Modeling non-standard pathways in early vision : role of the thalamus
Résumé
Behavioral reactions to fearful visual stimuli in mammals are considered by most authors to emerge from interactions between an emotional circuit implicating the amygdala and two visual systems sometimes called the high-‐road and the low-‐road. The high-‐road includes the Lateral Geniculate Nucleus (LGN) of the thalamus and cortical area 17, necessary for conscious perception of the fearful stimulus, whereas the low-‐road corresponds to a more ancient subcortical system including the superior colliculus, the LGN and the Pulvinar regions of the thalamus. As the consensus is less clear concerning the reciprocal influences between both roads (is there a supremacy?), a modeling approach may bring more concrete and technical elements to the discussion and propose predictions, possibly falsified in the future. The knowledge and data that we have collected in the Keops project are related to the standard and non-‐standard pathways from the retina to the thalamus, which is at the intersection between the high and low roads evoked above. We report our preliminary experience about implementing a model incorporating known connectivity and activation mechanisms in these regions. The corresponding numerical simulations underline the very powerful properties of the thalamus, seen as a major coordinator of the cortical processing rather than a simple pre-‐processing relay.