Topical organization of somatic projections in the fur seal cerebral cortex

Ladygina, T F; Попов, В. В.; Supin, Alexander Ya.

doi:10.1007/bf01052461

Cited by 16 publications

(25 citation statements)

References 7 publications

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“…Our anatomical data support the hypothesis that the pinniped mystacial array is finely tuned, with each vibrissa specialized to perceive different resonances, depending on its unique morphology [Marshall et al, 2006;GinterSummarell et al, 2015]. Moreover, because all northern fur seal (Callorhinus ursinus) mystacial vibrissae (except the most dorsal row) project similarly onto the somatosensory cortex [Ladygina et al, 1985], it appears that, despite innervation differences, harp seal microvibrissae are functionally as important as macrovibrissae, perhaps just tuned for different tactile functions.…”

Section: Functional Compartmentalization and Conclusionsupporting

confidence: 67%

“…Our mean maximum lateral F-SC length was similar to other measurements reported for harp seals, but it is the shortest value described among other pinnipeds so far [Yablokov and Klevezal, 1962;Ling, 1972;Hyvärinen and Katajisto, 1984;Marshall et al, 2006;McGovern et al, 2015]. Even with five vibrissal pads from adult specimens included in our dataset, the longest harp seal HS was shorter than other reported pinniped HS lengths, except for those found in Ross seals (Ommatophoca rossii) [Ling, 1966[Ling, , 1972Ladygina et al, 1985;Marshall et al, 2006;McGovern et al, 2015]. Decreases in HS length were apparent as vibrissae became more medial, a pattern also evident in other mammals [Brecht et al, 1997].…”

Section: General Morphologysupporting

confidence: 51%

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Follicle Microstructure and Innervation Vary between Pinniped Micro- and Macrovibrissae

Mattson

Marshall²

2016

Brain Behav Evol

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Histological data from terrestrial, semiaquatic, and fully aquatic mammal vibrissa (whisker) studies indicate that follicle microstructure and innervation vary across the mystacial vibrissal array (i.e. medial microvibrissae to lateral macrovibrissae). However, comparative data are lacking, and current histological studies on pinniped vibrissae only focus on the largest ventrolateral vibrissae. Consequently, we investigated the microstructure, medial-to-lateral innervation, and morphometric trends in harp seal (Pagophilus groenlandicus) vibrissal follicle-sinus complexes (F-SCs). The F-SCs were sectioned either longitudinally or in cross-section and stained with a modified Masson's trichrome stain (microstructure) or Bodian's silver stain (innervation). All F-SCs exhibited a tripartite blood organization system. The dermal capsule thickness, the distribution of major branches of the deep vibrissal nerve, and the hair shaft design were more symmetrical in medial F-SCs, but these features became more asymmetrical as the F-SCs became more lateral. Overall, the mean axon count was 1,221 ± 422.3 axons/F-SC and mean axon counts by column ranged from 550 ± 97.4 axons/F-SC (medially, column 11) to 1,632 ± 173.2 axons/F-SC (laterally, column 2). These values indicate a total of 117,216 axons innervating the entire mystacial vibrissal array. The mean axon count of lateral F-SCs was 1,533 ± 192.9 axons/ F-SC, which is similar to values reported in the literature for other pinniped F-SCs. Our data suggest that conventional studies that only examine the largest ventrolateral vibrissae may overestimate the total innervation by ∼20%. However, our study also accounts for variation in quantification methods and shows that conventional analyses likely only overestimate innervation by ∼10%. The relationship between axon count and cross-sectional F-SC surface area was nonlinear, and axon densities were consistent across the snout. Our data indicate that harp seals exhibit microstructural and innervational differences between their microvibrissae (columns 8-11) and macrovibrissae (columns 1-7). We hypothesize that this feature is conserved among pinnipeds and may result in functional compartmentalization within their mystacial vibrissal arrays.

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Section: Functional Compartmentalization and Conclusionsupporting

confidence: 67%

Section: General Morphologysupporting

confidence: 51%

Follicle Microstructure and Innervation Vary between Pinniped Micro- and Macrovibrissae

Mattson

Marshall²

2016

Brain Behav Evol

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“…The vibrotactile sense of pinnipeds relies on sturdy, specialized vibrissae and supporting hypertrophied neural architecture (Ladygina et al, 1985;Marshall et al, 2006;Hyvärinen et al, 2009;Ginter et al, 2012;Mcgovern et al, 2015), and can gather information from both terrestrial and marine environments. Pinnipeds use their vibrissae for the tactile discrimination of surfaces (Dehnhardt, 1994;Dehnhardt and Kaminski, 1995;Grant et al, 2013) and the detection and following of underwater wakes (Dehnhardt et al, 2001;Gläser et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Vibrissal sensitivity in a harbor seal (Phoca vitulina)

Murphy

Reichmuth

Mann

2015

Journal of Experimental Biology

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Prior efforts to characterize the capabilities of the vibrissal system in seals have yielded conflicting results. Here, we measured the sensitivity of the vibrissal system of a harbor seal (Phoca vitulina) to directly coupled sinusoidal stimuli delivered by a vibrating plate. A trained seal was tested in a psychophysical paradigm to determine the smallest velocity that was detectable at nine frequencies ranging from 10 to 1000 Hz. The stimulus plate was driven by a vibration shaker and the velocity of the plate at each frequency-amplitude combination was calibrated with a laser vibrometer. To prevent cueing from other sensory stimuli, the seal was fitted with a blindfold and headphones playing broadband masking noise. The seal was sensitive to vibrations across the range of frequencies tested, with best sensitivity of 0.09 mm s −1 at 80 Hz. Velocity thresholds as a function of frequency showed a characteristic U-shaped curve with decreasing sensitivity below 20 Hz and above 250 Hz. To ground-truth the experimental setup, four human subjects were tested in the same paradigm using their thumb to contact the vibrating plate. Threshold measurements for the humans were similar to those of the seal, demonstrating comparable tactile sensitivity for their structurally different mechanoreceptive systems. The thresholds measured for the harbor seal in this study were about 100 times more sensitive than previous in-air measures of vibrissal sensitivity for this species. The results were similar to those reported by others for the detection of waterborne vibrations, but show an extended range of frequency sensitivity.

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“…The same comparison can be made with the mechanoreceptor density in the ring sinus of the FSC, where the [79].…”

Section: Under the Skin: Structurementioning

confidence: 99%

“…In [79], different parts of a fur seal were stimulated while the activity of cortical neurons was recorded via microelectrodes inserted in the somatosensory cortex. Excitation of the vibrissae was found to stimulate a large portion of the somatosensory cortex (Figure 1-9).…”

Section: Under the Skin: Structurementioning

confidence: 99%

Passive wake detection using seal whisker-inspired sensing

Beem¹

2015

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This thesis is motivated by a series of biological experiments that display the harbor seal's extraordinary ability to track the wake of an object several seconds after it has swum by. They do so despite having auditory and visual cues blocked, pointing to use of their whiskers as sensors of minute water movements. In this work, I elucidate the basic fluid mechanisms that seals may employ to accomplish this detection. Key are the unique flow-induced vibration properties resulting from the geometry of the harbor seal whisker, which is undulatory and elliptical in cross-section.First, the vortex-induced vibration (VIV) characteristics of the whisker geometry are tested. Direct force measurements and flow visualizations on a rigid whisker model undergoing a range of 1-D imposed oscillations show that the geometry passively reduces VIV (factor of > 10), despite contributions from effective added mass and damping. Next, a biomimetic whisker sensor is designed and fabricated. The rigid whisker model is mounted on a four-armed flexure, allowing it to freely vibrate in both in-line and crossflow directions. Strain gauges on the flexure measure deflections at the base. Finally, this device is tested in a simplified version of the fish wake -seal whisker interaction scenario. The whisker is towed behind an upstream cylinder with larger diameter. Whereas in open water the whisker exhibits very low vibration when its long axis is aligned with the incoming flow, once it enters the wake it oscillates with large amplitude and its frequency coincides with the Strouhal frequency of the upstream cylinder. This makes the detection of an upstream wake as well as an estimation of the size of the wake-generating body possible. A slaloming motion among the wake vortices causes the whisker to oscillate in this manner. The same mechanism has been previously observed in energy-extracting foils and trout actively swimming behind bluff cylinders in a stream. Dave, Jason, Gabe, Pablo, Remi, and Yahya were postdocs when we first met.Thank you for being approachable and sharing much needed advice all along the way.Your love of science has inspired me to be more inquisitive.Brandon, Chris, Matthew, and Patrick were undergrads or high school students who spent their summers working in the Tow Tank with me. Thanks for giving me the chance to practice being a mentor, moving this research forward a lot faster than I could do on my own, and helping me lift the mega-whisker in and out of the tank! May you all keep on building and exploring.Thanks to Kathy Streeter and the New England Aquarium staff for helping me understand more about real harbor seals. They graciously collected shed whisker specimens and allowed me to take many close-up pictures of their seals.Thanks to all the people who helped me prepare for and make it through research cruises: Eric Hayden, Terry Hammar, and Hanu Singh for contributing their expertise 5 to help me make my first ocean-ready sensor, all parties involved in the first UNOLS Chief Scientist Training Cruise se...

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Topical organization of somatic projections in the fur seal cerebral cortex

Cited by 16 publications

References 7 publications

Follicle Microstructure and Innervation Vary between Pinniped Micro- and Macrovibrissae

Follicle Microstructure and Innervation Vary between Pinniped Micro- and Macrovibrissae

Vibrissal sensitivity in a harbor seal (Phoca vitulina)

Passive wake detection using seal whisker-inspired sensing

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