Brain activity patterns during phonological verbal fluency performance with varying levels of difficulty: a functional magnetic resonance imaging study in Portuguese-speaking healthy individuals - Senhorini, Maurien C. T.; Cerqueira, Carlos T.; Schaufelberger, Maristela S.; Almeida, Jorge Cury; Amaro, Edson; Sato, João R.; Barreiros, Maria A. M.; Ayres, Adriana M.; Castro, Cláudio Campi de; Scazufca, Márcia; Menezes, Paulo R.; Busatto Filho, Geraldo (Journal of clinical and experimental neuropsychology, 2011)