When modeling auditory responses to environmental sounds, results are satisfactory if both training and testing are restricted to datasets of one type of sound. To predict 'cross-sound' responses (i.e., to predict the response to one type of sound e.g., rat Eating sound, after training with another type of sound e.g., rat Drinking sound), performance is typically poor. Here we implemented a novel approach to improve such cross-sound modeling (single unit datasets were collected at the auditory midbrain of anesthetized rats). The method had two key features: (a) population responses (e.g., average of 32 units) instead of responses of individual units were analyzed; and (b) the long sound segment was first divided into short segments (single sound-bouts), their similarity was then computed over a new metric involving the response (called Stimulus Response Model map or SRM map), and finally similar sound-bouts (regardless of sound type) and their associated responses (peri-stimulus time histograms, PSTHs) were modelled. Specifically, a committee machine model (artificial neural networks with 20 stratified spectral inputs) was trained with datasets from one sound type before predicting PSTH responses to another sound type. Model performance was markedly improved up to 92%. Results also suggested the involvement of different neural mechanisms in generating the early and late responses to amplitude transients in the broad-band environmental sounds. We concluded that it is possible to perform rather satisfactory cross-sound modeling on datasets grouped together based on their similarities in terms of the new metric of SRM map.

• Klíčová slova
• Artificial neural network, Complex sound processing, Cross-sound modeling, Inferior colliculus, Rat,
• MeSH
• akustická stimulace metody   MeSH
• biologické modely * MeSH
• colliculus inferior fyziologie   MeSH
• krysa rodu Rattus MeSH
• neuronové sítě * MeSH
• neurony fyziologie   MeSH
• potkani Sprague-Dawley MeSH
• sluchové kmenové evokované potenciály fyziologie   MeSH
• systémová biologie MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

Two distinct neural circuits calculate the direction of incoming sound in mammals. Lower frequency sounds are processed in the medial superior olive (MSO) and higher frequencies are processed in the lateral superior olive (LSO); together they constitute the superior olivary complex. We show that the spike generation mechanisms of coincidence detection (CD) are employed in both these branches of sound localization pathway. Our description uses the concepts of probabilistic spike generation and spike timing jitter. We explain the notch in sound localization sensitivity described in human psychophysics. We estimate the processing time in the superior olivary complex and discuss possible spike processing mechanisms. Among them, we distinguish between the excitatory coincidence detection (ECD) and the inhibitory coincidence detection (ICD). We compare the latter to the mechanism of firing rate subtraction traditionally attributed to the lateral superior olive.

• MeSH
• akční potenciály * MeSH
• lokalizace zvuku * MeSH
• modely neurologické MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Modeling central auditory neurons in response to complex sounds not only helps understanding neural processing of speech signals but can also provide insights for biomimetics in neuro-engineering. While modeling responses of midbrain auditory neurons to synthetic tones is rather good, modeling those to environmental sounds is less satisfactory. Environmental sounds typically contain a wide range of frequency components, often with strong and transient energy. These stimulus features have not been examined in the conventional approach of auditory modeling centered on spectral selectivity. To this end, we firstly compared responses to an environmental sound of auditory midbrain neurons across 3 subpopulations of neurons with frequency selectivity in the low, middle and high ranges; secondly, we manipulated the sound energy, both in power and in spectrum, and compared across these subpopulations how their modeled responses were affected. The environmental sound was recorded when a rat was drinking from a feeding bottle (called the 'drinking sound'). The sound spectrum was divided into 20 non-overlapping frequency bands (from 0 to 20 kHz, at 1 kHz width) and presented to an artificial neural model built on a committee machine with parallel spectral inputs to simulate the known tonotopic organization of the auditory system. The model was trained to predict empirical response probability profiles of neurons to the repeated sounds. Results showed that model performance depended more on the strong energy components than on the spectral selectivity. Findings were interpreted to reflect general sensitivity to rapidly changing sound intensities at the auditory midbrain and in the cortex.

• Klíčová slova
• Artificial neural network, Committee machine, Environmental complex sound, Intensity transient, PSTH, Rat,
• MeSH
• akustická stimulace metody   MeSH
• krysa rodu Rattus MeSH
• mezencefalon * fyziologie   MeSH
• neurony fyziologie   MeSH
• řeč MeSH
• zvířata MeSH
• zvuk * MeSH
• Check Tag
• krysa rodu Rattus MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

• Klíčová slova
• CONVULSIONS/experimental *, REFLEX, CONDITIONED *, SOUND *,
• MeSH
• epilepsie reflexní * MeSH
• klasické podmiňování * MeSH
• krysa rodu Rattus MeSH
• nervový systém - fyziologické jevy * MeSH
• reflex * MeSH
• záchvaty * MeSH
• zvířata MeSH
• zvuk * MeSH
• Check Tag
• krysa rodu Rattus MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH

Individual nuclei of the auditory pathway contribute in a specific way to the processing of complex acoustical signals. We investigated the responses of single neurons to typical guinea pig vocalizations (purr, chutter, chirp and whistle) in the ventral part of the medial geniculate body (MGB) of anesthetized guinea pigs. The neuronal and population peristimulus time histograms (PSTHs) reflected the repetition frequency of individual phrases in the calls. The patterns of PSTHs correlated well with the sound temporal envelope in calls with short phrases (purr, chirp). The dominant onset character of the neuronal responses resulted in a lower correlation between the sound envelope and the PSTH pattern in the case of longer calls (chutter and whistle). A time-reversed version of whistle elicited on average a 13% weaker response than did the natural whistle. The rate-characteristic frequency (CF) profile provided only a coarse representation of the sound frequency spectrum without detailed information about the individual spectral peaks and their relative magnitudes. In comparison with the inferior colliculus (Suta et al. in J Neurophysiol 90:3794-3808, 2003), the processing of species-specific vocalizations in the MGB differs in: (1) a less precise representation of the temporal envelope in the case of longer calls, but not in the case of calls consisting of one or more short phrases; (2) a less precise rate-CF representation of the spectral envelope in the case of low-frequency calls, but not in the case of broad-band calls; (3) a smaller difference between the responses to natural and time-reversed whistle.

• MeSH
• akční potenciály fyziologie   MeSH
• akustická stimulace MeSH
• časové faktory MeSH
• druhová specificita MeSH
• metathalamus cytologie   fyziologie   MeSH
• morčata MeSH
• neurony fyziologie   MeSH
• reakční čas fyziologie   MeSH
• sluchová percepce fyziologie   MeSH
• spektrální analýza MeSH
• vokalizace zvířat fyziologie   MeSH
• vztah dávky záření a odpovědi MeSH
• zvířata MeSH
• Check Tag
• morčata MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Species-specific vocalizations represent an important acoustical signal that must be decoded in the auditory system of the listener. We were interested in examining to what extent anesthesia may change the process of signal decoding in neurons of the auditory cortex in the guinea pig. With this aim, the multiple-unit activity, either spontaneous or acoustically evoked, was recorded in the auditory cortex of guinea pigs, at first in the awake state and then after the injection of anesthetics (33 mg/kg ketamine with 6.6 mg/kg xylazine). Acoustical stimuli, presented in free-field conditions, consisted of four typical guinea pig calls (purr, chutter, chirp and whistle), a time-reversed version of the whistle and a broad-band noise burst. The administration of anesthesia typically resulted in a decrease in the level of spontaneous activity and in changes in the strength of the neuronal response to acoustical stimuli. The effect of anesthesia was mostly, but not exclusively, suppressive. Diversity in the effects of anesthesia led in some recordings to an enhanced response to one call accompanied by a suppressed response to another call. The temporal pattern of the response to vocalizations was changed in some cases under anesthesia, which may indicate a change in the synaptic input of the recorded neurons. In summary, our results suggest that anesthesia must be considered as an important factor when investigating the processing of complex sounds such as species-specific vocalizations in the auditory cortex.

• MeSH
• akustická stimulace MeSH
• druhová specificita MeSH
• morčata MeSH
• regresní analýza MeSH
• sluchová percepce fyziologie   MeSH
• sluchové evokované potenciály fyziologie   MeSH
• sluchové korové centrum fyziologie   MeSH
• vokalizace zvířat fyziologie   MeSH
• zvířata MeSH
• zvuková spektrografie MeSH
• Check Tag
• morčata MeSH
• mužské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

It is well known that auditory experience during early development shapes response properties of auditory cortex (AC) neurons, influencing, for example, tonotopical arrangement, response thresholds and strength, or frequency selectivity. Here, we show that rearing rat pups in a complex acoustically enriched environment leads to an increased reliability of responses of AC neurons, affecting both the rate and the temporal codes. For a repetitive stimulus, the neurons exhibit a lower spike count variance, indicating a more stable rate coding. At the level of individual spikes, the discharge patterns of individual neurons show a higher degree of similarity across stimulus repetitions. Furthermore, the neurons follow more precisely the temporal course of the stimulus, as manifested by improved phase-locking to temporally modulated sounds. The changes are persistent and present up to adulthood. The results document that besides basic alterations of receptive fields presented in our previous study, the acoustic environment during the critical period of postnatal development also leads to a decreased stochasticity and a higher reproducibility of neuronal spiking patterns.

• MeSH
• akční potenciály * MeSH
• akustická stimulace * MeSH
• neurony fyziologie   MeSH
• potkani Long-Evans MeSH
• sluchová percepce fyziologie   MeSH
• sluchové korové centrum fyziologie   MeSH
• životní prostředí MeSH
• zvířata MeSH
• zvuk MeSH
• Check Tag
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The processing of species-specific communication signals in the auditory system represents an important aspect of animal behavior and is crucial for its social interactions, reproduction, and survival. In this article the neuronal mechanisms underlying the processing of communication signals in the higher centers of the auditory system--inferior colliculus (IC), medial geniculate body (MGB) and auditory cortex (AC)--are reviewed, with particular attention to the guinea pig. The selectivity of neuronal responses for individual calls in these auditory centers in the guinea pig is usually low--most neurons respond to calls as well as to artificial sounds; the coding of complex sounds in the central auditory nuclei is apparently based on the representation of temporal and spectral features of acoustical stimuli in neural networks. Neuronal response patterns in the IC reliably match the sound envelope for calls characterized by one or more short impulses, but do not exactly fit the envelope for long calls. Also, the main spectral peaks are represented by neuronal firing rates in the IC. In comparison to the IC, response patterns in the MGB and AC demonstrate a less precise representation of the sound envelope, especially in the case of longer calls. The spectral representation is worse in the case of low-frequency calls, but not in the case of broad-band calls. The emotional content of the call may influence neuronal responses in the auditory pathway, which can be demonstrated by stimulation with time-reversed calls or by measurements performed under different levels of anesthesia. The investigation of the principles of the neural coding of species-specific vocalizations offers some keys for understanding the neural mechanisms underlying human speech perception.

• MeSH
• akční potenciály MeSH
• akustická stimulace MeSH
• anestezie MeSH
• Chiroptera MeSH
• colliculus inferior fyziologie   MeSH
• emoce MeSH
• kočky MeSH
• metathalamus fyziologie   MeSH
• morčata MeSH
• neurony fyziologie   MeSH
• primáti MeSH
• sluchová percepce fyziologie   MeSH
• sluchové korové centrum fyziologie   MeSH
• vokalizace zvířat * MeSH
• zpěvní ptáci MeSH
• zvířata MeSH
• Check Tag
• kočky MeSH
• morčata MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH

Interaural level difference (ILD) is one of the basic binaural clues in the spatial localization of a sound source. Due to the acoustic shadow cast by the head, a sound source out of the medial plane results in an increased sound level at the nearer ear and a decreased level at the distant ear. In the mammalian auditory brainstem, the ILD is processed by a neuronal circuit of binaural neurons in the lateral superior olive (LSO). These neurons receive major excitatory projections from the ipsilateral side and major inhibitory projections from the contralateral side. As the sound level is encoded predominantly by the neuronal discharge rate, the principal function of LSO neurons is to estimate and encode the difference between the discharge rates of the excitatory and inhibitory inputs. Two general mechanisms of this operation are biologically plausible: (1) subtraction of firing rates integrated over longer time intervals, and (2) detection of coincidence of individual spikes within shorter time intervals. However, the exact mechanism of ILD evaluation is not known. Furthermore, given the stochastic nature of neuronal activity, it is not clear how the circuit achieves the remarkable precision of ILD assessment observed experimentally. We employ a probabilistic model and complementary computer simulations to investigate whether the two general mechanisms are capable of the desired performance. Introducing the concept of an ideal observer, we determine the theoretical ILD accuracy expressed by means of the just-noticeable difference (JND) in dependence on the statistics of the interacting spike trains, the overall firing rate, detection time, the number of converging fibers, and on the neural mechanism itself. We demonstrate that the JNDs rely on the precision of spike timing; however, with an appropriate parameter setting, the lowest theoretical values are similar or better than the experimental values. Furthermore, a mechanism based on excitatory and inhibitory coincidence detection may give better results than the subtraction of firing rates. This article is part of a Special Issue entitled Neural Coding 2012.

• Klíčová slova
• AN, Binaural hearing, CD, CN, CV, Coincidence detection, FF, Fano factor, ILD, ISI, ITD, Ideal observer, Interaural level difference, JND, Just-noticeable difference, LSO, MSO, Neuronal arithmetic, RLF, SFR, Sound localization, Subtraction of firing rate, auditory nerve, cochlear nucleus, coefficient of variation, coincidence detection, interaural level difference, interaural time difference, interspike interval, just-noticeable difference, lateral superior olive, medial superior olive, rate-level function, subtraction of firing rates,
• MeSH
• akční potenciály MeSH
• lokalizace zvuku fyziologie   MeSH
• modely neurologické * MeSH
• neurony fyziologie   MeSH
• nucleus olivaris caudalis fyziologie   MeSH
• počítačová simulace MeSH
• Poissonovo rozdělení MeSH
• vnímání prostoru fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Acoustical environment plays an important role during the maturation of the auditory system. It has been shown that the sensory inputs to the developing centres influence the development of the structure of projections, neuronal responsiveness, excitatory-inhibitory balance, or tonotopical arrangement, throughout the auditory pathway. Our previous study (Bures et al., 2014) showed that rats reared in a complex acoustic environment (spectrally and temporally modulated sound reinforced by an active behavioural paradigm with a positive feedback) exhibit permanently improved response characteristics of the inferior colliculus (IC) neurons. Extending these results, the current work provides evidence that the changes occur also at the level of auditory cortex (AC). In particular, the enriched animals have lower excitatory thresholds, sharper frequency selectivity, and a lower proportion of non-monotonic rate-intensity functions. In contrast to the changes observed in the IC, the cortical neurons of enriched animals have lower response magnitudes. In addition, the enrichment changed the AC responsiveness to frequency-modulated and also to a lesser extent, amplitude-modulated stimuli. Significantly, the alterations span the entire hearing range and may be regarded as general and not directly linked to the characteristics of the acoustical stimulation. Furthermore, these developmentally induced changes are permanent and detectable in adulthood. The findings indicate that an acoustically enriched environment during the critical period of postnatal development influences basic properties of neuronal receptive fields in the AC, which may have implications for the ability to detect and discriminate sounds.

• Klíčová slova
• Auditory cortex, Critical period, Enriched environment, Neuronal receptive field, Postnatal development,
• MeSH
• akustická stimulace MeSH
• bydlení zvířat MeSH
• membránové potenciály fyziologie   MeSH
• neurony fyziologie   MeSH
• potkani Long-Evans MeSH
• sluchová dráha růst a vývoj   fyziologie   MeSH
• sluchová percepce fyziologie   MeSH
• sluchové kmenové evokované potenciály MeSH
• sluchové korové centrum růst a vývoj   fyziologie   MeSH
• životní prostředí MeSH
• zpětná vazba MeSH
• zvířata MeSH
• Check Tag
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH