Monaural and binaural inhibition underlying duration-tuned neurons in the inferior colliculus.

Duration-tuned neurons (DTNs) in the mammalian inferior colliculus (IC) arise from a combination of excitatory and inhibitory synaptic inputs. Previous research has shown that the inhibition responsible for creating DTNs has a shorter latency than that of excitation and lasts longer than the stimulus duration. We used monotic and dichotic paired tone stimulation and recorded responses of DTNs from the IC of the bat to assess the relative contributions of each ear in forming duration-tuned circuits.

Response properties and location of neurons selective for sinusoidal frequency modulations in the inferior colliculus of the big brown bat.

Most animal vocalizations, including echolocation signals used by bats, contain frequency-modulated (FM) components. Previous studies have described a class of neurons in the inferior colliculus (IC) of the big brown bat that respond exclusively to sinusoidally frequency modulated (SFM) signals and fail to respond to pure tones, noise, amplitude-modulated tones, or single FM sweeps. The aims of this study were to further characterize these neurons' response properties and to determine whether they are localized within a specific area of the IC.

Duration selectivity of neurons in the inferior colliculus of the big brown bat: tolerance to changes in sound level.

At and above the level of the inferior colliculus (IC), some neurons respond maximally to a limited range of sound durations, with little or no excitatory response to durations outside of this range. Such neurons have been termed "duration tuned" or "duration selective." In this study we examined the effects of varying signal amplitude on best duration, width of tuning, and first spike latency of duration tuned neurons in the IC of the big brown bat, Eptesicus fuscus.

Processing of modulated sounds in the zebra finch auditory midbrain: responses to noise, frequency sweeps, and sinusoidal amplitude modulations.

The avian auditory midbrain nucleus, the mesencephalicus lateralis, dorsalis (MLd), is the first auditory processing stage in which multiple parallel inputs converge, and it provides the input to the auditory thalamus. We studied the responses of single MLd neurons to four types of modulated sounds: 1) white noise; 2) band-limited noise; 3) frequency modulated (FM) sweeps, and 4) sinusoidally amplitude-modulated tones (SAM) in adult male zebra finches. Responses were compared with the responses of the same neurons to pure tones in terms of temporal response patterns, thresholds, characteristic frequencies, frequency tuning bandwidths, tuning sharpness, and spike rate/intensity relationships.

Response properties of single neurons in the zebra finch auditory midbrain: response patterns, frequency coding, intensity coding, and spike latencies.

The avian mesencephalicus lateralis, dorsalis (MLd) is the auditory midbrain nucleus in which multiple parallel inputs from lower brain stem converge and through which most auditory information passes to reach the forebrain. Auditory processing in the MLd has not been investigated in songbirds. We studied the tuning properties of single MLd neurons in adult male zebra finches.

Expression of the Kv1.1 ion channel subunit in the auditory brainstem of the big brown bat, Eptesicus fuscus.

Voltage-gated potassium channels play an important role in shaping membrane properties that underlie neurons' discharge patterns and the ways in which they transform their input. In the auditory system, low threshold potassium currents such as those created by Kv1.1 subunits contribute to precise phaselocking and to transient onset responses that provide time markers for temporal features of sounds.

Temporal masking reveals properties of sound-evoked inhibition in duration-tuned neurons of the inferior colliculus.

The inferior colliculus (IC) is the first place in the central auditory pathway where duration-selective neurons are found. Previous neuropharmacological and electrophysiological studies have shown that they are created there and have led to a conceptual model in which excitatory and inhibitory inputs are offset in time so that the cell fires only when sound duration is such that onset- and offset-evoked excitation coincide; the response is suppressed by inhibition at other durations. We tested predictions from the model using paired tone stimulation and extracellular recording in the IC of the big brown bat, Eptesicus fuscus.

Auditory Pontine Grey: Connections and Response Properties in the Horseshoe Bat.

This study investigates the role of the pontine grey as a link between the auditory system and the cerebellum in the bat, Rhinolophus rouxi. We recorded response properties of single neurons in the pontine grey and, in the same preparation, injected wheat germ agglutinin - horseradish peroxidase (WGA - HRP) in areas responsive to sound. Thus the functional evidence was correlated with retrograde and anterograde transport.