Somatosensory System of the Star-Nosed Mole PDF

The Somatosensory System of the Star Nosed Mole  A mole in the grass Description automatically generated Star Nosed Mole The “Star” of the Show Star Nosed Mole Condylura cristata Lives in wetlands in eastern USA and Canada...

The Somatosensory System of the Star Nosed Mole  A mole in the grass Description automatically generated Star Nosed Mole The “Star” of the Show Star Nosed Mole Condylura cristata Lives in wetlands in eastern USA and Canada Live in extensive tunnel system Forage for food in mud, water, or relatively dry soil Needs to sustain high rate of energy input Must consume large number of small prey Include earthworms and aquatic insects Fastest mammal at food handling How The Star Nosed Mole Feeds Explores ground with rays of nose Up to 13 different patches sampled each second If one of longer rays hits worm, mole immediately moves nose to examine worm in greater detail with shortest ray Ray number 11 Mole hardly ever bites and swallows food if not inspected with ray 11 How does the star decrease prey search time?  The Nose Nostrils surrounded by 22 fleshy and mobile appendages or rays Part of nose, but structure is highly specialized touch sensitive organ Only 1cm across Has 100,00 nerve fibers innervating the organ Can help identify and consume up to ten pieces of earthworm within 2.3 seconds Covered in more than 25,000 microscopic protuberances, or papillae Eimer’s organ Eimer’s Organ Marasco PD, Tsuruda PR, Bautista DM, Julius D, Catania KC. Neuroanatomical evidence for segregation of nerve fibers conveying light touch and pain sensation in Eimer's organ of the mole. Proc Natl Acad Sci U S A. 2006 Jun 13;103(24):9339-44. doi: 10.1073/pnas.0603229103. Epub 2006 Jun 2. An Array of Sensory Receptors Terminal Swellings of Free Nerve Endings Merkel-like Complex Encapsulated Corpuscle Myelinated Fibers Terminal Swellings of Free Nerve Endings Made of array of neural structures that signal different aspects of touch Originate from myelinated afferents in underlying dermis Single swelling in center surrounded by ring of closely opposed terminal swellings Central Inner Layer Low threshold mechanoreceptors Peripheral Outer Layer Use Substance P High threshold, peptidergic nociceptors Merkel Cell One Merkel cell neurite complex is located at bottom Signals only sustained depression of skin (slow adapting) Commonly found in mammalian skin  Encapsulated Corpuscle One lamellated corpuscle beneath Merkel cell Single nerve ending encircled by many concentric rings (lamellae) of tissue formed by Schwann Cells Type of Pacinian Corpuscle Transmits: Relatively simple information about vibrations When individual appendage first contacts object (rapidly adapting) Number of Eimer’s Organs J. Comp. Neurol. 1997 How is the star represented in the somatosensory cortex? J. Comp. Neurol. 1997 Using the Star Fastest Nose Around Nature 2005  Foveation! Number of touches to prey for each ray (10 J. Comp. Neurol. 1997 trials) * * J. Comp. Physiol. A. The Circuit V: Trigeminal Nerve (Cranial Nerve V) Pons: PrV: Principal Trigeminal Sensory Nucleus (discriminative touch) Spinal Trigeminal Nuclei SP50: Oral subnucleus (oral reflexes and nociception) Sp5I: Interpolar subnucleus (sensation of movement) Sp5C: caudal subnucleus (nociception and temperature) Catania KC, Leitch DB, Gauthier D (2011) A Star in the Brainstem Reveals the First Step of Cortical Magnification. PLOS ONE 6(7) The Circuit Catania KC, Leitch DB, Gauthier D (2011) A Star in the Brainstem Reveals the First Step of Cortical Magnification. PLOS ONE 6(7)  A Star in the Principal Trigeminal Sensory Nucleus Ray 11 takes up 14% of PrV Measured with: electrophysiology recordings cytochrome oxidase ICC Catania KC, Leitch DB, Gauthier D (2011) A Star in the Brainstem Reveals the First Step of Cortical Magnification. PLOS ONE 6(7) “Striped” Nature 2001 Primary Cortex: Topographic Relationships Catania KC, Leitch DB, Gauthier D (2011) A Star in the Brainstem Reveals the First Step of Cortical Magnification. PLOS ONE 6(7) Cortical Stripe Size: Why is the 11th ray so largely represented? Nature 2001 25 % Catania KC, Leitch DB, Gauthier D (2011) A Star in the Brainstem Reveals the First Step of Cortical Magnification. PLOS ONE 6(7) Brain Organization of Star Nosed Mole: Layer 4 Cortex  Scientific American 2002 “Mole-unculus”