A series of experiments investigated the influence harmonic resolvability on pitch of, and discriminability differences in fundamental frequency (F0) between, frequency-modulated (FM) complexes. Both F0 (62.5 to 250 Hz) spectral region (LOW: 125–625 Hz, MID: 1375–1875 HIGH: 3900–5400 were varied orthogonally. The harmonics that comprised each complex could be summed either sine (0°) phase (SINE) or alternating sine-cosine (0°–90°) (ALT). Stimuli presented a continuous pink-noise background....

Four experiments measured sensitivity (d′) to differences in fundamental frequency (F0) between two simultaneously presented groups of frequency-modulated harmonics. Each group was passed through a bandpass filter either LOW (125–625 Hz), MID (1375–1875 or HIGH (3900–5400 Hz) region. In the first experiments, dynamic F0 difference (ΔF0) created by introducing 180° disparity modulations imposed on groups. Experiment 1 such ΔF0’s with baseline 125 Hz and all components summed sine phase,...

Abstract Animal models of tinnitus allow us to study the relationship between changes in neural activity and percept. Here, guinea pigs were subjected unilateral noise trauma tested behaviourally for 8 weeks later. By comparing animals with those without, all which noise‐exposed, we able identify unique group. Three physiological markers known change following exposure examined: spontaneous firing rates ( SFR s) burst inferior colliculus IC ), evoked auditory brainstem responses ABR s),...

Sensitivity to changes in the interaural time difference (ITD) of 50 msec tones was measured single units inferior colliculus urethane-anesthetized guinea pigs. ITD functions were with 100 repeats and fine spacing (100 points per cycle). The just noticeable (jnd) for determined using receiver operating characteristic (ROC) analysis spike-count distribution at each ITD. jnd became progressively smaller as signal frequency increased from 800 Hz but unmeasurable above 1 kHz. lowest jnds (30...

Responses of low-frequency neurons in the inferior colliculus (IC) anesthetized guinea pigs were studied with binaural beats to assess their mean best interaural phase (BP) a range stimulating frequencies. Phase plots (stimulating frequency vs BP) produced, from which measures characteristic delay (CD) and (CP) for each neuron obtained. The CD provides an estimate difference travel time ear coincidence-detector brainstem. CP indicates mechanism underpinning coincidence detector responses. A...

A computational model of binaural lateralization is described. An accurate the auditory periphery feeds a tonotopically organized multichannel cross-correlation mechanism. Lateralization predictions are made on basis integrated activity across frequency channels. The explicitly weights peaks closer to center preferentially, and effectively information that consistent frequencies more heavily because they have greater impact in integration. This complementary weighted-image Stern et al. [J....

Tinnitus, the perception of sound in absence an external stimulus, is a particularly challenging condition to demonstrate animals. In any animal model, objective confirmation tinnitus essential before we can study neural changes that produce it. A gap detection method, based on prepulse inhibition whole-body startle reflex, often used as behavioural test for rodents. However, guinea pig reflex subject rapid habituation and hence not ideal measure. By contrast, this species Preyer or pinna...

Key points Neurons in the auditory midbrain, inferior colliculus, are selectively sensitive to combinations of sound frequency and level as illustrated by their frequency/level receptive fields. Different field shapes have been described, but we do not know if these represent discrete classes reflecting afferent inputs from individual sources, or a more complex pattern integration. In this study used objective methods analyse fields over 2000 neurons guinea pig colliculus. Subjectively...

Responses to sound stimuli that humans perceive as moving were obtained for 89 neurons in the inferior colliculus (IC) of urethan-anesthetized guinea pigs. Triangular and sinusoidal interaural phase modulation (IPM), which produced dynamically varying disparities (IPDs), was used present with different depths, directions, centers, rates apparent motion. Many appeared sensitive dynamic IPDs, responses at any given IPD depending strongly on IPDs stimulus had just passed through. However, it...

A computer model of a ventral-cochlear-nucleus (VCN) stellate cell with chop-S type response properties is presented and evaluated. The based on simplified spike generation preceded by stage that simulates dendritic low-pass filtering. Input to the in form simulated auditory-nerve spikes produced auditory periphery [Meddis Hewitt, J. Acoust. Soc. Am. 89, 2866–2882 (1991)]. Outputs from stellate-cell are shown qualitatively replicate wide range typical vivo responses. These include: (a)...

Sound localization in humans depends largely on interaural time delay (ITD). The ability to discriminate differences ITD is highly accurate. discrimination (Δ ITD) thresholds, under some circumstances, are as low 10–20 μs. It has been assumed that thresholds this could only be obtained if the outputs from many neurons were combined. Here we use Receiver Operating Characteristic analysis compute neuronal Δ 53 cells inferior colliculus guinea pigs. of single range several hundreds μs down...

Reversible inactivation of the cortex by surface cooling is a powerful method for studying function particular area. Implanted cryoloops have been used to study role individual cortical areas in auditory processing awake-behaving cats. Cryoloops also rodents reversible cortex, but recently there has concern that cryoloop may cool non-cortical structures either directly or via perfusion blood, cooled as it passed close loop. In this we confirmed loop can inactivate most without causing...

The directionality of hair cell stimulation combined with the vibration basilar membrane causes auditory nerve fiber action potentials, in response to low-frequency stimuli, occur at a particular phase stimulus waveform. Because direct mechanical measurements cochlear apex are difficult, such locking has often been used indirectly infer motion. Here, we confirm and extend earlier data from mammals using sine wave over wide range sound levels (up 90 dB pressure level). We recorded...

One of the fundamental questions auditory research is how sounds are segregated because, in natural environments, multiple tend to occur at same time. Concurrent sounds, such as two talkers, physically add together and arrive ear a single input sound wave. The system easily segregates this into coherent perception each sources. A common feature speech communication calls their harmonic structure report we used complexes study role corticofugal pathway processing concurrent sounds. We...

First spike latency has been suggested as a source of the information required for fast discrimination tasks. However, accuracy such mechanism not analyzed rigorously. Here, we investigate utility first encoding about location sound source, based on responses inferior colliculus (IC) neurons in guinea pig to interaural phase differences (IPDs). latencies many cells IC show unimodal tuning stimulus IPD. We investigated simple code that estimates IPD from preferred single cell fired first....

The central nucleus of the inferior colliculus (IC) is organized into a series fibro-dendritic laminae, orthogonal to tonotopic progression. Many neurons have their dendrites confined one lamina while others that cross over number laminae. Here, we used juxtacellular labeling in urethane anesthetized guinea pigs visualize cells with biocytin and analyzed response properties, order try link structure function. Out sample 38 filled cells, 15 had within laminae 13 were also able reconstruct...

We report the spectrotemporal response properties of single units in primary (A1) and dorsocaudal (DC) fields, ventrorostral belt urethane-anaesthetised guinea pig auditory cortex. Using reverse correlation analysis, receptive fields (STRFs) were constructed subsequently classified according to a novel qualitative scheme that was based on duration bandwidth excitatory inhibitory regions within STRF. The STRFs both A1 DC showed either broad-band (> or = 1 octave) narrow-band (< occurring...

The binaural masking level difference (BMLD) is a phenomenon whereby signal that identical at each ear (S0), masked by noise (N0), can be made 12–15 dB more detectable inverting the waveform of either tone or one (Sπ, Nπ). Single-cell responses to BMLD stimuli were measured in primary auditory cortex urethane-anesthetized guinea pigs. Firing rate was as function 500 Hz pure low-passed white noise. Responses similar those reported inferior colliculus. At low levels, response dominated masker....