title: Human cortical EEG rhythms during long-term episodic memory task. A high-resolution EEG study of the HERA model.
abstract: Many recent neuroimaging studies of episodic memory have indicated an asymmetry in prefrontal involvement, with the left prefrontal cortex more involved than the right in encoding, the right more than the left in retrieval (hemispheric encoding and retrieval asymmetry, or HERA model). In this electroencephalographic (EEG) high-resolution study, we studied brain rhythmicity during a visual episodic memory (recognition) task. The theta (4-6 Hz), alpha (6-12 Hz) and gamma (28-48 Hz) oscillations were investigated during a visuospatial long-term episodic memory task including an encoding (ENC) and retrieval (RET) phases. During the ENC phase, 25 figures representing interiors of buildings ("indoor") were randomly intermingled with 25 figures representing landscapes ("landscapes"). Subject's response was given at left ("indoor") or right ("landscapes") mouse button. During the RET phase (1 h later), 25 figures representing previously presented "indoor" pictures ("tests") were randomly intermingled with 25 figures representing novel "indoor" ("distractors"). Again, a mouse response was required. Theta and alpha EEG results showed no change of frontal rhythmicity. In contrast, the HERA prediction of asymmetry was fitted only by EEG gamma responses, but only in the posterior parietal areas. The ENC phase was associated with gamma EEG oscillations over left parietal cortex. Afterward, the RET phase was associated with gamma EEG oscillations predominantly over right parietal cortex. The predicted HERA asymmetry was thus observed in an unexpected location. This discrepancy may be due to the differential sensitivity of neuroimaging methods to selected components of cognitive processing. The strict relation between gamma response and perception suggests that retrieval processes of long-term memory deeply impinged upon sensory representation of the stored material.
authors.affiliation: Dipartimento di Fisiologia Umana e Farmacologia Sezione di EEG ad Alta Risoluzione Università degli Studi di Roma "La Sapienza" P.le Aldo Moro 5 00185 Rome, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Babiloni
authors.forename: Fabio
authors.initials: F
authors.lastname: Babiloni
authors.forename: Filippo
authors.initials: F
authors.lastname: Carducci
authors.forename: Stefano
authors.initials: S
authors.lastname: Cappa
authors.forename: Febo
authors.initials: F
authors.lastname: Cincotti
authors.forename: Claudio
authors.initials: C
authors.lastname: Del Percio
authors.forename: Carlo
authors.initials: C
authors.lastname: Miniussi
authors.forename: Davide Vito
authors.initials: DV
authors.lastname: Moretti
authors.forename: Patrizio
authors.initials: P
authors.lastname: Pasqualetti
authors.forename: Simone
authors.initials: S
authors.lastname: Rossi
authors.forename: Katiuscia
authors.initials: K
authors.lastname: Sosta
authors.forename: Paolo Maria
authors.initials: PM
authors.lastname: Rossini
mesh_terms: D000328:Adult; D000513:Alpha Rhythm; D001288:Attention / Q000502:physiology; D001931:Brain Mapping; D003344:Cortical Synchronization; D004193:Discrimination Learning / Q000502:physiology*; D004292:Dominance, Cerebral / Q000502:physiology*; D004569:Electroencephalography; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D017774:Long-Term Potentiation / Q000502:physiology; D008297:Male; D011939:Mental Recall / Q000502:physiology; D008959:Models, Neurological; D009949:Orientation / Q000502:physiology*; D010296:Parietal Lobe / Q000502:physiology; D010364:Pattern Recognition, Visual / Q000502:physiology*; D017397:Prefrontal Cortex / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology; D012153:Retention, Psychology / Q000502:physiology*; D012815:Signal Processing, Computer-Assisted; D013826:Theta Rhythm