Recent novel experimental techniques allowed to study the relationship between neurons’ property and connectivity. In particular, in the layer II/III of primary visual cortex, it has been shown that excitatory neurons with the same orientation preference have a high probability of being bidirectionally connected (Ko et al. Nature 2011). However, the refinement of intracortical connectivity is only happening after eye-opening (Ko et al. Nature 2013). We have recently hypothesized that this process is a result of experienced-dependent plasticity, modeled by Hebbian learning rule (Clopath et al. 2010, Ko et al. Nature 2013). In contrast to excitatory neurons, parvalbumin-expressing (PV) inhibitory cells are less specific: Hofer et al. (Hofer et al. Nat. Neur. 2011, Bock et al. Nature 2011) showed that PV neurons receive excitatory inputs from neurons with different orientation preferences. We investigated the mechanism by which excitatory to inhibitory connections are formed (how) and their potential function (why) in a small recurrent network. This work is done in collaboration with Jacopo Bono.