Crowd Sourced Development and Validation of Neuro-Computational Models of Affective Processes*
Crowd sourced development and validation of neuro-computational models of affective processes. Objective biomarkers of pathology exist for a number of diseases, and their development is one of the great advances of modern allopathic medicine. However, objective assessment of affective processes related to mental health disorders has lagged far behind. Currently, the only way to diagnose mental illnesses like depression is using self-reported symptoms such as increased feelings of sadness, guilt, or irritability and decreased interest in activities, concentration, and energy. Yet, these symptom-based diagnoses are astonishingly unreliable across providers (Kappa coefficient = 0.25)1 likely due to how such illnesses inherently degrade individuals’ ability to accurately make these judgments (e.g. depressive realism bias 2). Thus, developing reliable objective biomarkers could dramatically improve diagnosis and treatment by allowing mental health to be characterized on the basis of underlying neuropathology rather than external self-reported symptoms. Direct measures of brain function provide a promising area for developing biomarkers of emotion pathophysiology. In the past several years, major advances in combining functional magnetic resonance imaging (fMRI) with machine learning techniques—algorithms for finding predictive patterns in complex datasets—have brought the goal of fMRI-based assessment of affect within reach. We have recently demonstrated for the first time that fMRI activity can predict whether an individual person is experiencing high or low emotional responses to arousing pictures with over 90% accuracy 3. Critically, this biomarker is sensitive and specific to emotional responses, when compared with other salient and arousing affective events such as thermal pain.
This preliminary success raises a number of issues that must be addressed before fMRI-based biomarkers can be used in large-scale clinical trials and clinical practice, including demonstrating: a) robustness across laboratories and procedures, b) specificity to type of emotion and elicitation method, c) applicability to clinical populations, and d) sensitivity to responses in clinical interventions.
The goal of this project is to develop http://neuro-learn.org - an open-source web-based software platform that can facilitate neuroimaging data sharing and provide integrated machine-learning analysis tools. The Neurolearn platform will consist of three parts. First, it will provide an online repository that will facilitate the uploading, storing, viewing, and sharing of neuroimaging datasets. This repository will have user accounts with the ability to flexibly specify sharing permissions and also the ability to input metadata to accompany the imaging data. Second, the website will feature a server-side analysis toolkit running machine learning algorithms in Python that will facilitate the development and evaluation of brain based signatures of affect. This toolkit will provide an array of algorithms for performing regression and classification (e.g., support vector machines, penalized regressions, and random forests), multiple options for cross-validation (e.g., k-folds, and leave-one-subject-out), as well as methods to evaluate sensitivity and specificity of the brain patterns (e.g., receiver operator characteristic curves). Finally, this website will provide a clean, intuitive, and responsive web interface to use the machine learning tools built with Javascript, Bootstrap, HTML, CSS, and Flask. Neurolearn will store both person-level neuroimaging maps (with meta-data) and ‘research products’ or brain signatures (i.e. trained affect models) to be applied to new datasets. Users will be required to login to use the tool, and will be forced to specify the sharing permissions for their data, brain models, and test results (e.g., single user, a specific group of users, or the general public).
Neurolearn will leverage existing code from Neurosynth.org 4 and Neurovault.org 5 for uploading and storing image data, interactively viewing brain images, and searching and selecting data. Novel features that we will develop in our prototype include: (a) a database for neuroimaging “person-level maps” and “research products” (i.e., brain signature) data types; (b) meta-data specification and entry; (c) user accounts and sharing permissions; (c) server-side machine learning algorithms to generate new signature maps; and (d) server-side applications to apply signature maps to subject data and evaluate sensitivity/specificity related to user-specified outcomes. Finally, we will deploy our application to a local webserver that will be optimized to accommodate both the large storage demands for the imaging repository and the high RAM and CPU cores needed to simultaneously process multiple queued user jobs.