The pattern of M1 reorganization was studied in two groups of 7 albino rats whose facial nerve of one side, was severed two days (Birth-group) and three months (Adult-group) after bird. After weeks, under ketamine anaesthesia (50mg\Kg i.p.), movements evoked by intracortical microstimulation (ICMS) in the M1 were mapped in both (control and disconnected) hemispheres of each animal. Electrode penetrations 500μm spaced were performed. The ICMS (30 ms trains of 0.25 ms cathodal pulses at 350 Hz, stimulation current ≤60 μA) was delivered at a depth of 1.5mm from the pial surface using glass-insulated tungsten microelettrodes (impedance:0.6-1.2MΩ). To assess M1 reorganization we compared the percentages of different movements sites, expressed as a fraction of the number of movement sites 3 mm to the midline in control and disconnected hemispheres. No difference in the percentage of movement sites was obtained between the control hemispheres of the two groups of rats (t-test, P>0.05). In the disconnected hemispheres, in the region corresponding to the vibrissa representation, ipsilateral vibrissa, neck, forelimb and eye movement were evoked at threshold stimulation current. The percentage of sites yielding eye movement in Birth-group was significantly greater than the percentage obtained from Adult-group (Birth-group vs. Adult-group:11.2±6.5%vs4.6±4.4,P<0.05,t-test). In the contrast the percentage yielding neck movement was significantly greater in the Adult-group (Birth-group vs. Adult-group:3.9±3.8%vs.9.7±4.8,P<0.04,t-test). There was no significantly difference in the percentage of forelimb (Birth-group vs. Adult-group:43.1±4.9%vs.46±8.6,P>0.4,t-test) and ipsilateral vibrissa sites (Birth-group vs. Adult-group:8.3±6.7%vs.8.1±5.8,P>0.9,t-test) between the two groups of disconnected hemispheres. Abundant plasticity of cortical circuits in the neonate could account for the difference in the cortical reorganization between Birth- and Adult-group of rats.
Different pattern of motor cortical representations following facial nerve severing in adult and newborns rats
VERONESI, Carlo;FRANCHI, Gianfranco
2003
Abstract
The pattern of M1 reorganization was studied in two groups of 7 albino rats whose facial nerve of one side, was severed two days (Birth-group) and three months (Adult-group) after bird. After weeks, under ketamine anaesthesia (50mg\Kg i.p.), movements evoked by intracortical microstimulation (ICMS) in the M1 were mapped in both (control and disconnected) hemispheres of each animal. Electrode penetrations 500μm spaced were performed. The ICMS (30 ms trains of 0.25 ms cathodal pulses at 350 Hz, stimulation current ≤60 μA) was delivered at a depth of 1.5mm from the pial surface using glass-insulated tungsten microelettrodes (impedance:0.6-1.2MΩ). To assess M1 reorganization we compared the percentages of different movements sites, expressed as a fraction of the number of movement sites 3 mm to the midline in control and disconnected hemispheres. No difference in the percentage of movement sites was obtained between the control hemispheres of the two groups of rats (t-test, P>0.05). In the disconnected hemispheres, in the region corresponding to the vibrissa representation, ipsilateral vibrissa, neck, forelimb and eye movement were evoked at threshold stimulation current. The percentage of sites yielding eye movement in Birth-group was significantly greater than the percentage obtained from Adult-group (Birth-group vs. Adult-group:11.2±6.5%vs4.6±4.4,P<0.05,t-test). In the contrast the percentage yielding neck movement was significantly greater in the Adult-group (Birth-group vs. Adult-group:3.9±3.8%vs.9.7±4.8,P<0.04,t-test). There was no significantly difference in the percentage of forelimb (Birth-group vs. Adult-group:43.1±4.9%vs.46±8.6,P>0.4,t-test) and ipsilateral vibrissa sites (Birth-group vs. Adult-group:8.3±6.7%vs.8.1±5.8,P>0.9,t-test) between the two groups of disconnected hemispheres. Abundant plasticity of cortical circuits in the neonate could account for the difference in the cortical reorganization between Birth- and Adult-group of rats.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
