1 / 30

Sensorimotor Control of Behavior: Somatosensation

Sensorimotor Control of Behavior: Somatosensation. Lecture 8. Somatosensation. Sensory info from body Cutaneous senses exteroceptors touch / pain Kinesthesia interoceptors body position & movement ~. Somatosensory cortex. S1 - Postcentral Gyrus Somatotopic Organization

olesia
Download Presentation

Sensorimotor Control of Behavior: Somatosensation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Sensorimotor Control of Behavior: Somatosensation Lecture 8

  2. Somatosensation • Sensory info from body • Cutaneous senses • exteroceptors • touch / pain • Kinesthesia • interoceptors • body position & movement ~

  3. Somatosensory cortex • S1 - Postcentral Gyrus • Somatotopic Organization • topographic representation of body • Distorted Homunculus • disproportionate amount of cortex for body parts • high sensitivity: large cortical area ~

  4. Somatosensory Cortex • Formation of a Body Image • Does not simply respond to sensory input • Phantom Limbs • after amputation • also pain ~

  5. M1 PPC S1

  6. Kinesthesia

  7. Kinesthesia • Body Position & Movement • proprioception • Joint information • Pacinian corpuscles & Ruffini endings • Muscle & tendon information • changes in tension • Golgi tendon organ • muscle spindle fibers ~

  8. Cutaneous Receptors • Stretching of the skin • Limited role in proprioception • Ruffini Endings • slow adapting • population of neurons responding simultaneously ~

  9. Cutaneous Receptors • Role depends on location • Anesthetize skin • assess ability to detect passive movement • Knee: no affect on proprioception • Mouth, hands, & feet • proprioception significantly reduced ~

  10. Muscle Receptors • Major role in proprioception • Stretch receptors • detect changes in tension • 2 types of receptors • Muscle spindles & Golgi tendon organs • differences in threshold & location ~

  11. Muscle-Spindle Receptors • Muscle length detectors • Parallel with extrafusal fibers • Low threshold • Monosynaptic stretch reflex • Postural adjustments • Muscle tonus • Sensory neuron ---> alpha motor neurons monosynaptic excitation disynaptic inhibition ~

  12. Dorsal M S + + - + Ventral +

  13. Golgi Tendon Organ • Gauges muscle tension • high threshold • Stretch receptor • safety mechanism • controlled muscle contraction ~

  14. Dorsal GTO + - Ventral Inhibits alpha motor neuron +

  15. GTO: Function • Inhibits muscle contraction • Control of motor acts • slow contraction as force increases • e.g., holding an egg breaks if too much force • Autogenic inhibition • safety mechanism • too much tension ---> damage ~

  16. The Orienting Senses

  17. Orientation: The Vestibular System • Position & motion of body in space • critical for adaptive interaction • largely unnoticed • except unusual conditions • motion sickness: nausea, dizziness • Maintenance of balance & posture • coordinating body position with other sensory information ~

  18. Receptors for Orientation • Inner ear • Gravity detectors • plane of reference • Mechanoreceptors • Vestibular Organs • otocysts • saccule • utricle • semicircular canals ~

  19. Otocysts • Liquid-filled “ear sacs” • lined with hair cells • contain otoliths • “ear stones : direction of acceleration • saccule: vertical movement • utricle: horizontal movement ~

  20. Acceleration to right Acceleration to right tilted At rest Direction of gravity

  21. Semicircular Canals • Rotary acceleration • direction & extent of circular movement • any direction • 3 fluid-filled canals • right angles to each other • 1 for each major plane • Movement causes fluid to circulate • displaces cupula ~

  22. Ampulla Crista hair cells Cupula Semicircular canals Utricle

  23. Vestibular Pathway • Vestibulocochlear nerve (VIII) • Some axons directly to cerebellum • Most axons to medulla • vestibular nuclei • cerebellum, spinal cord, medulla & pons • motor nuclei for eyes (III, IV, & VI) • compensates for movement of head • temporal cortex (dizziness) ~

  24. Input to Vestibular System • Other sensory information • eyes • trunk & neck • limbs • cerebellum • Constant postural adjustments • Maintains visual image fixed on retina • maintains center of gravity during movement ~

  25. Sensorimotor Integration

  26. Sensorimotor Integration • Somatosensory cortex • provides spatial coordinates • Motor Cortex • executes movements • Results in meaningful behavior ~

  27. Posterior Parietal Cortex - PPC • Constructs spatial coordinates for behavior • Apraxia • inability to purposefully organize movements • Left parietal apraxia • bilateral inability to perform requested movements ~

  28. Constructional apraxia - damage to PPC

  29. Spatial Neglect • Contralateral neglect • neglect of left side of body and world • Damage to right PPC • map of body & space destroyed ~

More Related