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Ultra-fine frequency tuning revealed in single neurons of human auditory cortex


Just-noticeable differences of physical parameters are often limited by the resolution of the peripheral sensory apparatus. Thus, two-point discrimination in vision is limited by the size of individual photoreceptors. Frequency selectivity is a basic property of neurons in the mammalian auditory pathway1,2. However, just-noticeable differences of frequency are substantially smaller than the bandwidth of the peripheral sensors3. Here we report that frequency tuning in single neurons recorded from human auditory cortex in response to random-chord stimuli is far narrower than that typically described in any other mammalian species (besides bats), and substantially exceeds that attributed to the human auditory periphery. Interestingly, simple spectral filter models failed to predict the neuronal responses to natural stimuli, including speech and music. Thus, natural sounds engage additional processing mechanisms beyond the exquisite frequency tuning probed by the random-chord stimuli.

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Figure 1: Response selectivity.
Figure 2: Frequency tuning in the responses to the random-chord stimulus.
Figure 3: Frequency discrimination based on single-trial responses.
Figure 4: Natural versus artificial responses.

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We thank the patients for their cooperation in participating in the experiments. We thank E. Behnke, T. A. Fields, E. Ho and C. Wilson for technical assistance. This work was supported by an ISF grant (to I.N.), a NINDS grant (to I.F.), the US-Israel BSF fund (R.M. and I.F.) and a European Molecular Biology Organization and Human Frontier Science Program fellowship (R.M.).

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Correspondence to I. Fried or I. Nelken.

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The file contains Supplementary Notes and Supplementary Figure 1 with Legend, on the subjects of response reproducibility and evaluation of STRFs predictive power. (PDF 234 kb)

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Bitterman, Y., Mukamel, R., Malach, R. et al. Ultra-fine frequency tuning revealed in single neurons of human auditory cortex. Nature 451, 197–201 (2008).

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