The present invention relates to peptide compounds that are capable of stimulating neuronal differentiation, neurite outgrowth and survival of neural cells, and enhancing synaptic plasticity, learning and memory, methods of treating diseases and conditions of nervous system by administration of compositions comprising said compounds. The compounds and compositions of the invention include peptide sequences that are derived from the sequence of human erythropoietin or proteins that are homologous of human erythropoietin.