Tuning to Interaural Time Difference and Frequency Differs Between the Auditory Arcopallium and the External Nucleus of the Inferior Colliculus

Vonderschen, Katrin; Wagner, Hermann

doi:10.1152/jn.91196.2008

Cited by 35 publications

(39 citation statements)

References 62 publications

(84 reference statements)

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“…Because midbrain space-specific neurons have only been reported in ICx, the spatial tuning in the thalamus is likely computed within the thalamus itself. In addition, ICx neurons do not respond to frequencies as low and as high as those found in Ov and the forebrain (Pérez and Peña 2006;Vonderschen and Wagner 2009). This indicates that frequency convergence already differs from the midbrain at the entryway to the forebrain.…”

Section: Discussionmentioning

confidence: 99%

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Auditory Spatial Tuning at the Crossroads of the Midbrain and Forebrain

Pérez

Shanbhag

Peña³

2009

Journal of Neurophysiology

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Pérez ML, Shanbhag SJ, Peña JL. Auditory spatial tuning at the crossroads of the midbrain and forebrain. J Neurophysiol 102: 1472-1482, 2009. First published July 1, 2009 doi:10.1152/jn.00400.2009. The barn owl's midbrain and forebrain contain neurons tuned to sound direction. The spatial receptive fields of these neurons result from sensitivity to combinations of interaural time (ITD) and level (ILD) differences over a broad frequency range. While a map of auditory space has been described in the midbrain, no similar topographic representation has been found in the forebrain. The first nuclei that belong exclusively to the forebrain and midbrain pathways are the thalamic nucleus ovoidalis (Ov) and the external nucleus of the inferior colliculus (ICx), respectively. The midbrain projects to the auditory thalamus before sharp spatial receptive fields emerge; although Ov and ICx receive projections from the same midbrain nuclei, they are not directly connected. We compared the spatial tuning in Ov and ICx. Thalamic neurons respond to a broader frequency range and their ITD and ILD tuning varied more across frequency. However, neurons in Ov showed spatial receptive fields as selective as neurons in ICx. Thalamic spatial receptive fields were tuned to frontal and contralateral space and correlated with their tuning to ITD and ILD. Our results indicate that spatial tuning emerges in both pathways by similar combination selectivity to ITD and ILD. However, the midbrain and the thalamus do not appear to repeat exactly the same processing, as indicated by the difference in frequency range and the broader tuning to binaural cues. The differences observed at the initial stages of these soundlocalization pathways may reflect diverse functions and coding schemes of midbrain and forebrain.

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Section: Discussionmentioning

confidence: 99%

“…Auditory spatial tuning at the crossroads of the midbrain and forebrain. J Neurophysiol 102: 1472-1482, 2009. First published July 1, 2009 doi:10.1152/jn.00400.2009.…”

mentioning

confidence: 99%

Auditory Spatial Tuning at the Crossroads of the Midbrain and Forebrain

Pérez

Shanbhag

Peña³

2009

Journal of Neurophysiology

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“…Fig. 2, also Pérez et al, 2009;Vonderschen and Wagner, 2009). ICX neurons typically respond to frequencies Ͼ3 kHz.…”

Section: Contributions Of Low-frequency and High-frequency Ranges To mentioning

confidence: 94%

“…Recent findings indicated that low-frequency information substantially impacts ITD processing in the forebrain (Pérez and Peña, 2006;Vonderschen and Wagner, 2009). Thus, a parsimonious explanation for the emergence of nonzero CPs at the endpoint of the forebrain pathway lies in the remodeling of information through convergence of inputs from a broad frequency range (Fig.…”

Section: Frequency-dependent Delays In Single Neuronsmentioning

confidence: 99%

“…In fact, optimal tuning functions may reflect the variability of the motor output they support, according to a theoretical study (Salinas, 2006). While the midbrain pathway uses high-frequency auditory cues to govern head saccades (Knudsen et al, 1993;Wagner, 1993), the forebrain pathway has been implicated in low-frequency sound localization (Cohen and Knudsen, 1996;Pérez and Peña, 2006;Vonderschen and Wagner, 2009;Singheiser et al, 2010a), memory-based orienting (Knudsen and , novelty detection (Reches and Gutfreund, 2008), and top-down control (Winkowski and Knudsen, 2006). These functional differences supposedly affect the optimality criteria for the sensory representations leading to a frequency-dependent representation of ITD in the forebrain pathway and a frequency-independent representation of ITD in the midbrain pathway.…”

Section: Itd Sensitivity In Different Frequency Bands Across the Popumentioning

confidence: 99%

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Transformation from a Pure Time Delay to a Mixed Time and Phase Delay Representation in the Auditory Forebrain Pathway

Vonderschen¹,

Wagner²

2012

J. Neurosci.

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Birds and mammals exploit interaural time differences (ITDs) for sound localization. Subsequent to ITD detection by brainstem neurons, ITD processing continues in parallel midbrain and forebrain pathways. In the barn owl, both ITD detection and processing in the midbrain are specialized to extract ITDs independent of frequency, which amounts to a pure time delay representation. Recent results have elucidated different mechanisms of ITD detection in mammals, which lead to a representation of small ITDs in high-frequency channels and large ITDs in low-frequency channels, resembling a phase delay representation. However, the detection mechanism does not prevent a change in ITD representation at higher processing stages. Here we analyze ITD tuning across frequency channels with pure tone and noise stimuli in neurons of the barn owl's auditory arcopallium, a nucleus at the endpoint of the forebrain pathway. To extend the analysis of ITD representation across frequency bands to a large neural population, we employed Fourier analysis for the spectral decomposition of ITD curves recorded with noise stimuli. This method was validated using physiological as well as model data. We found that low frequencies convey sensitivity to large ITDs, whereas high frequencies convey sensitivity to small ITDs. Moreover, different linear phase frequency regimes in the high-frequency and low-frequency ranges suggested an independent convergence of inputs from these frequency channels. Our results are consistent with ITD being remodeled toward a phase delay representation along the forebrain pathway. This indicates that sensory representations may undergo substantial reorganization, presumably in relation to specific behavioral output.

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