Experience-driven neural plasticity: Evidence from neuroimaging of repetition priming

People accumulate knowledge about thousands of words and objects over the lifespan, but the neural processes used to represent and access this knowledge is not well understood. The present functional magnetic resonance imaging (fMRI) studies investigate the relationship between neural representations of knowledge for words and objects with which people have varying levels of experience. Each of the four studies examines the neural responses corresponding to disparities in prior experience and experience gained within the experimental context (measured via repetition priming). Study 1 shows that brain activation differences for processing low- vs. high-frequency words (word frequency effect) in a network of regions are diminished with repeated processing of those items. That is, activation patterns for repeated low-frequency words and high-frequency words are virtually indistinguishable. Study 2 compares low- and high-frequency words to pseudowords with which participants presumably had no prior experience. Results indicate that the brain activation pattern for pseudowords and low-frequency words are similar, and they show equivalent repetition effects. To dissociate functional subcomponents of the brain networks determined in Studies 1 and 2, Study 3 repeats the experiment in Study 2 with the exception of presenting words in the auditory modality. Modality-independent word frequency and repetition effects are found in prefrontal regions, but high-level modality-specific regions (e.g., fusiform cortex and superior temporal sulcus) show these effects separately across the visual and auditory studies. Study 4 tests findings from Studies 1--3 in the domain of object knowledge by presenting participants with initial and repeated presentations of common and novel objects.