Tzekov, Tz.

English

Varna Medical University Press: Journals

D E P E N D E N C E B E T W E E N R E A C T I O N T I M E A N D A M P L I T U D E C H A N G E S O F Н-REFLEX E V O K E D WITH I M P E R A T I V E S I G N A L P R E S E N T A T I O N B Y C O N T R A L A T E R A L L O W E R L I M B M U S C L E T z . Tzekov Key -words : reaction time - H-reflex - amplitude changes - contralateral lower l imb muscle The problem of organization of a forthcoming voluntary movement at spinal cord level cau­ses warrantable interest. Most authors accept that prior to its execution changes of excitability of alpha-motoneuron pool set in characterized as tuning and pretuning (1—3,8). There is a de­bate in how far this pretuning and tuning has a specific character and in how far it is of unspeci-fic nature (4 ) . According to Y a . M. Kotz (1975) , pretuning starts 5 5 - 6 0 msec prior to the be­ginning of voluntary movement and consists in an increase of excitability of motoneuron pool o f agonist muscles before its execution. B y this way, the possibility for other excitability chan­ges of muscular motoneuron pools related or not to performing of voluntary motor response is ignored to a great extent. In our previous investigations (9 ) we proved that 50 msec after presentation of a light signal requiring motor response there exists a characteristic correlation between reaction time and Fi­re flex amplitude changes in the case when this reflex is evoked by muscle - future agonist of forthcoming voluntary movement. However, such a correlation is not observed i f H-refiex is evoked by muscle-antagonists or muscles which do not practically participate in this movement (10) . I n order to exclude, on the one hand, the influence of motoneuron pool o f muscles of the one leg, agonists to forthcoming voluntary movement, on the motoneuron pool of correspond­ing muscles of the other leg, contralateral to movement, and on the other hand, to verify i f these changes established by us are unspecific and manifested in more muscles during organizing of a voluntary movement, we set us the task of investigating the dependence between reaction time and amplitude changes of reflex evoked by muscle which is analogous to an agonist of movement (rem the contralateral lower limb. Materia! and Methods Our experiments were carried out on three young individuals aged between 20 and 25 years. Subjects were sitting tranquilly on the chair and responding with maximal speed to light signal from blitz lamp through a red filter. Motor response was plantar flexion of the right foot. H-re flex was evoked by the lateral head of M t gastrocnemius of the left leg only once for every light signal simultaneously with its pre­sentation. One-day experimental programme consisted in 120 light signals divided into 3 blocks with 40 f i na l s each. Prior to beginning and after every block, Н-reflex was evoked by the same muscle without light signal presentations. The mean amplitude of these Н-reflexes was. consi­dered an amplitude of control Н-reflex at rest. Amplitudes of Н-reflexes evoked only once for every light signal were compared with control Н-reflex amplitude and their increase or decrease, respectively, was read. Dependence between react ion. 19 Results and Discussion Our data are presented on fig. 1. I t is evident that there is no dependence between reaction time and Н-reflex amplitude changes. This fact allows us to accept that correlation between, reaction time and amplitude changes of Н-reflex evoked by a muscle agonist tc forthcoming voluntary movement simultaneously with 'and 50 msec after signal presentation requiring a motor response has a specific charac­ter (9 ) . 300 -^230 -220 -• 1 1 1 1 1 1 I I I 07 0,9 1,1 13 1,5 Amplitude of H-reflex/Amplitude of Н-reflex control 4 Fig . 1. Mean values of reaction time o f three experimental subjects expressed as function o f Н-reflex ampli ­tude change's evoked f rom the lateral belly o f m. gastrocnemius o f the left leg (H to H control ) . The move­ment is plantar f lexion o f the right f o o t Conf idence interval o f arithmetic means designated by vertical line in every point is calculated at p = 0 .05. A. Eichenberger and D.C. Ruegg (1984) report also a specific Н-reflex amplitude increase. They read the difference between the increase of amplitude of the reflex evoked by one and the same muscle of the ipsilateral and contralateral side of movement. Experiments were carried out under conditions of a simple motor task and a choice motor task. On the other hand, Е. I . Paltzev and A. M. Elner (1983) establish dynamic changes of tun­ing to movement under conditions of induced increase of sensibility of human stretch-reflex mechanisms. They find out that 2 0 - 3 0 msec after signal for movement reflectory excitability decreases but then lightly increases. These facts provide still another confirmation of the significance of the changes of mono­synaptic reflex excitability as an index for voluntary movement organization despite Person's -20 T z . Tzekov opinion (1982) that Н-reflex can not be considered a reliable evaluation tool concerning moto­neuron pool excitability as far as response intensity depends also on presynaptic inhibition level in the arch of reflex tested. In contrast to Y a . M. Kotz (1975) , A . Eichenberger and D. G. Riiegg (1984) also suppose that specific Н-reflex increase prior to movement results from elimi­nation of presynaptic la terminal inhibition or from interneuronal activation in Н-reflex poly­synaptic components to a greater extent as compared with motoneuron sub-threshold activa­tion but that these changes have specific character. A l l that enables us to say that there is reason for continuing our research in this trend. R E F E R E N C E S 1. Г е p и л о в с к и, Л . , А. Г и д и к о в, А. К о с е в , Н. Р а д и ч е в а . Физиол. человека, 8, 1982 , № 5, 8 6 1 - 8 6 7 . - 2. Г у р ф и н к е л ь, В. С , Я. М. К о ц, М. Л. Ш и к. Регулация позы человека. Москва, Наука, 1965. - 3 . К о ц, Я. М. Организация произвольного движения. Москва, Наука, 1975 . - 4. К р ы л о в, И. Н., Н. А. Р о к о т о в а. Проблемы физиологии движений. Ленинград, Наука, 1980, 5 7 - 6 8 . - 5. П а л ь ц е в, Е. И., А. М. Э л ь н е р. Физиол. человека, 9, 1983, № 3, 4 9 2 - 4 9 3 . -6. П е р с о н, Р. С. Физиол. человека, 8, 1982, № 6, 1 0 1 8 - 1033. - 7. E i c h e n b e r g e r , A . , D. G . R u e g g . J . Physiol, 347 , 1984, 5 4 5 - 5 5 9 . - 8. Р i е г г о t - D е s e i ll i g п у, Е., P. L а с е г t, Н. Р. С а-t h a la Physiol Behav., 7, 1 9 7 1 , 4 9 5 - 5 0 8 . - 9 . T z е k о v, T z. Scr. Set Med., 19, 1982 , 4 1 - 4 3 . -10. T z e k о v, T z . Scr. Set Med,, 20 , 1983 , 4 5 - 4 7 . ЗАВИСИМОСТЬ МЕЖДУ РЕАКЦИОННЫМ ВРЕМЕНЕМ И АМПЛИТУДНЫМИ ИЗМ НЕНИЯМИ Н-РЕФЛЕКСА, ВЫЗВАННОГО ПОСЛЕ ПРЕДЪЯВЛЕНИЯ ИМПЕРАТИВНОГО С И Г Н А Л А МЫШ­ЦЕЙ ПРОТИВОПОШОЖНОЙ НОГИ Ц. Цеков Р Е З Ю М Е Исследования проводились на трех м о л о д ы х лицах в возрасте от 2 0 до 25- лет. Они сидели удобно на а у л е и отвечали с максимальной скоростью на световой сигнал, поднимая пятку правой ноги с пола. Н-рефлекс вызван боковой г о л о в к о й икроножной мышцы левой ноги, являющейся противо­положной движению. Зависимости между реакционным временем и амплитудными изменениями ЕЬ-рефлекса не было установлено. В работе обсуждаются аргументы за и против специфичного харак­тера зависимости между реакционным временем и амплитудными изменениями Н-рефлекса. 

DEPENDENCE BETWEEN REACTION TIME AND AMPLITUDE CHANGES OF НREFLEX EVOKED WITH IMPERATIVE SIGNAL PRESENTATION BY CONTRALATERAL LOWER LIMB MUSCLE

https://journals.mu-varna.bg/index.php/ssm/article/download/2981/2438

DEPENDENCE BETWEEN REACTION TIME AND AMPLITUDE CHANGES OF НREFLEX EVOKED WITH IMPERATIVE SIGNAL PRESENTATION BY CONTRALATERAL LOWER LIMB MUSCLE

Abstract

Similar works

Full text

Available Versions

Varna Medical University Press: Journals