Before revision:  We show that, if spike-timing-dependent-plasticity (STDP) is active during sleep, the connections among groups of neurons associated to instances of the same class (digit) are enhanced, and that the internal representation is hierarchical and orthogonalized.
After revision:  We show that, if spike-timing-dependent-plasticity (STDP) is active during slow oscillations, a differential homeostatic process is observed. It is characterized by both a specific enhancement of connections among groups of neurons associated to instances of the same class (digit) are enhanced, and that the internal representation is hierarchical and orthogonalized.