A study on the tonotopic organization in the auditory cortex of the cat; an application of the glycine labelling method.

3H-glycine was locally applied to the auditory cortex of chloralose anaesthetized cats. Upon tonal stimulation the 3H-glycine was taken up and incorporated into the proteins of nerve cells. The selectively activated neurons were visualized by serial light microscopic autoradiography. Systematic application of this experimental setup revealed tonotopic organization in the primary auditory cortex. The distribution of nerve cells responding to spectrally pure, continuous tones of 0.34, 3.3, 8.0, 16 and 30 kHz was mapped. At these frequencies, distinct but overlapping representations were found, whose area increased in parallel with the elevation of frequencies. Tone pips and ramp stimuli resulted in generalized labelling, independently of pitch.