Detecting the neural correlates of episodic memory with mobile EEG: Recollecting objects in the real world.

Episodic memory supports recognition of the details of complex real world experiences, providing a continuous record of events embedded within spatial and temporal context. Despite the inherently dynamic nature of real events, the bulk of neuroscientific research to date examines recognition in absence of the detailed contextual information that is known to be a defining characteristic. Given the importance of environmental context for episodic memory, examining ERP correlates of memory in more naturalistic settings is vital for progress in understanding how retrieval operates in daily life. The current study capitalized on recent advances in mobile EEG technology to address this issue and is the first to investigate ERP correlates of episodic retrieval in real world contexts. Participants were guided around a pre-defined route inside a building on campus, while performing a recognition memory task, which paired images of objects with actual physical locations in the building to provide context. Importantly, the findings clearly demonstrate that it is possible to observe reliable neural correlates of memory in real world contexts. Replicating two well established ERP correlates of episodic retrieval reported in prior laboratory based studies, we detected FN400 old/new effects traditionally associated with familiarity between 300 and 500 ms, and a late posterior negativity (LPN) often linked to reconstructive processing or evaluation of retrieval outcomes between 500 and 800 ms. Moreover, the FN400 effect was found to be sensitive to retrieval of context, with more sustained effects for objects encountered in a different context at study and test. Overall, the current work highlights the power of mobile EEG technology for examining complex cognitive functions in more naturalistic real world settings.