The density of ubiquitin-positive protein aggregates in the striatum and anterior cingulate cortex (ACC) of HD mice. Stereological analysis of ubiquitin immunoreactive protein aggregates was performed for the striatum (A) and ACC (B) of environmentally enriched (EE) HD mice at 9 months of age. The same analysis was performed for the striatum (C) and ACC (D) of wheel running (RW) HD mice. Neither environmental enrichment nor wheel running affect the density of aggregates in the striatum (A and C) or the anterior cingulate cortex (B and D) of HD mice at 9 months of age. As expected, these aggregates were never observed in wild-type mice.