Fast ripples are high-frequency oscillations (HFOs) >250 Hz recorded in epileptogenic hippocampal regions. In 2007, we proposed a mechanism by which fast ripples emerge from the pathological desynchronization of neuronal firing (Foffani et al. Neuron 2007). Later in 2010, we developed the out-of-phase firing hypothesis which is now accepted as a major mechanism of pathological HFOs (Ibarz et al. JNeurosc 2010). More recently, using unsupervised learning we disclosed synaptic mechanisms underlying firing selectivity collapse during fast ripples (Valero et al. Neuron 2017).