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Brain Research (1)
Current biology : CB (1)
The Journal of the Acoustical Society of America (1)
Winter, Ian M. (3)
Axon, Patrick (1)
Baguley, David (1)
Bleeck, Stefan (1)
Carlyon, Robert P. (1)
Deeks, John M. (1)
Long, Christopher J. (1)
Mahendran, Suresh (1)
Meddis, Ray (1)
Micheyl, Christophe (1)
Pressnitzer, Daniel (1)
Sayles, Mark (1)
Sumner, Christian J. (1)
Year of Publication
Perceptual organization of sound begins in the auditory periphery
Current biology : CB
Segmenting the complex acoustic mixture that makes a typical auditory scene into relevant perceptual objects is one of the main challenges of the auditory system , for both human and non-human species. Several recent studies indicate that perceptual auditory object formation, or “streaming”, may be based on neural activity within auditory cortex and beyond [2, 3]. Here, we find that scene analysis starts much earlier in the auditory pathways. Single units were recorded from a peripheral structure of the mammalian auditory brainstem, the cochlear nucleus. Peripheral responses were similar to cortical responses and displayed all of the functional properties required for streaming, including multi-second adaptation. Behavioral streaming was also measured in human listeners. Neurometric functions derived from the peripheral responses predicted accurately behavioral streaming. This reveals that sub-cortical structures may already contribute to the analysis of auditory scenes. This finding is consistent with the observation that species lacking a neocortex can still achieve and benefit from behavioral streaming . For humans, we argue that auditory scene analysis of complex scenes is likely to be based on interactions between sub-cortical and cortical neural processes, with the relative contribution of each stage depending on nature of the acoustic cues forming the streams.
The role of auditory nerve innervation and dendritic filtering in shaping onset responses in the ventral cochlear nucleus
Sumner, Christian J.
Neurons in the ventral cochlear nucleus (VCN) that respond primarily at the onset of a pure tone stimulus show diversity in terms of peri-stimulus-time-histograms (PSTHs), rate-level functions, frequency tuning, and also their responses to broad band noise. A number of different mechanisms have been proposed as contributing to the onset characteristic: e.g. coincidence, depolarisation block, and low-threshold potassium currents. We show that a simple point neuron receiving convergent inputs from high-spontaneous rate auditory nerve (AN) fibers, with no special currents and no peri-stimulatory shifts in firing threshold, is sufficient to produce much of the diversity seen experimentally. Three sub-classes of onset PSTHs: onset-ideal (OI), onset-chopper (OC) and onset-locker (OL) are reproduced by variations in innervation patterns and dendritic filtering. The factors shaping responses were explored by systematically varying key parameters. An OI response in this model requires a narrow range of AN input best frequencies (BF) which only produce supra-threshold depolarizations during the stimulus onset. For OC and OL responses, receptive fields were wider. Considerable low pass filtering of AN inputs away from BF results in an OL, whilst relatively unfiltered inputs produce an OC response. Rate-level functions in response to pure tones can be sloping, or plateau. These can be also reproduced in the model by the manipulation of the AN innervation. The model supports the coincidence detection hypothesis, and suggests that differences in excitatory innervation and dendritic filtering constant are important factors to consider when accounting for the variation in response characteristics seen in VCN onset units.
Onset; Stellate; Cochlear nucleus; Point-neuron; PSTH; Rate-level functions
Behavioral and physiological correlates of temporal pitch perception in electric and acoustic hearing
Carlyon, Robert P.
Deeks, John M.
Long, Christopher J.
The Journal of the Acoustical Society of America
In the “4-6” condition of experiment 1, normal-hearing (NH) listeners compared the pitch of a bandpass-filtered pulse train, whose inter-pulse intervals (IPIs) alternated between 4 and 6 ms, to that of isochronous pulse trains. Consistent with previous results obtained at a lower signal level, the pitch of the 4-6 stimulus corresponded to that of an isochronous pulse train having a period of 5.7 ms – longer than the mean IPI of 5 ms. In other conditions the IPI alternated between 3.5-5.5 ms and 4.5-6.5 ms. Experiment 2 was similar but presented electric pulse trains to one channel of a CI. In both cases, as overall IPI increased, the pitch of the alternating-interval stimulus approached that of an isochronous train having a period equal to the mean IPI. Experiment 3 measured compound action potentials (CAPs) to alternating-interval stimuli in guinea pigs and in NH listeners. The CAPs to pulses occurring after 4-ms intervals were smaller than responses to pulses occurring after 6-ms intervals, resulting in a modulated pattern that was independent of overall level. The results are compared to the predictions of a simple model incorporating auditory-nerve (AN) refractoriness, and where pitch is estimated from 1st-order intervals in the AN response.
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