title: Regional and inter-regional theta oscillation during episodic novelty processing.
abstract: Recent event-related potential (ERP) and functional magnetic resonance imaging (fMRI) studies suggest that novelty processing may be involved in processes that recognize the meaning of a novel sound, during which widespread cortical regions including the right prefrontal cortex are engaged. However, it remains unclear how those cortical regions are functionally integrated during novelty processing. Because theta oscillation has been assumed to have a crucial role in memory operations, we examined local and inter-regional neural synchrony of theta band activity during novelty processing. Fifteen right-handed healthy university students participated in this study. Subjects performed an auditory novelty oddball task that consisted of the random sequence of three types of stimuli such as a target (1000Hz pure tone), novel (familiar environmental sounds such as dog bark, buzz, car crashing sound and so on), and standard sounds (950Hz pure tone). Event-related spectra perturbation (ERSP) and the phase-locking value (PLV) were measured from human scalp EEG during task. Non-parametric statistical tests were applied to test for significant differences between stimulus novelty and stimulus targets in ERSP and PLV. The novelty P3 showed significant higher amplitude and shorter latency compared with target P3 in frontocentral regions. Overall, theta activity was significantly higher in the novel stimuli compared with the target stimuli. Specifically, the difference in theta power between novel and target stimuli was most significant in the right frontal region. This right frontal theta activity was accompanied by phase synchronization with the left temporal region. Our results imply that theta phase synchronization between right frontal and left temporal regions underlie the retrieval of memory traces for unexpected but familiar sounds from long term memory in addition to working memory retrieval or novelty encoding.
authors.affiliation: Department of Neurology, Korea University College of Medicine, 73 Inchon-Ro, Anam-Dong, Seongbuk-Gu, Seoul 136-705, Republic of Korea.
authors.forename: Gwan-Taek
authors.initials: GT
authors.lastname: Lee
authors.affiliation: Department of Neurology, Korea University College of Medicine, 73 Inchon-Ro, Anam-Dong, Seongbuk-Gu, Seoul 136-705, Republic of Korea.
authors.forename: Chany
authors.initials: C
authors.lastname: Lee
authors.affiliation: Department of Biomedical Engineering, College of Health Science, Yonsei University, 234 Maeji-ri, Heungup-myun, Wonju, Gangwon-do, Republic of Korea.
authors.forename: Kyung Hwan
authors.initials: KH
authors.lastname: Kim
authors.affiliation: Department of Neurology, Seoul National University College of Medicine, 101 Daehak-Ro, Jongno-Gu, Seoul 110-744, Republic of Korea. Electronic address: jungky10@gmail.com.
authors.forename: Ki-Young
authors.initials: KY
authors.lastname: Jung
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D001307:Auditory Perception / Q000502:physiology*; D001921:Brain / Q000502:physiology*; D003344:Cortical Synchronization / Q000502:physiology; D004569:Electroencephalography; D018913:Event-Related Potentials, P300; D005260:Female; D006801:Humans; D008297:Male; D061212:Memory, Episodic; D021641:Recognition, Psychology / Q000502:physiology*; D013826:Theta Rhythm; D055815:Young Adult
keywords: Event-related potentials; Novelty; Recognition; Theta rhythm