Differential neural coding of acoustic flutter within primate auditory cortex. Nat Neurosci

Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, United States
Nature Neuroscience (Impact Factor: 16.1). 07/2007; 10(6):763-71. DOI: 10.1038/nn1888
Source: PubMed


A sequence of acoustic events is perceived either as one continuous sound or as a stream of temporally discrete sounds (acoustic flutter), depending on the rate at which the acoustic events repeat. Acoustic flutter is perceived at repetition rates near or below the lower limit for perceiving pitch, and is akin to the discrete percepts of visual flicker and tactile flutter caused by the slow repetition of sensory stimulation. It has been shown that slowly repeating acoustic events are represented explicitly by stimulus-synchronized neuronal firing patterns in primary auditory cortex (AI). Here we show that a second neural code for acoustic flutter exists in the auditory cortex of marmoset monkeys (Callithrix jacchus), in which the firing rate of a neuron is a monotonic function of an acoustic event's repetition rate. Whereas many neurons in AI encode acoustic flutter using a dual temporal/rate representation, we find that neurons in cortical fields rostral to AI predominantly use a monotonic rate code and lack stimulus-synchronized discharges. These findings indicate that the neural representation of acoustic flutter is transformed along the caudal-to-rostral axis of auditory cortex.

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Available from: Daniel Bendor, Sep 03, 2014
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    • "A large proportion of neurons in marmoset A1 showed preferential responses to amplitude- or frequency-modulated tones and, interestingly, some of these neurons could only be driven by temporally modulated tones but not by unmodulated pure tones (Liang et al., 2002). Neurons in marmoset auditory cortex are also found to be responsive to periodic click train stimuli, by either stimulus synchronized or unsynchronized discharges in both A1 (Lu et al., 2001) and rostral fields (Bendor and Wang, 2007, 2008). "
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    • "These stimuli were band-pass filtered from 2–4kHz, with 1kHz smoothing. The design of these stimuli followed those that elicit a percept of “acoustic flutter” and are used to assess temporal processing in the auditory system distinctly from pitch [51-53]. "
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    • "Even higher rates of phase-locked activity have been observed in population responses elicited by click trains in primary auditory cortex of monkeys (Steinschneider et al., 1998) and humans (Brugge et al., 2009; Nourski and Brugge, 2011). Generally, however, the upper limit for phase-locking has been reported to occur at much lower rates (e.g., Lu et al., 2001; Liang et al., 2002; Bendor and Wang, 2007). There are at least two possible reasons for this disparity. "
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