Fig. 1.

Experimental treatment groups. Following a balanced design, each bird was placed alone in a sound isolation chamber on the afternoon of day 0. On day 1, birds in the habituated and trained-only groups heard repeated playback of the song stimulus for 3 h. On day 2, birds in the novel and habituated groups heard the song stimulus for 30 min. The initial combined microarray and proteomic analysis focused just on the first 3 groups (silence, novel, and habituated). A subsequent microarray experiment compared a separate trained-only group matched to a new habituated group collected at the same time. New cohorts representing all 4 groups were then prepared and assayed for mitochondrial enzyme activities.