Lesions of a higher auditory brain area during a sensorimotor period do not impair birdsong learning &amp;nbsp;

Alessandro Canopoli,Anja Zai,Richard Hahnloser

doi:10.19185/matters.201603000018

Abstract

One important function of the nervous system is to form and retrieve memories to direct behavior. A prime example of memorization occurs in songbirds when they imitate the songs of another bird heard early in life. Although many brain areas required for song learning have been identified, their separate roles in memory formation and retrieval remain unclear. In juvenile male zebra finches, we test the role of a higher auditory cortical area in memory retrieval. The Caudal Medial Nidopallium (NCM) has previously been shown to be necessary for song memory acquisition and is thus a likely location for holding the memory of tutor song necessary for learning. We extensively exposed young birds to tutor song after which we performed large bilateral lesions in NCM using injection of ibotenic acid. We observe successful song copying in lesioned animals, comparable to song behavior in untreated control birds. Our results show that intact NCM is not required to guide vocal learning based on a previously formed song memory.

Highlights

IntroductionWe study the organization of memory in a behavior of imitation learning based on observ-
We study the organization of memory in a behavior of imitation learning based on observ-3 x ing and copying a conspecifics’ performance
We make use of the fact that song learning is based on a memory of the father’s song which had already been acquired before 40 dph

Summary

Introduction

We study the organization of memory in a behavior of imitation learning based on observ-. The handling editor, the review- fants) typically at an age of 30 days post hatch (dph). Spectrograms in 43 days post hatch (dph) old juveniles (early, top) look different from spectrograms of tutor song (bottom). At 77 dph (late, middle), there is a good visual correspondence between juvenile and tutor song spectrograms. All three similarity scores are indistinguishable between control birds (light grey bars) and NCM-lesioned birds (dark grey bars, mean ± 1 standard deviation, t-test, p>0.05), which reveals that NCM lesions do not impair song development. D: The songs in 77 dph NCM-lesioned birds and of age-matched control birds exhibit similar averages of percent similarity, of sequential match, and of accuracy relative to their tutors’ songs (i.e., the 3 measures that define the similarity score in c): all three comparisons yield p>0.05 (t-test). The circles represent scores in individual birds, the colors correspond to the colors of outlines delimiting the spectrograms in b. d: The songs in 77 dph NCM-lesioned birds and of age-matched control birds exhibit similar averages of percent similarity, of sequential match, and of accuracy relative to their tutors’ songs (i.e., the 3 measures that define the similarity score in c): all three comparisons yield p>0.05 (t-test). e: Between 43 and 77 dph, the songs in NCM-lesioned birds typically change (arrows) in the direction of higher similarity with their tutors’ songs (horizontal) rather than with songs in unfamiliar birds (vertical)

Results & Discussion

Conclusions

Limitations

Methods and Supplementary