Fig. 2.

Representation of ultrasonic frequencies and cortical response properties. A: representative cortical characteristic frequency (CF) map showing representation of frequencies ≤74 kHz (k). Gray line indicates where typical maps would end when mapped with tone frequencies ≤32 kHz. Scale bar: 1 mm; r and d indicate rostral and dorsal directions, respectively. B: amount of cortical area representing 1-octave frequency bands. The representation of the 32- to 64-kHz band is significantly larger than that of the other bands. A1, primary auditory cortex (AI). C: distribution of CF across the tonotopic axis. D: BW (i), threshold (ii), maximal response magnitude (mag; iii), and response latency (iv) as a function of CF. Small gray points indicate individual recording sites; larger blue circles represent the octave-band average for each animal; the black lines indicate the average of all animals. *P < 0.05 in post hoc comparisons. SPL, sound-pressure level.