Physiology of octave equivalence

Carbamazepine induced pitch shift and octave space representation

Martin Braun and Vladimir Chaloupka

Hear Res 2005, 210, 85-92

Abstract
Octave-circular pitch perception, the repetition of pitch scale qualities when surpassing the octave interval, has been observed in behavioral data from humans and monkeys, but the underlying anatomy and physiology is still unknown. Here we analyze octave circularity in a concert pianist with absolute pitch, both under medication with the neurotropic drug carbamazepine (CBZ) and without medication. Analysis of 4619 responses in a pitch identification task revealed an internal tone-scale representation, based on the norm-tone scale re A4 = 440 Hz, with an octave-circular pattern of strongly and weakly represented tones. CBZ caused a global down-shift of pitch (ca. 1 semitone at 500 Hz), but no down-shift of the octave-circular pattern of tone characteristics. This pattern was similar in the six tested octave ranges (32.7-2093 Hz), both under the control and the CBZ condition. Pattern repetition always occurred at octave intervals and did not reflect the stretched octaves of piano tuning. The results indicate that CBZ influences pitch detection peripheral of an octave-circular pitch representation. Thus they support previous evidence for pitch detection in the auditory midbrain and for octave-circular pitch mapping in the auditory thalamus.

Keywords: Carbamazepine; Medial geniculate nucleus; Inferior colliculus; Octave mapping; Fundamental frequency f0; Pitch

Abbreviations: AP, absolute pitch; BF, best frequency; CBZ, Carbamazepine; f0, fundamental frequency; ICC, central nucleus of the inferior colliculus; MGN, medial geniculate nucleus; ST, semitone; TRP, trimipramine