Limits on reacquisition of song in adult zebra finches exposed to white noise

Abstract

Zebra finches (Taeniopygia guttata) learn a specific song pattern during a sensitive period of development, after which song changes little or not at all. However, recent studies have demonstrated substantial behavioral plasticity in song behavior during adulthood under a range of conditions. The current experiment examined song behavior of adult zebra finches temporarily deprived of auditory feedback by chronic exposure to loud white noise (WN). Long-term exposure to continuous WN resulted in disruption of song similar to that observed after deafening. When auditory feedback was restored by discontinuing WN, birds were either tutored using tape-recorded playback or housed with adult conspecific tutors. No evidence of learning new tutor syllables was observed, and recovery of pre-WN song patterns was very limited after restoration of hearing. However, many birds did reacquire some aspects of their pretreatment song, suggesting an adult form of learning that may retain some of the initial aspects of sensorimotor acquisition of song in which vocalizations are shaped to match a stored template representation. The failure to learn novel song elements and the modest degree of recovery observed overall suggest a limit on plasticity in adult birds that have acquired species-typical song patterns and may reflect an important species difference between zebra finches and Bengalese finches.

Figure 1.

Auditory brainstem recordings reveal a temporary increase in hearing threshold. Error bars indicate SD.

Figure 2.

Examples of severely disrupted song: a comparison between song before WN exposure (PRE) and immediately after discontinuation of WN (D1). Syllables labeled with a prime (′) were scored as visibly changed between PRE and D1. The y-axis is 0-10 kHz.

Figure 5.

An example of increasing stereotypy without increasing similarity to initial song. The y-axis is 0-10 kHz.

Figure 3.

Examples of moderately disrupted song: a comparison between song before WN exposure (PRE) and immediately after discontinuation of WN (D1). The y-axis is 0-10 kHz.

Figure 4.

Clockwise from top left panel: mean proportion of syllables lost or changed and syllable probability scores on D1 for severely disrupted (▪) and moderately disrupted (▦) birds; mean percentage similarity; syllable accuracy for control, severely disrupted, and moderately disrupted birds at D1 (▪) and D100 (▦); and spectral stereotypy. For control birds, results are for two time points separated by 3 months. Accuracy scores are also given for those syllables scored as increasing in similarity to their PRE renditions at D100. Error bars represent SE.

Figure 6.

Recovery of individual syllables for three birds. The y-axis is 0-10 kHz.