Time-varying envelopes are a common feature of acoustic communication signals like human speech and induce variety percepts in listeners. We studied the responses 109 single neurons inferior colliculus (IC) anesthetized Mongolian gerbil to contralaterally presented sinusoidally amplitude-modulated (SAM) tones with wide range parameters. Modulation transfer functions (MTFs) based on average spike rate (rMTFs) showed regions enhancement suppression, where rates increased or decreased...

1. Several studies of auditory cortex have examined the competitive inhibition that can occur when appropriate sounds are presented to each ear. However, most cortical neurons also show both excitation and in response presentation stimuli at one ear alone. The extent such has not been described. Forward masking, which a variable masking stimulus was followed by fixed probe (within excitatory area), used examine monaural for primary anesthetized cats (barbiturate or barbiturate-ketamine)....

1. The discharges of 632 units were isolated extracellularly during 42 penetrations the central nucleus inferior colliculus (ICC) in 21 adult cats lightly anesthetized with pentobarbital and ketamine. Microelectrode directed from caudal to rostral through ICC, parallel Horsley-Clarke (H-C) horizontal sagittal planes. 2. threshold best frequency (BF) binaural response properties examined for each unit, aim elucidating organization these discharge characteristics within ICC. 3. Binaural unit...

Previous physiological studies have identified a tonotopically organized primary auditory cortical field (AI) in the rat. Some of this prior research suggests that rat, like other mammals, may additional fields surrounding AI. We, therefore, recorded Sprague-Dawley rat extracellular responses single neurons throughout AI, and continued posteriorly to verify existence posterior (P) compare neuronal properties two regions. Acoustic stimuli, including tones, bandpass noise, broadband temporally...

1. We assessed mechanisms of binaural interaction underlying detection interaural phase disparity (IPD) by recording single-unit responses in the superior olivary complex (SOC) anesthetized gerbil (Meriones unguiculatus). Binaural were obtained from 58 IPD-sensitive single units, 44 which histologically localized. Monaural also for 52 units. Additionally, recorded 16 units (best frequency < 2.4 kHz) lateral SOC that excited ipsilateral stimulation and inhibited contralateral (EI), none...

The neural representation of meaningful stimulus features is thought to rely on precise discharge characteristics the auditory cortex. Precisely timed onset spikes putatively carry majority stimulus-related information in cortical neurons but make a small contribution midbrain. Because these conclusions derive primarily from anesthetized preparations, we reexamined temporal coding properties single awake gerbil inferior colliculus (IC) and compared them with primary cortex (AI)....

In the ascending auditory pathway, context in which a particular stimulus occurs can influence character of responses that encode it. Here we demonstrate cortical representation binaural cue to sound source location is profoundly context-dependent: spike rates elicited by 0° interaural phase disparity (IPD) were very different when preceded 90° versus −90° IPD. The changes firing rate associated with equivalent stimuli occurring contexts are comparable discharge establish tuning itself....

Monaural excitatory responses of 181 single units in the central nucleus inferior colliculus 15 anesthetized gerbils (Meriones unguiculatus) were examined quantitatively. Pure-tone stimuli presented monaurally through sealed, calibrated sound-delivery systems. Most excited only by contralateral stimulation (EO); 23% bilaterally excitable (EE). The threshold frequency tuning curves for EE significantly broader than those produced ipsilateral and EO units. at which was lowest (best frequency),...

Monaural responses of single units isolated in the inferior colliculus adult gerbils that have developed postnatally with one cochlea were compared monaural recorded animals both cochleas. One 2-day-old was ablated, and at approximately 6 mo age, excitatory to stimulation nonoperated ear ipsilateral colliculus. These quantitatively evoked by contralateral normal gerbils. Responses subjected 2 days age ablation are significantly different from In several respects they very similar...

The detection of a sensory stimulus arises from significant change in neural activity, but neuron's response is rarely identical to successive presentations the same stimulus. Large trial-to-trial variability would limit central nervous system's ability reliably detect stimulus, presumably affecting perceptual performance. However, if were decrease while firing rate remained constant, then sensitivity could improve. Here, we asked whether engagement an auditory task can modulate variability,...

Abstract The ability of an animal to localize a sound in space requires the precise innervation superior olivary complex by ventral cochlear nuclei on each side lower brainstem. This pattern could require immutable recognition appropriate targets afferent processes arising from these nuclei. possibility was investigated destroying one cochlea gerbil pups ( Meriones unguiculatus ) second postnatal day and assessing projections nucleus (VCN) unablated during subsequent 2 weeks after animals...

1. Motion of sound sources results in temporal variation the binaural cues for localization. We evaluated influence virtual motion on neural tuning to one these cues, interaural phase disparity (IPD). Responses dichotic stimuli were recorded from single units inferior colliculus anesthetized cat and gerbil (Meriones unguiculatus). Static IPDs generated by presenting tone pairs with a constant offset maintained duration stimulus. Time-varying simultaneously pure ear phase-modulated other ear....

In many animals, the information most important for processing communication sounds, including speech, consists of temporal envelope cues below approximately 20 Hz. Physiological studies, however, have typically emphasized upper limits modulation encoding. Responses to sinusoidal AM (SAM) are generally summarized by transfer functions (MTFs), which emphasize tuning frequency rather than representation instantaneous stimulus amplitude. Unfortunately, MTFs fail capture but nonlinear aspects...

A laterally located sound source stimulates the two ears at slightly different times, generating interaural phase disparities (IPDs) that are used for localization. Under natural conditions, such cues likely to be constantly changing, or dynamic. In inferior colliculus of gerbils and cats, nonlinearities in coding dynamic demonstrated. Responses ecologically realistic more reflective change IPD than absolute IPDs over which occurs. This observation is inconsistent with established view...

The central auditory system could encode information about the location of a high-frequency sound source by comparing pressure levels at ears. Two potential computations are interaural intensity difference (IID) and average binaural (ABI). In this study nucleus inferior colliculus (ICC) anesthetized gerbil, we demonstrate that responses 85% 97 single units in our sample were jointly influenced IID ABI. For given ABI, discharge rate most is sigmoidal function IID, peak rates occur IIDs...

The anatomy and connectivity of the primate auditory cortex has been modeled as a core region receiving direct thalamic input surrounded by belt secondary fields. contains multiple tonotopic fields (including primary cortex, AI, rostral field, R), but available data only partially address degree to which those are functionally distinct. This report, based on single-unit recordings across four hemispheres in awake macaques, argues that functional organization is best understood terms temporal...

Transformation of binaural response properties in the ascending auditory pathway: influence time-varying interaural phase disparity. J. Neurophysiol. 80: 3062-3076, 1998. Previous studies demonstrated that tuning inferior colliculus (IC) neurons to disparity (IPD) is often profoundly influenced by temporal variation IPD, which simulates cue produced a moving sound source. To determine whether sensitivity simulated motion arises IC or at an earlier stage processing we compared responses with...

1. The posterior field (field P) of the cat's auditory cortex contains a higher proportion neurons whose response/level functions for characteristic frequency (CF) tones are nonmonotonic than does primary (AI). general purpose present study is to assess whether P generated by same mechanisms as those cells in AI. All data came from single cortices barbiturate-anesthetized cats, which we presented tonal stimuli through sealed, calibrated stimulating systems. 2. We obtained quantitative 123...

Abstract The postnatal development of the projection from ventral cochlear nucleus to principal nuclei in superior olivary complex gerbil ( Meriones unguiculatus ) was studied an age‐graded series pups ranging 0 18 days old. Small crystals 1, 1′‐dioctadecyl3, 3, 3′, 3′‐tetramethylindocarbocyanine perchlorate (DiI) were inserted into aldehyde‐fixed brains, and labeled projections examined with epifluorescence microscopy. Selected sections photooxidized a solution diaminobenzidine subsequently...

1. Single-neuron responses were recorded in high-frequency regions of primary auditory cortex (AI) anesthetized cats. Best-frequency tone pips presented to each ear independently via sealed stimulus delivery systems, and the sound pressure level (SPL) at was manipulated. Each neuron studied with many dichotic combinations SPL, chosen incorporate a broad range two synthetic interaural variables, difference (ILD) average binaural (ABL). This paper illustrates common forms SPL selectivity...

Primary auditory cortex plays a crucial role in spatially directed behavior, but little is known about the effect of behavioral state on neural representation spatial cues. Macaques were trained to discriminate binaural cues sound localization, eventually allowing measurement thresholds comparable human hearing. During behavior and passive listening, single units low-frequency showed robust consistent tuning interaural phase difference (IPD). In most neurons, exerted an peak discharge rate...

Neurons in the medial superior olive (MSO) are tuned to interaural time difference (ITD) of sound arriving at two ears. MSO neurons evoke a strongest response their best delay (BD), which internal between bilateral inputs matches external ITD. We performed extracellular recordings olivary complex anesthetized gerbil and found majority single units localized exhibit BDs that shifted with tone frequency. The relation phase frequency revealed nonlinearities some others linear relations...