This study was undertaken to compare the recovery of the vibrissa movement representation in the motor cortex (M1) and in the superior colliculus (SC) following facial nerve reinnervation. To this purpose in five rats, the facial nerve was exposed, transacted and immediately repaired by end-to-end anastomosis (Reinnervated-group). Other 5 untouched rats were used as Control-group. In each rat, 4 months after facial nerve surgery, under ketamine anaesthesia (50mg\Kg i.p.), microstimulation (ICMS: 40 ms trains of 0.25 ms cathodal pulses at 300 Hz, stimulation current ≤60 μA) was performed to map the M1 and the SC motor output on the side contralateral to severed nerve. Electrode penetrations were performed using glass-insulated tungsten microelettrodes to explore the V layer of the M1 and the intermediate and deep layers of SC. In the M1 of all Reinnervated rats, there was a partial recovery of the vibrissae movement representation localized in the medial part of its normal cortical territory. In comparison to Control-group, the Reinnervated group evidenced a significant decrease in the sites percentage of the vibrissa movement in M1 (mean sites: 47.186.04% vs. 11.694.49%, P=2,84E-07, ANOVA). In contrast, in the SC of all Reinnervated rats, there was a complete recovery of the vibrissa movement representation. There was no statistical differences in vibrissa movement sites percentage in the SC of the Control- vs. Reinnervated-group (mean sites: 78.28±5.41% vs. 77.62±12.92%, p=0.68, ANOVA). We propose that the complete recovery of the vibrissa motor output in SC vs. the incomplete recovery in M1 probably reflects the direct SC connections with facial motoneurons and evidences an imbalance in the motor control upon reinnervated facial motoneurons.
Cortical and subcortical motor output reorganization following facial nerve reinnervation in adult rats
VERONESI, Carlo;FRANCHI, Gianfranco
2005
Abstract
This study was undertaken to compare the recovery of the vibrissa movement representation in the motor cortex (M1) and in the superior colliculus (SC) following facial nerve reinnervation. To this purpose in five rats, the facial nerve was exposed, transacted and immediately repaired by end-to-end anastomosis (Reinnervated-group). Other 5 untouched rats were used as Control-group. In each rat, 4 months after facial nerve surgery, under ketamine anaesthesia (50mg\Kg i.p.), microstimulation (ICMS: 40 ms trains of 0.25 ms cathodal pulses at 300 Hz, stimulation current ≤60 μA) was performed to map the M1 and the SC motor output on the side contralateral to severed nerve. Electrode penetrations were performed using glass-insulated tungsten microelettrodes to explore the V layer of the M1 and the intermediate and deep layers of SC. In the M1 of all Reinnervated rats, there was a partial recovery of the vibrissae movement representation localized in the medial part of its normal cortical territory. In comparison to Control-group, the Reinnervated group evidenced a significant decrease in the sites percentage of the vibrissa movement in M1 (mean sites: 47.186.04% vs. 11.694.49%, P=2,84E-07, ANOVA). In contrast, in the SC of all Reinnervated rats, there was a complete recovery of the vibrissa movement representation. There was no statistical differences in vibrissa movement sites percentage in the SC of the Control- vs. Reinnervated-group (mean sites: 78.28±5.41% vs. 77.62±12.92%, p=0.68, ANOVA). We propose that the complete recovery of the vibrissa motor output in SC vs. the incomplete recovery in M1 probably reflects the direct SC connections with facial motoneurons and evidences an imbalance in the motor control upon reinnervated facial motoneurons.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
