Individual Differences and Episodic Memory: Examining Behaviour, Genetics, and Brain Activity.

Abstract

Dual-process models propose that two processes support recognition memory; familiarity, a general sense that something has been previously encountered; and recollection, the retrieval of details concerning the context in which a previous encounter occurred. Event-related potential (ERP) studies of recognition memory have identified a set of old/new effects that are thought to reflect these processes: the 300-500ms bilateral-frontal effect, thought to reflect familiarity and the 500-800ms left-parietal effect, thought to reflect recollection. Whilst the exact functional role of these effects remains unclear, they are widely viewed as reliable indices of retrieval. The ERP literature reviewed in this thesis suggests that the characteristics of these recognition effects vary with task specific details and individual participant differences, suggesting that the recognition effects purported to index retrieval may be conditional on both task and participant. This thesis examined the influence of individual differences on behavioural measures of recognition and the neural correlates of recognition memory, focusing on factors of stimulus material, task performance and participant genotype. Clear evidence of stimulus differences were found, with pictures eliciting more anteriorly distributed effects than words, and a late onsetting frontopolar old/new effect that was unique for voices. Furthermore, the pattern of ERP activity associated with successful recognition of faces appeared to vary as a function of general face recognition ability, with participants poorer at remembering faces exhibiting a 300-500ms old/new effect not present for those good at remembering faces. The data also suggested that activity over right-frontal electrodes, evident in some previous studies, may be participant specific and could reflect additional retrieval support processes. Contrary to expectations, behavioural task performance was not found to significantly modulate the ‘typical’ recognition memory effects. However, a number of genetic polymorphisms were found to significantly influence both behavioural scores and the pattern of ERP activity associated with recognition memory. These results therefore suggest that inherent participant differences influence the neural correlates of recognition memory, in a way that variations in task performance do not. Overall, the results from this thesis therefore suggest that the ‘typical’ bilateral-frontal and left-parietal effects thought to index retrieval are not universal. Furthermore the results suggest that the specific processes engaged during retrieval (as indexed by variations in ERP activity) may be dependent on specific task requirements, stimulus material and the genetic makeup of the individual.