The neuronal representation of pitch in primate auditory cortex Daniel Bendor and Xiaoqin Wang Nature, 2005 Aug 25, 436 (7054), 1161-1165 Laboratory of Auditory Neurophysiology, Department of Biomedical Engineering,
Johns Hopkins University School of Medicine, Baltimore, Maryland 21025,
USA. Abstract: Pitch perception is critical for identifying and segregating auditory objects, especially in the context of music and speech. The perception of pitch is not unique to humans and has been experimentally demonstrated in several animal species. Pitch is the subjective attribute of a sound's fundamental frequency (f(0)) that is determined by both the temporal regularity and average repetition rate of its acoustic waveform. Spectrally dissimilar sounds can have the same pitch if they share a common f(0). Even when the acoustic energy at f(0) is removed ('missing fundamental') the same pitch is still perceived. Despite its importance for hearing, how pitch is represented in the cerebral cortex is unknown. Here we show the existence of neurons in the auditory cortex of marmoset monkeys that respond to both pure tones and missing fundamental harmonic complex sounds with the same f(0), providing a neural correlate for pitch constancy. These pitch-selective neurons are located in a restricted low-frequency cortical region near the anterolateral border of the primary auditory cortex, and is consistent with the location of a pitch-selective area identified in recent imaging studies in humans. (Bold text emphasis by Martin Braun) Comment: Pitch neurons had previously been recorded in the auditory midbrain,
i.e. two synaptic levels below the primary auditory cortex, by Biebel
and Langner (1997 and 2002). The new findings of Bendor and Wang agree
well with the earlier ones, and they provide an important missing link
for the hypothesis of Langner (1992) that pitch is extracted by periodicity
analysis in the midbrain and then coded, and transmitted up to
the cortex, as part of the low-frequency section of the auditory neural
pathway. While the exact location of the now discovered pitch neurons
in the cortex remains to be determined by future anatomical studies, the
new physiological data indicate that they may not only be present in the
low-frequency section of the primary auditory cortex, but also
in adjacent low-frequency sections of secondary auditory fields.
Such a distribution would agree with the important role of pitch in the
high-order processes that underlie sound identification and acoustic
communication. Biebel, U.W., Langner, G. (1997). Evidence for "pitch neurons" in the auditory midbrain of chinchillas. In: Syka, J. (Ed.), Acoustic Signal Processing in the Central Auditory System. Plenum Press, New York, pp. 263-269. Biebel, U.W., Langner, G. (2002). Evidence for interactions across frequency channels in the inferior colliculus of awake chinchilla. Hear. Res. 169, 151-168. Braun, M., (1999). Auditory midbrain laminar structure appears adapted to f0 extraction: further evidence and implications of the double critical bandwidth. Hear. Res. 129, 71-82. Braun, M., (2000). Inferior colliculus as candidate for pitch extraction: multiple support from statistics of bilateral spontaneous otoacoustic emissions. Hear. Res. 145, 130-140. Langner, G., (1992). Periodicity coding in the auditory system. Hear. Res. 60, 115-142. Langner, G., Schreiner, C.E., Biebel, U.W., (1998). Functional implications of frequency and periodicity coding in auditory midbrain. In: Palmer, A.R., Rees, A., Summerfield, A.Q., Meddis, R. (Eds.), Psychophysical and Physiological Advances in Hearing. Whurr, London, pp. 277-285. Rees, A. and Sarbaz, A. (1997) The influence of intrinsic oscillations on the encoding of amplitude modulation by neurons in the inferior colliculus. In: J. Syka (Ed.), Acoustic Signal Processing in the Central Auditory System, Plenum Press, New York, pp. 239-252. Schreiner, C.E., Langner, G., (1997). Laminar fine structure of frequency
organization in auditory midbrain. Nature 388, 383-386. |