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. 2017 Dec 6;37(49):12006–12017. doi: 10.1523/JNEUROSCI.5722-12.2017

Figure 1.

Figure 1.

Avian auditory pathway, acoustic features of song stimuli, and experimental protocol. A, Ascending auditory pathways in songbirds are indicated by arrows. Auditory nuclei of avian hindbrain innervate MLd (homolog of the inferior colliculus). MLd innervates OV (homolog of the medial geniculate). OV projects to forebrain field L2 (orange; analog of lay IV of A1). Field L2 innervates L1, L3, NCM, and CLM (red; analogs of superficial layers of A1) (modified from Fig. 1 in Theunissen and Shaevitz, 2006). B, Example spectrograms of a ZF song (top) and a canary song (bottom). Songs of the two species differ both in their spectra and temporal structure. C, Spectral envelopes of canary and ZF songs used as context stimuli in these experiments. D, Differences between canary and ZF songs used as context stimuli in these experiments quantified in five acoustic dimensions. Each vertical panel represents measurement in one dimension: pitch, peak frequency, frequency modulation, amplitude modulation, and Wiener entropy (a measure of the width and uniformity of the power spectrum). In each panel, the test song is shown as a red asterisk for comparison with ZF context songs (red circles) and canary context songs (blue circles). Values for ZF and canary songs overlap somewhat in each dimension but differ in central tendency and/or variance. The test song (red asterisk) in canary context is at the edge or outside of the distribution of canary songs in four of five dimensions. Specialized software was used to extract and quantify the different acoustic features (SAP2011;Tchernichovski et al., 2000). E, Schematic of the stimulus presentation sequence in Experiment 1. Each row represents one test condition. The stimulus order in the preadapting phase and the postcontext phase is the same for all conditions (red boxes, 20 repeats of the test stimulus), but differs in the context-modulated phase, as follows. Canary context: ZF test song in the context of 7 canary songs (c1 to c7) in shuffled order; silence context: ZF song in silent context in shuffled order; context stimuli were replaced by same duration of silence; ZF context: ZF song in the context of 7 ZF songs (z1 to z7) in shuffled order.