Recent evidence suggests that temporal expectation is beneficialto memory formation. Rhythmic presentation of stimuliduring encoding enhances subsequent recognition and is associatedwith distinct neural activity compared with when stimuliare presented in an arrhythmic manner. However, no prior studyhas examined how temporal expectation interacts with anotherimportant form of facilitation—spatial attention—to affectmemory. This study systematically manipulated temporal expectationand spatial attention during encoding to examine theircombined effect on behavioral recognition and associated ERPs.Participants performed eight experimental blocks consisting of anencoding phase and recognition test, with EEG recordedthroughout. During encoding, pairs of objects and checkerboardswere presented and participants were cued to attend to the left orright stream and detect targets as quickly as possible. In fourblocks, stimulus presentation followed a rhythmic (constant, predictable)temporal structure, and in the other four blocks, stimulusonset was arrhythmic (random, unpredictable). An interactionbetween temporal expectation and spatial attention emerged,with greater recognition in the rhythmic than the arrhythmic conditionfor spatially attended items. Analysis of memory-specificERP components uncovered effects of spatial attention. Therewere late positive component and FN400 old/new effects in theattended condition for both rhythmic and arrhythmic items,whereas in the unattended condition, there was an FN400old/new effect and no late positive component effect. The studyprovides new evidence that memory improvement as a functionof temporal expectation is dependent upon spatial attention.
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