An organizing principle of thalamic plasticity

grantor: University of TorontoThree dimensional reconstructions of thalamic (ventroposterolateral nucleus; VPL) sensory maps were used to detect somatotopic reorganization in the thalamus. Hindlimb input was removed (>60%) by nucleus gracilis lesions in adult rats (control (n = 8); acute (n = 6); 1-week post-lesion (n = 8); 1-month post-lesion (n = 8)). The removal of hindlimb input by nucleus gracilis lesions revealed a focal zone of reorganization within the VPL (300 m m thick) at times 1-week and 1-month post-lesion. Shoulder sensory maps in the thalamus were found to increase in total volume by 25% as early as 1-week post-lesion (p 0.05). Importantly, if cortical lesions were performed after thalamic reorganization had occurred, thalamic plasticity was unaffected (n = 6; p < 0.05). 'In conclusion', 'there is a focal zone of somatotopic plasticity in the thalamus that appears to be independent of the form of deafferentation, which requires the presence of an intact cortex for the induction of somatotopic reorganization', but not its maintenance.Ph.D