In a recent study, Sebastian Guderian and colleagues examined the relation between theta oscillations and memory performance. During the study phase of this memory experiment, participants were presented with words and either performed a semantic or phonemic encoding task (there were two levels of processing used in this experiment). During the study phase, the researchers obtained whole-head MEG recordings. Later on during the test phase, the participants were given a free-recall test on the words that were presented to them during the study phase.
Interestingly, Guderian and colleagues found that amplitudes of theta oscillations that shortly preceded the presentation of the words were higher for those words that were later recalled during the free-recall test, compared to those words that were later forgotten.
Although past studies have shown that specific patterns of brain activity are associated with the encoding of items, this study by Guderian and colleagues is one of a handful of more recent studies that demonstrate pre-stimulus brain activity that is associated with later memory performance (another example is a study by Otten and colleagues).
Moreover, although semantic study tasks typically lead to better memory performance compared to phonemic tasks, the results of the study by Guederian and colleagues suggest that this study task benefit is not only statistically independent from the theta-related recall benefit, but that these benefits are additive.
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