Differential processing of immediately repeated verbal and non-verbal stimuli: an evoked-potential study.
Stimuli are better retained in memory if they are repeated after a delay than if they are immediately repeated. This effect is called the spacing effect (SE). Recent electroencephalographic (EEG) studies showed that delayed repetition of meaningful designs in a continuous recognition task induces an evoked response very similar to new presentations. In contrast, immediately repeated designs induced circumscribed, stronger activation of the left medio-temporal lobe (MTL) at 200-300 ms. In amnesic subjects, this signal was missing, indicating that it has a memory-protective effect. Here, high-density EEG was used in humans to explore whether meaningless verbal (non-words) and non-verbal (geometric designs) stimuli also have a SE associated with such lateralized, temporally limited activation of the left MTL upon immediate repetition. The results revealed a SE for both materials. Timing and localization of brain activity differed as a function of stimulus material. Specific responses to immediate repetitions occurred at 200-285 ms for non-verbal stimuli and at 285-380 ms for verbal material. Source estimations revealed increased activity in right inferior frontal areas for immediate non-verbal repetitions and in left fronto-parietal areas for immediate verbal repetition in comparison to new presentations. These findings show that, while the SE is a ubiquitous phenomenon, the neural processes underlying it vary according to stimulus material.
Laboratory of Cognitive Neurorehabilitation, Division of Neurorehabilitation, Department of Clinical Neurosciences, University of Geneva and University Hospital of Geneva, Av. de Beau-Séjour 26, 1206, Genèva, Switzerland.
Aurélie L
AL
Manuel
Laboratory of Cognitive Neurorehabilitation, Division of Neurorehabilitation, Department of Clinical Neurosciences, University of Geneva and University Hospital of Geneva, Av. de Beau-Séjour 26, 1206, Genèva, Switzerland.
Armin
A
Schnider
D000293:Adolescent; D000328:Adult; D001307:Auditory Perception / Q000502:physiology*; D002540:Cerebral Cortex / Q000502:physiology*; D004569:Electroencephalography; D005072:Evoked Potentials, Auditory; D005074:Evoked Potentials, Visual; D005260:Female; D006801:Humans; D008297:Male; D021641:Recognition, Psychology / Q000502:physiology*; D013702:Temporal Lobe / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
consolidation; electroencephalographic; episodic memory; source localization; spatio-temporal analysis