Other linkage and association studies used quantitative phenotypes, mostly spectral band powers. A genome-wide association study (GWAS) performed in a sample of 322 Plains American Indians reported a significant association between theta-band EEG power and a SNP in the SGIP1 gene (SH3-domain GRB2-like endophilin-interacting protein 1). A similar trend was observed in North American Caucasian replication sample, but the association was non-significant after multiple comparisons correction (Hodgkinson et al., 2010).
