Abstract

Introduction

Materials & Methods

Results

Discussion & Conclusion

References

Discussion
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Experiment 1 Summary

1. Animals with transection of the corpus callosum along with forced use of the opposite limb had a significantly higher number of layer V pyramidal neuron basilar dendrites in comparison to animals that experienced transections alone or forced-use alone.
2. Increases in arborization were significant in higher order branches, consistent with previous findings of of dendritic growth patterns (e.g. Uylings et al., 1978).
3. These data suggest that mild degeneration may enhance neuronal growth in the presence of appropriate behavioral demand.

1. Sham-operated male rats given motor skills training showed an increase in average Purkinje cell volume and a decrease in Purkinje cell density, compared to animals given simple exercise, consistent with findings from previous studies using female rats (e.g., Black et al., 1990; Kleim et al., 1998; Klintsova et al., 1998).
2. Skills training given after a unilateral lesion to the motor cortex affected the two cerebellar hemispheres differently. Increased average cell volume and decreased cell density were found ipsilateral to the lesion (on the side corresponding to the non-impaired forelimb), but not contralateral to the lesion. These results contrast with a bilateral tendency toward increased cell volume and decreased density among animals given simple exercise after a lesion.
3. Preliminary findings indicate a tendency toward an increase in synapses per neuron among intact animals given motor skills training. This tendency was not found in either hemisphere when the training was given following a unilateral motor cortex lesion.

Both of these experiments demonstrate that changes in neuronal structure following cortical injury are affected by changes in behavioral experience. In the motor cortex, injury-induced degeneration may facilitate neuronal restructuring and growth in the presence of behavioral demand. These results suggest an important role for degeneration in post-injury plasticity. As in the motor cortex, changes in behavioral demand affect neuronal restructuring in the cerebellum. However, unlike growth in the homotopic sensorimotor cortex following unilateral FLsmc lesions, some forms of cerebellar plasticity following motor skills training seem to be muted or reduced when the training follows a lesion, especially in the hemisphere corresponding to the impaired limb.

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