A comparative study of the behavioral deficits following lesions of various parts of the zebra finch song system: implications for vocal learning

Song production in song birds is controlled by an efferent pathway. Appended to this pathway is a “recursive loop” that is necessary for song acquisition but not for the pro-duction of learned song. Since zebra finches learn their song by imitating external models, we speculated that the impor-tance of the recursive loop for learning might derive from its processing of auditory feedback during song acquisition. This hypothesis was tested by comparing the effects on song in birds deafened early in life and birds with early lesions in either of two nuclei-Area X and the lateral mag-nocellular nucleus of the anterior neostriatum (LMAN). These nuclei are part of the recursive loop. The three treatments affected song development differently, as reflected by var-ious parameters of the adult song of these birds. Whereas LMAN lesions resulted in songs with monotonous repetition