Complex Cell-like Direction Selectivity through Spike-Timing Dependent Plasticity.

Complex cells in primary visual cortex exhibit highly nonlinear receptive field properties such as phase-invariant direction selectivity and antagonistic interactions between individually excitatory stimuli. Traditional models assume that these properties are governed by the outputs of antecedent simple cells, but these models are at odds with studies showing that complex cells may receive direct inputs from the lateral geniculate nucleus (LGN) or can be driven by stimuli that fail to activate simple cells. Using a biophysically detailed model of recurrently connected cortical neurons, we show that complex cell-like direction selectivity may emerge without antecedent simple cell inputs, as a consequence of spike-timing dependent synaptic plasticity during visual development. The directionally-selective receptive fields of model neurons, as determined by reverse correlation and 2-bar interaction maps, were similar to those obtained from complex cells in awake monkey primary visual cortex. These results suggest a new interpretation of complex cells as integral components of an adaptive cortical circuit for motion detection and prediction.