Fig. 2.

Comparisons of response amplitudes and correlation coefficients between naïve birds and birds exposed to the stimulus stream. (A) Mean response amplitude to all stimuli in the test phase. Response amplitude was significantly lower in birds that had heard the stimulus stream (solid bar) in the part-word experiment than in naïve birds (open bar) in a control experiment. (B) Representative PSTHs of responses to 12 stimuli (six words and six part-words) in one neuron recorded from a naïve bird. For most stimuli, PSTHs showed clear peaks in response to each syllable onset (black vertical ticks) and to final offset (red tick). (C) Representative PSTHs of responses to the same 12 stimuli as in A in a neuron recorded from a bird exposed to the stimulus stream. Response peaks at syllable onsets showed heterogeneous response patterns for different stimuli. (D) Mean of correlation coefficients between response PSTH waveforms in birds exposed to the stimulus stream and in naïve birds. Correlation coefficients were significantly lower in birds that had heard the stimulus stream. Error bars show ± SEM.