Biology subjects

Bajo, V. M.

Publications and source records attributed to Bajo, V. M..

5 recordsLinked to original sources

bioRxiv2026

Sleep immediately after noise overexposure worsens tinnitus in mice

Subjective tinnitus is the most common auditory phantom perception in the absence of an acoustic stimulus yet there is no cure nor widely effective treatment to date. Previously, we suggested that sleep may contribute to tinnitus development after a triggering event, such as noise overexposure (NOE). Here, we investigated the effect of natural sleep on tinnitus development following NOE in mice. One group of mice was kept awake for 6 hours immediately after NOE, whereas a control group could sleep ad libitum. Tinnitus and hearing loss were assessed before and after NOE by determining gap prepulse inhibition of the acoustic startle reflex (GPIAS) and by recording auditory brainstem responses (ABRs). Only mice that were allowed to sleep in the first six hours after NOE developed a significant change in the GPIAS ratio one week after NOE, indicative of tinnitus. Habituation to the startle stimulus was largely similar between both groups, except that at eight weeks after NOE, when GPIAS ratio had returned to baseline levels in both groups, the sleep deprived group showed less habituation to the startle stimulus. Notably, animals in neither group showed significantly elevated ABR thresholds after NOE, yet the control group showed signs of elevated evoked activity in the auditory brainstem one week after NOE. These findings demonstrate that sleep early after noise overexposure may amplify subsequent tinnitus development. Our results suggest that sleep represents a temporal window that may be harnessed for potential modulation or mitigation of noise-induced hearing loss and tinnitus-related impairments.

neuroscience↗

bioRxiv2025

Auditory midbrain encodes training-induced plasticity in soundlocalization behavior

The ability of the brain to learn from experience and to compensate for changes in sensory inputs is usually associated with plasticity in the cerebral cortex. Descending corticofugal pathways have been implicated in learning but there is limited evidence that subcortical processing is shaped by training. We show that sound-source location can be accurately decoded from neuronal populations recorded in the inferior colliculus of one or both hemispheres while ferrets perform a localization task. Furthermore, changes in neural decoding performance matched improvements in localization accuracy of individual animals when ferrets were trained to adapt to abnormal spatial cues resulting from reversible occlusion of one ear. These findings demonstrate that the activity patterns of populations of neurons in the inferior colliculus can account for sound localization behavior in different hearing contexts, and that training-dependent plasticity in the auditory midbrain may support spatial learning following monaural hearing loss.

neuroscience↗

bioRxiv2024

Cortical evoked activity is modulated by the sleep state in a ferret model of tinnitus. A case study.

Subjective tinnitus is a phantom auditory perception in the absence of an actual acoustic stimulus. It affects 15% of the global population and can be associated with disturbed sleep, poor mental health and quality of life. To date, there is no effective treatment for tinnitus. We used adult ferrets exposed to mild noise trauma as an animal model of tinnitus. We assessed the phantom percept using two operant paradigms sensitive to tinnitus, silent gap detection and silence detection, before and up to six months after the mild acoustic trauma. The integrity of the auditory brainstem was assessed over the same period using auditory brainstem response recordings. Following noise overexposure, ferrets developed lasting, frequency-specific impairments in operant behaviour and evoked brainstem activity. To explore the interaction between sleep and tinnitus, in addition to tracking the behavioural markers of noise-induced tinnitus and hearing impairment after noise overexposure, we evaluated sleep-wake architecture and spontaneous and auditory-evoked EEG activity across vigilance states. Behavioural performance and auditory-evoked activity measurements after noise overexposure suggested distinct degrees of tinnitus and hearing impairment between individuals. Animals that developed signs of tinnitus consistently developed sleep impairments, suggesting a link between the emergence of noise-induced tinnitus and sleep disruption. However, neural markers of tinnitus were reduced during sleep, suggesting that sleep may transiently mitigate tinnitus. These results reveal the importance of sleep-wake states in tinnitus and suggest that understanding the neurophysiological link between sleep and tinnitus may provide a new angle for research into the causes of phantom percepts and inform future treatments.

neuroscience↗

bioRxiv2020

Neural circuits for somatosensory control of auditory thalamocortical processing

Integration of information across the senses is critical for perception and is a common property of neurons in the cerebral cortex, where it is thought to arise primarily from corticocortical connections. Much less is known about the role of subcortical circuits in shaping the multisensory properties of cortical neurons. We show that stimulation of the whiskers causes widespread suppression of sound-evoked activity in mouse primary auditory cortex (A1). This suppression depends on the primary somatosensory cortex (S1), and is implemented through a descending circuit that links S1, via the auditory midbrain, with thalamic neurons that project to A1. Furthermore, a direct pathway from S1 has a facilitatory effect on auditory responses in higher-order thalamic nuclei that project to other brain areas. Crossmodal corticofugal projections to the auditory midbrain and thalamus therefore play a pivotal role in integrating multisensory signals and in enabling communication between different sensory cortical areas.

neuroscience↗

bioRxiv2019

Auditory contrast gain control predicts perceptual performance and is not dependent on cortical activity

Neural adaptation enables sensory information to be represented optimally in the brain despite large fluctuations over time in the statistics of the environment. Auditory contrast gain control represents an important example, which is thought to arise primarily from cortical processing. We find, however, that neurons in both the auditory thalamus and midbrain of mice show robust contrast gain control, and that this is implemented independently of cortical activity. Although neurons at each level exhibit contrast gain control to similar degrees, adaptation time constants become longer at later stages of the processing hierarchy, resulting in progressively more stable representations. We also show that auditory discrimination thresholds in human listeners compensate for changes in contrast, and that the strength of this perceptual adaptation can be predicted from physiological measurements. Contrast adaptation is therefore a robust property of both the subcortical and cortical auditory system and accounts for the short-term adaptability of perceptual judgments.

neuroscience↗