçrama sayısını anlamlı olarak baskıladı. Lokal L-NAME tedavisi diş gıcırdatma skorunu değiştirmediği halde agmatin tedavisi anlamlı düzeyde baskıladı. Lokal L-NAME ve agmatin tedavisinden sonra ıslak köpek silkinmesi ve defekasyon gibi yoksunluk bulgularında anlamlı farklılık saptanmadı. NAcc bölgesine lokal enjekte edilen agmatin stereotipik hareketleri artırdığı halde ambulatuvar ve toplam kat edilen mesafe gibi lokomotor aktivite davranışlarında anlamlı değişiklik yapmadı. NAcc bölgesine lokal enjekte edilen L-NAME naloksonla tetiklenen yoksunluk sendromunda stereotipik hareketlerde, ambulatuvar hareketlerde ve toplam kat edilen mesafede artışa yol açmadı. Sonuç: Bu bulgular nitrik oksit üretiminin NAcc bölgesinde baskılanmasının morfin yoksunluk sendromunda rol oynadığını, fakat tek başına sorumlu olmadığını göstermektedir.Publication Metadata only The role of adenosine A1 receptors in the nucleus accumbens during morphine withdrawal(2020) Jafarova Demirkapu, Mahluga; Yananlı, Hasan Raci; Kaleli, Melisa; Sakallı, Halil Eren; Gören, Mehmet Zafer; N/A; Topkara, Betilay; PhD Student; Graduate School of Health Sciences; 353320Opioids are effective analgaesic agents, but serious adverse effects such as tolerance and withdrawal contribute to opioid dependence and limit their use. Opioid withdrawal is a common occurrence in human opiate addicts that is not life-threatening. Studies have shown that the mesocorticolimbic system, especially the nucleus accumbens, is an important region in drug addiction and adenosine receptors play a modulatory role in the mechanism of action of drug dependence and withdrawal. The aim of this study was to investigate the effects of the selective A1 receptor agonist CPA (N6-cyclopentyladenosine) on withdrawal symptoms, and the concentration of dopamine and noradrenaline in the nucleus accumbens and locomotor activity behaviour during naloxone-precipitated withdrawal in morphine-dependent rats. The local administration of CPA (1.5, 3.0, and 6.0 mmol/L bilateral 250 nL) into the nucleus accumbens decreased the Gellert–Holtzman withdrawal scale, and increased concentrations of dopamine and noradrenaline in the same region during naloxone-induced withdrawal. Our findings suggest that administration of the A1 receptor agonist significantly decreased withdrawal behaviours and increased dopamine and noradrenaline concentrations in opioid withdrawal in a dose-dependent manner. These results demonstrate that adenosine receptors should be examined as a potential mechanism that could be exploited for the treatment of morphine withdrawal.Publication Metadata only Amyotrophic lateral sclerosis weakens spinal recurrent inhibition and post-activation depression(Elsevier Ireland Ltd, 2020) İsak, Barış; N/A; Özyurt, Mustafa Görkem; Topkara, Betilay; Türker, Kemal Sıtkı; PhD Student; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; Graduate School of Health Sciences; School of Medicine; N/A; 353320; 6741Objectives: Amyotrophic lateral sclerosis (ALS) disrupts motoneurons that control movement and some vital functions, however, exact details of the neuronal circuits involved in ALS have yet to be fully endorsed. To contribute to our understanding of the responsible neuronal circuits, we aimed to investigate the spinal recurrent inhibition (RI) and post-activation depression (P-AD) in ALS patients. Methods: In two groups of ALS patients, i.e. lumbar-affected (clinical signs in leg muscles) and nonlumbar-affected (clinical signs in arms or bulbar region but not in the legs), RI and P-AD on the soleus muscle were investigated using single motor units and amplitude changes of H-reflex in surface electromyography, respectively. The data were compared with healthy subjects. Results: Compared to controls, P-AD of H-reflex was reduced severely in lumbar-affected patients and reduced to a certain degree in nonlumbar-affected patients. Similarly, a significant reduction in the duration of RI on firing motoneurons was found in lumbar-affected patients (11.5 +/- 2.6 ms) but not in nonlumbar-affected patients (29.7 +/- 12.4 ms, P < 0.0001) compared to controls (30.8 +/- 7.2 ms, P < 0.0001). Conclusion: The current study revealed that spinal inhibitory circuits are impaired in ALS. Significance: These findings may provide insight for proposing new therapeutic approaches and following disease progression in humans.Publication Metadata only Motor units as tools to evaluate profile of human Renshaw inhibition(Wiley, 2019) Piotrkiewicz, Maria; Weisskircher, Hans-Werner; Turker, Kemal Sitki; N/A; Özyurt, Mustafa Görkem; Topkara, Betilay; Türker, Kemal Sıtkı; PhD Student; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; School of Medicine; Graduate School of Health Sciences; School of Medicine; N/A; 353320; 6741Although Renshaw inhibition (RI) has been extensively studied for decades, its precise role in motor control is yet to be discovered. One of the main handicaps is a lack of reliable methods for studying RI in conscious human subjects. We stimulated the lowest electrical threshold motor axons (thickest axons) in the tibial nerve and analysed the stimulus-correlated changes in discharge of voluntarily recruited low-threshold single motor units (SMUs) from the soleus muscle. In total, 54 distinct SMUs from 12 subjects were analysed. Stimuli that generated only the direct motor response (M-only) on surface electromyography induced an inhibitory response in the low-threshold SMUs. Because the properties of RI had to be estimated indirectly using the background discharge rate of SMUs, its profile varied with the discharge rate of the SMU. The duration of RI was found to be inversely proportional to the discharge rate of SMUs. Using this important finding, we have developed a method of extrapolation for estimating RI as it develops on motoneurons in the spinal cord. The frequency methods indicated that the duration of RI was between 30 and 40ms depending on the background firing rate of the units, and the extrapolation indicated that RI on silent motoneurons was approximate to 55ms. The present study establishes a novel methodology for studying RI in human subjects and hence may serve as a tool for improving our understanding of the involvement of RI in human motor control.Publication Metadata only Post-activation depression of primary afferents reevaluated in humans(Elsevier, 2020) N/A; N/A; N/A; N/A; N/A; N/A; N/A; Özyurt, Mustafa Görkem; Topkara, Betilay; Şenocak, Beatrice Selen; Budan, Abdullah Salih; Yüce, Murat Necdet; Türker, Kemal Sıtkı; PHD Student; PHD Student; Master Student; Undergraduate Student; Undergraduate Student; Faculty Member; Graduate School of Sciences and Engineering; Graduate School of Health Sciences; Graduate School of Sciences and Engineering; School of Medicine; School of Medicine; School of Medicine; N/A; N/A; N/A; N/A; N/A; N/A; 6741Amplitude variation of Hoffmann Reflex (H-reflex) was used as a tool to investigate many neuronal networks. However, H-reflex itself is a subject to intrinsic changes including post-activation depression (P-AD). We aimed to investigate P-AD and its implication on motor control in humans. Upon tibial nerve stimulation in 23 healthy participants, peak-to-peak amplitude change of H-reflex was investigated using surface electromyography (SEMG) of soleus muscle. Variety of stimulus intensities, interstimulus intervals (ISIs), voluntary contraction levels/types and force recording were used to investigate the nature of P-AD. We have shown that P-AD was significantly stronger in the shorter ISIs. The only exception was the ISI of 200 msecs which had a weaker P-AD than some of the longer ISIs. Sudden muscle relaxation, on the other hand, further increased the effectiveness of the ongoing P-AD. Moreover, P-AD displayed its full effect with the first stimulus when there was no muscle contraction and was efficient to reduce the muscle force output by about 30%. These findings provide insight about the variations and mechanism of P-AD and could lead to improvements in diagnostic tools in neurological diseases.