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Titolo:
MOTOR CORTEX AND PYRAMIDAL TRACT AXONS RESPONSIBLE FOR ELECTRICALLY-EVOKED FORELIMB FLEXION - REFRACTORY PERIODS AND CONDUCTION VELOCITIES
Autore:
CHAPMAN CA; YEOMANS JS;
Indirizzi:
UNIV TORONTO,DEPT PSYCHOL TORONTO M5S 1A2 ON CANADA UNIV TORONTO,DEPT PSYCHOL TORONTO M5S 1A2 ON CANADA
Titolo Testata:
Neuroscience
fascicolo: 3, volume: 59, anno: 1994,
pagine: 699 - 711
SICI:
0306-4522(1994)59:3<699:MCAPTA>2.0.ZU;2-Q
Fonte:
ISI
Lingua:
ENG
Soggetto:
SELF-STIMULATION NEURONS; ELECTROPHYSIOLOGICAL CHARACTERISTICS; CORTICOSPINAL AXONS; BEHAVIORAL-METHODS; RAT; SUMMATION; MICROSTIMULATION; ORGANIZATION; CONNECTIONS; MOTONEURONS;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
55
Recensione:
Indirizzi per estratti:
Citazione:
C.A. Chapman e J.S. Yeomans, "MOTOR CORTEX AND PYRAMIDAL TRACT AXONS RESPONSIBLE FOR ELECTRICALLY-EVOKED FORELIMB FLEXION - REFRACTORY PERIODS AND CONDUCTION VELOCITIES", Neuroscience, 59(3), 1994, pp. 699-711

Abstract

Double-pulse methods are used here to measure the refractory periods and conduction velocities of the pyramidal tract axons which cause forelimb flexion in pentobarbital anesthetized rats. In the refractory period experiments, conditioning and test pulses were delivered to the motor cortex, the ipsilateral internal capsule, or the ipsilateral pyramid, and the maximum force exerted by the contralateral forelimb was measured at various conditioning-test intervals. The movements increased as conditioning-test interval increased from 0.5 to 1.0 ms in pyramid sites, from 0.6 to 1.5 in internal capsule sites, and from 0.6 to 2.0 ms in surface cortical sites, suggesting longer refractory periods for the substrates at more rostral sites. In cortical sites, as the conditioning-test interval increased from 4.0 to 20.0 ms, the movements decreased gradually to the single-pulse level, suggesting decreasing temporal summation at longer conditioning-test intervals. In the collision experiments, when conditioning pulses were delivered to one site and test pulses to a second site, the movements increased at conditioning-test intervals that were longer by 0.5-1.3 ms than the refractory periods in either site. This suggests that collisions occurred between orthodromic and antidromic action potentials in the pyramidal tract axons responsible for the limb movement. The collision-like increase was greater between internal capsule and pyramid than between cortex and pyramid, or between cortex and internal capsule. The estimated conduction times were 0.9-1.5 ms between cortex and pyramid, 0.4-0.8 ms between cortex and internal capsule, and 0.5-0.8 ms between internal capsuleand pyramid. The range of conduction velocities, therefore, was quitenarrow between all pairs (8.8-16.8 m/s). The largest pyramidal tract axons appear to be responsible for most of the force of forelimb flexion in pentobarbital anesthetized rats.

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Documento generato il 03/07/20 alle ore 22:48:55