One segment of the passerine song system, the anterior forebrain pathway (AFP), is required for song learning, but not singing per se. The AFP appears to process and convey song-related auditory feedback to the motor system, where it guides learning. The objective of this proposal is to understand the physiological mechanisms by which the AFP accomplishes this task. This proposal focuses on area X, the least studied and potential most complicated nucleus of the AFP. To learn how area X processes and transmits information, it is necessary to know the intrinsic physiological properties of its neurons (Specific Aim 1), the physiological properties of synapses on these neurons (Specific Aim 2), and the anatomical connections of these neurons (Specific Aim 3). To simplify this task, it is useful to note an accumulating body of evidence that argues that area X is a component of the avian basal ganglia. This hypothesis makes specific predictions concerning the outcome of each specific aim, i.e., that the intrinsic properties, synaptic properties, and anatomical connections of area X neurons should match those known in the mammalian basal ganglia. Furthermore, this hypothesis suggests that mechanisms of those known in the mammalian basal ganglia. Furthermore, this hypothesis suggests that mechanisms of motor learning in the song system may be directly applicable to other vertebrates, since the basal ganglia are thought to play a role in motor learning in mammals. This research may ultimately contribute to the understanding and treatment of learning deficits in humans and diseases affecting the basal ganglia.
