Neural Substrates of Forward and Backward Associative Priming: A Functional MRI Study

Forward associative priming results of an association moves from the prime to the target whereas backward associative priming results of an association from the target to the prime (Koivisto, 1998). Little is known about this dissociation of process and the associated cerebral substrates. Fourteen healthy participants were included in this study. The task consisted in a lexical decision task using an fMRI-adapted semantic priming paradigm. Contrasts between forward related and forward unrelated conditions showed activation in the left temporal gyrus, left inferior prefrontal cortex, fusiform gyrus and occipital regions and cerebellum. Investigation of the different patterns of activation between forward and backward priming shows significant results: during the contrast between the forward priming effect and the backward priming effect, we observe a deactivation of BOLD response in temporal and frontal areas, which may reflect the post-lexical integration process. So, areas responsible for language and for decoding spelling seem not to be involved in the backward process. An adaptation of this research in event-related brain potentials is underway to better explore the temporality of post-lexical process.