The popular notion of subliminal information is that it streams into an unguarded mind, unchecked and unprocessed. However, neurobiologists' experiments are now revealing that the brain does consciously process subliminal information and that such processing influences how that subliminal information is perceived. In an article in the November 9, 2006, issue of the journal Neuron, published by Cell Press, Kimihiro Nakamura and colleagues report experiments with human volunteers demonstrating such "top-down" processing of subliminal information. Their findings also shed light on the neural mechanism by which reading a printed word evokes the representation of the spoken form. This "lexical-phonological" linkage is critical to learning to read and is disrupted in some forms of reading disorders.In the researchers' experiments, they showed volunteers either words or pronounceable nonwords and asked them to perform either a lexical task or a pronunciation task on the words. The lexical task was to identify whether the word they saw was a real word or a nonsense word.However, unbeknownst to the subjects, they had been first presented with a subliminal word that either matched or didn't match the target word. Such subliminal words were "masked" with nonsense characters that would render the presentation subliminal. The researchers' initial experiments showed that presenting subliminal words identical to the target word produced a "priming" effect in which subjects responded faster on the lexical or pronunciation tasks.The researchers next applied a harmless magnetic pulse--called transcranial magnetic stimulation (TMS)--to two key regions of the brain involved in such perception, before presenting the priming word. The two regions were known to be involved in either converting visually perceived words to phonological representations or to integrating perceived words across visual and auditory modes. TMS is known to transiently affect neural function in a target area.Nakamura and colleagues found that TMS applied to one brain area or the other could selectively disrupt the priming effect for either the lexical or pronunciation task. The researchers concluded that the conscious task instruction for either of the tasks caused a different neural network to be engaged for generating the appropriate behavioral response.