The prevalence of one of these opposite phenomena might account for a significant difference in the direct comparison between group A and B. Accordingly, in a previous study, we found that SOD1-ALS patients, who typically have low clinical UMN burden, showed motor cortex relative hypermetabolism compared to HC, while relative hypometabolism in the same regions was found in sporadic ALS compared to SOD1 carriers [14, 43]. The gene discussed is SOD1; the disease is amyotrophic lateral sclerosis.