Effective auditory-verbal encoding activates the left prefrontal and the medial temporal lobes: A generalization to illiterate subjects

Recent event-related FMRI studies indicate that the prefrontal (PFC) and th e medial temporal lobe ((MTL) regions are more active during effective enco ding than during ineffective encoding. The within-subject design and the us e of well-educated young college students in these studies makes it importa nt to replicate these results in other study populations. In this PET study , we used an auditory word-pair association cued-recall paradigm and invest igated a group of healthy upper middle-aged/older illiterate women. We obse rved a positive correlation between cued-recall success and the regional ce rebral blood flow of the left inferior PFC (BA 47) and the MTLs. Specifical ly, we used the cued-recall success as a covariate in a general linear mode l and the results confirmed that the left inferior PFC and the MTL are more active during effective encoding than during ineffective encoding. These e ffects were observed during encoding of both semantically and phonologicall y related word pairs, indicating that these effects are robust in the studi ed population, that is, reproducible within group. These results generalize the results of Brewer et al. (1998, Science 281, 1185-1187) and Wagner ct al. (1998, Science 281, 1188-1191) to an upper middle aged/older illiterate population. In addition, the present study indicates that effective relati onal encoding correlates positively with the activity of the anterior media l temporal lobe regions. (C) 1999 Academic Press.