Interaural Level Difference Discrimination Thresholds for Single Neurons in the Lateral Superior Olive

Tollin, Daniel J.; Koka, Kanthaiah; Tsai, Jeffrey

doi:10.1523/jneurosci.5421-07.2008

Cited by 51 publications

(45 citation statements)

References 65 publications

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“…Given that neurons will differ in their firing rates across any type of map, the absolute firing rates may not be of significance. The azimuth locations around which each neuron provides maximum information (partly dependent on the azimuth of the steepest ARF slope) will be of significance (Harper and McAlpine 2004; Jazayeri and Movshon, 2006; Tollin et al, 2008). This depends on the shape of the ARF, and not on the absolute firing rates.…”

Section: Discussionmentioning

confidence: 99%

Systematic Representation of Sound Locations in the Primary Auditory Cortex

Razak

2011

J. Neurosci.

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The primary auditory cortex (A1) is involved in sound localization. A consistent observation in A1 is a clustered representation of binaural properties, but how spatial tuning varies within binaural clusters is unknown. Here, this issue was addressed in A1 of the pallid bat, a species that relies on passive hearing (as opposed to echolocation) to localize prey. Evidence is presented for systematic representations of sound azimuth within two binaural clusters in the pallid bat A1: the binaural inhibition (EI) and peaked (P) binaural interaction clusters. The representation is not a ‘point-to-point’ space map as seen in the superior colliculus, but in the form of a systematic increase in the area of activated cortex as azimuth changes from ipsilateral to contralateral locations. The underlying substrate in the EI cluster is a systematic representation of the medial boundary of azimuth receptive fields. The P cluster is activated mostly for sounds near the midline, providing a spatial acoustic fovea. Activity in the P cluster falls off systematically as the sound is moved to more lateral locations. Sensitivity to interaural intensity differences (IID) predicts azimuth tuning in the vast majority of neurons. Azimuth receptive field properties are relatively stable across intensity over a moderate range (20–40 dB above threshold) of intensities. This suggests the maps will be similar across the intensities tested. These results challenge the current view that no systematic representation of azimuth is present in A1 and show that such representations are present locally within individual binaural clusters.

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Section: Discussionmentioning

confidence: 99%

Systematic Representation of Sound Locations in the Primary Auditory Cortex

Razak

2011

J. Neurosci.

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“…The frequency response area is the 2D pattern of spike counts as a function of frequency and level. Best frequencies were derived offline using the automated method described previously (Palmer et al, 2013;Sumner and Palmer, 2012) with visual confirmation.…”

Section: Methodsmentioning

confidence: 99%

The Neural Substrate for Binaural Masking Level Differences in the Auditory Cortex

et al. 2015

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The binaural masking level difference (BMLD) is a phenomenon whereby a signal that is identical at each ear (S0), masked by a noise that is identical at each ear (N0), can be made 12-15 dB more detectable by inverting the waveform of either the tone or noise at one ear (S, N). Single-cell responses to BMLD stimuli were measured in the primary auditory cortex of urethane-anesthetized guinea pigs. Firing rate was measured as a function of signal level of a 500 Hz pure tone masked by low-passed white noise. Responses were similar to those reported in the inferior colliculus. At low signal levels, the response was dominated by the masker. At higher signal levels, firing rate either increased or decreased. Detection thresholds for each neuron were determined using signal detection theory. Few neurons yielded measurable detection thresholds for all stimulus conditions, with a wide range in thresholds. However, across the entire population, the lowest thresholds were consistent with human psychophysical BMLDs. As in the inferior colliculus, the shape of the firing-rate versus signal-level functions depended on the neurons' selectivity for interaural time difference. Our results suggest that, in cortex, BMLD signals are detected from increases or decreases in the firing rate, consistent with predictions of cross-correlation models of binaural processing and that the psychophysical detection threshold is based on the lowest neural thresholds across the population.

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“…Park et al (1997) found that characteristic ILDs are independent of the excitatory stimulus level in the LSO but not the ILDs associated with the 50% response rate. Although responses at the threshold and slope of a tuning curve both provide information about stimuli (Seung and Sompolinsky 1993;Tollin et al 2008), the level-invariant feature associated with characteristic ILD is more desirable for encoding ILDs when the overall sound level is not static.…”

Section: Balanced Excitation and Inhibition For "Characteristic" Ildsmentioning

confidence: 99%

A Modeling Study of the Effects of Membrane Afterhyperpolarization on Spike Interval Statistics and on ILD Encoding in the Lateral Superior Olive

Zhou

Colburn

2010

Journal of Neurophysiology

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Zhou Y, Colburn HS. A modeling study of the effects of membrane afterhyperpolarization on spike interval statistics and on ILD encoding in the lateral superior olive. J Neurophysiol 103: 2355-2371, 2010. First published January 27, 2010 doi:10.1152/jn.00385.2009. The lateral superior olive (LSO) is the first nucleus in the ascending auditory pathway that encodes acoustic level information from both ears, the interaural level difference (ILD). This sensitivity is believed to result from the relative strengths of ipsilateral excitation and contralateral inhibition. The study reported here simulated soundevoked responses of LSO chopper units with a focus on the role of the heterogeneity in membrane afterhyperpolarization (AHP) channels on spike interval statistics and on ILD encoding. A relatively simplified cell model was used so that the effects of interest could be isolated. Specifically, the amplitude and time constant of the AHP conductance within a leaky integrate-and-fire (LIF) cell model were studied. This extends the work of others who used a more physiologically detailed model. Results show that differences in these two parameters lead to both the distinctive chopper response patterns and to the leveldependent interval statistics as observed in vivo. In general, diverse AHP characteristics enable an enhanced contrast across population responses with respect to rate gain and temporal correlations. This membrane heterogeneity provides an internal, cell-specific dimension for the neural representation of stimulus information, allowing sensitivity to ILDs of dynamic stimuli.

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Interaural Level Difference Discrimination Thresholds for Single Neurons in the Lateral Superior Olive

Cited by 51 publications

References 65 publications

Systematic Representation of Sound Locations in the Primary Auditory Cortex

Systematic Representation of Sound Locations in the Primary Auditory Cortex

The Neural Substrate for Binaural Masking Level Differences in the Auditory Cortex

A Modeling Study of the Effects of Membrane Afterhyperpolarization on Spike Interval Statistics and on ILD Encoding in the Lateral Superior Olive

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