How do we remember events?

Episodic memory was first described as the memory system that receives and stores information about events [1]. Since then, studies of episodic memory have tended to use simple, highly controlled stimuli to probe its cognitive and neural underpinnings. By contrast, the study of ‘event memory’ has focussed on memory function in more real-world situations, or used naturalistic stimuli such as movies as a stand-in for reality [2]. Recently there has been an explosion in studies that have combined cognitive experiments using naturalistic stimuli with neuroimaging techniques such as fMRI and EEG, to shed light on how the brain underpins event memory. This review summarises the achievements of these studies and highlights areas that await further work

The use of writing strategies to increase organ donation intentions

Organ shortage has been a big problem for a relatively long time. A variety of interventions from the policy level to the individual level have been used to expand the organ donation pool. The goal of this project is to examine the influence of the content and structure of narrative writing on attitudes and behavioral intentions towards organ donation. In Study 1, participants were randomly assigned into one of the three writing groups. Two of the groups were asked to create a character and then write a narrative either related (Narrative Group-NG) or unrelated (Control Group-CG) to organ donation. The other group was asked to answer some open-ended questions related to organ donation (Fragmented Group-FG). The results indicated that the intention change toward organ donation for NG was significantly different from the other two groups in two of the five items in the scale, which suggested that both topic and format can somewhat influence the organ donation intention. When comparing the writing content, the NG differed from the FG in both linguistic structure and psychological processes while the NG and CG differed mainly in their use of psychological processes and pronouns. In Study 2, a more vivid character creating procedure was developed to further shape the personality of the character. Participants were randomly assigned into one of the four writing groups. Two of the groups were asked to create a character either similar (Similar Vivid Narrative Group-SVN) or dissimilar (Dissimilar Vivid Narrative Group-DVN) to the writer and then write a short story to shape the personality of the character. They were then asked to write another short story where this character was in need of kidney transplant. The other two groups were asked to write about the room they were in first. And then, they were asked to write a short story of a character, either similar (Similar Narrative Control Group-SNC) to dissimilar (Dissimilar Narrative Control Group-DNC) to them, was in need of kidney transplant. Participant who were more transported into the narrative story they wrote and were more similar to the character they wrote tended to have more positive change of organ donation intention. Analysis of the narrative writing content revealed that the use of social process words and less gender reference words were associated with a greater increase in organ donation intention.Includes bibliographical references (pages 47-56)

Content Representation in Lateral Parietal Cortex

While the lateral parietal cortex (LPC) in the human brain is traditionally investigated for its functions in visual perception, more recent evidence has highlighted its substantial contribution to supporting human episodic memory. Early univariate neuroimaging studies suggest that the strength and direction of LPC activation during memory-related tasks is closely related to memory performance. Moreover, recent multivariate fMRI studies show that the neural activity patterns of LPC actively represent mnemonic contents at various granularities. Despite advances in understanding parietal contributions to episodic memory, the relationship between LPC multivariate content representation and univariate activation changes remains unexplored. Moreover, the mechanisms through which the LPC content representation supports episodic memory success are yet unidentified. In the current dissertation, I aim to investigate these topics by incorporating fMRI techniques with neural networks and multivariate pattern analysis methods in a set of two experiments. In chapter II, I demonstrate that repetition-related neural activity differences in the lateral parietal cortex represent stimulus-specific content information, and a greater amount of decodable content information contributes to memory success. In chapter III, I show that content representations in lateral parietal cortex can be adaptively distorted along a feature dimension in order to resolve memory interference, and the degree of such adaptive change contributes to memory success. Together, these studies provide new insights into the nature of content representation in the lateral parietal cortex and how it supports memory success

The Cognitive and Neural Correlates of Rich and Vivid Memory for Real World Events

Episodic memories are composed of rich, perceptual details, and are re-experienced from a specific visual perspective. The aim of this thesis was to investigate the processes which allow us to remember in a rich and vivid way and the neural underpinnings of rich, successful retrieval. The behavioural studies conducted in Chapters 2 and 3 used a newly created video stimulus set, depicting real-world events. In Chapter 2, these stimuli were used to investigate retrieval differences following the encoding of unisensory (audio, visual), compared to multisensory (audio-visual) versions of the videos. Accuracy, vividness and amount of descriptive details retrieved were not positively affected by the presentation of multisensory stimuli. Chapter 3 compared the effects of encoding the videos from a field or an observer perspective on subsequent retrieval performance. No performance differences were observed when comparing the two perspectives, but observer memories contained a greater amount of sensory details, compared to field ones. Chapter 4 reviewed existing literature on the role of the angular gyrus in episodic memory retrieval and proposed that the angular gyrus is sensitive to the richness of recollected information and amount of details retrieved. This hypothesis was tested in an fMRI study in Chapter 5, focusing on the role of the angular gyrus in the retrieval of autobiographical memories. Results indeed demonstrated a positive relationship between angular gyrus activity and amount of details remembered. This association was seen for the retrieval of both episodic (specific) and semantic (categoric) events. This study also illustrated differential involvement of angular gyrus subregions, PGa and PGp in the retrieval of episodic and semantic memories. Taken together, these chapters outline behavioural processes and neural correlates that support our ability to retrieve memories in a rich and vivid manner, giving us a sense of re-living an event

Valence-specific Enhancements in Visual Processing Regions Support Negative Memories:

Thesis advisor: Elizabeth A. KensingerResearch in four parts examines the effects of valence on the neural processes that support emotional memory formation and retrieval. Results show a consistent valence-specific enhancement of visuocortical engagement along the ventral visual stream and occipital cortex that supports negative memories to a greater extent than positive memories. Part I investigated the effects of valence on the interactions between trial-level physiological responses to emotional stimuli (i.e., heart rate deceleration) during encoding and subsequent memory vividness. Results showed that negative memory vividness, but not positive or neutral memory vividness, is tied to arousal-related enhancements of amygdala coupling with early visual cortex during encoding. These results suggest that co-occurring parasympathetic arousal responses and amygdala connectivity with early visual cortex during encoding influence subsequent memory vividness for negative stimuli, perhaps reflecting enhanced memory-relevant perceptual enhancements during encoding of negative stimuli. Part II examined links between individual differences in post-encoding increases is amygdala functional connectivity at rest and the degree and direction of emotional memory biases at retrieval. Results demonstrated that post-encoding increases in amygdala resting state functional connectivity with visuocortical and frontal regions predicted the degree of negative memory bias (i.e., better memory for unpleasant compared to pleasant stimuli) and positive memory bias, respectively. Further, the effect of amygdala-visuocortical post-encoding coupling on behavioral negative memory bias was completely mediated by greater retrieval-related activity for negative stimuli in visuocortical areas. These findings suggest that those individuals with a negative memory bias tend to engage visual processing regions across multiple phases of memory more than individuals with a positive memory bias. While Parts I-II examined encoding-related memory processes, Part III examined the effects of valence on true and false subjective memory vividness at the time of retrieval. The findings showed valence-specific enhancements in regions of the ventral visual stream (e.g., inferior temporal gyrus and parahippocampal cortex) support negative memory vividness to a greater extent than positive memory vividness. However, activation of the parahippocampal cortex also drove a false sense of negative memory vividness. Together, these findings suggest spatial overlap in regions that support negative true and false memory vividness. Lastly, Part IV utilized inhibitory repetitive transcranial magnetic stimulation (rTMS) to test if a portion of occipito-temporal cortex that showed consistent valence-specific effects of negative memory in Parts I-III was necessary for negative memory retrieval. Although some participants showed the hypothesized effect, there was no group-level evidence of a neuromodulatory effect of occipito-temporal cortex rTMS on negative memory retrieval. Together, the results of the current dissertation work highlight the importance of valence-based models of emotional memory and consistently implicated enhanced visuosensory engagement across multiple phases of memory. By identifying valence-specific effects of trial-level physiological arousal during encoding, post-encoding amygdala coupling during early consolidation, and similarities and differences between true and false negative memories, the present set of work has important implications for how negative and positive memories are created and remembered differently.Thesis (PhD) — Boston College, 2019.Submitted to: Boston College. Graduate School of Arts and Sciences.Discipline: Psychology