Sub-optimality of the early visual system explained through biologically plausible plasticity

Abstract

The early visual cortex is the site of crucial pre-processing for more complex, biologically relevant computations that drive our perception and, ultimately, behaviour. In literature, this pre-processing is often viewed as an optimisation which enables the most efficient (in terms of information, spikes, energy, etc.) representation of the visual input. However, measurements in monkey and cat suggest that receptive fields in the primary visual cortex are often noisy, blobby, and symmetrical, making them sub-optimal for operations such as edge-detection.Here, we propose that this suboptimality occurs because the receptive fields do not emerge through a global minimisation of the generative error, but through locally operating biological mechanisms such as spike-timing dependent plasticity. Furthermore, using an orientation discrimination paradigm we show that while sub-optimal, such models offer a much better description of biology, both at a physiological and a perceptual level.