Fig. 2.

Summary of frequency map plasticity. (a and b) The percent of the surface of primary auditory cortex (A1) that responds to each tone is represented as a color in experimentally naïve rats (a, n = 15) and those conditioned with 2 and 14 kHz tones paired with nucleus basalis (NB) stimulation (b, n = 4). The percent of A1 responding was quantified as the sum of the areas of all the recording sites that responded to the tone frequency-intensity combination of interest divided by the total area of A1 (as in Kilgard and Merzenich, 1998a). (c) The difference in the percent cortical area of the naive group and the conditioned group illustrates the magnitude of the cortical map reorganization. Solid vertical lines (b and c) mark the tone frequencies paired with nucleus basalis activation for the group conditioned with asynchronous tonal inputs. The white dots in (c) indicate frequency-intensity combinations (described in the text) that were statistically different between the naïve controls and experimental animals.