The Experts below are selected from a list of 54 Experts worldwide ranked by ideXlab platform
Daniel J Tollin - One of the best experts on this subject based on the ideXlab platform.
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spatial hearing ability of the Pigmented Guinea Pig cavia porcellus minimum audible angle and spatial release from masking in azimuth
2018Co-Authors: Nathaniel T Greene, Kelsey L Anbuhl, Alexander T Ferber, Marisa C Deguzman, Paul D Allen, Daniel J TollinAbstract:Abstract Despite the common use of Guinea Pigs in investigations of the neural mechanisms of binaural and spatial hearing, their behavioral capabilities in spatial hearing tasks have surprisingly not been thoroughly investigated. To begin to fill this void, we tested the spatial hearing of adult male Guinea Pigs in several experiments using a paradigm based on the prepulse inhibition (PPI) of the acoustic startle response. In the first experiment, we presented continuous broadband noise from one speaker location and switched to a second speaker location (the “prepulse”) along the azimuth prior to presenting a brief, ∼110 dB SPL startle-eliciting stimulus. We found that the startle response amplitude was systematically reduced for larger changes in speaker swap angle (i.e., greater PPI), indicating that using the speaker “swap” paradigm is sufficient to assess stimulus detection of spatially separated sounds. In a second set of experiments, we swapped low- and high-pass noise across the midline to estimate their ability to utilize interaural time- and level-difference cues, respectively. The results reveal that Guinea Pigs can utilize both binaural cues to discriminate azimuthal sound sources. A third set of experiments examined spatial release from masking using a continuous broadband noise masker and a broadband chirp signal, both presented concurrently at various speaker locations. In general, animals displayed an increase in startle amplitude (i.e., lower PPI) when the masker was presented at speaker locations near that of the chirp signal, and reduced startle amplitudes (increased PPI) indicating lower detection thresholds when the noise was presented from more distant speaker locations. In summary, these results indicate that Guinea Pigs can: 1) discriminate changes in source location within a hemifield as well as across the midline, 2) discriminate sources of low- and high-pass sounds, demonstrating that they can effectively utilize both low-frequency interaural time and high-frequency level difference sound localization cues, and 3) utilize spatial release from masking to discriminate sound sources. This report confirms the Guinea Pig as a suitable spatial hearing model and reinforces prior estimates of Guinea Pig hearing ability from acoustical and physiological measurements.
Salvador Gonzalez - One of the best experts on this subject based on the ideXlab platform.
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detection of uv induced Pigmentary and epidermal changes over time using in vivo reflectance confocal microscopy
2006Co-Authors: Maritza A Middelkamphup, Heeyoung Park, Barbara A Gilchrest, Salvador GonzalezAbstract:In vivo reflectance confocal microscopy (RCM) provides high-resolution optical sections of the skin in its native state, without needing to fix or section the tissue. Melanin provides an excellent contrast for RCM, giving a bright signal in the confocal images. The Pigmented Guinea-Pig is a common animal model to study human Pigment induction and modulation, as its tanning response is comparable to human tanning after exposure to ultraviolet radiation (UVR). We investigated the applicability of RCM to detecting UVR-induced Pigmentary changes in this model. Animals were exposed to solar simulator radiation for 7 days. RCM was performed during the irradiation and follow-up period. Compared to non-irradiated skin, an increase in melanocyte size, dendricity, and number, as well as increased Pigment in keratinocytes, was seen in the irradiated epidermis. Interestingly, these changes could be detected even before a tanning response was clinically visible. UVR-induced epidermal hyperplasia could also be detected and quantified. In conclusion, in vivo RCM is a sensitive non-invasive imaging technique that can repeatedly measure epidermal Pigmentation and thickness, as demonstrated in the Guinea-Pig model. This technique should greatly enhance our appreciation of dynamic Pigmentary changes in human or animal skin over time and in response to specific stimuli.
S Lofgren - One of the best experts on this subject based on the ideXlab platform.
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high lenticular tolerance to ultraviolet radiation b by Pigmented Guinea Pig application of a safety limit strategy for uvr induced cataract
2012Co-Authors: V Mody, M Kakar, Per G Soderberg, S LofgrenAbstract:. Purpose: The purpose of this study was to determine a threshold measure, maximum tolerable dose (MTD), for avoidance of UVR-B-induced cataract in the Pigmented Guinea-Pig. Methods: Thirty pupil-dilated anesthetized young female Guinea-Pigs, divided into five equal groups, received between 0 and 84.9 kJ/m2 unilateral UVR-B. Lens extraction and in vitro lens photography occurred 24 hr after exposure. Measurement of intensity of lens light scattering served as quantifying tool for the degree of cataract. Data analysis included regression, using a second order polynomial model. The applied MTD concept was based on the UVR-B dose–response curve obtained for the Pigmented Guinea-Pig. A smaller number of Pigmented Guinea-Pigs, Pigmented rats and albino rats underwent morphometric analysis of the anterior segment geometry. Results: All eyes exposed to UVR-B developed cataract in the anterior subcapsular region. MTD for avoidance of UVR-B-induced cataract was 69.0 kJ/m2 in the Pigmented Guinea-Pig. Iris was considerably thicker in the Guinea-Pig than in the rats. Lens blockage by the dilated iris was lowest in the Guinea-Pig. Conclusions: Maximum tolerable dose for avoidance of UVR-B-induced cataract in the Pigmented Guinea-Pig was 69.0 kJ/m2, over 10-fold higher than the threshold 5 kJ/m2 obtained by Pitts et al. in the Pigmented rabbit. Maximum tolerable dose is an appropriate method for estimation of toxicity for UVR-B-induced cataract in the Guinea-Pig. The Pigmented Guinea-Pig is significantly less sensitive to UVR-B exposure than the Pigmented rabbit and Pigmented rat.
Nathaniel T Greene - One of the best experts on this subject based on the ideXlab platform.
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spatial hearing ability of the Pigmented Guinea Pig cavia porcellus minimum audible angle and spatial release from masking in azimuth
2018Co-Authors: Nathaniel T Greene, Kelsey L Anbuhl, Alexander T Ferber, Marisa C Deguzman, Paul D Allen, Daniel J TollinAbstract:Abstract Despite the common use of Guinea Pigs in investigations of the neural mechanisms of binaural and spatial hearing, their behavioral capabilities in spatial hearing tasks have surprisingly not been thoroughly investigated. To begin to fill this void, we tested the spatial hearing of adult male Guinea Pigs in several experiments using a paradigm based on the prepulse inhibition (PPI) of the acoustic startle response. In the first experiment, we presented continuous broadband noise from one speaker location and switched to a second speaker location (the “prepulse”) along the azimuth prior to presenting a brief, ∼110 dB SPL startle-eliciting stimulus. We found that the startle response amplitude was systematically reduced for larger changes in speaker swap angle (i.e., greater PPI), indicating that using the speaker “swap” paradigm is sufficient to assess stimulus detection of spatially separated sounds. In a second set of experiments, we swapped low- and high-pass noise across the midline to estimate their ability to utilize interaural time- and level-difference cues, respectively. The results reveal that Guinea Pigs can utilize both binaural cues to discriminate azimuthal sound sources. A third set of experiments examined spatial release from masking using a continuous broadband noise masker and a broadband chirp signal, both presented concurrently at various speaker locations. In general, animals displayed an increase in startle amplitude (i.e., lower PPI) when the masker was presented at speaker locations near that of the chirp signal, and reduced startle amplitudes (increased PPI) indicating lower detection thresholds when the noise was presented from more distant speaker locations. In summary, these results indicate that Guinea Pigs can: 1) discriminate changes in source location within a hemifield as well as across the midline, 2) discriminate sources of low- and high-pass sounds, demonstrating that they can effectively utilize both low-frequency interaural time and high-frequency level difference sound localization cues, and 3) utilize spatial release from masking to discriminate sound sources. This report confirms the Guinea Pig as a suitable spatial hearing model and reinforces prior estimates of Guinea Pig hearing ability from acoustical and physiological measurements.
Brett R Schofield - One of the best experts on this subject based on the ideXlab platform.
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superior paraolivary nucleus in the Pigmented Guinea Pig separate classes of neurons project to the inferior colliculus and the cochlear nucleus
1991Co-Authors: Brett R SchofieldAbstract:The superior paraolivary nucleus is a large component of the superior olivary complex in rodents and a major source of input to the inferior colliculi and the cochlear nuclei. In the present study, retrograde transport of the fluorescent tracers Fluoro-Gold, Fluoro-Ruby (tetramethyl rhodamine conjugated to dextran), fluorescein-coated microspheres, and Fast Blue were used to reveal the morphology and collateral projection patterns of cells in the superior paraolivary nucleus. The ascending projections to the inferior colliculus from the superior paraolivary nucleus arise mainly from round, multipolar cells, including large cells that project exclusively to the inferior colliculi and not to the cochlear nuclei. Projections to the ipsilateral and contralateral inferior colliculi arise from cells with similar morphology and, in fact, many of the cells that project contralaterally project ipsilaterally as well. Projections to the ipsilateral and contralateral cochlear nuclei arise primarily from cells that do not have collicular projections. On average, the somas of these cells are significantly smaller and more elongated than those that project to the inferior colliculi. Overlap between these ascending and descending systems is restricted to a small percentage of cells that send collateral projections to both the ipsilateral cochlear nucleus and the ipsilateral inferior colliculus. These cells are small and moderately elongated. Thus the ascending and descending projections examined here arise largely from different cells that belong to different morphological classes.