Modulation ratio of layer 2/3 cells in primary visual cortex: A model based study

Through a reaction-diffusion based model we have studied modulation ratio (MR) in layer 2/3 cells in cat primary visual cortex. The reaction-diffusion based developmental model is based on resource limited competition and diffusive cooperation among neighboring cells. We have obtained receptive fields (RFs) and responses of binocular cells in layer 2/3. The ON-OFF subregion overlap in RF is quantified. We observe a significant correlation between RF ON-OFF subregion overlap and MR. For almost all the cells in layer 2/3 MR <; 1 when MR is obtained from membrane potential. Non-linearity of spiking mechanism makes a significant number of cells to have MR> 1 and behave as simple cells. Based on modulation index from spiking response our modelled layer 2/3 cell population has 76% complex cells and 24% simple cells. We find that local lateral connections have less influence on MR but improve the tuning characteristics of cells significantly.