The dual-route hypothesis: Evaluating a neurocomputational model of fear conditioning in rats

Research on the neural bases of emotion raises much controversy and few quantitative models exist that can help address the issues raised. Here we replicate and dissect one of those models, Armony and colleagues'neurocomputational model of fear conditioning, which is based on LeDoux's dual-route hypothesis regarding the rat fear circuitry. The importance of the model's modular abstraction of the neuroanatomy, its use of population coding, and in particular the interplay between thalamo-amygdala and thalamo-cortical pathways are tested. We show that a trivially minimal version of the model can produce conditioning to a reinforced stimulus without recourse to the dual pathway structure, but a modification of the original model, which nevertheless preserves the thalamo-amygdala and (reduced) thalamo-cortical pathways, enables stronger conditioning to a conditioned stimulus. Implications for neurocomputational modelling approaches are discussed. © 2009 Taylor & Francis.