Fig. 2.

Sensory responses in nucleus HVC are selective at both the population level and the level of individual neurons. A: multiunit recordings from HVC in an awake song sparrow during auditory playback of the bird's own song (BOS) and reversed playback of the BOS (REV). Responses are clearly selective for the BOS, revealing that HVC neurons selectively respond to vocal sequences. Top: raster of auditory responses. Middle: peristimulus time histogram of auditory responses. Bottom: oscillogram of song stimulus. [Adapted from Fig. 4 of Nealen and Schmidt (2006).] B: single-unit activity of an identified HVC_X projection neuron is also highly selective in an awake swamp sparrow. This cell reponded strongly to one song in the bird's adult repertoire (primary song type), but there was little or no response to other songs in the bird's adult repertoire (other BOS types) or to randomly selected songs from other conspecifics (random CON song). This cell was responsive to one song type in the bird's adult repertoire. Other HVC_X cells in the same bird were selectively responsive to the other elements of the adult repertoire (data not shown). Top: raw trace of a response to a playback; remaining three panels are as in A. [Adapted from Fig. 1 of Prather et al. (2008).]