Gap encoding by parvalbumin-expressing interneurons in auditory cortex.

Synaptic inhibition shapes the temporal processing of sounds in auditory cortex, but the contribution of specific inhibitory cell types to temporal processing remains unclear. We recorded from parvalbumin-expressing (PV+) interneurons in auditory cortex to determine how they encode gaps in noise, a model of temporal processing more generally. We found that PV+ cells had stronger and more prevalent on-responses, off-responses, and postresponse suppression compared with presumed pyramidal cells.

Spike timing precision changes with spike rate adaptation in the owl's auditory space map.

Spike rate adaptation (SRA) is a continuing change of responsiveness to ongoing stimuli, which is ubiquitous across species and levels of sensory systems. Under SRA, auditory responses to constant stimuli change over time, relaxing toward a long-term rate often over multiple timescales. With more variable stimuli, SRA causes the dependence of spike rate on sound pressure level to shift toward the mean level of recent stimulus history.

[Infection related fertility disorders in Swiss pig breeding farms at the end of the postweaning multisystemic wasting syndrome (PMWS) epizooty].

Porcine Circovirus type 2 (PCV2) is able to induce reproductive failures. 286 fetuses from 113 sows of 59 farms with increased reproductive disorders which included abortions, mummies, stillborn and weak born piglets were studied six years after the beginning of the epizooty of postweaning multisystemic wasting syndrome (PMWS) in Switzerland. 14 % of the cases were bacterial infections based on histological signs of inflammation and pathogen isolation.

Cuffed endotracheal tubes in children reduce sevoflurane and medical gas consumption and related costs.

Background: This study aims to evaluate sevoflurane and anaesthetic gas consumption using uncuffed vs. cuffed endotracheal tubes (ETT) in paediatric surgical patients.

Methods: Uncuffed or cuffed ETT were used in paediatric patients (newborn to 5 years) undergoing elective surgery in a randomized order.

Spontaneous myometrial contractility in cows suffering from endometritis-Influence of localisation, smooth muscle layer and cycle phase. An in vitro study.

Contractility of the healthy bovine myometrium depends on the reproductive state. Furthermore, contractility is influenced by localisation and the direction of smooth muscle strips. However, little is known about the contractile behaviour of the uterus when affected by endometritis.

Object localization in cluttered acoustical environments.

In nature, sounds from objects of interest arrive at the ears accompanied by sound waves from other actively emitting objects and by reflections off of nearby surfaces. Despite the fact that all of these waveforms sum at the eardrums, humans with normal hearing effortlessly segregate one sound source from another. Our laboratory is investigating the neural basis of this perceptual feat, often called the "cocktail party effect", using the barn owl as an animal model.

Localization and identification of concurrent sounds in the owl's auditory space map.

In nature, sounds from multiple sources sum at the eardrums, generating complex cues for sound localization and identification. In this clutter, the auditory system must determine "what is where." We examined this process in the auditory space map of the barn owl's (Tyto alba) inferior colliculus using two spatially separated sources simultaneously emitting uncorrelated noise bursts, which were uniquely identified by different frequencies of sinusoidal amplitude modulation.

The synthesis and use of the owl's auditory space map.

The barn owl ( Tyto alba) is capable of capturing prey by passive hearing alone, guided by a topographic map of auditory space in the external nucleus of its inferior colliculus. The neurons of this auditory space map have discrete spatial receptive fields that result from the computation of interaural differences in the level (ILD) and time-of-arrival (ITD) of sounds. Below we review the synthesis of the spatial receptive fields from the frequency-specific ITDs and ILDs to which the neurons are tuned, concentrating on recent studies exploiting virtual auditory space techniques to analyze the contribution of ILD.

Long-term performance summary for the Boot Wetland Treatment System.

The Boot WTS is a 46.5-ha, hydrologically altered cypress-gum wetland in Polk County, Florida. Poinciana Wastewater Treatment Plant No.

Representation of temporal features of complex sounds by the discharge patterns of neurons in the owl's inferior colliculus.

The spiking pattern evoked in cells of the owl's inferior colliculus by repeated presentation of the same broadband noise was found to be highly reproducible and synchronized with the temporal features of the noise stimulus. The pattern remained largely unchanged when the stimulus was presented from spatial loci that evoke similar average firing rates. To better understand this patterning, we computed the pre-event stimulus ensemble (PESE)-the average of the stimuli that preceded each spike.

Head-related transfer functions of the Rhesus monkey.

Head-related transfer functions (HRTFs) are direction-specific acoustic filters formed by the head, the pinnae and the ear canals. They can be used to assess acoustical cues available for sound localization and to construct virtual auditory environments. We measured the HRTFs of three anesthetized Rhesus monkeys (Macaca mulatta) from 591 locations in the frontal hemisphere ranging from -90 degrees (left) to 90 degrees (right) in azimuth and -60 degrees (down) to 90 degrees (up) in elevation for frequencies between 0.

Head-related transfer functions of the barn owl: measurement and neural responses.

Sounds arriving at the eardrum are filtered by the external ear and associated structures in a frequency and direction specific manner. When convolved with the appropriate filters and presented to human listeners through headphones, broadband noises can be precisely localized to the corresponding position outside of the head (reviewed in Blauert, 1997). Such a 'virtual auditory space' can be a potentially powerful tool for neurophysiological and behavioral work in other species as well.

Submicrosecond pacemaker precision is behaviorally modulated: the gymnotiform electromotor pathway.

What are the limits and modulators of neural precision? We address this question in the most regular biological oscillator known, the electric organ command nucleus in the brainstem of wave-type gymnotiform fish. These fish produce an oscillating electric field, the electric organ discharge (EOD), used in electrolocation and communication. We show here that the EOD precision, measured by the coefficient of variation (CV = SD/mean period) is as low as 2 x 10(-4) in five species representing three families that range widely in species and individual mean EOD frequencies (70-1,250 Hz).

Motor control of the jamming avoidance response of Apteronotus leptorhynchus: evolutionary changes of a behavior and its neuronal substrates.

The two closely related gymnotiform fishes, Apteronotus and Eigenmannia, share many similar communication and electrolocation behaviors that require modulation of the frequency of their electric organ discharges. The premotor linkages between their electrosensory system and their medullary pacemaker nucleus, which controls the repetition rate of their electric organ discharges, appear to function differently, however. In the context of the jamming avoidance response, Eigenmannia can raise or lower its electric organ discharge frequency from its resting level.

Binaural cross-correlation predicts the responses of neurons in the owl's auditory space map under conditions simulating summing localization.

Summing localization describes the perceptions of human listeners to two identical sounds from different locations presented with delays of 0-1 msec. Usually a single source is perceived to be located between the two actual source locations, biased toward the earlier source. We studied neuronal responses within the space map of the barn owl to sounds presented with this same paradigm.

Responses to simulated echoes by neurons in the barn owl's auditory space map.

The natural acoustical environment contains many reflective surfaces that give rise to echoes, complicating the task of sound localization and identification. The barn owl (Tyto alba), as a nocturnal predator, relies heavily on its auditory system for tracking and capturing prey in this highly echoic environment. The external nucleus of the owl's inferior colliculus (ICx) contains a retina-like map of space composed of "space-specific" auditory neurons that have spatially limited receptive fields.

An anatomical substrate for the inhibitory gradient in the VLVp of the owl.

The interaural difference in the level of sounds is an important cue for the localization of the sound's source. In the barn owl, a keen auditory predator, this binaural cue is first computed in the nucleus ventralis lemnisci laterale, pars posterior (VLVp), a cell group found within the fibers of the lateral lemniscus. Its neurons are excited by inputs from the contralateral ear and inhibited by inputs to the ipsilateral ear and are therefore sensitive indicators of interaural level difference.

Representation of multiple sound sources in the owl's auditory space map.

The barn owl's inferior colliculus contains a retina-like map of space on which a sound generates a focus of activity whose position corresponds to the location of the sound source. When there is more than one source of sound, the sound waves sum and may generate spurious binaural cues that degrade the auditory image. We investigated the signal conditions under which neurons in the owl's auditory space map are able to resolve two simultaneously active sound sources.

Simulated motion enhances neuronal selectivity for a sound localization cue in background noise.

In nature, sound sources move and signals are accompanied by background noise. Noting that motion helps the perception of visual stimuli, we tested whether motion similarly facilitates the detection of acoustic targets, at the neuronal level. Auditory neurons in the central nucleus of the barn owl's inferior colliculus (ICc), due to their selectivity for interaural phase difference (delta phi), are sharply tuned to the azimuth of sound sources and are arrayed to form a topographic map of delta phi.

Commissural connections mediate inhibition for the computation of interaural level difference in the barn owl.

In the barn owl (Tyto alba), the posterior nucleus of the ventral lateral lemniscus (VLVp) is the first site of binaural convergence in the pathway that processes interaural level difference (ILD), an important sound-localization cue. The neurons of VLVp are sensitive to ILD because of an excitatory input from the contralateral ear and an inhibitory input from the ipsilateral ear. A previously described projection from the contralateral cochlear nucleus, can account for the excitation.

The control of pacemaker modulations for social communication in the weakly electric fish Sternopygus.

Nearly sinusoidal electric organ discharges (EODs) of the weakly electric fish Sternopygus, occur at a regular rate within a range from 50 to 200 Hz and are commanded by a medullary pacemaker nucleus (Pn). During courtship and aggression, the rate of EODs is modulated as smooth EOD-frequency rises or brief EOD-interruptions (Hopkins 1974b). The present study examines the control of such modulations.

Structure and function of neurons in the complex of the nucleus electrosensorius of the gymnotiform fish Eigenmannia: detection and processing of electric signals in social communication.

The complex of the diencephalic nucleus electrosensorius (nE) provides an interface between the electrosensory processing performed by the torus semicircularis and the control of specific behavioral responses. The rostral portion of the nE comprises two subdivisions that differ in the response properties and projection patterns of their neurons. First, the nEb, which contains neurons that are driven almost exclusively by beat patterns generated by the interference of electric organ discharges (EODs) of similar frequencies.

Spontaneous discharge of afferents in a neuroma reflects original receptor tuning.

Injured afferent axons trapped in chronic nerve-end neuromas frequently generate spontaneous discharge. We asked whether the patterns of discharge originating at such sites of ectopic electrogenesis bear a consistent relationship to the patterns of discharge characteristic of the corresponding intact afferent types before injury. Nerve-end neuromas were created in electrosensory lateral line nerves in 3 species of weakly electric Gymnotiform fish.