A Monotonic Code for Sound Azimuth in Primate Inferior Colliculus

Groh, Jennifer M.; Kelly, Kristin N.; Underhill, Abigail M.

doi:10.1162/089892903322598166

Cited by 54 publications

(53 citation statements)

References 72 publications

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“…Neurons responsive only to high frequencies were too rare (one neuron) to include as a separate category for analysis. This bias for low frequencies and/or broad tuning is consistent with our previous studies in primate IC (Groh et al, 2003;Porter et al, 2006). As we noted previously (Porter et al, 2006), a possible explanation for this pattern comes from various studies that have found asymmetries in frequency tuning curves: the cutoff for high frequencies tends to be sharper than that for low frequencies (mouse IC, Egorova et al, 2001;Hage and Ehret, 2003;Yan et al, 2005; cat primary auditory cortex, Sutter, 2000; mouse auditory nerve fibers, Taberner and Liberman, 2005).…”

Section: Methodssupporting

confidence: 91%

Effects of Reward and Behavioral Context on Neural Activity in the Primate Inferior Colliculus

2006

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Neural activity in the inferior colliculus (IC) likely plays an integral role in the processing of various auditory parameters, such as sound location and frequency. However, little is known about the extent to which IC neural activity may be influenced by the context in which sounds are presented. In this study, we examined neural activity of IC neurons in the rhesus monkey during an auditory task in which a sound served as a localization target for a saccade. Correct performance was rewarded, and the magnitude of the reward was varied in some experiments. Neural activity was also assessed during a task in which the monkey maintained fixation of a light while ignoring the sound, as well as when sounds were presented in the absence of any task. We report that neural activity increased late in the trial in the saccade task in 58% of neurons and that the level of activity throughout the trials could be modulated by reward magnitude for many neurons. The late-trial neural activity similarly increased in the fixation task in 39% of the neurons tested for this task but was not observed when sounds were presented in the absence of a behavioral task and reward. Together, these results suggest that a rewardrelated signal influences neural activity in the IC.

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Section: Methodssupporting

confidence: 91%

Effects of Reward and Behavioral Context on Neural Activity in the Primate Inferior Colliculus

2006

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“…We based this simple model on the observations that, within the measurement range of azimuths (Ϯ30°) and intensities (40 -60 dB SPL), (1) typical responses to soundsource azimuth were monotonic for contralateral azimuths (Figs. 3, 4) (Groh et al, 2003), (2) the activity of the majority of cells (ϳ70%) tested in the sound-level paradigm (see Materials and Methods) depended monotonically on absolute sound intensity (Fig. 1b), and (3) some neurons had a monotonic sensitivity to changes in sound-source elevation, too.…”

Section: Systematic Sensitivity To 2d Sound Position and Sound Levelmentioning

confidence: 91%

“…The spatial tuning of auditory neurons in the mammalian SC varies with eye position Sparks, 1984, 1987;Hartline et al, 1995;Peck et al, 1995), suggesting that the initial head-centered auditory input has been transformed into oculocentric coordinates. Recently, also IC neurons were reported to be modulated by eye position and sound location in the horizontal plane (Groh et al, 2001(Groh et al, , 2003. These cells were proposed to form an intermediate stage in this coordinate transformation.…”

Section: Introductionmentioning

confidence: 99%

Involvement of Monkey Inferior Colliculus in Spatial Hearing

Zwiers¹,

Versnel²,

Opstal³

2004

J. Neurosci.

117

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The midbrain inferior colliculus (IC) is implicated in coding sound location, but evidence from behaving primates is scarce. Here we report single-unit responses to broadband sounds that were systematically varied within the two-dimensional (2D) frontal hemifield, as well as in sound level, while monkeys fixated a central visual target.Results show that IC neurons are broadly tuned to both sound-source azimuth and level in a way that can be approximated by multiplicative, planar modulation of the firing rate of the cell. In addition, a fraction of neurons also responded to elevation. This tuning, however, was more varied: some neurons were sensitive to a specific elevation; others responded to elevation in a monotonic way. Multiple-linear regression parameters varied from cell to cell, but the only topography encountered was a dorsoventral tonotopy.In a second experiment, we presented sounds from straight ahead while monkeys fixated visual targets at different positions. We found that auditory responses in a fraction of IC cells were weakly, but systematically, modulated by 2D eye position. This modulation was absent in the spontaneous firing rates, again suggesting a multiplicative interaction of acoustic and eye-position inputs. Tuning parameters to sound frequency, location, intensity, and eye position were uncorrelated. On the basis of simulations with a simple neural network model, we suggest that the population of IC cells could encode the head-centered 2D sound location and enable a direct transformation of this signal into the eye-centered topographic motor map of the superior colliculus. Both signals are required to generate rapid eye-head orienting movements toward sounds.

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“…The inferior colliculus (IC) is at the core of the ascending auditory pathway, receiving converging inputs from all auditory brainstem nuclei, and is thought to encode the spectral and temporal features of sounds, and of sound locations (Knudsen and Konishi, 1978;Schreiner and Langner, 1997;Groh et al, 2003;Zwiers et al, 2004;Ehret and Schreiner, 2005;Palmer and Kuwada, 2005;Rees and Langner, 2005). It constitutes an obligatory relay between auditory brainstem and cortex and with the midbrain superior colliculus (SC), which is crucial for rapid orienting (Robinson, 1972;Sparks, 1986).…”

Section: Introductionmentioning

confidence: 99%

Spectrotemporal Response Properties of Inferior Colliculus Neurons in Alert Monkey

Versnel¹,

Zwiers²,

Opstal³

2009

J. Neurosci.

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Because of its central position in the ascending auditory pathway, its large number of converging auditory brainstem inputs, and its fundamental role as a relay to auditory cortex and midbrain superior colliculus, the mammalian inferior colliculus (IC) is regarded pivotal for the integration of acoustic spectral-temporal cues to mediate sound-evoked behavior. However, detailed quantitative analyses of spectrotemporal neural responses are scarce. Moreover, most studies have been performed in anesthetized preparations, and it is unclear how to extrapolate findings to awake and behaving animals. Here, we characterize spectrotemporal receptive fields (STRFs) of single units in alert monkey IC by using a variety of broadband sounds with rippled amplitude spectra. We measured the response sensitivity to the ripple parameters density, ⍀ (cycles/octave), velocity, w (hertz), and direction selectivity, D. We observed a variety of dynamic STRFs, with a strong preference for low ripple densities, and a generally weak direction selectivity. Most cells preferred dynamic rippled stimuli above pure amplitude modulated noise (i.e., ⍀ ϭ 0). Half of the cells could be characterized by good spectral-temporal separability, in which the ripple transfer function can be written as T(w, ⍀) ϭ F(w) ϫ G(⍀). Inseparability could be attributed to a difference in responses to up and downward direction with respect to both amplitude and temporal phase. We tested linearity of IC neurons by using the STRF to predict neural responses to natural stimuli and broadband noise and discuss our results in the light of findings obtained from auditory cortex.

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A Monotonic Code for Sound Azimuth in Primate Inferior Colliculus

Cited by 54 publications

References 72 publications

Effects of Reward and Behavioral Context on Neural Activity in the Primate Inferior Colliculus

Effects of Reward and Behavioral Context on Neural Activity in the Primate Inferior Colliculus

Involvement of Monkey Inferior Colliculus in Spatial Hearing

Spectrotemporal Response Properties of Inferior Colliculus Neurons in Alert Monkey

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