Top-down modulation of hemispheric differences and spatial attention effects for verbal and non-verbal stimuli

Public Significance StatementWe show that the brain's ability to recognize words and faces is driven by a top-down process that involves directing our attention to enhance recognition, such that attention benefits recognition of real words and faces, but not rejection of made-up words and inverted faces. Likewise, the brain's hemispheric advantages (left hemisphere specialized for words, right hemisphere for faces) are larger for recognition of real stimuli vs. rejection of false ones. These findings clarify that hemispheric advantages, whether innate (e.g., left hemisphere language superiority) or "on-the-fly" (directing attention to one side of space) apply mainly to real recognizable stimuli, and therefore involve a top-down processing mechanism.