This study uses brain activity measures to examine the relationship between television advertising and changes in consumer brand preference. Prior to and after viewing a television programme that included grocery advertisements 198 right-handed females selected six ‘door prizes’ from six grocery categories. One of the advertisements featured a jam that was available as a door prize. Steady-state topography (SST) was used to estimate brain activity at eight scalp sites, including left and right lateral prefrontal sites previously shown to index the strength of long-term memory (LTM) encoding. Our hypothesis, that lateral prefrontal activity would be higher during branding for the 18 participants who shifted to the advertised jam compared to those consistently selecting the competitor jam, was confirmed, but only for the left hemisphere. Our findings suggest that SST activity at lateral prefrontal sites during television advertisement branding may be a useful indicator of advertising effectiveness.