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.
Animals ; Evoked Potentials, Auditory ; Finches ; physiology ; High Vocal Center ; physiology ; Learning ; Male ; Neuronal Plasticity ; Synapses ; physiology

The synaptic connection from high vocal center (HVC) to robust nucleus of the arcopallium (RA) is a pivotal part of vocal motor pathway in songbirds. Electrophysiological properties of HVC-RA synaptic transmission in adult male zebra finch (Taeniopygia guttata) in vivo was investigated by using field potential recording method. Following electrical stimulation of HVC, the evoked field potentials recorded in RA were feeble. The results showed that the remarkable paired-pulse facilitation was induced by paired-pulse stimulation at HVC-RA synapses. The results also showed that the evoked field potentials were significantly decreased after a conditioning tetanic stimulation and finally recovered gradually within 15 min, which indicates tetanic stimulation-induced transient depression is present at HVC-RA synaptic transmission. These results suggest that properties of synaptic transmission in this pathway might play a role in controlling song production.
Animals ; Electrophysiological Phenomena ; physiology ; Evoked Potentials ; Finches ; physiology ; High Vocal Center ; physiology ; Male ; Prosencephalon ; cytology ; physiology ; Synaptic Transmission ; physiology ; Vocalization, Animal ; physiology