Topic: inferior colliculus

Categorical perception of sensory inputs, including human speech, enables adaptive behavior and is thought to emerge in the sensory cortex. There would be significant computational advantages, however, to functional specialization before cortical processing. To what extent do categorical representations emerge earlier in the auditory hierarchy? To address this, we reasoned that the ideal species would exhibit expert auditory sensing and a rich repertoire of vocalizations, akin to human listening and speech. The big brown bat, Eptesicus fuscus, stands out in the animal kingdom for its acoustic

Perception of vocalizations is critical for many species. In mammals, the central auditory pathway is highly interconnected, with corticofugal feedback projections from auditory cortex (AC) to the auditory midbrain that rival the density of feed-forward auditory input. These projections support sound localization, feature coding, and noise invariance. Because vocalizations are acoustically complex and carry social significance, we hypothesize that feedback projections from AC enable behavioral responses. Infant vocalizations that elicit parental care are highly conserved in mammals. In mice, e

The computational principles driving the transformation of sound information throughout the auditory system remains an intense subject of research. Here, we used large-scale samples of neuronal activity from the auditory cortex, thalamus and inferior colliculus in mice and from a detailed cochlea model to identify key transformations of population representations of simple, short (~500ms) time-varying sounds in the auditory pathway. Using noise-corrected metrics, we measured the similarity of evoked population patterns across sounds. In subcortical regions, this measure shows that the full tem

To date, most studies of neural representation have focused on how a single stimulus is encoded in the spiking activity of neurons. Consequently, little is known about how sensory neurons can preserve information from multiple stimuli – a problem given that many sensory neurons have relatively broad receptive fields. Multiplexing is a neural encoding theory that posits that neurons temporally switch between encoding various stimuli when more than one stimulus is present. To date, the strongest statistical evidence for this theory comes from spike counts measured over long time windows, leading

How does the brain derive meaning from social vocalizations and drive behavior in response? Vocalizations are temporally complex, requiring integration across multiple time-scales for appropriate contextualization. We hypothesize that corticofugal projections modulate temporal integration in feed-forward auditory circuits to facilitate this. We tested this using an ethological mouse behavior that depends on left auditory cortex. Mothers find and retrieve isolated pups into the nest when pups emit ultrasonic vocalizations (USVs). Virgin females don’t usually retrieve pups, but learn after sever

Corticocollicular (CC) projections arise in deep layers of the auditory cortex and modulate upstream auditory information in the inferior colliculus (IC), forming feedback loops. They are crucially involved in auditory-related learning and frequency response modulations in auditory brainstem. Through widefield and 2-photon calcium imaging in awake mice we prior were able to show that layer 5 CC neurons display only a subtle topographic organization when compared to other layer 5 neuron types (Schmitt et al., 2023, Front Neural Circuit). However, these data were acquired under passive listening

In cases of profound cochlear dysfunction, electrical cochlear implants (eCIs) offer partial restoration of hearing. Nevertheless, the auditory experience with eCIs remains imperfect due to the broad excitation of auditory nerve neurons by electrical signals that limits the perceptual channels available to users. Optogenetics offers a breakthrough by enabling the stimulation of the auditory nerve by an optical cochlear implant (oCI). Light, unlike electrical signals, can be precisely confined in space, resulting in reduced spread of excitation and improved frequency selectivity. However, optog

Hearing loss in the elderly has been associated with cognitive impairments and an increased risk of dementia. Social withdrawal due to difficulties in verbal interaction may play an important role. Previous research on deafened rats, ruling out language as a potential confounding factor, showed only initial and mild cognitive deficits during learning, whereas electrophysiological recordings in the prefrontal cortex revealed compromised neuronal activity to some extent. The present study tested whether hearing loss would lead to altered expression of the GABA and dopamine (DA) systems in key re

Numerous computational models of the cochlea have been developed that faithfully capture the transformation of incoming sound into basilar membrane motion and auditory nerve spike patterns, with widespread uptake across academia and industry. Models of sensory processing in the brain, however, are generally much less accurate, with even the best failing to explain most of the variance in sub-cortical and cortical neural activity.Here, we used large-scale neural recordings from measurement sites spanning the inferior colliculus (IC) of normal-hearing gerbils to develop a deep learning model of

The optical cochlear implant (oCI) utilizes optogenetic stimulation of the spiral ganglion neurons (SGNs) in the cochlea to improve hearing restoration. Preclinical data has shown that this may improve bionic hearing in CI users by targeting smaller areas of the cochlea compared to electrical stimulation.This study investigates the influence of the light emitter characteristics (one/two laser-coupled glass fibers) on the spread of excitation, through a combination of computer simulations and in-vivo multiunit recordings of inferior colliculus activity in Mongolian gerbils that postnatally rece

Over the last decades, a large number of studies have described the robustness of auditory cortex responses when target stimuli are presented in situations of acoustic degradations (Nagarajan et al.2002, Mesgarani et al. 2014, Town et al, 2018). In few experiments, comparisons have been made with the resistance to noise observed from subcortical neurons recordings (Schneider and Woolley.2013, Rabinowitz et al .2013). Moreover, several studies claimed that the behavioural discrimination performance correlates with the auditory cortex neuronal responses. In previous experiments performed in anae

The giant synaptic terminals play an important role transmitting information with exquisite precision and speed. The thalamus, an important center for the integration and relay of sensory information, is the brain region innervated by more giant terminals. These giant terminals act like drivers, delivering primary sensory information from the somatosensory, visual and auditory pathways. In the auditory thalamus, the drivers arise from the inferior colliculus. Surprisingly, we have observed a population of giant synaptic terminals in the auditory thalamus arising from the medial superior olive

To make sense of the acoustic environment, the auditory system must segregate, based on their history, streams of sounds arriving at the ear simultaneously. This requires sensitivity to both the probability and the predictability of the different sounds in the stream. That the auditory system is sensitive to the probability of appearance of a sound is well established. Here we presented complex sound sequences of varying predictability to anesthetized mice. Neuronal responses in the mouse inferior colliculus (IC) were recorded using Cambridge NeuroTech and Neuropixels probes. Neurons exhibited

The auditory system must accurately represent sounds over a wide range of sound intensities. Spike-rate adaptation is one proposed mechanism for enhancing discrimination between salient foreground stimuli and background noise through dynamic adjustments in response sensitivity to the unfolding statistical structure of soundscapes. A critical aspect of this form of statistical learning is the interplay between feedforward and feedback pathways forming “listening loops” in the auditory brain. We performed simultaneous recordings of neuronal activity in the inferior colliculus (IC) and the primar

Binaural cues, such as interaural time difference (ITD), are pivotal for sound localization in the auditory system. However, contemporary cochlear implant (CI) processors convey only envelope ITD, neglecting pulse-timing ITD in the temporal fine structure, possibly contributing to CI users' spatial hearing challenges.To assess CI-implanted rats' sensitivity to envelope and pulse timing ITD, we utilized a stimulus involving a 900pps pulse train modulated by a 20 Hz sine envelope, allowing independent variation of PT_ITD and ENV_ITD {-0.1, 0, 0.1 ms}. Neural activity from the inferior colliculus

Bilateral cochlear implants (biCIs) are increasingly used to treat severe hearing loss. However, human biCI users usually exhibit relatively poor binaural cue sensitivity, with interaural time difference (ITD) sensitivity in prelingually deaf patients being particularly poor. To better understand these shortcomings in prosthetic binaural hearing, it would be helpful to know what the “innate” ITD and ILD sensitivity of the neonatally deafened (ND), mature mammalian auditory pathway is like, but this cannot easily be investigated in humans. We therefore recorded neural responses in the inferior