Investigating the neural bases of self-relevant memories with event-related potentials
In five ERP studies and one behavioural study the neural bases of the self were investigated during encoding and retrieval of self-relevant memories. The studies provide the first detailed report of ERP effects associated with self-referential processing. These effects were investigated in a range of tasks from self-trait evaluation, self-trait generation and remember/know recognition to yes/no recognition and source memory tasks. The self-reference effect was defined by the difference between memories evoked in reference to oneself and memories evoked in reference to a friend or other semantic material. Three ERP self-reference effects were found and interpreted in terms of levels of self-awareness according to the degree of introspection that is required by the memory task. A left temporo-parietal negative component was interpreted as a correlate of awareness associated with the feeling of a "minimal" self. A left frontal negative component was interpreted in terms of spontaneous self-referential mental activity of the medial prefrontal cortex that is disengaged when an attentionally demanding cognitive task is required. These two negative components were considered to be different manifestations of the same level of minimal self-awareness. A right central-frontal positive component was interpreted as a correlate of awareness associated with the "narrative" self. It is proposed that the self can be identified by specific ERP components and that their distribution across the scalp depend on the degree of introspection of the task as well as on the occurrence of other interacting processes. Two components of the self (minimal and narrative) were identified in these studies indicating for the first time that the self can be dissociated from episodic memory and within memory. Additionally, the effect of the self on the parietal and frontal ERP old/new effects was observed, and it indicated that to some extent both memory effects were modulated by the self-referential quality of the information retrieved.