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1637 Morphology of bulbospinal axons and their discharge properties during fictive locomotion in the cat
S182 SITE SPECIFIC AUGMENTING EFFECTS OF POSTURAL MUSCLE TONE INDUCED BY THE STIMULATION TO THE MIDLINE AREA OF THE CEREBELLUM IN DECEREBRATE CATS. MITSURU ASANOME, KATSUMI NAKAJIMA, KIYOJI MATSUYAMA AND SHIGEMI MORI, National Institute for Physiological Sciences, Okazaki, 444, Japan.
1636
In a reflexively standing acute decerebrate cat, an attempt was made to identify the effective cerebellar region for augmenting postural muscle tone of both the fore- and hindlimbs. To do this, a stimulating microelectrode, a glass insulated tungsten electrode, was inserted into the midline area of the cerebellum. The stimuli consisted of 5 to 50pA pulses of 0.2 ms duration with 50 pulses/s that lasted S-10 s. Changes in the levels of postural muscle tone were studied by recording the force exerted by each of the fore- and hindlimbs with a force transducer placed underneath the font. and by recording EMGs of representative fore- (triceps brachii) and hindlimb (quadriceps femoris and gastrocnemius-soleus) muscles with bipolar electrodes made of thin (lOOp.m) copper wires. The stimulating electrode was moved rostrocaudally, mediolaterally and dorsoventrally at 1OOpm steps. Stimulation of the cerebellar white matter along its midline resulted in an increase in the levels of postural muscle tone in all four limbs. Stimulation of the surrounding region resulted in either forelimb or hindlimb dominant and/or stimulus side dominant augmentation of postural muscle tone.
1637
MORPHOLOGY OF BULBOSPINAL AXONS AND THEIR DISCHARGE PROPERTIES DURING FICTIVE LOCOMOTION IN THE CAT. KIYOJI MATSUYAMA. KATSUMI NAKAJIMA. TOSHI.HIRO MATSUI. BUNYA KUZE AND SHIGEMI MORI. National Institute for Phvsiological Sciences. Okazaki. 444. Japan. This study was undertaken to investigate the relation between the morphology of bulbospinal axons and their discharge properties during fictive locomotion in the cat. In decerebrate cats paralyzed with pancuronium bromide, intra-axonal recordings were made from bulbospinal axons in the lumbar spinal cord via a glass micropipette filled with lk KC1 solution including 2% neurobiotin. Hindlimb nerve activities were also recorded. After recording the axonal discharge during fictive locomotion, which was evoked by a microstimulation to the mesencephalic locomotor region, neurobiotin was injected iontophoretically into bulbospinal axons. After more than 5 hours, animals were perfused transcardially, and serial transverse sections of the lumbar spinal cord were made. Bulbospinal axons were either silent or engaged in tonic or phasic discharge during fictive locomotion. Trajectories could be traced for up to about 40 mm in the ventral funiculus. Most axons gave off axon collaterals over the traceable distances. One axon, which discharged in phase with ipsilateral hindlimb flexor nerve activity, had axon collaterals densely distributed in the lumbar enlargement but not in other regions.
1638 MOVEMENT INTERRUPTION PROCESS DURING REPETITIVE FINGER TAPPING. A BEHAVIORAL EMPHASIS. EIICHI NAITO, MICHIKAZU MATSUMURA, Faculty of Human Studies, Kyoto Univ., Kyoto, 606-01, Japan Behavior: This study examined the movement interruption process that operates for suppression of repetitive finger tapping. Eight subjects were instructed to stop tapping as soon as possible when a stop signal was synchronously presented at various times during a sequence of keystrokes. The estimated time needed for movement interruption was similar (about 180-270 ms) in a single-finger task and a double-finger task. However, the time required when the movement was interrupted in the initial stage of tapping tended to be longer than that in the later stages in both tasks. EMG recording showed that motor activities were sustained longer in the initial stage than in the later stage. It was concluded that the estimated interruption time was exceptionally prolonged when a stop signal was presented at the movement initiation, but the time course of the onset of the interruption varied little regardless of the type of the ongoing motor program.
1636
In a reflexively standing acute decerebrate cat, an attempt was made to identify the effective cerebellar region for augmenting postural muscle tone of both the fore- and hindlimbs. To do this, a stimulating microelectrode, a glass insulated tungsten electrode, was inserted into the midline area of the cerebellum. The stimuli consisted of 5 to 50pA pulses of 0.2 ms duration with 50 pulses/s that lasted S-10 s. Changes in the levels of postural muscle tone were studied by recording the force exerted by each of the fore- and hindlimbs with a force transducer placed underneath the font. and by recording EMGs of representative fore- (triceps brachii) and hindlimb (quadriceps femoris and gastrocnemius-soleus) muscles with bipolar electrodes made of thin (lOOp.m) copper wires. The stimulating electrode was moved rostrocaudally, mediolaterally and dorsoventrally at 1OOpm steps. Stimulation of the cerebellar white matter along its midline resulted in an increase in the levels of postural muscle tone in all four limbs. Stimulation of the surrounding region resulted in either forelimb or hindlimb dominant and/or stimulus side dominant augmentation of postural muscle tone.
1637
MORPHOLOGY OF BULBOSPINAL AXONS AND THEIR DISCHARGE PROPERTIES DURING FICTIVE LOCOMOTION IN THE CAT. KIYOJI MATSUYAMA. KATSUMI NAKAJIMA. TOSHI.HIRO MATSUI. BUNYA KUZE AND SHIGEMI MORI. National Institute for Phvsiological Sciences. Okazaki. 444. Japan. This study was undertaken to investigate the relation between the morphology of bulbospinal axons and their discharge properties during fictive locomotion in the cat. In decerebrate cats paralyzed with pancuronium bromide, intra-axonal recordings were made from bulbospinal axons in the lumbar spinal cord via a glass micropipette filled with lk KC1 solution including 2% neurobiotin. Hindlimb nerve activities were also recorded. After recording the axonal discharge during fictive locomotion, which was evoked by a microstimulation to the mesencephalic locomotor region, neurobiotin was injected iontophoretically into bulbospinal axons. After more than 5 hours, animals were perfused transcardially, and serial transverse sections of the lumbar spinal cord were made. Bulbospinal axons were either silent or engaged in tonic or phasic discharge during fictive locomotion. Trajectories could be traced for up to about 40 mm in the ventral funiculus. Most axons gave off axon collaterals over the traceable distances. One axon, which discharged in phase with ipsilateral hindlimb flexor nerve activity, had axon collaterals densely distributed in the lumbar enlargement but not in other regions.
1638 MOVEMENT INTERRUPTION PROCESS DURING REPETITIVE FINGER TAPPING. A BEHAVIORAL EMPHASIS. EIICHI NAITO, MICHIKAZU MATSUMURA, Faculty of Human Studies, Kyoto Univ., Kyoto, 606-01, Japan Behavior: This study examined the movement interruption process that operates for suppression of repetitive finger tapping. Eight subjects were instructed to stop tapping as soon as possible when a stop signal was synchronously presented at various times during a sequence of keystrokes. The estimated time needed for movement interruption was similar (about 180-270 ms) in a single-finger task and a double-finger task. However, the time required when the movement was interrupted in the initial stage of tapping tended to be longer than that in the later stages in both tasks. EMG recording showed that motor activities were sustained longer in the initial stage than in the later stage. It was concluded that the estimated interruption time was exceptionally prolonged when a stop signal was presented at the movement initiation, but the time course of the onset of the interruption varied little regardless of the type of the ongoing motor program.