In this paper, the authors introduce an algorithm for locating sound-producing fish in a small rectangular tank that can be used, e.g., in behavioral bioacoustical studies to determine which fish in a group is sound-producing. The technique consists of locating a single sound source in the tank using signals gathered by four hydrophones placed in the tank together with a group of fish under study. The localization algorithm used in this paper is based on a ratio of two spectra ratios: the spectra ratio between the sound pressure measured by hydrophones at two locations and the spectra ratio between the theoretical Green's functions at the same locations. The results are compared to a localization based on image processing technique and with video recordings acquired synchronously with the acoustic recordings.
- MeSH
- akustika MeSH
- Batrachoidiformes fyziologie MeSH
- lokalizace zvuku fyziologie MeSH
- motorová vozidla MeSH
- pohyb těles MeSH
- ryby MeSH
- teoretické modely MeSH
- voda * MeSH
- vokalizace zvířat fyziologie MeSH
- zvířata MeSH
- zvuk * MeSH
- zvuková spektrografie metody MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The red fox (Vulpes vulpes) is the carnivore with the widest distribution in the world. Not much is known about the visual system of these predominantly forest-dwelling animals. The closely related Arctic fox (Vulpes lagopus) lives in more open tundra habitats. In search for corresponding adaptations, we examined the photoreceptors and retinal ganglion cells (RGCs), using opsin immunohistochemistry, lucifer yellow injections and Nissl staining. Both species possess a majority of middle-to-longwave-sensitive (M/L) and a minority of shortwave-sensitive (S) cones, indicating dichromatic color vision. Area centralis peak cone densities are 22,600/mm2 in the red fox and 44,800/mm2 in the Arctic fox. Both have a centro-peripheral density decrease of M/L cones, and a dorsoventrally increasing density of S cones. Rod densities and rod/cone ratios are higher in the red fox than the Arctic fox. Both species possess the carnivore-typical alpha and beta RGCs. The RGC topography shows a centro-peripheral density gradient with a distinct area centralis (mean peak density 7,900 RGCs/mm2 in the red fox and 10,000 RGCs/mm2 in the Arctic fox), a prominent visual streak of higher RGC densities in the Arctic fox, and a moderate visual streak in the red fox. Visual acuity and estimated sound localization ability were nearly identical between both species. In summary, the red fox retina shows adaptations to nocturnal activity in a forest habitat, while the Arctic fox retina is better adapted to higher light levels in the open tundra.
- MeSH
- čípky retiny fyziologie MeSH
- druhová specificita MeSH
- fotoreceptory obratlovců fyziologie MeSH
- imunohistochemie MeSH
- lišky fyziologie MeSH
- lokalizace zvuku fyziologie MeSH
- oči anatomie a histologie MeSH
- opsiny metabolismus MeSH
- retinální gangliové buňky fyziologie MeSH
- tyčinky retiny fyziologie MeSH
- vidění barevné fyziologie MeSH
- životní prostředí MeSH
- zraková ostrost fyziologie MeSH
- zvířata MeSH
- Check Tag
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- srovnávací studie MeSH
Localization of sound source azimuth within horizontal plane uses interaural time differences (ITDs) between sounds arriving through the left and right ear. In mammals, ITDs are processed primarily in the medial superior olive (MSO) neurons. These are the first binaural neurons in the auditory pathway. The MSO neurons are notable because they possess high time precision in the range of tens of microseconds. Several theories and experimental studies explain how neurons are able to achieve such precision. In most theories, neuronal coincidence detection processes the ITDs and encodes azimuth in ascending neurons of the auditory pathway using modalities that are more tractable than the ITD. These modalities have been described as firing rate codes, place codes (labeled line codes) and similarly. In this theoretical model it is described how the ITD is processed by coincidence detection and converted into spikes by summing the postsynaptic potentials. Particular postsynaptic conductance functions are used in order to obtain an analytical solution in a closed form. Specifically, postsynaptic response functions are derived from the exponential decay of postsynaptic conductances and the MSO neuron is modeled as a simplified version of the Spike Response Model (SRM0) which uses linear summations of the membrane responses to synaptic inputs. For plausible ratios of time constants, an analytical solution used to describe properties of coincidence detection window is obtained. The parameter space is then explored in the vicinity of the analytical solution. The variation of parameters does not change the solution qualitatively.
- MeSH
- akční potenciály fyziologie MeSH
- lidé MeSH
- lokalizace zvuku fyziologie MeSH
- modely neurologické * MeSH
- nervová síť fyziologie MeSH
- nervové receptory fyziologie MeSH
- nervový přenos fyziologie MeSH
- počítačová simulace MeSH
- sluchová dráha fyziologie MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Klíčová slova
- HRTF,
- MeSH
- anatomické modely MeSH
- echolokace fyziologie MeSH
- lidé MeSH
- lokalizace zvuku fyziologie MeSH
- prospektivní studie MeSH
- sluchová dráha MeSH
- sluchová percepce * fyziologie MeSH
- sluchové korové centrum fyziologie MeSH
- teoretické modely * MeSH
- virtuální realita MeSH
- zvuk MeSH
- zvuková spektrografie metody přístrojové vybavení využití MeSH
- Check Tag
- lidé 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.
- 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
Interaural time difference (ITD) is a major cue for sound azimuth localization at lower sound frequencies. We review two theories of how the sound localization neural circuit works. One of them proposes labeling of sound direction in the array of delay lines by maximal response of the tuning curve (Jeffress model). The other proposes detection of the direction by calculating the maximum slope of tuning curves. We formulate a simple hypothesis from this that stochastic neural response infers sound direction from this maximum slope, which supports the second theory. We calculate the output spike time density used in the readout of sound direction analytically. We show that the numerical implementation of the model yields results similar to those observed in experiments in mammals. We then go one step further and show that our model also gives similar results when a detailed implementation of the cochlear implant processor and simulation of implant to auditory nerve transduction are used, instead of the simplified model of auditory nerve input. Our results are useful in explaining some recent puzzling observations on the binaural cochlear implantees.
- MeSH
- akční potenciály fyziologie MeSH
- akustická stimulace MeSH
- kochleární implantáty MeSH
- lidé MeSH
- lokalizace zvuku fyziologie MeSH
- modely neurologické MeSH
- nervový přenos fyziologie MeSH
- nervus cochlearis fyziologie MeSH
- sluchová dráha fyziologie MeSH
- stochastické procesy MeSH
- teoretické modely MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
Funkční neuroanatomie sluchového systému je složitější než u systému zrakového. Neuronální reprezenta¬ce sluchových informací neodpovídá čistě fyzikálním vlastnostem zvuku, ale extrakci jejich statistických vlastností a sluchovým objektům. Mapování korových sluchových oblastí AI a A2 dokazuje existenci podo¬blastí, odkud směřují projekce do dalších korových polí. Vzájemně odlišná funkční pole sluchové kůry mapu¬jí frekvenci zvuku, jakož i lokalizaci a pohyb zdroje zvuku. I sluchový systém má, podobně jako systém zra¬kový, funkční podsystémy CO? a KDE?, a kromě toho i podsystém KDY? Stavbu a funkci sluchového systému ovlivňují pohlavní rozdíly. Centrální sluchové poruchy jsou slovní hluchota, sluchová agnózie a korová hluchota.
Functional neuroanatomy of the centrál auditory systém is more complicated than the functional neuroana- tomy of the visual systém. Neuronal and mental representations of the acoustic information are formed by extraction of its statistical properties and by construction of acoustic objects. The mapping of the acoustic cor- tex discovered root, core, belt and parabelt zones and their projections to other cortical areas. The acoustic systems WHAT, WHERE and WHEN are shortly described. Central acoustic disorders are word deafness, acoustic agnosia and cortical deafness.
- MeSH
- kochlea fyziologie inervace MeSH
- lokalizace zvuku fyziologie MeSH
- mozkový kmen cytologie fyziologie MeSH
- reakční čas MeSH
- Publikační typ
- přehledy MeSH
