Neural activity differs between explicit and implicit learning of artificial grammar strings: An fMRI study

Functional magnetic resonance imaging was used to investigate the neural ar eas underlying retrieval of implicit and explicit knowledge about letter st rings. Participants studied strings formed according to an artificial gramm ar, then performed implicit-learning-based judgments (judging the grammatic al status of the string) or explicit-learning-based judgments (recognition) on novel grammatical strings. In comparison with a baseline task, recognit ion and grammatical judgments led to different patterns of neural activatio n: Recognition activated the right frontal cortex, whereas grammatical judg ment activated the left frontal cortex. Recognition led to higher activity in the precuneus and medial occipital cortex, whereas grammatical judgments led to suppression of activity in the precuneus and activation in the late ral occipital cortex. When the surface structure of the strings was changed , grammatical judgments led to bilateral frontal activity and bilateral but left-lateralized activity in the occipital and parietal lobes. These resul ts provide further evidence for a dissociation between the neural bases of implicit and explicit learning.