The involvement of alpha oscillations in voluntary attention directed towards encoding episodic memories

Forming episodic memories is often driven by top-down processes of allocating attention towards voluntarily remembering the details of an episode. This attention orientation is needed to make sure that information is encoded for later remembering. Here we designed an episodic long-term memory (LTM) EEG experiment where we examined brain oscillatory activity associated with attention allocation towards the temporal link between an item and its context. The remembering of this temporal conjunction is crucial for item-context binding and hence for the formation of episodic memories. Participants saw a background picture and a word in a central position on a computer screen and were instructed to memorise (a) the picture only, (b) the word, (c) both individually (i.e. ignoring their co-occurrence) and (d) both with them being presented together. Attention allocation towards item-context binding was associated with oscillatory alpha desynchronization in the upper alpha band (10-13 Hz) over dominantly left posterior brain areas. The results highlight the role of alpha desynchronization in voluntary attention allocation towards the temporal conjunction of item and its context in episodic binding and the involvement of posterior brain areas. The pattern of results suggest that they most likely reflect additional visual processes recruited by attentional mechanisms and do not tap into neural processes of item-context binding per se. Moreover, it indicates that the involvement of alpha oscillations in cognitive processes may be more complex.