Abstract
Recently, elevated ongoing pre-stimulus beta power (13–17 Hz) at encoding has been associated with subsequent memory formation for visual stimulus material. It is unclear whether this activity is merely specific to visual processing or whether it reflects a state facilitating general memory formation, independent of stimulus modality. To answer that question, the present study investigated the relationship between neural pre-stimulus oscillations and verbal memory formation in different sensory modalities. For that purpose, a within-subject design was employed to explore differences between successful and failed memory formation in the visual and auditory modality. Furthermore, associative memory was addressed by presenting the stimuli in combination with background images. Results revealed that similar EEG activity in the low beta frequency range (13–17 Hz) is associated with subsequent memory success, independent of stimulus modality. Elevated power prior to stimulus onset differentiated successful from failed memory formation. In contrast, differential effects between modalities were found in the theta band (3–7 Hz), with an increased oscillatory activity before the onset of later remembered visually presented words. In addition, pre-stimulus theta power dissociated between successful and failed encoding of associated context, independent of the stimulus modality of the item itself. We therefore suggest that increased ongoing low beta activity reflects a memory promoting state, which is likely to be moderated by modality-independent attentional or inhibitory processes, whereas high ongoing theta power is suggested as an indicator of the enhanced binding of incoming interlinked information.
Highlights
The ability to encode new information into long-term memory is essential in every human’s day-to-day life
These effects were largest at frontal and temporal electrodes, starting about one second before stimulus onset. These findings were used to take a deeper look into the functional relevance of pre-stimulus activity for subsequent memory formation by utilizing the detected neural oscillations in a brain computer interface (BCI)
Effect of beta and theta power on memory formation remembered with an average probability of 67.3% (SEM ± 3.1%) and a false positive rate of 11.1% (SEM ± 1.5%)
Summary
The ability to encode new information into long-term memory is essential in every human’s day-to-day life. Other research investigated SMEs by analyzing time-frequency decomposed neurophysiological data These studies typically found increased pre-stimulus activity in the theta frequency band to be associated with successful later retrieval of an item [4, 5, 16], with the source of this activity being localized in the medial temporal lobe structures [5, 7]. Salari and Rose [18] on the other hand, investigated ongoing neural activity and revealed an increase in ongoing EEG theta and low beta activity to be associated with successful memory encoding These effects were largest at frontal and temporal electrodes, starting about one second before stimulus onset. Schneider and Rose [19] compared pre-stimulus beta activity during intentional and incidental encoding of information and revealed that the mere intention to encode a stimulus increased the pre-stimulus SME in the lower beta band, suggesting that this effect might reflect encoding-specific processes
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