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Reports on differences between remembering the past and imagining the future have led to the hypothesis that constructing future events is a more cognitively demanding process. However, factors that influence these increased demands, such as whether the event has been previously constructed and the types of details comprising the event, have remained relatively unexplored. Across two experiments, we examined how these factors influence the process of constructing event representations by having participants repeatedly construct events and measuring how construction times and a range of phenomenological ratings changed across time points. In Experiment 1, we contrasted the construction of past and future events and found that, relative to past events, the constructive demands associated with future events are particularly heightened when these events are imagined for the first time. Across repeated simulations, future events became increasingly similar to past events in terms of construction times and incorporated detail. In Experiment 2, participants imagined future events involving two memory details (person, location) and then reimagined the event either (a) exactly the same, (b) with a different person, or (c) in a different location. We predicted that if generating spatial information is particularly important for event construction, a change in location will have the greatest impact on constructive demands. Results showed that spatial context contributed to these heightened constructive demands more so than person details, consistent with theories highlighting the central role of spatial processing in episodic simulation. We discuss the findings from both studies in the light of relational processing demands and consider implications for current theoretical frameworks.

Laser threshold magnetometry using the negatively charged nitrogen-vacancy (NV−) centre in diamond as a gain medium has been proposed as a technique to dramatically enhance the sensitivity of room-temperature magnetometry. We experimentally explore a diamond-loaded open tunable fibre-cavity system as a potential contender for the realisation of lasing with NV− centres. We observe amplification of the transmission of a cavity-resonant seed laser at 721 nm when the cavity is pumped at 532 nm and attribute this to stimulated emission. Changes in the intensity of spontaneously emitted photons accompany the amplification, and a qualitative model including stimulated emission and ionisation dynamics of the NV− centre captures the dynamics in the experiment very well. These results highlight important considerations in the realisation of an NV− laser in diamond.

Background: White matter hyperintensities (WMHs) are common in normally functioning older adults. While greater WMH volume may be associated with an increased risk of cognitive dysfunction and dementia, the impact of the location of WMHs is less well understood. We investigated whether WMH burden in specific white matter (WM) tracts is associated with clinical classification and global cognitive scores in at‐risk groups for Alzheimer's disease (AD). Method: Participants from Dementia Prevention Research Clinics, New Zealand, were classified as control, subjective cognitive decline, single‐domain amnestic mild cognitive impairment (MCI), multiple‐domain amnestic MCI, or early AD by a multidisciplinary team (Table 1). Several tract‐WMH "overlap scores" (the percentage of total tract voxels containing WMHs) were calculated for each participant's binarised WMH map (Lesion Segmentation Toolbox, SPM) using seven tract probability templates from a 140‐subject tract atlas (www.megatrackatlas.org). Tract templates were of the superior longitudinal fasciculus (SLF), inferior longitudinal fasciculus (ILF), inferior fronto‐occipital fasciculus (IFOF), uncinate fasciculus (UF), cingulum (CB), fornix, and corpus callosum (CC). Between‐group differences in overlap scores were tested with ANOVAs. Pearson's correlations examined associations between tract‐WMH overlap and global cognitive scores. Result: Figure 1 shows WMH overlap with one tract, the IFOF, in a representative participant. Considering the whole sample, the highest tract‐WMH overlap scores can be seen in the IFOF and CC. Significant between‐group differences were found for the SLF, ILF, IFOF, UF, and CC (p <.05), but not the CB or fornix (Fig. 2), with significant linear trends describing the relationship between overlap scores and clinical classification. Post‐hoc tests confirmed significant pairwise comparisons for overlap scores in all aforementioned tracts except the SLF (Fig. 2). We found Addenbrooke's Cognitive Examination‐III scores negatively correlated with overlap scores in the ILF (r = ‐0.19), IFOF(r = ‐0.22), UF(r = ‐0.22), and CC(r = ‐0.19) (all p <.01), but not the SLF, CB, or fornix (p >.05). Conclusion: Our findings highlight that WMH burden within specific WM tracts is associated with degree of clinical impairment in groups at‐risk of AD. Future research will investigate relationships between overlap scores in specific WM tracts and executive functioning, episodic memory, and processing speed performance. [ABSTRACT FROM AUTHOR]

Aotearoa New Zealand's population is ageing. Increasing life expectancy is accompanied by increases in prevalence of Alzheimer's Disease (AD) and ageing-related disorders. The multicentre Dementia Prevention Research Clinic longitudinal study aims to improve understanding of AD and dementia in Aotearoa, in order to develop interventions that delay or prevent progression to dementia. Comprising research clinics in Auckland, Christchurch and Dunedin, this multi-disciplinary study involves community participants who undergo biennial investigations informed by international protocols and best practice: clinical, neuropsychological, neuroimaging, lifestyle evaluations, APOE genotyping, blood collection and processing. A key research objective is to identify a 'biomarker signature' that predicts progression from mild cognitive impairment to AD. Candidate biomarkers include: blood proteins and microRNAs, genetic, neuroimaging and neuropsychological markers, health, cultural, lifestyle, sensory and psychosocial factors. We are examining a range of mechanisms underlying the progression of AD pathology (e.g. faulty blood–brain barrier, excess parenchymal iron, vascular dysregulation). This paper will outline key aspects of the Dementia Prevention Research Clinic's research, provide an overview of data collection, and a summary of 266 participants recruited to date. The national outreach of the clinics is a strength; the heart of the Dementia Prevention Research Clinics are its people. [ABSTRACT FROM AUTHOR]

Background: Alzheimer's disease (AD) is associated with poorer memory and reduced grey matter volume. Non‐amnestic cognition and white matter (WM) changes are an alternative line of enquiry and may reveal earlier changes. We investigated how inhibitory control relates to the superior longitudinal fasciculus (SLF) in groups at‐risk of AD. Method: Participants (n = 229; aged > 55 years) from the Dementia Prevention Research Clinic, New Zealand were classified as control (C; n = 35), subjective cognitive decline (SCD; n = 60), single‐domain amnestic MCI (aMCI; n = 55), multiple‐domain MCI (mMCI; n = 52), and AD (n = 27). Using diffusion MRI, we measured WM fiber density (FD), fiber cross‐section (FC), and fiber density cross‐section (FDC) in the SLF (SLF1, SLF2, SLF3 in each hemisphere, Figure 1). We also measured inhibition (Trail‐Making B, Stroop Inhibition, Switching, Hayling Incongruency), generativity (Letter Fluency, Category Fluency), and processing speed (Trail‐Making A, Stroop Color Naming, Word Reading). Result: Multivariate analyses showed impaired cognition across groups, with stronger impairments in inhibition (F(4, 206) = 5.41, p <.001; Wilk's Λ = 0.55, η2p = 0.12) than processing speed (F(4, 217) = 2.45, p =.001; Wilk's Λ = 0.84, η2p = 0.04). Generativity was also impaired across groups (p <.01). Significant variation in FD was found across groups in all SLF tracts, except for left SLF1 (Figure 2a). Between‐group differences (Figure 2c) included greater FD in C in the right SLF2 than mMCI (p =.04, d = 0.58), in the right SLF3 than SCD (p =.04, d = 0.57) and mMCI (p =.003, d = 0.77), and in the left SLF3 than SCD (p =.04, d = 0.65), mMCI (p =.01, d = 0.69), and AD (p =.02, d = 0.67). Two separate partial least‐squares analyses showed that poorer inhibition, but not processing speed, was associated with lower FD in the SLF (Figure 3). Conclusion: Overall, we found that reduced FD in the SLF was associated with poorer inhibitory control in risk groups of AD. Therefore, WM alterations in the SLF may provide an early marker in AD. [ABSTRACT FROM AUTHOR]

Task-related functional connectivity ( fc-MRI ) indexes the interaction of brain regions during cognitive tasks. Two general classes of methods exist to investigate fc-MRI: the most widely-used method calculates temporal correlations between voxels/regions within subjects, and then determines if within-subject correlations are reliable across subjects ( ws-fcMRI ); the other calculates the average (BOLD) signal within voxels/regions and then performs correlations across subjects ( as-fcMRI ). That is, while both methods rely on correlational techniques, the level at which correlations are calculated is fundamentally different. While conceptually distinct, it is not known how well these two methods of fc-MRI analyses converge on the same findings. The current study addresses this question across a number of analyses. First, using default-mode network regions as seeds, we show that as-fcMRI does not strongly predict ws-fcMRI during episodic simulation tasks. Next, we show that the relationship between as-fcMRI and ws-fcMRI is contingent on whether correlations are calculated between regions from the same functional network (default mode or dorsal attention networks) or between regions from different functional networks. Lastly, we compare seed partial least squares (PLS) – a well-established as-fcMRI method – with a novel version of seed PLS that combines the multivariate approach of PLS analyses and within-subject correlations. The results showed that while many regions exhibited congruent as-fcMRI and ws-fcMRI effects, in some regions the two analyses produced effects in opposite directions. Results are discussed in relation to the Simpson's Paradox, a phenomenon in which across-subject correlations are reversed within individuals present in a sample. Overall, our results suggest that the findings of as-fcMRI do not always map onto those from ws-fcMRI . We end by discussing the advantages associated with using ws-fcMRI to assess the task-related interactions between brain regions. [ABSTRACT FROM AUTHOR]

Most people are right-handed and left-cerebrally dominant for speech, leading historically to the general notion of left-hemispheric dominance, and more recently to genetic models proposing a single lateralizing gene. This hypothetical gene can account for higher incidence of right-handers in those with left cerebral dominance for speech. It remains unclear how this dominance relates to the right-cerebral dominance for some nonverbal functions such as spatial or emotional processing. Here we use functional magnetic resonance imaging with a sample of 155 subjects to measure asymmetrical activation induced by speech production in the frontal lobes, by face processing in the temporal lobes, and by spatial processing in the parietal lobes. Left-frontal, right-temporal, and right-parietal dominance were all intercorrelated, suggesting that right-cerebral biases may be at least in part complementary to the left-hemispheric dominance for language. However, handedness and parietal asymmetry for spatial processing were uncorrelated, implying independent lateralizing processes, one producing a leftward bias most closely associated with handedness, and the other a rightward bias most closely associated with spatial attention. [ABSTRACT FROM AUTHOR]

According to Mahr & Csibra (M&C), the view that the constructive nature of episodic memory is related to its role in simulating future events has difficulty explaining why memory is often accurate. We hold this view, but disagree with their conclusion. Here we consider ideas and evidence regarding flexible recombination processes in episodic retrieval that accommodate both accuracy and distortion. [ABSTRACT FROM PUBLISHER]