Cortical potentials associated with vocalization in the rhesus monkey.

Cortical potentials associated with vocalization have been investigated in two rhesus monkeys. In both animals a slow negative potential shift beginning approximately 1 sec prior to the onset of vocalization has been observed in transcortical recordings from precentral areas. It is suggested that this slow potential change might be the phylogenetic antecedent of the voluntary control of speech in humans.