Developmentally restricted synaptic plasticity in a songbird nucleus required for song learning

Area of Science:

• Neuroscience
• Behavioral Neuroscience
• Neurobiology

Background:

• Song learning in songbirds relies on specific forebrain areas, including the lateral magnocellular nucleus of the anterior neostriatum (LMAN).
• Understanding the mechanisms of synaptic plasticity is crucial for elucidating the neural basis of learning, particularly vocal learning.

Purpose of the Study:

• To investigate long-term synaptic plasticity in the LMAN.
• To determine if this plasticity is restricted to the critical period for song learning.
• To explore the potential role of observed plasticity in forming tutor song memories.

Main Methods:

• Electrophysiological recordings in the LMAN of songbirds.
• Stimulation of recurrent collateral synapses and thalamic afferent synapses.
• Pairing synaptic stimulation with postsynaptic bursting in principal neurons.
• Investigating spike timing- and NMDA receptor-dependence of plasticity.

Main Results:

• Demonstrated spike timing- and NMDA receptor-dependent long-term potentiation (LTP) of recurrent synapses in LMAN.
• Observed long-term depression (LTD) of thalamic afferent synapses when stimulated out of phase with postsynaptic bursting.
• Both LTP and LTD were specific to the sensory critical period for song learning.

Conclusions:

• The observed synaptic plasticity in LMAN is temporally restricted to the song learning critical period.
• This plasticity can establish recurrent circuitry within LMAN that mirrors tutor song input patterns.
• Such circuit organization may serve as a neural substrate for tutor song memory, aiding vocal sequence learning.