Parallel pathways for vocal learning in basal ganglia of songbirds

Abstract

The cortical nucleus LMAN (lateral magnocellular nucleus of the anterior nidopallium) provides the output of a basal ganglia pathway that is necessary for vocal learning in juvenile songbirds. The shell subregion of LMAN (LMAN(shell)) gives rise to recurrent loops that may subserve specific learning-related functions. We found that lesions in the LMAN(shell) pathway caused no immediate disruption of vocal behavior, but prevented the development of stable vocal sequences and the ability to imitate vocal sounds.

Figure 1. Distribution of pitch in lesioned versus control birds

Scatter plots of Pitch against Duration for all syllables produced by one control bird (top panels; W688) and one lesioned bird (bottom panels; Lb772) at three different time points: immediately prior to surgery (PreOp), within one week post-surgery (PostOp), and in adulthood (Final). Each data point represents an individual syllable, such that discrete clusters signify repeated production of a specific syllable type.

Figure 2. Imitation of tutor (father) songs by lesioned versus control birds

Left set of bars show (a) the percent of syllables in the tutor songs copied by the sons, and (b) the percent of syllables in the sons’ songs copied from the tutors in lesioned versus control birds by the time they reached adulthood. Right set of bars depict a comparable “bootstrap” analysis showing (a) the percent of syllables in randomly chosen tutor songs copied by the sons and (b) the percent of syllables in the sons’ songs copied from random tutors in lesioned versus control birds as adults. An average of 78% of Ad was lesioned in these 5 birds. Scores are depicted as mean + SEM.