Everyday environments often contain multiple concurrent sound sources that fluctuate over time. Normally hearing listeners can benefit from high signal-to-noise ratios (SNRs) in energetic dips of temporally fluctuating background sound, a phenomenon called dip-listening. Specialized mechanisms of dip-listening exist across the entire auditory pathway.
View Article and Find Full Text PDFDuring development, early-life stress (ELS) impairs cognition, learning, and emotional regulation, in part by disrupting neural circuitry in regions underlying these higher-order functions. In addition, our recent work indicates that ELS also alters simple sensory perception: ELS impaired auditory perception and neural encoding of short gaps in sounds, which are essential for vocal communication. The combination of higher-order and basic sensory disruption suggests that ELS is likely to affect both the perception and interpretation of communication signals.
View Article and Find Full Text PDFDuring developmental critical periods (CPs), early-life stress (ELS) induces cognitive deficits and alters neural circuitry in regions underlying learning, memory, and attention. Mechanisms underlying critical period plasticity are shared by sensory cortices and these higher neural regions, suggesting that sensory processing may also be vulnerable to ELS. In particular, the perception and auditory cortical (ACx) encoding of temporally-varying sounds both mature gradually, even into adolescence, providing an extended postnatal window of susceptibility.
View Article and Find Full Text PDFThe startle reflex (SR), a robust, motor response elicited by an intense auditory, visual, or somatosensory stimulus has been widely used as a tool to assess psychophysiology in humans and animals for almost a century in diverse fields such as schizophrenia, bipolar disorder, hearing loss, and tinnitus. Previously, SR waveforms have been ignored, or assessed with basic statistical techniques and/or simple template matching paradigms. This has led to considerable variability in SR studies from different laboratories, and species.
View Article and Find Full Text PDFAn increasing number of studies show that listeners often have difficulty hearing in situations with background noise, despite normal tuning curves in quiet. One potential source of this difficulty could be sensorineural changes in the auditory periphery (the ear). Signal in noise detection deficits also arise in animals raised with developmental conductive hearing loss (CHL), a manipulation that induces acoustic attenuation to model how sound deprivation changes the central auditory system.
View Article and Find Full Text PDFJ Assoc Res Otolaryngol
June 2020
The ability to detect a silent gap within a sound is critical for accurate speech perception, and gap detection has been shown to have an extended developmental trajectory. In certain conditions, the detectability of the gap decreases as the gap is placed closer to the beginning of the signal. Early in development, the detection of gaps shortly after signal onset may be especially difficult due to immaturities in the encoding and perception of rapidly changing sounds.
View Article and Find Full Text PDFJ Acoust Soc Am
August 2018
The perception of temporally changing auditory signals has a gradual developmental trajectory. Speech is a time-varying signal, and slow changes in speech (filtered at 0-4 Hz) are preferentially processed by the right hemisphere, while the left extracts faster changes (filtered at 22-40 Hz). This work examined the ability of 8- to 19-year-olds to both perceive and learn to perceive filtered speech presented diotically for each filter type (low vs high) and dichotically for preferred or non-preferred laterality.
View Article and Find Full Text PDFSpeech perception relies on the accurate resolution of brief, successive sounds that change rapidly over time. Deficits in the perception of such sounds, indicated by a reduced ability to detect signals during auditory backward masking, strongly relate to language processing difficulties in children. Backward masking during normal development has a longer maturational trajectory than many other auditory percepts, implicating the involvement of central auditory neural mechanisms with protracted developmental time courses.
View Article and Find Full Text PDFIn childhood, partial hearing loss can produce prolonged deficits in speech perception and temporal processing. However, early therapeutic interventions targeting temporal processing may improve later speech-related outcomes. Gap detection is a measure of auditory temporal resolution that relies on the auditory cortex (ACx), and early auditory deprivation alters intrinsic and synaptic properties in the ACx.
View Article and Find Full Text PDFPerceptual learning (training-induced performance improvement) can be elicited by task-irrelevant stimulus exposure in humans. In contrast, task-irrelevant stimulus exposure in animals typically disrupts perception in juveniles while causing little to no effect in adults. This may be due to the extent of exposure, which is brief in humans while chronic in animals.
View Article and Find Full Text PDFBackground: The acoustic startle reflex (ASR) is a rapid, involuntary movement to sound, found in many species. The ASR can be modulated by external stimuli and internal state, making it a useful tool in many disciplines. ASR data collection and interpretation varies greatly across laboratories making comparisons a challenge.
View Article and Find Full Text PDFListeners with hearing loss have difficulty processing sounds in noisy environments. This is most noticeable for speech perception, but is reflected in a basic auditory processing task: detecting a tonal signal in a noise background, i.e.
View Article and Find Full Text PDFThe acoustic rearing environment can alter central auditory coding properties, yet altered neural coding is seldom linked with specific deficits to adult perceptual skills. To test whether developmental hearing loss resulted in comparable changes to perception and sensory coding, we examined behavioral and neural detection thresholds for sinusoidally amplitude modulated (sAM) stimuli. Behavioral sAM detection thresholds for slow (5 Hz) modulations were significantly worse for animals reared with bilateral conductive hearing loss (CHL), as compared to controls.
View Article and Find Full Text PDFThe relationship between behavioral and neural performance has been explored in adult animals, but rarely during the developmental period when perceptual abilities emerge. We used these naturally occurring changes in auditory perception to evaluate underlying encoding mechanisms. Performance of juvenile and adult gerbils on an amplitude modulation (AM) detection task was compared with response properties from auditory cortex of age-matched animals.
View Article and Find Full Text PDFDuring development, detection for many percepts matures gradually. This provides a natural system in which to investigate the neural mechanisms underlying performance differences: those aspects of neural activity that mature in conjunction with behavioral performance are more likely to subserve detection. In principle, the limitations on performance could be attributable to either immature sensory encoding mechanisms or an immature decoding of an already-mature sensory representation.
View Article and Find Full Text PDFStimuli from a broad spectrum of sensory modalities, including visual, auditory, thermal, and chemical, can elicit walking responses in animals, reflecting neural activity in sensorimotor pathways. We have developed an integrated walking measurement system with sub-millisecond temporal accuracy capable of detecting position changes on the order of 100 microm. This tracking system provides the experimenter with a means by which to map out the response spectrum of a tethered animal to any number of sensory inputs on time scales relevant to propagation in the nervous system.
View Article and Find Full Text PDFStimulus-dependent synaptic interactions underlying selective sensory representations in neural circuits specialized for sensory processing and sensorimotor integration remain poorly understood. The songbird telencephalic nucleus HVC is a sensorimotor area essential to learned vocal control with one projection neuron (PN) type (HVC(RA)) innervating a song premotor pathway, another PN (HVC(X)) innervating a basal ganglia pathway essential to vocal plasticity, and interneurons (HVC(Int)). Playback of the bird's own song (BOS), but not other songs, evokes action potential bursts from both PNs, but HVC(RA) and HVC(X) display distinct BOS-evoked subthreshold responses.
View Article and Find Full Text PDFSpeech and birdsong require auditory feedback for their development and maintenance, necessitating precise auditory encoding of vocal sounds. In songbirds, the telencephalic song premotor nucleus HVC contains neurons that respond highly selectively to the bird's own song (BOS), a property distinguishing HVC from its auditory afferents. We examined the contribution of inhibitory and excitatory synaptic inputs to BOS-evoked firing in those HVC neurons innervating a pathway essential for audition-dependent vocal plasticity.
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