Abstract: People can efficiently recognize an object even under some extremely poor viewing conditions. Such efficient visual processing depends on both bottom-up input and top-down regulations. The present study used a novel illusory detection paradigm to investigate the neural network involved in top-down letter processing. This paradigm required participants to detect letters in pure noise images that actually contained no letters. By using of psychophysiological interaction (PPI) analysis, it revealed that some regions’ responses were influenced by the enhanced connectivity from the right fusiform. These findings suggested that the top-down letter processing network not only contains the regions that process the visual appearance of letters and their phonological information, but also involves neural regions involved in such high-level cognitive processes as memory retrieval and attention.

Key words: letter processing, top-down, fMRI, psychophysiological interaction