Visual nudging of navigation strategies improves frequency discrimination during auditory-guided locomotion.

Perception in natural environments requires integrating multisensory inputs while navigating our surroundings. During locomotion, sensory cues such as vision and audition change coherently, providing crucial environmental information. This integration may affect perceptual thresholds due to sensory interference.

Latency correction in sparse neuronal spike trains with overlapping global events.

Background: In Kreuz et al., J Neurosci Methods 381, 109703 (2022) two methods were proposed that perform latency correction, i.e.

Development of myelination and axon diameter for fast and precise action potential conductance.

Axons of globular bushy cells in the cochlear nucleus convey hyper-accurate signals to the superior olivary complex, the initial site of binaural processing via comparably thick axons and the calyx of the Held synapse. Bushy cell fibers involved in hyper-accurate binaural processing of low-frequency sounds are known to have an unusual internode length-to-axon caliber ratio (L/d) correlating with higher conduction velocity and superior temporal precision of action potentials. How the L/d-ratio develops and what determines this unusual myelination pattern is unclear.

Temporal hyper-precision of brainstem neurons alters spatial sensitivity of binaural auditory processing with cochlear implants.

The ability to localize a sound source in complex environments is essential for communication and navigation. Spatial hearing relies predominantly on the comparison of differences in the arrival time of sound between the two ears, the interaural time differences (ITDs). Hearing impairments are highly detrimental to sound localization.

An Active Sensing Paradigm for Studying Human Auditory Perception.

Our perception is based on active sensing, i.e., the relationship between self-motion and resulting changes to sensory inputs.

Ketamine-xylazine anesthesia depth affects auditory neuronal responses in the lateral superior olive complex of the gerbil.

Studies of in vivo neuronal responses to auditory inputs in the superior olive complex (SOC) are usually done under anesthesia. However, little attention has been paid to the effect of anesthesia itself on response properties. Here, we assessed the effect of anesthesia depth under ketamine-xylazine anesthetics on auditory evoked response properties of lateral SOC neurons.

Source identity shapes spatial preference in primary auditory cortex during active navigation.

Information about the position of sensory objects and identifying their concurrent behavioral relevance is vital to navigate the environment. In the auditory system, spatial information is computed in the brain based on the position of the sound source relative to the observer and thus assumed to be egocentric throughout the auditory pathway. This assumption is largely based on studies conducted in either anesthetized or head-fixed and passively listening animals, thus lacking self-motion and selective listening.

Endogenous Cholinergic Signaling Modulates Sound-Evoked Responses of the Medial Nucleus of the Trapezoid Body.

The medial nucleus of trapezoid body (MNTB) is a major source of inhibition in auditory brainstem circuitry. The MNTB projects well-timed inhibitory output to principal sound-localization nuclei in the superior olive (SOC) as well as other computationally important centers. Acoustic information is conveyed to MNTB neurons through a single calyx of Held excitatory synapse arising from the cochlear nucleus.

Sensory Island Task (SIT): A New Behavioral Paradigm to Study Sensory Perception and Neural Processing in Freely Moving Animals.

A central function of sensory systems is the gathering of information about dynamic interactions with the environment during self-motion. To determine whether modulation of a sensory cue was externally caused or a result of self-motion is fundamental to perceptual invariance and requires the continuous update of sensory processing about recent movements. This process is highly context-dependent and crucial for perceptual performances such as decision-making and sensory object formation.

Cooperative population coding facilitates efficient sound-source separability by adaptation to input statistics.

Our sensory environment changes constantly. Accordingly, neural systems continually adapt to the concurrent stimulus statistics to remain sensitive over a wide range of conditions. Such dynamic range adaptation (DRA) is assumed to increase both the effectiveness of the neuronal code and perceptual sensitivity.

Precisely timed inhibition facilitates action potential firing for spatial coding in the auditory brainstem.

The integration of excitatory and inhibitory synaptic inputs is fundamental to neuronal processing. In the mammalian auditory brainstem, neurons compare excitatory and inhibitory inputs from the ipsilateral and contralateral ear, respectively, for sound localization. However, the temporal precision and functional roles of inhibition in this integration process are unclear.

Input timing for spatial processing is precisely tuned via constant synaptic delays and myelination patterns in the auditory brainstem.

Precise timing of synaptic inputs is a fundamental principle of neural circuit processing. The temporal precision of postsynaptic input integration is known to vary with the computational requirements of a circuit, yet how the timing of action potentials is tuned presynaptically to match these processing demands is not well understood. In particular, action potential timing is shaped by the axonal conduction velocity and the duration of synaptic transmission delays within a pathway.

Differences in synaptic and intrinsic properties result in topographic heterogeneity of temporal processing of neurons within the inferior colliculus.

The identification and characterization of organization principals is essential for the understanding of neural function of brain areas. The inferior colliculus (IC) represents a midbrain nexus involved in numerous aspects of auditory processing. Likewise, neurons throughout the IC are tuned to a diverse range of specific stimulus features.

Tuning of Ranvier node and internode properties in myelinated axons to adjust action potential timing.

Action potential timing is fundamental to information processing; however, its determinants are not fully understood. Here we report unexpected structural specializations in the Ranvier nodes and internodes of auditory brainstem axons involved in sound localization. Myelination properties deviated significantly from the traditionally assumed structure.

The natural history of sound localization in mammals--a story of neuronal inhibition.

Our concepts of sound localization in the vertebrate brain are widely based on the general assumption that both the ability to detect air-borne sounds and the neuronal processing are homologous in archosaurs (present day crocodiles and birds) and mammals. Yet studies repeatedly report conflicting results on the neuronal circuits and mechanisms, in particular the role of inhibition, as well as the coding strategies between avian and mammalian model systems. Here we argue that mammalian and avian phylogeny of spatial hearing is characterized by a convergent evolution of hearing air-borne sounds rather than by homology.

Experience-dependent specialization of receptive field surround for selective coding of natural scenes.

At eye opening, neurons in primary visual cortex (V1) are selective for stimulus features, but circuits continue to refine in an experience-dependent manner for some weeks thereafter. How these changes contribute to the coding of visual features embedded in complex natural scenes remains unknown. Here we show that normal visual experience after eye opening is required for V1 neurons to develop a sensitivity for the statistical structure of natural stimuli extending beyond the boundaries of their receptive fields (RFs), which leads to improvements in coding efficiency for full-field natural scenes (increased selectivity and information rate).

Emphasis of spatial cues in the temporal fine structure during the rising segments of amplitude-modulated sounds II: single-neuron recordings.

Recently, with the use of an amplitude-modulated binaural beat (AMBB), in which sound amplitude and interaural-phase difference (IPD) were modulated with a fixed mutual relationship (Dietz et al. 2013b), we demonstrated that the human auditory system uses interaural timing differences in the temporal fine structure of modulated sounds only during the rising portion of each modulation cycle. However, the degree to which peripheral or central mechanisms contribute to the observed strong dominance of the rising slope remains to be determined.

Adaptation in sound localization: from GABA(B) receptor-mediated synaptic modulation to perception.

Across all sensory modalities, the effect of context-dependent neural adaptation can be observed at every level, from receptors to perception. Nonetheless, it has long been assumed that the processing of interaural time differences, which is the primary cue for sound localization, is nonadaptive, as its outputs are mapped directly onto a hard-wired representation of space. Here we present evidence derived from in vitro and in vivo experiments in gerbils indicating that the coincidence-detector neurons in the medial superior olive modulate their sensitivity to interaural time differences through a rapid, GABA(B) receptor-mediated feedback mechanism.

Mechanisms of sound localization in mammals.

The ability to determine the location of a sound source is fundamental to hearing. However, auditory space is not represented in any systematic manner on the basilar membrane of the cochlea, the sensory surface of the receptor organ for hearing. Understanding the means by which sensitivity to spatial cues is computed in central neurons can therefore contribute to our understanding of the basic nature of complex neural representations.

Enhancement of ITD coding within the initial stages of the auditory pathway.

Sensory systems use a variety of strategies to increase the signal-to-noise ratio in their inputs at the receptor level. However, important cues for sound localization are not present at the individual ears but are computed after inputs from the two ears converge within the brain, and we hypothesized that additional strategies to enhance the representation of these cues might be employed in the initial stages after binaural convergence. Specifically, we investigated the transformation that takes place between the first two stages of the gerbil auditory pathway that are sensitive to differences in the arrival time of a sound at the two ears (interaural time differences; ITDs): the medial superior olive (MSO), where ITD tuning originates, and the dorsal nucleus of the lateral lemniscus (DNLL), to which the MSO sends direct projections.

Retrograde GABA signaling adjusts sound localization by balancing excitation and inhibition in the brainstem.

Central processing of acoustic cues is critically dependent on the balance between excitation and inhibition. This balance is particularly important for auditory neurons in the lateral superior olive, because these compare excitatory inputs from one ear and inhibitory inputs from the other ear to compute sound source location. By applying GABA(B) receptor antagonists during sound stimulation in vivo, it was revealed that these neurons adjust their binaural sensitivity through GABA(B) receptors.

Interaural time difference processing in the mammalian medial superior olive: the role of glycinergic inhibition.

The dominant cue for localization of low-frequency sounds are microsecond differences in the time-of-arrival of sounds at the two ears [interaural time difference (ITD)]. In mammals, ITD sensitivity is established in the medial superior olive (MSO) by coincidence detection of excitatory inputs from both ears. Hence the relative delay of the binaural inputs is crucial for adjusting ITD sensitivity in MSO cells.

Synaptic transmission at the calyx of Held under in vivo like activity levels.

One of the hallmarks of auditory neurons in vivo is spontaneous activity that occurs even in the absence of any sensory stimuli. Sound-evoked bursts of discharges are thus embedded within this background of random firing. The calyx of Held synapse in the medial nucleus of the trapezoid body (MNTB) has been characterized in vitro as a fast relay that reliably fires at high stimulus frequencies (< or =800 Hz).

Inhibiting the inhibition: a neuronal network for sound localization in reverberant environments.

The precedence effect describes the phenomenon whereby echoes are spatially fused to the location of an initial sound by selectively suppressing the directional information of lagging sounds (echo suppression). Echo suppression is a prerequisite for faithful sound localization in natural environments but can break down depending on the behavioral context. To date, the neural mechanisms that suppress echo directional information without suppressing the perception of echoes themselves are not understood.

Binaural response properties of low-frequency neurons in the gerbil dorsal nucleus of the lateral lemniscus.

Differences in intensity and arrival time of sounds at the two ears, interaural intensity and time differences (IID, ITD), are the chief cues for sound localization. Both cues are initially processed in the superior olivary complex (SOC), which projects to the dorsal nucleus of the lateral lemniscus (DNLL) and the auditory midbrain. Here we present basic response properties of low-frequency (< 2 kHz) DNLL neurons and their binaural sensitivity to ITDs and IIDs in the anesthetized gerbil.