Predictive maps in rats and humans for spatial navigation.

Much of our understanding of navigation comes from the study of individual species, often with specific tasks tailored to those species. Here, we provide a novel experimental and analytic framework integrating across humans, rats, and simulated reinforcement learning (RL) agents to interrogate the dynamics of behavior during spatial navigation. We developed a novel open-field navigation task ("Tartarus maze") requiring dynamic adaptation (shortcuts and detours) to frequently changing obstructions on the path to a hidden goal. Humans and rats were remarkably similar in their trajectories. Both species showed the greatest similarity to RL agents utilizing a "successor representation," which creates a predictive map. Humans also displayed trajectory features similar to model-based RL agents, which implemented an optimal tree-search planning procedure. Our results help refine models seeking to explain mammalian navigation in dynamic environments and highlight the utility of modeling the behavior of different species to uncover the shared mechanisms that support behavior.

Diagnosing Alzheimer's disease: are we any nearer to useful biomarker-based, non-invasive tests?

BACKGROUND: Alzheimer's disease (AD) accounts for 60-80% of cases of dementia and causes significant morbidity in patients and carers, and expense for health and social services. There is a need for a validated, non-invasive and cheap test to diagnose early AD, as diagnosis may enable prompt treatment and service planning. AIM: To identify emerging biomarker-based tests for the early diagnosis of AD which could be available for use in primary or generalist care in the near future. DESIGN: Horizon scanning review. METHODS: We searched online sources to identify emerging non-invasive, biomarker-based tests. Tests were included if they used blood, saliva or urine; and there was evidence of use in trials in patients with AD. For tests licensed for use in clinical or research settings we requested information from the developer on the intended place of use and plans for availability in Europe. RESULTS: We identified 6 biomarker-based tests of which 5 are available for research or clinical use. The closest to market were AclarusDX™ (ExonHit Therapeutics) a gene signature test, and INNO-BIA plasma Aß forms assay (Innogenetics N.V.) which may be CE marked for clinical use in 2015. We found no evidence of clinical utility or cost. CONCLUSION: Although biomarker-based tests are nearing clinical availability and may have a future role to help target AD-specific treatment and guide prognosis, they are not yet ready for trials of clinical utility in primary care.

A clinical and radiological assessment of incisional hernias following closure of temporary stomas.

AIMS: The rate of incisional hernia at stoma closure sites is unclear. This study aimed to describe this rate in patients with closed stomas who had definitive post-operative imaging of their abdominal wall. METHODS: A retrospective review of patients who had undergone stoma reversal and had a CT or MRI scan of the abdomen ≥2 months following reversal was performed. A radiologist, blinded to the original radiological report and clinical results, reviewed all scans for abdominal wall herniation. This was correlated to documented clinical findings. RESULTS: Fifty-nine patients were included: 49 loop ileostomy and 10 end colostomy reversals. CT scans were performed for 57 patients and MRI for two. The median time from closure to imaging was 10 months (range 3-32 months). The combined clinical and radiological hernia rate was 34% (20/59). Imaging alone produced a rate of 31% (18/59). The clinical rate of hernia detection was 14% (8/59). Using the rate of clinical herniation as the detection standard, imaging had a low positive predictive value (33%, 6/18) but a high negative predictive value (95%, 39/41). Four patients required surgical repair of their stoma site hernia (20%, 4/20). CONCLUSIONS: One in three patients undergoing stoma closure developed an incisional hernia. One in five of those with a hernia underwent surgical repair. Definitive imaging may provide an early surrogate marker for late clinically relevant hernias. Consideration of methods to prevent stoma closure site hernias should be considered.