Human cortical EEG rhythms during long-term episodic memory task. A high-resolution EEG study of the HERA model.
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.
Babiloni
Claudio
C
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.
Babiloni
Fabio
F
Carducci
Filippo
F
Cappa
Stefano
S
Cincotti
Febo
F
Del Percio
Claudio
C
Miniussi
Carlo
C
Moretti
Davide Vito
DV
Pasqualetti
Patrizio
P
Rossi
Simone
S
Sosta
Katiuscia
K
Rossini
Paolo Maria
PM
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