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Psychological distress, depression and anxiety are common in most physical diseases, and self-help interventions, if effective, might be an important approach to improve outcomes as they are inexpensive to provide to large numbers of patients. The primary aim of this review was to assess randomised controlled trials examining the impact of self-help interventions on symptoms of depression, anxiety and psychological distress in patients with physical illness. Systematic searches of electronic databases resulted in twenty-five eligible studies for meta-analysis (n=4211). The results of the primary meta-analyses revealed a significant improvement in depression symptoms, in favour of the intervention group (SMD=-0.13, 95% CI: -0.25, -0.02, p=0.02, I(2)=50%). There were no significant differences in symptoms of anxiety (SMD=-0.10, 95% CI: -0.24, 0.05, p=0.20, I(2)=63%) or psychological distress (SMD=-0.14, 95% CI: -0.40, 0.12, p=0.30, I(2)=72%) between intervention and control conditions. Several subgroup and sensitivity analyses improved effect sizes, suggesting that optimal mental health outcomes may be obtained in patients without neurological conditions, and with interventions based on a therapeutic model (such as cognitive behavioural therapy), and with stress management components. This review demonstrates that with appropriate design and implementation, self-help interventions may potentially improve symptoms of depression in patients with physical conditions.

Highlights Evidence is mixed about whether hippocampal volume affects cognitive task performance. This is particularly the case concerning individual differences in healthy people. We collected structural MRI data from 217 healthy people. They also had widely-varying performance on cognitive tasks linked to the hippocampus. In-depth analyses showed little evidence hippocampal volume affected task performance.

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Autobiographical memory, future thinking, and spatial navigation are critical cognitive functions that are thought to be related and are known to depend upon a brain structure called the hippocampus. Surprisingly, direct evidence for their interrelatedness is lacking, as is an understanding of why they might be related. There is debate about whether they are linked by an underlying memory-related process or, as has more recently been suggested, because they each require the endogenous construction of scene imagery. Here, using a large sample of participants and multiple cognitive tests with a wide spread of individual differences in performance, we found that these functions are indeed related. Mediation analyses further showed that scene construction, and not memory, mediated (explained) the relationships between the functions. These findings offer a fresh perspective on autobiographical memory, future thinking, navigation, and also on the hippocampus, where scene imagery appears to play an influential role.

The hippocampus and ventromedial prefrontal cortex (vmPFC) play key roles in numerous cognitive domains including mind-wandering, episodic memory, and imagining the future. Perspectives differ on precisely how they support these diverse functions, but there is general agreement that it involves constructing representations composed of numerous elements. Visual scenes have been deployed extensively in cognitive neuroscience because they are paradigmatic multielement stimuli. However, it remains unclear whether scenes, rather than other types of multifeature stimuli, preferentially engage hippocampus and vmPFC. Here, we leveraged the high temporal resolution of magnetoencephalography to test participants as they gradually built scene imagery from three successive auditorily presented object descriptions and an imagined 3-D space. This was contrasted with constructing mental images of nonscene arrays that were composed of three objects and an imagined 2-D space. The scene and array stimuli were, therefore, highly matched, and this paradigm permitted a closer examination of step-by-step mental construction than has been undertaken previously. We observed modulation of theta power in our two regions of interest—anterior hippocampus during the initial stage and vmPFC during the first two stages, of scene relative to array construction. Moreover, the scene-specific anterior hippocampal activity during the first construction stage was driven by the vmPFC, with mutual entrainment between the two brain regions thereafter. These findings suggest that hippocampal and vmPFC neural activity is especially tuned to scene representations during the earliest stage of their formation, with implications for theories of how these brain areas enable cognitive functions such as episodic memory.

Autobiographical memory, future thinking and spatial navigation are critical cognitive functions that are thought to be related, and are known to depend upon a brain structure called the hippocampus. Surprisingly, direct evidence for their interrelatedness is lacking, as is an understanding of why they might be related. There is debate about whether they are linked by an underlying memory-related process or, as has more recently been suggested, because they each require the endogenous construction of scene imagery. Here, using a large sample of participants and multiple cognitive tests with a wide spread of individual differences in performance, we found that these functions are indeed related. Mediation analyses further showed that scene construction, and not memory, mediated (explained) the relationships between the functions. These findings offer a fresh perspective on autobiographical memory, future thinking, navigation, and also on the hippocampus, where scene imagery appears to play an influential role.

46Marked disparities exist across healthy individuals in their ability to imagine scenes, recall 47 autobiographical memories, think about the future and navigate in the world. The importance 48 of the hippocampus in supporting these critical cognitive functions has prompted the question 49 of whether differences in hippocampal grey matter volume could be one source of performance 50 variability. Evidence to date has been somewhat mixed. In this study we sought to mitigate 51 issues that commonly affect these types of studies. Data were collected from a large sample of 52 217 young, healthy adult participants, including whole brain structural MRI data (0.8mm 53 isotropic voxels) and widely-varying performance on scene imagination, autobiographical 54 memory, future thinking and navigation tasks. We found little evidence that hippocampal grey 55 matter volume was related to task performance in this healthy sample. This was the case using 56 different analysis methods (voxel-based morphometry, partial correlations), when whole brain 57 or hippocampal regions of interest were examined, when comparing different sub-groups 58 (divided by gender, task performance, self-reported ability), and when using latent variables 59 derived from across the cognitive tasks. Hippocampal grey matter volume may not, therefore, 60 significantly influence performance on tasks known to require the hippocampus in healthy 61 people. Perhaps only in extreme situations, as in the case of licensed London taxi drivers, are 62 measurable ability-related hippocampus volume changes consistently exhibited. 63 64 65 KEYWORDS 66 Hippocampal volume; scene construction; autobiographical memory; future thinking; spatial 67 navigation; individual differences 68 69 A larger number of studies have investigated the relationship between hippocampal 103 volume and memory ability in healthy individuals, but with mixed results. On the one hand, 104