İnsan motor nöronlarında sinaptik gürültünün ve postsinaptik potansiyellerin hesaplanması

Bu çalışmanın amacı, insan motor nöronları üzerinde oluşan sinaptik gürültüyü (SG) ve eksite edici postsinaptik potansiyel (EPSP) genliğini peristimulus time histogram (PSTH) ve peristimulus frekansgram (PSF) yöntemlerini kullanarak, membran potansiyeli trajektörü (yolu) yöntemi üzerinden hesaplamaktır. Gereç ve Yöntem: Araştırmaya herhangi bir nörolojik rahatsızlığı olmayan dokuz kadın ve beş erkek gönüllü katıldı. Denekler yüzükoyun olarak bir fizyoterapi masasına yatırıldı. Elektriksel uyarılar sağ bacak popliteal fossa (fossa poplitea / popliteal çukur / diz ardı çukuru) üzerinden tibial sinire 1–2 saniye aralıklarla rastgele olarak verildi. Kayıtlar soleus kasından, yüzeysel elektromiyogram (SEMG) ve tek motor ünite aksiyon potansiyelleri (SMUP) şeklinde kaydedildi. Bulgular: On dört denekten toplam olarak 42 tek motor ünite (SMU) elde edildi. Elde edilen bu motor üniteler, ortalaması alınmış SEMG’deki genlik büyüklüklerine göre, sadece H-refleksi, büyük genlikli H ile birlikte küçük genlikli m (m+H) ve büyük genlikli M ile birlikte küçük genlikli h (M+h) olacak şekilde üç gruba ayrıldı. Sonuçlar incelendiğinde PSTH-EPSP genliği ile PSF-EPSP2 genliği değerleri arasında istatistiksel olarak anlamlı bir farkın bulunmadığı görüldü (p>0,017). Her iki yöntemde hesaplanan EPSP genlikleri yaklaşık olarak 2 mV civarında bulundu. Sadece PSF yöntemi ile hesaplanan insan motor nöronlarındaki toplam sinaptik gürültü (TSG) değeri ise 5,2 mV olarak tespit edildi. Sonuç: PSF yöntemi EPSP genliğinin hesaplanmasında PSTH yöntemi kadar güvenilir bir yöntemdir. Dahası bu yöntem, insan motor nöronlarındaki SG genliğinin hesaplanması için güvenle kullanılabilir bir yöntem olup, bu anlamda PSTH yönteminden daha başarılıdır.

Estimation of synaptic noise and postsynaptic potentials on human motoneurones

Aim: The objective of this experiment is to estimate amount of synaptic noise (SN) and excitatory post-synaptic potential (EPSP) on human motoneurones using peristimulus time histogram (PSTH), peristimulus frequencygram (PSF) and membrane potential trajectory methods. Material and Methods: Nine female and 5 male healthy subjects who did not have any neurological disorders were tested. The subjects layed prone on a physiotherapy table. Electrical stimuli were delivered to the tibial nerve in popliteal fossa randomly every 1 to 2 s. The data were recorded using both surface electromyogram (SEMG) and single motor unit potentials (SMUP) in soleus muscle. Results: A total of 42 soleus motor units were analysed. The average SEMG recordings showed three conditions: H- reflex only (H-only), high amplitude H-reflex with low amplitude M-response (m+H), and low amplitude H-reflex with high amplitude M-response (M+h). Thus, the data were analysed according to the three groups. Our results demonstrated that there were no statistically significant differences between PSTH-EPSP and PSF-EPSP2 amplitudes in all groups (p>0,017). Furthermore, the EPSP amplitudes calculated by both methods were found to be about 2 mV. The total synaptic noise (TSN) on the human motoneurones was estimated using only PSF method and was found to be 5,2 mV. Conclusion: We concluded that both methods can be used with confidence to estimate the EPSP amplitude and SN amplitude can be estimated only by the PSF method on the human motoneurones.

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