| disruption of auditory spatial working memory by inactivation of the forebrain archistriatum in barn owls. | barn owls not only localize auditory stimuli with great accuracy, they also remember the locations of auditory stimuli and can use this remembered spatial information to guide their flight and strike. although the mechanisms of sound localization have been studied extensively, the neurobiological basis of auditory spatial memory has not. here we show that the ability of barn owls to orient their gaze towards and fly to the remembered location of auditory targets is lost during pharmacological in ... | 1996 | 8837773 |
| safety in numbers: sophisticated vigilance by allenby's gerbil. | since 1963, nonlinear predation theory has predicted that, at low population densities, victim species may well be mutualistic rather than competitive. theory identifies this mutualism as a principal source of dynamic instability in the interaction. using gerbils and trained barn owls, we conducted the first (to our knowledge) field tests of the theory's prediction of mutualism. the behavior of the gerbils confirms its existence. | 1997 | 9159138 |
| phase locking to high frequencies in the auditory nerve and cochlear nucleus magnocellularis of the barn owl, tyto alba. | the auditory system of the barn owl is an important model for temporal processing on a very fast time scale and for the neural mechanisms and circuitry underlying sound localization. phase locking has been shown to be the behaviorally relevant temporal code. this study examined the quality and intensity dependence of phase locking in single auditory nerve fibers of the barn owl to define the input to the known brainstem circuit for temporal processing. for direct comparison in the same individua ... | 1997 | 9096164 |
| low-frequency pathway in the barn owl's auditory brainstem. | the cytology of the nucleus magnocellularis and the nucleus laminaris in the barn owl, as well as the axonal pathways connecting them, were studied. the interest was focussed on those regions of both nuclei coding the low-frequency end of the tonotopic spectrum (below approximately 2 khz) because many previous reports on a variety of bird species had indicated significant differences to higher frequencies, both in morphology and physiology. standard light- and electron microscopy, as well as imm ... | 1997 | 9120065 |
| localization of ampa-selective glutamate receptors in the auditory brainstem of the barn owl. | ampa receptor subunit-specific antibodies were used to determine if the distribution of excitatory amino acid receptors in the owl's auditory brainstem and midbrain nuclei reflected specializations for temporal processing. each auditory nucleus displays characteristic levels of immunostaining for the ampa receptor subunits glur1-4, with high levels of the subtypes which exhibit rapid desensitization (glur4 and 2/3). in the auditory brainstem, levels of glur2/3 and glur4 were very high in the coc ... | 1997 | 9120063 |
| genetic, environmental, and condition-dependent effects on female and male ornamentation in the barn owl tyto alba. | secondary sexual characters are thought to indicate individual quality. expression of sex-limited traits in an extravagant state may require both the underlying genes and the available nutrient resources. the assessment of the relative contribution of genes, environment, and body condition is relevant for understanding to that extent the extravagant trait may signal genotypic or phenotypic quality of the individual. in birds, usually only the males are ornamented. in the barn owl, tyto alba, bot ... | 1998 | 28565392 |
| general characteristics and suppression tuning properties of the distortion-product otoacoustic emission 2f1-f2 in the barn owl. | the distortion-product otoacoustic emission (dpoae) 2f1-f2 was measured in the ear canal of the barn owl. dpoae were elicited by primary tones in 11 frequency regions from 1 to 9 khz. the highest dpoae output levels and best thresholds were found for f1 frequencies of 4 to 7 khz and additionally at the lowest f1 frequency investigated. in some cases, the dpoae sound pressures were only 37 db below the primary-tone levels (ptl). the optimal primary-tone frequency ratios ranged from 1.05 to 1.45 a ... | 1998 | 9745966 |
| contribution of the forebrain archistriatal gaze fields to auditory orienting behavior in the barn owl. | a region in the barn owl forebrain, referred to as the archistriatal gaze fields (agf), is shown to be involved in auditory orienting behavior. in a previous study, electrical microstimulation of the agf was shown to produce saccadic movements of the eyes and head, and anatomical data revealed that neurons in the agf region of the archistriatum project directly to brainstem tegmental nuclei that mediate gaze changes. in this study, we investigated the effects of agf inactivation on the auditory ... | 1996 | 8721152 |
| newly learned auditory responses mediated by nmda receptors in the owl inferior colliculus. | alignment of auditory and visual receptive fields in the optic tectum of the barn owl (tyto alba) is maintained through experience-dependent modification of auditory responses in the external nucleus of the inferior colliculus (icx), which provides auditory input to the tectum. newly learned tectal auditory responses, induced by altered visual experience, were found to be pharmacologically distinct from normal responses expressed at the same tectal sites. n-methyl-d-aspartate (nmda) receptor ant ... | 1996 | 8560271 |
| development of ampa-selective glutamate receptors in the auditory brainstem of the barn owl. | ampa receptor specific antibodies were used to study the distribution and development of glutamate receptor subtypes (glur1-4) in nucleus magnocellularis, angularis, laminaris, and the superior olive of the barn owl. each nucleus in the adult barn owl expresses characteristic levels of ampa receptor subtypes, and all are enriched in the subunits associated with rapid desensitization (glur2 and 4). in the auditory hindbrain of the barn owl, the levels of expression of all ampa receptors were very ... | 1998 | 9605336 |
| frequency tuning and spontaneous activity in the auditory nerve and cochlear nucleus magnocellularis of the barn owl tyto alba. | single-unit recordings were obtained from the brain stem of the barn owl at the level of entrance of the auditory nerve. auditory nerve and nucleus magnocellularis units were distinguished by physiological criteria, with the use of the response latency to clicks, the spontaneous discharge rate, and the pattern of characteristic frequencies encountered along an electrode track. the response latency to click stimulation decreased in a logarithmic fashion with increasing characteristic frequency fo ... | 1997 | 9120577 |
| pharmacological specialization of learned auditory responses in the inferior colliculus of the barn owl. | neural tuning for interaural time difference (itd) in the optic tectum of the owl is calibrated by experience-dependent plasticity occurring in the external nucleus of the inferior colliculus (icx). when juvenile owls are subjected to a sustained lateral displacement of the visual field by wearing prismatic spectacles, the itd tuning of icx neurons becomes systematically altered; icx neurons acquire novel auditory responses, termed "learned responses," to itd values outside their normal, pre-exi ... | 1998 | 9526024 |
| registration of neural maps through value-dependent learning: modeling the alignment of auditory and visual maps in the barn owl's optic tectum. | in the optic tectum (ot) of the barn owl, visual and auditory maps of space are found in close alignment with each other. experiments in which such alignment has been disrupted have shown a considerable degree of plasticity in the auditory map. the external nucleus of the inferior colliculus (icx), an auditory center that projects massively to the tectum, is the main site of plasticity; however, it is unclear by what mechanisms the alignment between the auditory map in the icx and the visual map ... | 1997 | 8987759 |
| forebrain pathway for auditory space processing in the barn owl. | the forebrain plays an important role in many aspects of sound localization behavior. yet, the forebrain pathway that processes auditory spatial information is not known for any species. using standard anatomic labeling techniques, we used a "top-down" approach to trace the flow of auditory spatial information from an output area of the forebrain sound localization pathway (the auditory archistriatum, aar), back through the forebrain, and into the auditory midbrain. previous work has demonstrate ... | 1998 | 9463450 |
| representation of binaural spatial cues in field l of the barn owl forebrain. | this study examined the representation of spatial information in the barn owl field l, the first telencephalic processing stage of the classical auditory pathway. field l units were recorded extracellularly, and their responses to dichotically presented interaural time differences (itd) and interaural level differences (ild) were tested. we observed a variety of tuning profiles in field l. some sites were not sensitive to itd or ild. other sites, especially those in the high-frequency region, we ... | 1998 | 9463449 |
| responses of neurons in the auditory pathway of the barn owl to partially correlated binaural signals. | 1. extracellular single-unit recording in anesthetized barn owls was used to study neuronal response to dichotic stimuli of variable binaural correlation (bc). recordings were made in the output fibers of nucleus laminaris (nl), the anterior division of the ventral lateral lemniscal nucleus (vlva), the core of the central nucleus of the inferior colliculus (iccc), the lateral shell of the central nucleus of the inferior colliculus (iccls), and the external nucleus of the inferior colliculus (icx ... | 1995 | 8989405 |
| 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. ... | 1995 | 7560288 |
| inhibition sensitive to interaural time difference in the barn owl's inferior colliculus. | in spontaneously active neurons in the external nucleus of the inferior colliculus of the barn owl, a stimulus-driven discharge was followed by a quiescent period lasting tens of milliseconds before the spontaneous activity resumed. the more favorable the interaural time difference, the longer the quiet period. the duration of the quiescent period also depended on stimulus frequency. frequencies different from the neuron's best frequency induced shorter quiescent periods, although they could eli ... | 1997 | 9259240 |
| biomonitoring heavy metals using the barn owl (tyto alba guttata): sources of variation especially relating to body condition. | the feasibility of using the barn owl (tyto alba guttata) to monitor environmental quality in the netherlands was investigated, using cd, cu, pb, mn, and fe as indicators for environmental contamination. throughout 1992, bird-watchers, volunteers, and officials submitted 53 birds. the age and geographical distribution of these birds, formed a representative sample of the population. the following interrelationships were investigated: cause of death, nutrient reserve, age, time of death, place of ... | 1995 | 7755402 |
| dynamics of visually guided auditory plasticity in the optic tectum of the barn owl. | 1. in the optic tectum of normal barn owls, bimodal (auditory-visual) neurons are tuned to the values of interaural time difference (itd) that are produced by sounds at the locations of their visual receptive fields (vrfs). the auditory tuning of tectal neurons is actively guided by visual experience during development: in the tectum of adult owls reared with an optically displaced visual field, neurons are tuned to abnormal values of itd that are close to the values produced by sounds at the lo ... | 1995 | 7760121 |
| development of the time coding pathways in the auditory brainstem of the barn owl. | the barn owl's head grows after hatching, causing interaural distances to more than double in the first 3 weeks posthatch. these changes expose the bird to a constantly increasing range of interaural time cues. we have used golgi and ultrastructural techniques to analyze the development of the connections and cell types of the nucleus magnocellularis (nm) and the nucleus laminaris (nl) with reference to the growth of the head. the time coding circuit is formed but immature at the time of hatchin ... | 1996 | 8889939 |
| influence of stimulus level on acoustic motion-direction sensitivity in barn owl midbrain neurons. | 1. many neurons in the owl's midbrain are able to discriminate by their responses the motion of an acoustic source in one direction, the preferred direction, from the motion of the source in the opposite direction, the null direction. this differential response can be understood by the action of an acoustic motion detector. however, the motion detector would work in an effective way only if the motion direction-sensitive responses of a cell were largely independent of stimulus level. 2. we inves ... | 1994 | 8064356 |
| a neuronal learning rule for sub-millisecond temporal coding. | a paradox that exists in auditory and electrosensory neural systems is that they encode behaviorally relevant signals in the range of a few microseconds with neurons that are at least one order of magnitude slower. the importance of temporal coding in neural information processing is not clear yet. a central question is whether neuronal firing can be more precise than the time constants of the neuronal processes involved. here we address this problem using the auditory system of the barn owl as ... | 1996 | 8779718 |
| ventriloquism against audio-visual speech: or, where japanese-speaking barn owls might help | | 1994 | 11540553 |
| quantitative tem analysis of the barn owl basilar papilla. | the morphology of the barn owl's basilar papilla was quantitatively analyzed using tem methods. the hair-cell (hc) parameters studied in the basal two-thirds of the papilla are remarkably constant. this large portion represents an extended high frequency area, or fovea [köppl et al. (1993) j. comp. physiol. a 171, 695-704]. in the apical third of the papilla, in contrast, these parameters change regularly, as they do in other avian species. the hc in the most neural position remain morphological ... | 1994 | 8157497 |
| 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 field ... | 1996 | 8847663 |
| the effect of barn owls (tyto alba) on the activity and microhabitat selection of gerbillus allenbyi and g. pyramidum. | predation plays an important role in ecological communities by affecting prey behavior such as foraging and by physical removal of individual prey. in regard to foraging, animals such as desert rodents often balance conflicting demands for food and safety. this has been studied in the field by indirectly manipulating predatory risk through the alteration of cues associated with increased risk such as cover or illumination. it has also been studied by directly manipulating the presence of predato ... | 1996 | 28307103 |
| capacity for plasticity in the adult owl auditory system expanded by juvenile experience. | in the process of creating a multimodal map of space, auditory-visual neurons in the optic tectum establish associations between particular values of auditory spatial cues and locations in the visual field. in the barn owl, tectal neurons reveal these associations in the match between their tuning for interaural time differences (itds) and the locations of their visual receptive fields (vrfs). in young owls itd-vrf associations can be adjusted by experience over a wide range, but the range of ad ... | 1998 | 9488651 |
| representation of sound localization cues in the auditory thalamus of the barn owl. | barn owls can localize a sound source using either the map of auditory space contained in the optic tectum or the auditory forebrain. the auditory thalamus, nucleus ovoidalis (n.ov), is situated between these two auditory areas, and its inactivation precludes the use of the auditory forebrain for sound localization. we examined the sources of inputs to the n.ov as well as their patterns of termination within the nucleus. we also examined the response of single neurons within the n.ov to tonal st ... | 1997 | 9294226 |
| site of auditory plasticity in the brain stem (vlvp) of the owl revealed by early monaural occlusion. | 1. the optic tectum of the barn owl contains a physiological map of interaural level difference (ild) that underlies, in part, its map of auditory space. monaural occlusion shifts the range of ilds experienced by an animal and alters the correspondence of ilds with source locations. chronic monaural occlusion during development induces an adaptive shift in the tectal ild map that compensates for the effects of the earplug. the data presented in this study indicate that one site of plasticity und ... | 1994 | 7897496 |
| adaptive plasticity of the auditory space map in the optic tectum of adult and baby barn owls in response to external ear modification. | 1. this study demonstrates the influence of experience on the establishment and maintenance of the auditory map of space in the optic tectum of the barn owl. auditory experience was altered either by preventing the structures of the external ears (the facial ruff and preaural flaps) from appearing in baby barn owls (baby ruff-cut owls) or by removing these structures in adults (adult ruff-cut owls). these structures shape the binaural cues used for localizing sounds in both the horizontal and ve ... | 1994 | 8158243 |
| orienting head movements resulting from electrical microstimulation of the brainstem tegmentum in the barn owl. | the size and direction of orienting movements are represented systematically as a motor map in the optic tectum of the barn owl (du lac and knudsen, 1990). the optic tectum projects to several distinct regions in the medial brainstem tegmentum, which in turn project to the spinal cord (masino and knudsen, 1992). this study explores the hypothesis that a fundamental transformation in the neural representation of orienting movements takes place in the brainstem tegmentum. head movements evoked by ... | 1993 | 8423480 |
| vision-independent adjustment of unit tuning to sound localization cues in response to monaural occlusion in developing owl optic tectum. | neurons in the developing optic tectum adjust their tuning to auditory localization cues in response to chronic monaural occlusion so that auditory spatial fields align with visual receptive fields (vrfs). we tested whether this adaptive adjustment of auditory tuning requires visual instruction. both eyelids were sutured closed at the same time that one ear was occluded in two barn owls that were 1 month old. after 70 and 100 d, respectively, the tuning of units to interaural level difference (i ... | 1992 | 1527592 |
| differential calbindin-like immunoreactivity in the brain stem auditory system of the chinchilla. | calbindin is a 28 kd calcium-binding protein found in neural tissue. although its functional role in neurons is unknown, it has been proposed that calbindin is involved in intracellular buffering and could therefore influence temporal precision of neuronal firing. in the barn owl, calbindin-like immunoreactivity was found to be selectively present in brain stem auditory pathways used to process interaural time differences, but was absent from the interaural intensity pathway. the present study d ... | 1992 | 1619049 |
| experience-dependent plasticity in the inferior colliculus: a site for visual calibration of the neural representation of auditory space in the barn owl. | the optic tectum (homolog of the superior colliculus) contains mutually aligned neural maps of auditory and visual space. during development, the organization of the auditory map is guided by spatial information provided by vision: barn owls raised wearing prismatic spectacles, which optically shift the visual field and the visual map in the optic tectum, develop an auditory map that is shifted by an approximately equivalent amount, such that alignment between the two maps is preserved (knudsen ... | 1993 | 8229186 |
| bilateral inhibition generates neuronal responses tuned to interaural level differences in the auditory brainstem of the barn owl. | i investigated the neural algorithms by which neurons gain selectivity for interaural level difference in the brainstem of the barn owl (tyto alba). differences in the timing and in the level of sounds at the ears are used by this owl to encode, respectively, azimuthal and vertical position of sound sources in space. these two cues are processed in two parallel neural pathways. below the level of the inferior colliculus, all neurons in the pathway that processes level differences show responses ... | 1993 | 7690063 |
| disparity-sensitive cells in the owl have a characteristic disparity. | we experience the visual world as being three-dimensional. a major source of depth information derives from the slightly different views of each eye, leading to small variations in the retinal images ('disparities'). neurons sensitive to visual disparities are thought to form the neural basis of stereo vision. barn owls as well as several mammalian species have neurons that are sensitive to visual disparities. but how visual disparities are represented in the brain has been a matter of discussio ... | 1993 | 8355804 |
| on the ability of neurons in the barn owl's inferior colliculus to sense brief appearances of interaural time difference. | this paper investigates the ability of neurons in the barn owl's (tyto alba) inferior colliculus to sense brief appearances of interaural time difference (itd), the main cue for azimuthal sound localization in this species. in the experiments, itd-tuning was measured during presentation of a mask-probe-mask sequence. the probe consisted of a noise having a constant itd, while the mask consisted of binaurally uncorrelated noise. collicular neurons discriminated between the probe and masking noise ... | 1992 | 1573569 |
| sensitive and critical periods for visual calibration of sound localization by barn owls. | this study describes developmental changes in the capacity of owls to adjust sound localization in response to chronic prismatic displacement of the visual field and to recover accurate sound localization following the restoration of normal vision. matched, binocular displacing prisms were mounted over the eyes of 19 barn owls (tyto alba) beginning at ages ranging from 10 to 272 d. in nearly all cases, the visual field was shifted 23 degrees to the right. sound localization was assessed on the b ... | 1990 | 2299394 |
| nmda and non-nmda glutamate receptors in auditory transmission in the barn owl inferior colliculus. | the pharmacology of auditory responses in the inferior colliculus (ic) of the barn owl was investigated by iontophoresis of excitatory amino acid receptor antagonists into two different functional subdivisions of the ic, the external nucleus (icx) and the lateral shell of the central nucleus (lateral shell), both of which carry out important computations in the processing of auditory spatial information. combined application of the nmda receptor antagonist 2-amino-5-phosphonovaleric acid (ap5) a ... | 1994 | 7931555 |
| auditory tuning for spatial cues in the barn owl basal ganglia. | 1. the basal ganglia are known to contribute to spatially guided behavior. in this study, we investigated the auditory response properties of neurons in the barn owl paleostriatum augmentum (pa), the homologue of the mammalian striatum. the data suggest that the barn owl pa is specialized to process spatial cues and, like the mammalian striatum, is involved in spatial behavior. 2. single- and multiunit sites were recorded extracellularly in ketamine-anesthetized owls. spatial receptive fields we ... | 1994 | 7965012 |
| central projections of auditory nerve fibers in the barn owl. | the central projections of the auditory nerve were examined in the barn owl. each auditory nerve fiber enters the brain and divides to terminate in both the cochlear nucleus angularis and the cochlear nucleus magnocellularis. this division parallels a functional division into intensity and time coding in the auditory system. the lateral branch of the auditory nerve innervates the nucleus angularis and gives rise to a major and a minor terminal field. the terminals range in size and shape from sm ... | 1991 | 1723997 |
| visual instruction of the neural map of auditory space in the developing optic tectum. | neural maps of visual and auditory space are aligned in the adult optic tectum. in barn owls, this alignment of sensory maps was found to be controlled during ontogeny by visual instruction of the auditory spatial tuning of neurons. large adaptive changes in auditory spatial tuning were induced by raising owls with displacing prisms mounted in spectacle frames in front of the eyes; neurons became tuned to sound source locations corresponding to their optically displaced, rather than their normal ... | 1991 | 2063209 |
| stretched and upside-down maps of auditory space in the optic tectum of blind-reared owls; acoustic basis and behavioral correlates. | vision during early life plays an important role in calibrating sound localization behavior. this study investigates the effects of visual deprivation on sound localization and on the neural representation of auditory space. nine barn owls were raised with eyelids sutured closed; one owl was congenitally anophthalmic. data from these birds were compared with data from owls raised with normal visual experience. sound localization behavior was significantly less precise in blind-reared owls than i ... | 1991 | 2045884 |
| early visual deprivation results in a degraded motor map in the optic tectum of barn owls. | the optic tectum contains a precise map of orienting movements: the size and direction of movements of the eyes, head, and/or body vary systematically with the locus of neural activation within the tectum. in adult animals, this motor map aligns closely with the tectal map of visual space. this study addressed the question of whether the motor map develops entirely independently of visual experience. we found that in barn owls (tyto alba) raised without vision, although a tectal map of head move ... | 1991 | 2014263 |
| vision calibrates sound localization in developing barn owls. | this study demonstrates that continuous exposure of baby barn owls to a displaced visual field causes a shift in sound localization in the direction of the visual displacement. this implies an innate dominance of vision over audition in the development and maintenance of sound localization. twelve owls were raised from the first day of eye opening wearing binocular prisms that displaced the visual field to the right by 11 degrees, 23 degrees, or 34 degrees. the prisms were worn for periods of up ... | 1989 | 2795164 |
| the role of gabaergic inhibition in processing of interaural time difference in the owl's auditory system. | the barn owl uses interaural time differences (itds) to localize the azimuthal position of sound. itds are processed by an anatomically distinct pathway in the brainstem. neuronal selectivity for itd is generated in the nucleus laminaris (nl) and conveyed to both the anterior portion of the ventral nucleus of the lateral lemniscus (vlva) and the central (icc) and external (icx) nuclei of the inferior colliculus. with tonal stimuli, neurons in all regions are found to respond maximally not only t ... | 1991 | 2002359 |
| a circuit for detection of interaural time differences in the brain stem of the barn owl. | detection of interaural time differences underlies azimuthal sound localization in the barn owl tyto alba. axons of the cochlear nucleus magnocellularis, and their targets in the binaural nucleus laminaris, form the circuit responsible for encoding these interaural time differences. the nucleus laminaris receives bilateral inputs from the cochlear nucleus magnocellularis such that axons from the ipsilateral cochlear nucleus enter the nucleus laminaris dorsally, while contralateral axons enter fr ... | 1990 | 2213141 |
| organization of the nucleus magnocellularis and the nucleus laminaris in the barn owl: encoding and measuring interaural time differences. | the circuit from the cochlear nucleus magnocellularis to the nucleus laminaris supports the encoding and measurement of interaural time differences in the auditory brainstem. specializations for the encoding of temporal information include the few and/or short dendrites and thick axons of the magnocellular and laminaris neurons, and the high degree of convergence in the circuit. magnocellular cells have large cell bodies covered with somatic spines. the cells have few dendrites, and the number o ... | 1993 | 8376623 |
| early monaural occlusion alters the neural map of interaural level differences in the inferior colliculus of the barn owl. | monaural occlusion during early life causes adaptive changes in the tuning of units in the owl's optic tectum to interaural level differences (ild) that tend to align the auditory with the visual map of space. we investigated whether these changes could be due to experience-dependent plasticity occurring in the auditory pathway prior to the optic tectum. units were recorded in the external nucleus of the inferior colliculus (icx), which is a major source of auditory input to the optic tectum. th ... | 1993 | 8374783 |
| parallel pathways mediating both sound localization and gaze control in the forebrain and midbrain of the barn owl. | the hypothesis that sound localization and gaze control are mediated in parallel in the midbrain and forebrain was tested in the barn owl. the midbrain pathway for gaze control was interrupted by reversible inactivation (muscimol injection) or lesion of the optic tectum. auditory input to the forebrain was disrupted by reversible inactivation or lesion of the primary thalamic auditory nucleus, nucleus ovoidalis (homolog of the medial geniculate nucleus). barn owls were trained to orient their ga ... | 1993 | 8331375 |
| acetylcholinesterase staining differentiates functionally distinct auditory pathways in the barn owl. | the aim of this study was to examine how the functional specialization of the barn owl's auditory brainstem might correlate with histochemical compartmentalization. the barn owl uses interaural intensity and time differences to encode, respectively, the vertical and azimuthal positions of sound sources in space. these two auditory cues are processed in parallel ascending pathways that separate from each other at the level of the cochlear nuclei. sections through the auditory brainstem were stain ... | 1993 | 7681456 |
| neurons in the midbrain of the barn owl are sensitive to the direction of apparent acoustic motion. | | 1990 | 2250726 |
| horizontal and vertical components of head movement are controlled by distinct neural circuits in the barn owl. | to generate behaviour, the brain must transform sensory information into signals that are appropriate to control movement. sensory and motor coordinate frames are fundamentally different, however: sensory coordinates are based on the spatiotemporal patterns of activity arising from the various sense organs, whereas motor coordinates are based on the pulling directions of muscles or groups of muscles. results from psychophysical experiments suggest that in the process of transforming sensory info ... | 1990 | 2342573 |
| trace metals in primary feathers of the barn owl (tyto alba guttatus) in the netherlands. | the number of barn owls in the netherlands has been reduced substantially over the last few decades. death as a result of poisoning seems unlikely, but the pathology of all bird species found dead in the netherlands between 1975 and 1988 (n = 15 422) shows that 21% of all the birds were contaminated. however, the most important factor responsible for the decline in barn owl numbers in the netherlands has not yet been established. as a part of a new national protection plan for the barn owl, the ... | 1993 | 15091780 |
| sound-localization deficits induced by lesions in the barn owl's auditory space map. | barn owls possess a two-dimensional map of auditory space. the map appears in its final form in the external nucleus of the inferior colliculus (icx) and is projected from there to the optic tectum (ot). to determine the role of the map in icx or its projected version in ot in the localization of acoustic stimuli, head movements of three adult owls were recorded before and after lesioning parts of the map either in icx or in ot. small electrolytic lesions caused sound-localization deficits that ... | 1993 | 8423481 |
| visuomotor adaptation to displacing prisms by adult and baby barn owls. | the capacity of barn owls to adapt visuomotor behavior in response to prism-induced displacement of the visual field was tested in babies and adults. matched, binocular fresnel prisms, which displaced the visual field 11 degrees, 23 degrees, or 34 degrees to the right, were placed on owls for periods of up to 99 d. seven baby owls wore the prisms from the day the eyelids first opened; 2 owls wore them as adults. prism adaptation was measured by the accuracy with which a target was approached and ... | 1989 | 2795163 |
| neural maps of interaural time and intensity differences in the optic tectum of the barn owl. | this report describes the binaural basis of the auditory space map in the optic tectum of the barn owl (tyto alba). single units were recorded extracellularly in ketamine-anesthetized birds. unit tuning for interaural differences in timing and intensity of wideband noise was measured using digitally synthesized sound presented through earphones. spatial receptive fields of the same units were measured with a free field sound source. auditory units in the optic tectum are sharply tuned for both t ... | 1989 | 2746340 |
| bi-coordinate sound localization by the barn owl. | 1. binaurally time-shifted and intensity-unbalanced noise, delivered through earphones, induced owls to respond with a head-orienting behavior similar to that which occurs to free field auditory stimuli. 2. owls derived the azimuthal and elevational coordinates of a sound from a combination of interaural time difference (itd) and interaural intensity difference (iid). 3. iid and itd each contained information about the azimuth and elevation of the signal. thus, iid and itd formed a coordinate sy ... | 1989 | 2709344 |
| segregation of stimulus phase and intensity coding in the cochlear nucleus of the barn owl. | the cochlear nucleus of the barn owl is composed of two anatomically distinct subnuclei, n. magnocellularis (the magnocellular nucleus) and n. angularis (the angular nucleus). in the magnocellular nucleus, neurons tend to respond at a particular phase of a stimulus sine wave. phase locking was observed for frequencies up to 9.0 khz. the intensity-spike count functions of magnocellular units are characterized by high rates of spontaneous activity, a narrow range of intensities over which spike co ... | 1984 | 6737041 |
| monaural occlusion alters sound localization during a sensitive period in the barn owl. | sound localization was disrupted in young barn owls by chronically plugging one ear. owls that were younger than 8 weeks of age at the time of ear plugging recovered normal localization accuracy while plugged, whereas those that were older than 8 weeks at the time of ear plugging did not. the end of the sensitive period for the adjustment of sound localization accuracy coincides with the maturation of the head and ears, suggesting that the exposure of the auditory system to stable, adult-like ac ... | 1984 | 6716127 |
| binaural characteristics of units in the owl's brainstem auditory pathway: precursors of restricted spatial receptive fields. | the barn owl uses binaural phase and intensity differences for sound localization. these two cues also determine the receptive fields of specialized neurons in the inferior colliculus. the main aim of this study was to investigate where neuronal sensitivity to the binaural cues emerges in the brainstem auditory nuclei, and how this sensitivity reaches the neurons in the inferior colliculus. the owl's phase-sensitive neurons are selective to microsecond phase differences of high frequency signals ... | 1983 | 6655499 |
| early blindness results in a degraded auditory map of space in the optic tectum of the barn owl. | the optic tectum of the barn owl (tyto alba) contains a neural map of auditory space consisting of neurons that are sharply tuned for sound source location and organized precisely according to their spatial tuning. the importance of vision for the development of this auditory map was investigated by comparing space maps measured in normal owls with those measured in owls raised with both eyelids sutured closed. the results demonstrate that owls raised without sight, but with normal hearing, deve ... | 1988 | 3413089 |
| a neural map of interaural intensity differences in the brain stem of the barn owl. | the nucleus ventralis lemnisci lateralis pars posterior (vlvp) is the first binaural station in the intensity-processing pathway of the barn owl. contralateral stimulation excites and ipsilateral stimulation inhibits vlvp cells. the strength of the inhibition declines systematically from dorsal to ventral within the nucleus. cells selective for different intensity disparities occur in an orderly sequence from dorsal to ventral within each isofrequency lamina. cells at intermediate depths in the ... | 1988 | 3411346 |
| the basilar papilla of the barn owl tyto alba: a quantitative morphological sem analysis. | the barn owl has the longest basilar papilla (about 12 mm) of all bird species studied. in the apical half several morphological parameters change regularly: stereovillar number per hair cell, length of the stereovillar bundle and cell surface area decrease from basal to apical. cell number across the papilla, width of stereovillar bundle, diameter of a single stereovillus and height of stereovilli increase in the same direction. the orientation of the stereovillar bundles' long axis is parallel ... | 1988 | 3403388 |
| directional hearing in the barn owl (tyto alba). | the acoustical properties of the external ear of the barn owl (tyto alba) were studied by measuring sound pressure in the ear canal and outer ear cavity. under normal conditions, pressure amplification by the external ear reaches about 20 db between 3-9 khz but decreases sharply above 10 khz. the acoustic gain curve of the outer ear cavity alone is close to that of a finite-length exponential horn between 1.2-13 khz with maximum gain reaching 20 db between 5-9 khz. pressure gain by the facial ru ... | 1988 | 3385664 |
| binaural disparity cues available to the barn owl for sound localization. | 1. bilateral recording of cochlear potentials was used to measure the variations in interaural time differences (itds) and interaural intensity differences (iids) as a free-field auditory stimulus was moved to different positions around a barn owl's head. 2. itd varied smoothly with stimulus azimuth across a broad frequency range. 3. itd varied minimally with stimulus elevation, except at extreme angles from the horizontal. 4. iid varied with both stimulus elevation and stimulus azimuth. lower f ... | 1989 | 2590278 |
| fused binocular vision is required for development of proper eye alignment in barn owls. | the eyes of adult barn owls (tyto alba) are virtually fixed in the head in positions that are highly consistent from one individual to the next. however, early in development the eyes are exodeviated; the eyes achieve their adult positions during the owl's second month of life. disruption of binocular vision in baby owls leads to permanent, highly abnormal eye positions and interocular alignment. of three owls raised with both eyelids sutured closed, two developed exotropic strabismus and one de ... | 1989 | 2487636 |
| projections of the cochlear nuclei and nucleus laminaris to the inferior colliculus of the barn owl. | the barn owl determines the directions from which sounds emanate by computing the interaural differences in the timing and intensity of sounds. these cues for sound localization are processed in independent channels originating at nucleus magnocellularis (nm) and nucleus angularis (na), the cochlear nuclei. the cells of nm are specialized for encoding the phase of sounds in the ipsilateral ear. the cells of na are specialized for encoding the intensity of sounds in the ipsilateral ear. nm projec ... | 1988 | 2463286 |
| classification of response patterns in cochlear nucleus of barn owl: correlation with functional response properties. | response patterns of neurons in the cochlear nuclei of the barn owl (tyto alba) were studied by obtaining poststimulus time histograms (psths) and interspike interval histograms for the response to short tone bursts at the neuron's characteristic frequency. the observed response patterns can be classified according to the scheme developed for neurons of the mammalian cochlear nuclear complex (22). neurons of the magnocellular cochlear nucleus (n. magnocellularis), which respond in a phase-locked ... | 1985 | 3973658 |
| accuracy of the haldane method as an indirect measure of metabolism. | metabolic rates of barn owls increased as ambient temperature decreased below the thermoneutral zone. the haldane method was as reliable as an o2 analyzer in measuring the metabolic rates of captive barn owls. however, at lowered ambient temperature (below 5 degrees c) there was a slight disparity in the metabolic rates determined by the two methods. the haldane method has the potential of being used in a field situation (i.e. it is reliable, portable and relatively inexpensive). | 1985 | 2864191 |
| food and energy requirements of captive barn owls tyto alba. | food and energy requirements of captive barn owls were determined at 5, 15 and 25 degrees c. food consumption, gross energy intake, dry matter intake, and existence metabolism increased as ambient temperature decreased. barn owl energy assimilation efficiencies at the three test temperatures were approximately 78%. an increase in bioenergetic parameters might be anticipated when a bird is cold-stressed and must increase its metabolism for thermoregulation. | 1985 | 2858314 |
| auditory properties of space-tuned units in owl's optic tectum. | auditory units in the optic tectum of the barn owl (tyto alba) were studied under free-field conditions with a movable sound source. these units are selective for sound location and their spatial tuning varies systematically across the tectum, forming a map of space (8). i found that frequency tuning, response latencies, and thresholds of units changed in parallel with their spatial tuning, suggesting that as a consequence these properties also are topographically distributed in the optic tectum ... | 1984 | 6491713 |
| a critical period for the recovery of sound localization accuracy following monaural occlusion in the barn owl. | we studied the ability of barn owls to recover accurate sound localization after being raised with one ear occluded. most of the owls had ear plugs inserted before they reached adult size, and therefore they never experienced normal adult localization cues until their ear plugs were removed. upon removal of their ear plugs, these owls exhibited large systematic sound localization errors. the rate at which they recovered accurate localization decreased with the age of the bird at the time of plug ... | 1984 | 6716128 |
| representation of interaural time difference in the central nucleus of the barn owl's inferior colliculus. | this paper investigates the role of the central nucleus of the barn owl's inferior colliculus in determination of the sound-source azimuth. the central nucleus contains many neurons that are sensitive to interaural time difference (itd), the cue for azimuth in the barn owl. the response of these neurons varies in a cyclic manner with the itd of a tone or noise burst. response maxima recur at integer multiples of the period of the stimulating tone, or, if the stimulus is noise, at integer multipl ... | 1987 | 3668618 |
| calcium binding protein-like immunoreactivity labels the terminal field of nucleus laminaris of the barn owl. | nucleus laminaris (nl) is the site at which the timing of sounds arriving in the 2 ears is compared in the auditory system of the barn owl. earlier studies have reported vitamin d-dependent calcium binding protein (cabp)-like immunoreactivity in the somata of nl. we report here that cabp-like immunoreactivity stains the terminal field of nl. the specific cabp immunoreactivity is localized to a dense plexus of fibers that have bouton-like swellings, usually around unstained somata. this type of i ... | 1987 | 2439666 |
| organochlorine pesticide levels in barn owls collected in león, spain. | | 1987 | 3801698 |
| fluoride in the prey of barn owls (tyto alba). | bone fluoride in short-tailed voles (microtus agrestis) and common shrews (sorex araneus), the prey of barn owls (tyto alba), was studied on anglesey, north wales. the average fluoride content of m. agrestis skulls obtained from a location 0.9 km from an aluminium reduction plant was significantly greater than that of skulls from another location 22 km from the source of industrial fluoride pollution. at both locations, mean fluoride levels of skulls extracted from owl pellets and those of voles ... | 1987 | 15092770 |
| a sharp retinal image increases the topographic precision of the goldfish retinotectal projection during optic nerve regeneration in stroboscopic light. | locally-correlated neural activity appears to play a key role in refining topographically mapped projections. the retinotectal projection of the goldfish normally regains a high degree of spatial precision after regeneration of a cut optic nerve, but it fails to do so if retinal ganglion cell activity is blocked by tetrodotoxin, or if local correlations in activity are masked by the synchronizing effect of stroboscopic light. a sharp retinal image is not normally needed for a sharp map because l ... | 1987 | 3691705 |
| neural derivation of sound source location in the barn owl. an example of a computational map. | | 1987 | 3324875 |
| selectivity for interaural time difference in the owl's midbrain. | the barn owl uses the interaural difference in the timing of sounds to determine the azimuth of the source. when the sound has a wide frequency band, localization is precise. when localizing tones, however, the barn owl errs in a manner that suggests that it is confused by phantom targets. we report a neural equivalent of these phenomena as they are observed in the space-specific neuron of the owl's inferior colliculus. when stimulated with a tone, the space-specific neuron discharges maximally ... | 1986 | 3794779 |
| neural map of interaural phase difference in the owl's brainstem. | neurons of the barn owl's (tyto alba) nucleus laminaris, the first site of binaural convergence, respond in a phase-locked fashion to a tone delivered to either ear. it may take longer to elicit phase-locked spikes from one ear than from the other. this disparity in delay differs from neuron to neuron and is independent of tonal frequency. in binaural stimulation, neurons respond best when sound in one ear leads that in the other by an amount equal to their delay disparities but opposite in sign ... | 1986 | 3022292 |
| the sensitive period for auditory localization in barn owls is limited by age, not by experience. | early in life, the barn owl passes through a sensitive period during which it can interpret and make use of abnormal auditory cues for accurate sound localization. this capacity is lost at about 8 weeks of age, just after the head and ears reach adult size (knudsen et al. 1984a). the end of the sensitive period could be triggered either by an age-dependent process or by the exposure of the auditory system to stable or adult-like cues. to distinguish between these alternatives, we subjected baby ... | 1986 | 3734867 |
| low prevalence of west nile virus antibodies in select northern california owl species (2007-2014). | the objective of this study was to determine evidence of previous west nile virus (wnv) infection in northern california owls. owl serum samples were collected from birds presenting to a veterinary medical teaching hospital between 2007 and 2014 and were screened for the presence of wnv antibodies by an indirect enzyme immunoassay (eia). only one of 71 samples (1.41%) tested was positive by eia and confirmed by a plaque reduction neutralization test; it was the most recent sample collected. the ... | 2017 | 29297801 |
| the horizontal cells in the retina of the owl, tyto alba, and owlet, carinae noctua. | one type of short-axon horizontal cell (hc) and one type of axonless hc are described in the retina of carinae noctua, a crepuscular bird and tyto alba, a pure nocturnal bird. the axonless hcs in both birds are similar to type ii axonless hc found in diurnal birds. the short-axon hc of carinae noctua is similar to the same cell type found in diurnal birds; the only difference being the axon length. the short-axon hc of the tyto alba retina is morphologically different from the same cell type fou ... | 1986 | 3709701 |
| predictive modelling in paleoenvironmental reconstruction: the micromammals of manot cave, israel. | this paper describes the micromammalian remains and paleoenvironment of the upper paleolithic sequence of manot cave (46-34 ka), southern levant. micromammal remains were identified from ahmarian (46-42 ka), levantine aurignacian (38-34 ka) and post-levantine aurignacian (34-33 ka) layers. to identify taphonomic agents, molar digestion was modelled for seven local raptor species, and model predictions were compared with observed digestion scores in the manot cave material. raptor species differe ... | 2019 | 31623862 |
| time coding in electric fish and barn owls. | a comparison of the coding and processing of temporally ordered information in electric fish and barn owls demonstrates a number of similar design features including different time and intensity channels and distinct morphological characteristics. similar mechanisms, such as the presence of delay lines, underlie the sensitivity of both animals to small temporal disparities. differences between the two systems may reflect the different substrates upon which evolution acted, and the different requ ... | 1986 | 3567536 |
| vision guides the adjustment of auditory localization in young barn owls. | barn owls raised with one ear plugged make systematic errors in auditory localization when the earplug is removed. young owls correct their localization errors within a few weeks. however, such animals did not correct their auditory localization errors when deprived of vision. moreover, when prisms were mounted in front of their eyes, they adjusted their auditory localization to match the visual error induced by the prisms, as long as the visual and auditory errors were within the same quadrant ... | 1985 | 4048948 |
| early auditory experience aligns the auditory map of space in the optic tectum of the barn owl. | auditory and visual space are mapped in the optic tectum of the barn owl. normally, these maps of space are in close mutual alignment. ear plugs inserted unilaterally in young barn owls disrupted the binaural cues that constitute the basis of the auditory map. yet when recordings were made from the tecta of these birds as adults, the auditory and visual maps were in register. when the ear plugs were removed from these adult birds and binaural balance was restored, the auditory maps were shifted ... | 1983 | 6635667 |
| subdivisions of the inferior colliculus in the barn owl (tyto alba). | the inferior colliculus in the barn owl contains three subdivisions: the central (icc), external (icx), and superficial (ics) nuclei. the nuclei are distinguished on the basis of their cyto- and myeloarchitecture, connectivity, and physiological properties. the icc may be further divided into dorsal (iccd) and ventral (iccv) parts. auditory fibers ascending in the lateral lemniscus enter the iccd and iccv, but not the icx or ics. the icx receives its auditory input from the icc. the icc and icx ... | 1983 | 6886070 |
| metabolism of parathion and brain cholinesterase inhibition in aroclor 1254-treated and untreated caspian terrapin (mauremys caspica rivulata, emydidae, chelonia) in comparison with two species of wild birds. | the mean level of pcb residues in the liver of the caspian turtle collected in nature was 23 ppm, or approximately 20-fold greater than that detected in the two bird species tested. treatment of the turtles with aroclor 1254 resulted in a 30-fold increase in the level of pcb residues in the liver but did not cause any increase in the content of cytochrome p-450 and the desulfurase activity of this hemoprotein. the ki value for acetylcholinesterase inhibition by paraoxon in brain homogenate of th ... | 1983 | 6138207 |
| auditory and visual maps of space in the optic tectum of the owl. | the receptive field properties and functional organization of visual and auditory responses were studied in the optic tectum of the barn owl (tyto alba). most units throughout the depth of the tectum responded to both visual and auditory stimuli. the entire visual field of each eye was represented topographically in the contralateral tectum. in the portion of the tectal map representing the zone of binocular vision, 50% of the superficial layer units and 100% of the deep; layer units were driven ... | 1982 | 7119872 |
| intercontinental test of constraint-breaking adaptations: testing behavioural plasticity in the face of a predator with novel hunting strategies. | constraint-breaking adaptations are evolutionary tools that provide a mechanism for incumbent-replacement between species filling similar ecological roles. in common-garden experiments, we exposed populations of two desert rodents to two different viper species, testing their ability to adjust to novel predators that use different hunting strategies. we aimed to understand whether both predators and prey with constraint-breaking adaptations actually manifest comparative advantage over their coun ... | 2020 | 32271948 |
| use of blood levels to infer carcass levels of contaminants. | inferences may be made about the carcass levels of a contaminant based on the contaminant level in blood samples. a method is given for comparing such populations that utilizes bivariate normal distributions and their principal axes, thereby avoiding a dilemma arising from the use of regression techniques. confidence intervals and power calculations are given. data from captive barn owls provide partial justification for the use of this method. | 1982 | 7092327 |
| neuronal and behavioral sensitivity to binaural time differences in the owl. | we demonstrated that ongoing time disparity (otd) was a sufficient cue for the azimuthal component of receptive fields of auditory neurons in the owl (tyto alba) midbrain and that otds were sufficient to mediate meaningful behavioral responses. we devised a technique which enabled us to change easily between free field and dichotic stimuli while recording from single auditory neurons in the owl mesencephalicus lateralis pars dorsalis (mld). mld neurons with restricted spatial receptive fields (" ... | 1981 | 7346557 |
| combination of interaural level and time difference in azimuthal sound localization in owls. | a function of the auditory system is to accurately determine the location of a sound source. the main cues for sound location are interaural time (itd) and level (ild) differences. humans use both itd and ild to determine the azimuth. thus far, the conception of sound localization in barn owls was that their facial ruff and asymmetrical ears generate a two-dimensional grid of itd for azimuth and ild for elevation. we show that barn owls also use ild for azimuthal sound localization when itds are ... | 2018 | 29379866 |
| visual search in barn owls: task difficulty and saccadic behavior. | how do we find what we are looking for? a target can be in plain view, but it may be detected only after extensive search. during a search we make directed attentional deployments like saccades to segment the scene until we detect the target. depending on difficulty, the search may be fast with few attentional deployments or slow with many, shorter deployments. here we study visual search in barn owls by tracking their overt attentional deployments-that is, their head movements-with a camera. we ... | 2018 | 29322165 |
| estimation and comparison of parameters in stochastic growth models for barn owls. | alternative methods for parameter estimation and the incorporation of stochasticity into growth models are investigated and compared to the commonly used sampling error model in which error terms are simply added-on to the integrated form of the growth equation. a process error model, in which the process of growth is assumed to have stochastic variation or error incorporated within it, was found to be more appropriate for use with nonlinear estimation procedures based on a minimization of sigma ... | 1980 | 7439774 |
| morphological and molecular characterization of avian trypanosomes in raptors from thailand. | from september 2012 to may 2018, blood samples from 364 raptors (mostly adults) were collected and screened for trypanosomes and haemosporidians by microscopic examination and nested polymerase chain reactions (pcr). trypanosoma spp. were identified in 15 birds from eight different species. light microscopy revealed 14 cases of infection with trypanosoma cf. corvi, including one each in black-shouldered kite (elanus caeruleus, n = 49), brahminy kite (haliastur indus, n = 50), and spotted owlet ( ... | 2019 | 31230161 |
| center-surround organization of auditory receptive fields in the owl. | the spinal receptive fields of specialized auditory units in the midbrain of the barn owl (tyto abla) contain two functionally antagonistic areas: an excitatory center and an inhibitory surround. the response of these units represents the balance of acoustic activation of the two areas, which in turn depends upon the location, intensity, and spectral content of the sound stimulus. | 1978 | 715444 |