The Neural Correlates of Repeated Memory Encoding and Content Reinstatement

The present thesis reports findings from experiments investigating the neural correlates of subsequent source memory performance, repetition and reinstatement of item and source information. Electrophysiological and haemodynamic response data were obtained in two experimental paradigms further investigating effects of encoding modality and encoding context. The primary aim was to identify how neural pattern similarity was influenced by changes to perceptual stimulus features or changes to encoding task instructions, with a particular focus on the role of pattern reactivation. The first set of experiments (Chapters 3 & 4) examined the effects of encoding modality on source memory processes and repetition during study and test phases. Representational similarity analysis of the fMRI data revealed modality independent and modality-dependent source memory effects, suggesting that reactivation of different stimulus features predicted source memory performance when stimuli are repeatedly presented. Overall, the results provide evidence for pattern reactivation to benefit source memory formation and retrieval. The second set of experiments (Chapters 5 & 6) investigated the effects of encoding items repeatedly in the same context or across multiple contexts. Pattern reactivation in the same task condition was shown to enhance source memory for the encoding context. However, lower levels of reactivation were associated with successful source memory performance when stimuli were associated with multiple contexts. Together with the EEG data, the results provide evidence for distinct mechanisms to underlie successful context encoding when items were either repeatedly encoded in the same context or in different contexts. Moreover, results from the EEG analyses suggested that repetition effects predict subsequent source memory performance when they occur in a similar time window as the late parietal component, which is commonly related to recollection. Taken together, the present research advances our understanding of repeated encoding of item and source memory information and leads to novel directions for future research

Predicting memory formation over multiple study episodes

Repeated study typically improves episodic memory performance. Two different types of explanations of this phenomenon have been put forward: 1) reactivating the same representations strengthens and stabilizes memories, or 2) greater encoding variability benefits memory by promoting richer traces. The present experiment directly compared these predictions in a design with multiple repeated study episodes, allowing to dissociate memory for studied items and their context of study. Participants repeatedly encoded names of famous people four times, either in the same task, or in different tasks. During the test phase, an old/new judgement task was used to assess item memory, followed by a source memory judgement about the encoding task. Consistent with predictions from the encoding variability view, encoding stimulus in different contexts resulted in higher item memory. In contrast, consistent with the reactivation view, source memory performance was higher when participants encoded stimuli in the same task repeatedly. Taken together, our findings indicate that encoding variability benefits episodic memory, by increasing the number of items that are recalled. These benefits are however at the expenses of source recollection and memory for details, which are decreased, likely due to interference and generalisation across contexts

The ERP correlates of self-knowledge: Are assessments of one’s past, present, and future traits closer to semantic or episodic memory?

Self-knowledge concerns one’s own preferences and personality. It pertains to the self (similar to episodic memory), yet does not concern events. It is factual (like semantic memory), but also idiosyncratic. For these reasons, it is unclear where self-knowledge might fall on a continuum in relation to semantic and episodic memory. In this study, we aimed to compare the event-related potential (ERP) correlates of self-knowledge to those of semantic and episodic memory, using N400 and Late Positive Component (LPC) as proxies for semantic and episodic processing, respectively. We considered an additional factor: time perspective. Temporally distant selves have been suggested to be more semantic compared to the present self, but thinking about one’s past and future selves may also engage episodic memory. Twenty-eight adults answered whether traits (e.g., persistent) were true of most people holding an occupation (e.g. soldiers; semantic memory condition), or true of themselves 5 years ago, in the present, or 5 years from now (past, present, and future self-knowledge conditions). The study ended with an episodic recognition memory task for previously seen traits. Present self-knowledge produced mean LPC amplitudes at posterior parietal sites that fell between semantic and episodic memory. Mean LPC amplitudes for past and future self-knowledge were greater than for semantic memory, and not significantly different from episodic memory. Mean N400 amplitudes for the self-knowledge conditions were smaller than for semantic memory at sagittal sites. However, this N400 effect was not separable from a preceding P200 effect at these same electrode sites. This P200 effect can be interpreted as reflecting the greater emotional salience of self as compared to general knowledge, which may have facilitated semantic processing. Overall, our findings are consistent with a distinction between knowledge of others and self-knowledge, but the closeness of self-knowledge’s neural correlates to either semantic or episodic memory appears to depend to some extent on time perspective

Predictors and outcomes in primary depression care (POKAL) – a research training group develops an innovative approach to collaborative care

BACKGROUND: The interdisciplinary research training group (POKAL) aims to improve care for patients with depression and multimorbidity in primary care. POKAL includes nine projects within the framework of the Chronic Care Model (CCM). In addition, POKAL will train young (mental) health professionals in research competences within primary care settings. POKAL will address specific challenges in diagnosis (reliability of diagnosis, ignoring suicidal risks), in treatment (insufficient patient involvement, highly fragmented care and inappropriate long-time anti-depressive medication) and in implementation of innovations (insufficient guideline adherence, use of irrelevant patient outcomes, ignoring relevant context factors) in primary depression care. METHODS: In 2021 POKAL started with a first group of 16 trainees in general practice (GPs), pharmacy, psychology, public health, informatics, etc. The program is scheduled for at least 6 years, so a second group of trainees starting in 2024 will also have three years of research-time. Experienced principal investigators (PIs) supervise all trainees in their specific projects. All projects refer to the CCM and focus on the diagnostic, therapeutic, and implementation challenges. RESULTS: The first cohort of the POKAL research training group will develop and test new depression-specific diagnostics (hermeneutical strategies, predicting models, screening for suicidal ideation), treatment (primary-care based psycho-education, modulating factors in depression monitoring, strategies of de-prescribing) and implementation in primary care (guideline implementation, use of patient-assessed data, identification of relevant context factors). Based on those results the second cohort of trainees and their PIs will run two major trials to proof innovations in primary care-based a) diagnostics and b) treatment for depression. CONCLUSION: The research and training programme POKAL aims to provide appropriate approaches for depression diagnosis and treatment in primary care

Lessons learned from applying established cut-off values of questionnaires to detect somatic symptom disorders in primary care: a cross-sectional study

IntroductionBased on two diagnostic accuracy studies in high-prevalence settings, two distinctly different combinations of cut-off values have been recommended to identify persons at risk for somatic symptom disorder (SSD) with the combination of the Patient-Health Questionnaire-15 (PHQ-15) and the Somatic Symptom Disorder—B Criteria Scale (SSD-12). We investigated whether the reported sensitivity and specificity of both recommended cut-off combinations are transferable to primary care.MethodsIn a cross-sectional study, 420 unselected adult primary care patients completed PHQ-15 and SSD-12. Patients scoring ≥9 and ≥ 23 (recommended cut-off combination #1) or ≥ 8 and ≥ 13 (recommended cut-off combination #2) were considered test-positive for SSD, respectively. To assess the validity of the reported sensitivity and specificity in different low- to high-prevalence settings, we compared correspondingly expected proportions of test positives to the proportion observed in our sample.ResultsBased on combination #1, 38 participants (9%) were found to be test positive, far fewer than expected, based on the reported values for sensitivity and specificity (expected minimum frequency 30% with a true prevalence ≥1%). This can only be explained by a lower sensitivity and higher specificity in primary care. For combination #2, 98 participants (23%) were test positive, a finding consistent with a true prevalence of SSD of 15% or lower.DiscussionOur analyzes strongly suggest that the sensitivity and specificity estimates reported for combination #1 are not applicable to unselected primary care patients and that the cut-off for the SSD (≥23) is too strict. Cut-off combination #2 seems more applicable but still needs to be tested in studies that compare screening findings by questionnaires with validated diagnostic interviews as reference standards in primary care populations

Predicting memory formation over multiple study episodes

Repeated study typically improves episodic memory performance. Two different types of explanations of this phenomenon have been put forward: 1) reactivating the same representations strengthens and stabilizes memories, or, in contrast, 2) greater encoding variability - through changes in context - benefits memory by promoting richer traces and a larger variety of retrieval cues. The present experiment was designed to directly compare these predictions in a design with multiple repeated study episodes, allowing to dissociate memory for studied items and their context of study. Participants repeatedly encoded names of famous people four times, either in the same task (optimal encoding for a reactivation view), or in different tasks (optimal encoding for an encoding variability view). During the test phase, an old/new judgement task was used to assess item memory, followed by a source memory judgement about the encoding task. Consistent with predictions from the encoding variability view, encoding stimulus in different contexts resulted in higher item memory and lower rates of forgetting. In contrast, consistent with the reactivation view, source memory performance was higher when participants encoded stimuli in the same task repeatedly. Taken together, our findings indicate that encoding variability benefits episodic memory, by increasing the number of items that are recalled and by decreasing forgetting. These benefits are however at the expenses of source recollection and memory for details, which are decreased, likely due to interference and generalisation across contexts

Functional connectivity between interoceptive brain regions is associated with distinct health-related domains: A population-based neuroimaging study.

Funder: Aarhus Universitets Forskningsfond; Id: http://dx.doi.org/10.13039/501100002739Funder: Health Data Research UK; Id: http://dx.doi.org/10.13039/501100023699Funder: Jabbs Foundation; Id: http://dx.doi.org/10.13039/501100016132Funder: National Institute of Health Research Biomedical Research CentreInteroception is the sensation, perception, and integration of signals from within the body. It has been associated with a broad range of physiological and psychological processes. Further, interoceptive variables are related to specific regions and networks in the human brain. However, it is not clear whether or how these networks relate empirically to different domains of physiological and psychological health at the population level. We analysed a data set of 19,020 individuals (10,055 females, 8965 males; mean age: 63 years, age range: 45-81 years), who have participated in the UK Biobank Study, a very large-scale prospective epidemiological health study. Using canonical correlation analysis (CCA), allowing for the examination of associations between two sets of variables, we related the functional connectome of brain regions implicated in interoception to a selection of nonimaging health and lifestyle related phenotypes, exploring their relationship within modes of population co-variation. In one integrated and data driven analysis, we obtained four statistically significant modes. Modes could be categorised into domains of arousal and affect and cardiovascular health, respiratory health, body mass, and subjective health (all p < .0001) and were meaningfully associated with distinct neural circuits. Circuits represent specific neural "fingerprints" of functional domains and set the scope for future studies on the neurobiology of interoceptive involvement in different lifestyle and health-related phenotypes. Therefore, our research contributes to the conceptualisation of interoception and may lead to a better understanding of co-morbid conditions in the light of shared interoceptive structures

Building capacities for transdisciplinary research challenges and recommendations for early-career researchers

While transdisciplinarity offers a way to tackle complex social-ecological challenges, transdisciplinary research is a challenging task in itself. The integration of research methods across academic disciplines, the collaboration between researchers and practitioners, and the need to balance societal and disciplinary academic impacts pose many difficulties even to experienced applied scientists and even more so to early-career researchers. Young scholars face particular problems, given their lack of longer-term experience and their still fragile position within academia. Drawing on existing literature, an early-career researcher workshop, and our own experience as junior research group leaders, we discuss specific challenges and respective solution strategies of transdisciplinary research within the context of sustainability