Social familiarity strengthens neural and vocal responses to conspecific calls in zebra finches
Fig 2
Interneuron activity is differentially modulated by caller familiarity.
(a) Example cells recorded during familiar and unfamiliar call playbacks. Top: Spike-sorted waveforms with average (black) and spectrogram of call playback. Middle: Spike dot raster plot. Bottom: peri-stimulus time histogram (PSTH). (b) Normalized firing rate for interneurons that changed activity beyond 2 standard deviations from baseline (169/210 Interneurons, recordings = 9, birds = 8). Neurons are ordered by their peak firing time during familiar call playbacks. The same neuron order is maintained for unfamiliar call playback, showing corresponding activity patterns across conditions. White dashed lines depict call onsets and offsets. (c) Average normalized firing rate (z-score) across significantly responsive neurons. Shaded area represents the 95% confidence intervals (1.96*standard error). (d) Left: Response trajectories in PC space for neurons shown in b (Variance explained by first 2PCs = 55.34%). Lines connecting dots represent 10ms. Right: Euclidean distance between conditions in PC space across time. Red dotted lines represent ±2std from mean baseline values. (e) Average classification accuracy for call playback familiarity based on the firing rate of neurons shown in b (time window = 0 to 400ms from playback onset, model = support vector machine, iterations = 1000, test size = 0.1). Left: Confusion matrix. Top Right: Distribution of accuracies across runs (61.1 ± 7.78%). Bottom Right: Kernel density estimate distribution derived from shuffled data. The solid gray line indicates the 95% confidence interval of the shuffled distribution (56.78%), while the black solid line represents the mean accuracy of the observed data (61.1%, permutation test, p = 0.005). Chance level = 50%. (f) Distribution of different features extracted from the neural activity. Conditions compared using linear mixed model (lmm, see S8 Fig). Firing rate (familiar)=1.46 ± 2.32 (z score), firing rate (unfamiliar)=1.14 ± 1.65 (z score), lmm, p = 0.011. Max firing rate (familiar)=8.4 ± 6.9 (z score), max firing rate (unfamiliar)=7.63 ± 6.38 (z score), lmm, p = 0.051. Time of max firing rate (familiar)=94.85 ± 103.51ms, time of max firing rate (unfamiliar)=88.52 ± 96.22ms, lmm, p = 0.491. Response duration (familiar)=108.87 ± 112.98ms, response duration (unfamiliar)=88.87 ± 95.62ms, lmm, p = 0.001. Black line depicts the identity line where slope = 1. Red line represents fitted regression line for significant comparisons and shaded region shows the 95% confidence interval for the regression estimate. *** denote p < 0.001, * p < 0.05 and ns not significant.