Cross-Correlation in the Auditory Coincidence Detectors of Owls

Abstract

Interaural time difference (ITD) plays a central role in many auditory functions, most importantly in sound localization. The classic model for how ITD is computed was put forth by Jeffress (1948). One of the predictions of the Jeffress model is that the neurons that compute ITD should behave as cross-correlators. Whereas cross-correlation-like properties of the ITD-computing neurons have been reported, attempts to show that the shape of the ITD response function is determined by the spectral tuning of the neuron, a core prediction of cross-correlation, have been unsuccessful. Using reverse correlation analysis, we demonstrate in the barn owl that the relationship between the spectral tuning and the ITD response of the ITD-computing neurons is that predicted by cross-correlation. Moreover, we show that a model of coincidence detector responses derived from responses to binaurally uncorrelated noise is consistent with binaural interaction based on cross-correlation. These results are thus consistent with one of the key tenets of the Jeffress model. Our work sets forth both the methodology to answer whether cross-correlation describes coincidence detector responses and a demonstration that in the barn owl, the result is that expected by theory.

Physiology, Psychoacoustics and Cognition in Normal and Impaired Hearing

“…Our current recordings support the hypothesis that within NL, latencies vary by multiples of 2π, and may be precisely regulated at a fine time scale, in order to create a cycle by cycle representation of the stimulus at the point(s) of coincidence detection (Funabiki et al 2011;Ashida et al 2013). Modulation by multiples of 2π is also consistent with cross-correlation and spike timing dependent plasticity models (Gerstner et al 1996;Kempter et al 1998;Pena and Konishi 2000;Fischer et al 2008). Variability in response latency also characterizes mammalian auditory nerve and cochlear nucleus recordings (Sanes and Constantine-Paton 1985;Carney and Yin 1988;Young et al 1988).…”

Reverse Correlation Analysis of Auditory-Nerve Fiber Responses to Broadband Noise in a Bird, the Barn Owl

“…In particular, the ITD curve, i.e., the firing rate of an ITD sensitive neuron as a function of ITD, is well approximated by the cross-correlation of the STAs from both sides (not taking into account internal delays). ITD curves take the shape of quasi-periodic functions characterized by a fine structure and an envelope, consistent with the fine structure and envelope of the STAs of the inputs from both sides (Fischer et al 2008). The ITD where the envelope of the ITD curve is maximal is the difference between the STA envelope delays from both sides (red point in Fig.…”

“…In the barn owl, ITD processing is thought to be based on a cross correlation (Fischer et al 2008). In particular, the ITD curve, i.e., the firing rate of an ITD sensitive neuron as a function of ITD, is well approximated by the cross-correlation of the STAs from both sides (not taking into account internal delays).…”

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

“…Sensitivity to ITD first emerges in brainstem coincidence detector neurons that cross-correlate narrow-band inputs from the two ears (Carr and Konishi, 1990;Fischer et al, 2008). In a simple approach, the input may be regarded as sinusoidal, resulting in an output resembling a cosine function.…”