[Long-term plasticity of HVC-RA synapses in adult male zebra finches]

Long-term synaptic plasticity is considered as a key part of the neural mechanism of learning and memory. The production of learned vocalization of male zebra finches is closely related to high vocal center (HVC)-robust nucleus of the arcopallium (RA) pathway. However, the long-term plasticity of HVC-RA synapses is unclear. This study investigated the long-term plasticity of HVC-RA synapses in adult male zebra finches through in vivo field potential recording. The results showed that physiologic stimulation, i.e., δ rhythmic stimulation and low frequency stimulation could not effectively induce long-term synaptic plasticity. The former leaded to no change of the amplitudes of evoked population spikes, and the latter induced short-term depression (STD) of the amplitudes of the second evoked population spikes caused by paired pulses. But high frequency stimulation induced long-term depression (LTD) of the amplitudes of evoked population spikes to show out long-term synaptic plasticity. These results suggest that LTD represents the long-term plasticity of HVC-RA synapses in adult male zebra finches, which may be a key part of the neural mechanism of vocal learning and memory and can explain the plasticity of adult song to some degree.