Why Biological Systems Suddenly Change State: An Intuitive Guide to Freidlin–Wentzell Theory

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  Stochasticity is ubiquitous in biology and neuroscience, manifesting in various forms, including ion channel noise, synaptic variability, gene regulatory fluctuations, noisy population dynamics, and more. Many biological systems spend long periods in a stable “state” and only rarely transition to another state due to noise. For instance, a neuron typically remains inactive but may occasionally trigger a spontaneous spike. Similarly, a gene can switch from the OFF state to the ON state due to rare bursts of transcription factors. Cells can also transition out of metabolic or epigenetic states, populations might shift between different ecological equilibria, and a viral infection can fluctuate between phases of control and uncontrollability. Freidlin–Wentzell theory provides a mathematically rigorous framework to study these phenomena when noise is small but nonzero . It tells you, firstly, h ow likely rare transitions are,    secondly,   h ow fast they occ...
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MRI Helps Depict Clinically Undetectable Risk Factors in Advanced Stage Retinoblastomas

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If diagnosed early, retinoblastoma is a highly curable cancer. Conservative treatment options have significantly improved in the last decades. The main aims in the management of retinoblastoma are maintaining the eye and reducing the systemic toxicity. A combination of local treatments, systemic and/or peri-ocular chemotherapy, external beam radiation, and enucleation have been used to successfully treat the tumour.
Our data [http://neu.sagepub.com/content/28/1/53.full] confirm the usefulness of high-resolution brain and orbit MRI in combination with clinical examinations in detecting possible risk factors for metastasis in advanced stages retinoblastomas leading to correct “customized” treatments. In particular, pre-laminar optic nerve and scleral infiltration suspected at MRI were strongly associated with the histology findings, and overall choroid provided good performances in sensitivity, NPV and accuracy. LEICR sign could be included in optic nerve evaluation at MRI, and AASE has been confirmed as a valuable additional sign alerting an increasing risk of metastasis.

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