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Abstract:
Artificial grammar learning (AGL) is a form of nondeclarative
memory that involves the nonconscious acquisition of grammatical
rules. While AGL does not depend on the medial temporal lobe, the
neural basis of this type of memory is unknown, and was therefore
examined using event-related fMRI. Prior to scanning, participants
studied 25 letter strings constructed according to an artificial
grammar by observing the string for 3s and then reproducing it from
memory. Participants then made grammaticality judgments about 50
novel grammatical (G) and 50 nongrammatical (NG) strings while fMRI
data were collected (1.5T Siemens Vision, 24x6mm axial slices,
TR=2.0s). The participants successfully acquired knowledge of the
grammar as evidenced by correct identification of the G letter
strings (60.2% correct; S.E. 1.7). During grammaticality judgments
(both G and NG trials versus rest), widespread increases in
activity were observed throughout the dorsal and ventral visual
cortical areas, anterior cingulate, bilateral inferior frontal
cortex, and right dorsolateral prefrontal cortex (DLPFC). Analyses
contrasting the two trial types (G versus NG strings) identified
increased activity in the superior frontal gyrus (BA 8), right
angular gyrus (BA 39), right DLPFC, and bilateral fusiform gyri.
Increases in activity during grammatical (G) letter strings suggest
the recruitment of working memory, attention, and word-form
networks in support of AGL performance.
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