Avtor/Urednik		Avčin, T; Korošec, M
Naslov		Drget kortikospinalne proge
Prevedeni naslov		Corticospinal tract jitter
Tip		članek
Vir		Med Razgl
Vol. in št.		Letnik 33, št. 4
Leto izdaje		1994
Obseg		str. 419-41
Jezik		slo
Abstrakt		Corticospinal influences on distal and proximal muscles of the upper limb were studied in 14 normal volunteers. The techniques of electrical and magnetic corticospinal tract activation through intact scalp were used. Recordings were made of the discharges of single motor units from the abductor digiti minimi and biceps brachii muscles. Poststimulus time histograms (PSTHs) of the motor unit discharges were constructed. The latency variation of consecutive single motor unit responses (the corticospinal tract jitter) was determined for each period of increased firing probability (peak). The rise time of excitatory postsynaptic potential (EPSP) was estimated from the duration of the period of increased firing probability, and its amplitude from the size of the PSTH peak. The threshold stimuli produced one or more narrow periods of increased firing probability in the PSTHs of all the motor units studied. A relatively small corticospinal tract jitter (289-428 us in abductor digiti minimi and 358-431 us in biceps brach muscle) with no statistically significant differences between the muscles was found in each period of increased firing probability. The rise time of EPSP in both muscles ranged between 1.1 and 1.5 ms. The size of the first peaks after the anodal stimulation indicated that of the underlying EPSP amplitude was approx. 5.0 mV for the abductor digiti minimi and approx. 4.7 m V for the biceps brachii motor units. The finding of relatively small corticospinal tract jitter and short EPSPs rise times seem to support the existence of a monosynaptic projection from the brain to the motoneurones innervating both muscles. The estimated sizes of EPSPs aiso suggest similar effectiveness of synaptic transmission in both cases. Our results do not support the anticipated greater effectiveness of corticospinal tract connexions to the motoneurones supplying distal muscles of the upper limb.
Izvleček		Pri 14 zdravih prostovoljcih smo preučevali učinkovitost nadzora kortikospinalne proge nad spinalnimi motonevroni, ki pripadajo mišicam zgornjega uda. Domnevali smo, da je nadzor nad motonevroni distalnih mišic učinkovitejši. Motorično možgansko skorjo smo dražili z neinvazivnim električnim in magnetnim draženjem. Odzive posamičnih motoričnih enot smo detektirali v mišicah abduktor mezinca in biceps brah?. Pogostnost odzivanja motoričnih enot na draženje smo prikazali v obliki frekvenčnih histogramov podražljajne verjetnosti proženja. Za obdobja povečane verjetnosti proženja smo določili latenčno spremenljivost zaporednih odzivov - drget kortikospinalne proge. Z merjenjem njihovih širin smo ocenili trajanje rastočih faz ekscitacijskih postsinaptičnih potencialov (EPSP). iz deleža odzivov v prvem obdobju pa velikosti le-teh. Motorične enote so se na draženje odzivale v enem ali v več obdobjih povečane verjetnosti proženja. Velikost drgeta kortikospinalne proge je bila statistično neznačilno različna in majhna za obe mišici (za mišico abduktor mezinca med 289 in 428 mikro s, za mišico biceps brahii med 358 in 431 mikro s). Tudi trajanje rastočih faz EPSP je bilo za obe mišici enako (med 1.1 in l,5ms). Povprečna velikost EPSP je bila za motonevrone mišice abduktor mezinca 5,0 m V, za motonevrone mišice biceps brahii pa 4,7 mV. Razmeroma majhne vrednosti drgeta kortikospinalne proge in kratko trajanje rastočih faz EPSP podpirajo omnevo, da ima pri človeku kortikospinalna proga z motonevroni lahko monosinaptičen stik. Približno enake velikosti EPSP kažejo na enako učinkovit sinaptični prenos v obeh mišicah. Rezultati raziskave ne podpirajo delovne hipoteze o učinkovitejšem nadzoru kortikospinalne proge nad motonevroni distalnih mišic.
Deskriptorji		ARM MOTOR NEURONS MOTOR CORTEX SYNAPTIC TRANSMISSION PYRAMIDAL TRACTS ELECTRIC STIMULATION