Tuning in relevant auditory stimuli needs Hebb and anti-Hebb synaptic mechanisms  in central pathways (Sacha B. Nelson, Hebb and anti-Hebb meet in the brasinstem Nature Neuroscience 7, 687-688, 2004). In a brainstem auditory nucleus, excitatory synapses from the same presynaptic neuron are shown to cause opposing forms of spike timing-dependent plasticity  in projection neurons and GABAergic interneurons at low frequencies, but to cause the same form of plasticity at high frequencies. The net effect is to enhance activation of the projection neurons by relevant stimuli.


                                                                                            BM&L-July 2004