and unaffected members of an affected family, including offspring at risk, providing a more direct connection with underlying biological vulnerability. Most importantly, these brain oscillations are highly heritable; thus, 76 percent of the variation in δ waves, 89 percent of the variation in θ and α waves, and 86 percent of the variation in β waves are genetically determined (van Beijsterveldt et al. 1996). This makes these brain oscillations highly useful for large genetic studies. For example, the Collaborative Study on the Genetics of Alcoholism (COGA) from its inception has utilized heritable and reliable neurophysiological traits that differentiate between alcoholics from densely affected alcoholic families and nonalcoholics from control families, as well as between high-risk unaffected offspring from the alcoholic families and low-risk offspring from control families, as endophenotypes to search for genes that are associated with the risk for alcohol dependence and related psychiatric disorders (Porjesz and Rangaswamy 2007).
