The Impact of Emotion on Associative Memory

Abstract

The effect of emotion on associative memory remains unclear. Inconsistent findings in the literature are leading to theories with opposite predictions. Obtaining a clearer view of the impact of emotion on associative memory remains of crucial importance, particularly as it could shed light on the mechanisms leading to the emergence of posttraumatic stress disorder (PTSD). PTSD is a condition which may develop following exposure to a traumatic event and is characterised by intrusive memories and disorganised recall of the trauma. One theory about PTSD, the dual representation account, posits that PTSD symptoms arise due to an inability to store the trauma within a coherent spatiotemporal representation because of a disrupted associative memory for the trauma. While it is clear that emotion impacts memory, the debate persists regarding reduced associative memory for an emotional situation. As reviewed in Chapter 1, studies with healthy volunteers revealed discrepant findings and computational models looking at the impact of emotion on memory simulate robust binding between emotional items and their context. The primary objective of this thesis is to clarify the confused picture of the emotional effect on associative memory. To achieve that, Chapter 2 disentangles various types of associative memory tested in past literature and introduces a novel paradigm to assess them within the same experiment. This chapter investigates whether emotion impacts differently order memory, temporal source memory, contextual memory, and subjective recollection. Findings indicate that emotion may decrease contextual memory but does not affect order memory, temporal source memory and subjective recollection. Understanding the impact of emotion on associative memory may be challenging because of the various types of associative memory which may be relying on different mechanisms. However, the discrepant results in the literature may also be due to additional factors. For instance, integration of stimuli during encoding is believed to influence associative memory. Similarly, evaluative conditioning is an effect that appears to interact with associative memory. Hence examining these processes could potentially explain the mixed findings in the literature. Taking this into account, Chapter 3 assesses how emotion impacts integration and whether evaluative conditioning can arise in a paradigm designed to test emotional associative memory. Results show that integration was reduced for emotional stimuli while associative memory remained unaffected. Evaluative conditioning was observed in Experiment 1 using a paradigm not intended to induce this effect, nonetheless, evaluative conditioning effects were not found when other paradigms were used in Experiments 2 and 3. Lastly, Experiment 4 shows that evaluative conditioning and associative memory were related. Finally, Chapter 4 aims to obtain a comprehensive view of the interaction between emotion and memory for associations by focusing on hippocampal-independent associative memory. Using a task enabling a direct comparison between hippocampal-dependent and hippocampal-independent associative memory, this chapter tests whether the emotional effect differs for both types of memory. Overall, mixed findings were found on the emotional impact on both types of memory. The findings reported in this thesis mostly suggest that emotion has limited impact on associative memory. It therefore does not support the dual representation theory. However, these findings also do not show increased associative memory for emotional items, contradicting assumptions from other theories and computational models.