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Titolo:
Patterns of fusimotor activity during locomotion in the decerebrate cat deduced from recordings from hindlimb muscle spindles
Autore:
Taylor, A; Durbaba, R; Ellaway, PH; Rawlinson, S;
Indirizzi:
Univ London Imperial Coll Sci Technol & Med, Charing Cross Hosp, Sch Med,Dept Sensorimotor Syst, Div Neurosci & Psychol Med, London W6 8RF, England Univ London Imperial Coll Sci Technol & Med London England W6 8RF ngland
Titolo Testata:
JOURNAL OF PHYSIOLOGY-LONDON
fascicolo: 3, volume: 522, anno: 2000,
pagine: 515 - 532
SICI:
0022-3751(20000201)522:3<515:POFADL>2.0.ZU;2-U
Fonte:
ISI
Lingua:
ENG
Soggetto:
ANTERIOR THIGH MUSCLES; PREMAMMILLARY CATS; FICTIVE LOCOMOTION; GAMMA-MOTONEURONS; NORMAL MOVEMENTS; IMPULSE RATES; AFFERENTS; DISCHARGE; SENSITIVITY; RESPIRATION;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
54
Recensione:
Indirizzi per estratti:
Indirizzo: Taylor, A Univ London Imperial Coll Sci Technol & Med, Charing Cross Hosp,Sch Med,Dept Sensorimotor Syst, Div Neurosci & Psychol Med, fulham Palace Rd, LondonW6 8RF, England Univ London Imperial Coll Sci Technol & Med fulham Palace Rd London England W6 8RF
Citazione:
A. Taylor et al., "Patterns of fusimotor activity during locomotion in the decerebrate cat deduced from recordings from hindlimb muscle spindles", J PHYSL LON, 522(3), 2000, pp. 515-532

Abstract

1.Recordings have been made from multiple single muscle spindle afferents from medial gastrocnemius (MG) and tibialis anterior (TA) muscles of one hindlimb in decerebrate cats, together with ankle rotation and EMG signals, during treadmill locomotion. Whilst the other three limbs walked freely, theexperimental limb was denervated except for the nerves to MG and TA and secured so that it could rotate only at the ankle joint, without any externalload. Each afferent was characterised by succinylcholine testing with regard to its intrafusal fibre contacts. Active movements were recorded and then replayed through a servo mechanism Do reproduce the muscle length changespassively after using a barbiturate to suppress gamma-motor firing.2. The difference in secondary afferent firing obtained by subtracting thedischarge during passive movements from that during active movements was taken to represent the profile of static fusimotor activity. This indicated an increase before the onset of movement followed by a strongly modulated discharge in parallel with muscle shortening during locomotion. The pattern of static firing matched the pattern of unloaded muscle shortening wry closely in the case of TA and with some phase advance in the case of MG. The same effects were observed in primary afferents.3. Primary afferents with bag(1) (b(1)) contacts in addition showed higherfiring frequencies during muscle lengthening in active than in passive movements. This indicated increased dynamic fusimotor firing during active locomotion. There was no evidence as to whether this fluctuated during the movement cycles.4. When the mean active minus passive difference profile of firing in bag(2)-chain (b(2)c) type primary afferents was subtracted from that for b(1)b(2)c afferents, the difference was dominated by a peek centred on the momentof maximum lengthening velocity (v).5. The component of the active minus passive difference firing due to b(1)fibre contacts could be modelled by f(t) = av (where a is a constant) during lengthening and by f(t) = 0.2av during shortening. The remainder of the difference signal matched the predictions of the static fusimotor signal derived from secondary afferents.6. The findings are discussed in relation to the concept that the modulated static fusimotor pattern may represent a 'temporal template' of the expected movement, though the relationship of the results to locomotion in the intact animal will require further investigation. The analysis of the data indicates that the combined action of muscle length changes and static and dynamic fusimotor activity to determine primary afferent firing can be understood in terms of the interaction between the b(1) and b(2)c impulse initiation sites.

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Documento generato il 23/09/20 alle ore 11:18:45