Hyperactivity following posterior cortical injury in lateralized, sensitive to lesion size and independent of the nigrostriatal dopamine system

In a previous study, we reported that a specific size cortical suction lesion of the right posterior cortex in rats produced hyperactivity and increased concentrations of dopamine in the nigrostriatal pathway. The present study extended those findings by addressing whether this phenomenon is lateralized to the right posterior cortex and whether the increases in nigrostriatal dopamine are necessary for the behavioral changes produced by the lesion. Right posterior cortical lesions of 1.8 mm diameter produced spontaneous hyperactivity over a 30-day postoperative period while identically placed 1.3 mm or 2.4 mm diameter lesions did not. Left hemisphere lesiond of 1.3 mm, 1.8 mm or 2.4 mm diameter also failed to produced hyperactivity. The hyperactivity response to 1.8 mm diameter lesions of the right posterior cortex was not blocked by 70% depletions in nigrostriatal dopamine produced by bilateral nigral injections of 6-hydroxydopamine two weeks prior to cortical lesions. These findings suggest that hyperactivity following right posterior cortical lesions is lateralized and is not dependent upon changes in the nigrostriatal dopaminergic pathway.