In five rats, 4 weeks after the facial nerve had been severed on one side, microstimulation (40 ms trains of 0.25 ms cathodal pulses at 300 Hz, stimulation current ≤60 μA) was performed to map the motor output of the superior colliculus (SC). In each rat, the SC contralateral to severed nerve (VIIcut SC) and the SC contralateral to intact nerve (Intact SC) was explored. The SC motor map in five untouched rats was used as reference (Control SC). Under ketamine anaesthesia (50mg\Kg i.p.), glass-insulated tungsten microelectrodes (impedance:0.6-1.2MΩ) were used to explore the intermediate and deep layers of the SC. In the Control and Intact SC, the microstimulation at threshold current level showed contralateral vibrissa movement (Control:84.85±11.86%; Intact:75.44±13.87%) flanked medially by lower trunk movement (Control:16.11±2.46%; Intact:18.24±3.06%); suprathreshold-evoked lower and upper trunk movements overlap the medial and lateral part of the SC, respectively, where the contralateral vibrissa was the threshold-evoked movement. In the Control SC suprathreshold-evoked ipsilateral vibrissa movement was also observed. In the VIIcut SC, lower trunk, upper trunk and ipsilateral vibrissa threshold-evoked movements were observed. There was no statistical difference between Control, Intact and VII cut SC in movement sites percentage of lower trunk (Intact vs. VIIcut:40.49±8.09 vs.35.33±14.54, P>0.05,paired t-test), upper trunk (Intact vs. VIIcut: 47.88±10.02vs.35.91±6.92, P>0.05,paired t-test) and ipsilateral vibrissa (Control vs. VIIcut: 10.35±6.81 vs.14.12±8.62; P>0.05,t-test). We conclude that, after facial nerve severing, there is no reorganization in the SC motor map but the normally represented suprathreshold-evoked movements emerge.
Changes in the superior colliculus motor map following facial nerve severing in adult rats
VERONESI, Carlo;FRANCHI, Gianfranco
2004
Abstract
In five rats, 4 weeks after the facial nerve had been severed on one side, microstimulation (40 ms trains of 0.25 ms cathodal pulses at 300 Hz, stimulation current ≤60 μA) was performed to map the motor output of the superior colliculus (SC). In each rat, the SC contralateral to severed nerve (VIIcut SC) and the SC contralateral to intact nerve (Intact SC) was explored. The SC motor map in five untouched rats was used as reference (Control SC). Under ketamine anaesthesia (50mg\Kg i.p.), glass-insulated tungsten microelectrodes (impedance:0.6-1.2MΩ) were used to explore the intermediate and deep layers of the SC. In the Control and Intact SC, the microstimulation at threshold current level showed contralateral vibrissa movement (Control:84.85±11.86%; Intact:75.44±13.87%) flanked medially by lower trunk movement (Control:16.11±2.46%; Intact:18.24±3.06%); suprathreshold-evoked lower and upper trunk movements overlap the medial and lateral part of the SC, respectively, where the contralateral vibrissa was the threshold-evoked movement. In the Control SC suprathreshold-evoked ipsilateral vibrissa movement was also observed. In the VIIcut SC, lower trunk, upper trunk and ipsilateral vibrissa threshold-evoked movements were observed. There was no statistical difference between Control, Intact and VII cut SC in movement sites percentage of lower trunk (Intact vs. VIIcut:40.49±8.09 vs.35.33±14.54, P>0.05,paired t-test), upper trunk (Intact vs. VIIcut: 47.88±10.02vs.35.91±6.92, P>0.05,paired t-test) and ipsilateral vibrissa (Control vs. VIIcut: 10.35±6.81 vs.14.12±8.62; P>0.05,t-test). We conclude that, after facial nerve severing, there is no reorganization in the SC motor map but the normally represented suprathreshold-evoked movements emerge.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
