Abstract
Self-knowledge is a type of personal semantic knowledge that concerns one’s self-image and personal identity. It has most often been operationalized as the summary of one’s personality traits (“I am a stubborn person”). Interestingly, recent studies have revealed that the neural correlates of self-knowledge can be dissociated from those of general semantic and episodic memory in young adults. However, studies of “dedifferentiation” or loss of distinctiveness of neural representations in ageing suggest that the neural correlates of self-knowledge might be less distinct from those of semantic and episodic memory in older adults. We investigated this question in an event-related potential (ERP) study with 28 young and 26 older adults while they categorised personality traits for their self-relevance (self-knowledge conditions), and their relevance to certain groups of people (general semantic condition). Participants then performed a recognition test for previously seen traits (episodic condition). The amplitude of the late positive component (LPC), associated with episodic recollection processes, differentiated the self-knowledge, general semantic, and episodic conditions in young adults, but not in older adults. However, in older adults, participants with higher composite episodic memory scores had more differentiated LPC amplitudes across experimental conditions. Moreover, consistent with the fact that age-related neural dedifferentiation may be material and region specific, in both age groups some differences between memory types were observed for the N400 component, associated with semantic processing. Taken together, these findings suggest that declarative memory subtypes are less distinct in ageing, but that the amount of differentiation varies with episodic memory function.
Highlights
Self-knowledge is a type of personal semantic knowledge that concerns one’s self-image and personal identity
Summary of the results for the N400 time window At sagittal sites there was a main effect of memory type with a less negative N400 amplitude for episodic memory compared with all other memory types
At parasagittal sites episodic memory was less negative than all other memory types in the left hemisphere while future self-knowledge was less negative than episodic memory, past self-knowledge, and general semantic memory
Summary
Self-knowledge is a type of personal semantic knowledge that concerns one’s self-image and personal identity. Very few studies have examined the neural correlates that underlie distinctions between self-knowledge, semantic, and episodic memory Another relatively unexplored issue is whether personal semantics mainly concerns knowledge of facts and events from our past and present, or applies to the future (but see Conway et al, 2019, for a recent overview). A recent event-related potential (ERP) study observed similar N400 amplitudes, reliably associated with semantic processing (Kutas & Federmeier, 2011), whether participants thought about their present traits or about their past or future self (Tanguay et al, 2018). The amplitude of the LPC, typically associated with episodic recollection (Wilding & Ranganath, 2012), was larger when participants considered their past or future traits than their present selves, and these amplitudes were undistinguishable from those elicited in an episodic recognition task (Tanguay et al, 2018; see Tanguay et al, 2020)
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