title: The brain's response to incidental intruded words during focal text processing.
abstract: The functional neuroanatomy associated with processing single words incidentally, outside focal attention, was investigated. We asked subjects (n = 15) to listen, focus on, and comprehend a story narrative, and then single, unrelated but meaningful words were intruded into the ongoing narrative. We also manipulated the type of intruded word, using either neutral or emotionally valent words, to evaluate the extent of semantic processing and a potential encoding advantage for one type of material. Analyses emphasized the areas of activation unique to the intruded words as distinguished from the narrative text. Subjects were normal, healthy adults (n = 15). Compared to narrative text, the intruded words were associated with activation in the right middle temporal gyrus (BA 39) and posterior cingulate/precuneus regions (BA 30, 23). We conclude that the intruded words did make contact with word-level lexical but not necessarily semantic structures in the middle temporal region. The data suggested that the intruded words were processed by a "nonexecutive" monitoring system implemented by a pairing of activation in posterior, medial structures such as the posterior cingulate with deactivation in brain stem structures. This pattern induced a shift to more passive, less effortful, nonstrategic monitoring of the words. Thus, attention processing, not semantic processing, changes best characterized the brain activation unique to the intruded words. This posterior, medial region is discussed as a substrate dedicated to processing a second, incidental stream of information and thereby providing a crucial mechanism for implementing dual processing of the kind examined here.
authors.affiliation: Thomas Jefferson University/Jefferson Medical College, Philadelphia, Pennsylvania 19107, USA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Tracy
authors.forename: Adam
authors.initials: A
authors.lastname: Flanders
authors.forename: Saaussan
authors.initials: S
authors.lastname: Madi
authors.forename: Peter
authors.initials: P
authors.lastname: Natale
authors.forename: Nicole
authors.initials: N
authors.lastname: Delvecchio
authors.forename: Ayis
authors.initials: A
authors.lastname: Pyrros
authors.forename: Joseph
authors.initials: J
authors.lastname: Laskas
mesh_terms: D000328:Adult; D001288:Attention / Q000502:physiology*; D001306:Auditory Pathways / Q000502:physiology; D001931:Brain Mapping; D001933:Brain Stem / Q000502:physiology; D002540:Cerebral Cortex / Q000502:physiology*; D004644:Emotions / Q000502:physiology; D005260:Female; D006179:Gyrus Cinguli / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D009415:Nerve Net / Q000502:physiology; D012660:Semantics; D013067:Speech Perception / Q000502:physiology*; D013702:Temporal Lobe / Q000502:physiology; D014793:Visual Cortex / Q000502:physiology