[The Role of Backward Connections in Generation of Brain Electrical Responces Elicited by Simple Visual Stimuli]

The role of backward connections (from higher to lower hierarchical layers) in the generation of evoked brain esponses. to simple visual stimuli was explored using Dynamic Causal Modelling approach (DCM), and the contribution of backward connections to evoked responses was quantified as a function of post-stimulus time. The early components of visual evoked related potential (ERP) reflect exogenous (sensory) inputs and can be explained by connections from the lower to higher layers'(forward connections). The ERP components after 200 ms reflect endogenous activity and require the inclusion of both forward and backward connections in the model. Our results complement the work of other authors who showed earlier using DCM that the backward connections occur at the late latencies in auditory oddball experiment.