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A Touching Experience: Somatosensation Image removed due to copyright considerations.Please see "Squire, Larry R., ed. Fundamental Neuroscience. 2nd ed.

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Presentation on theme: "A Touching Experience: Somatosensation Image removed due to copyright considerations.Please see "Squire, Larry R., ed. Fundamental Neuroscience. 2nd ed."— Presentation transcript:

1 A Touching Experience: Somatosensation Image removed due to copyright considerations.Please see "Squire, Larry R., ed. Fundamental Neuroscience. 2nd ed. Boston,MA: Academic Press, 2003, Figure 25-14. ISBN: 0126603030."

2 Overview I.Peripheral encoding in 2 pathways II. Central Nervous System encoding in 2 pathways III. Cortex: Basic organizational principles IV. Cortex: Plasticity & its perceptual implications

3 Head lesioned the nerve in his own hand to feel how sensation returned as the nerve recovered. Found there were 2 distinct recovery phases: Image removed due to copyright reasons. Protopathic--> Temperature and Pain Epicritic -->Non-painful touch, spatially and temporally precise sensations Henry Head: The Vincent Van Gogh of Somatosensory Neuroscience

4 Distinct Pathways : Peripheral Encoding of Fine Temporal & Spatial Info * Defining features of receptive field properties: Firing properties & receptive field size * Slowly adapting vs rapidly adapting: Distinction? * Why is this distinction needed? Image removed due to copyright reasons. Please see "Squire, Larry R., ed. Fundamental Neuroscience. 2nd ed. Boston, MA: Academic Press, 2003, Figure 25-3. ISBN: 0126603030."

5 Peripheral Receptors: Slowly Adapting (SA), Merkels * Merkel cells/disks, SA Type I -> Dense innervation of skin (100/cm2) -> Respond with SA discharge, sensitive to edges, points and surface features -> Spatial rf size: 2-3 mm2 * Perceptual abilities we need these for? 2-Point Discrimination Images removed due to copyright reasons. Please see "Squire, Larry R., ed. Fundamental Neuroscience. 2nd ed. Boston, MA: Academic Press, 2003, Figures 25-1 and 25-5. ISBN: 0126603030."

6 Peripheral Receptors: Slowly Adapting, Ruffini * SA Type II (Ruffini corpuscles?) -> Only in humans -> 2-4 x less sensitive than SAI -> Respond to skin stretch * Perceptual abilities we need these for?. Image removed due to copyright reasons. Please see "Squire, Larry R., ed. Fundamental Neuroscience. 2nd ed. Boston, MA: Academic Press, 2003, Figure 25-5. ISBN: 0126603030."

7 Peripheral Receptors: Rapidly Adapting/Meissners Meissners Corpuscle Image removed due to copyright reasons.

8 Peripheral Receptors: Pacinian Corpuscles Pacinian Corpuscle Image removed due to copyright reasons.

9 Peripheral Receptors: Anatomical/Structual Determinants of Functional Capability Image removed due to copyright reasons.

10 Structural Determinants of Displacement Sensitivity & Spatial/Temporal Specificity Images removed due to copyright reasons. Please see "Squire, Larry R., ed. Fundamental Neuroscience. 2nd ed. Boston, MA: Academic Press, 2003, Figure 25-5. ISBN: 0126603030."

11 Structural Determinants of Displacement Sensitivity & Spatial/Temporal Specificity Image removed due to copyright reasons. Please see "Squire, Larry R., ed. Fundamental Neuroscience. 2nd ed. Boston, MA: Academic Press, 2003. ISBN: 0126603030."

12 Distinct Pathways : Peripheral Encoding of Pain &Temperature Paradoxical Cold Hot stimuli applied to a very discrete point on the skin can be perceived as cold in some cases…Why?

13 Distinct Pathways : Perception is not only a Labeled Line What is a labeled line? The Coca-Cola Illusion…

14 Overview I.Peripheral encoding in 2 pathways II. Central Nervous System encoding in 2 pathways III. Cortex: Basic organizational principles IV.Cortex: Plasticity & its perceptual implications Image removed due to copyright reasons.

15 PNS vs CNS: Dorsal Root * Pseudounipolar Neuron Image removed due to copyright reasons. * Dorsal Root Ganlgion * PNS/CNS division point

16 Dermatomes * Dorsal roots cover a distinct body region * 4 distinct ascending segments of the cord Image removed due to copyright reasons. Please see "Squire, Larry R., ed. Fundamental Neuroscience. 2nd ed. Boston, MA: Academic Press, 2003, Figure 25-9. ISBN: 0126603030.

17 Entoumbences: Why? Image removed due to copyright reasons. Please see "Squire, Larry R., ed. Fundamental Neuroscience. 2nd ed. Boston, MA: Academic Press, 2003, Figure 25-9. ISBN: 0126603030."

18 Spinal Cord: Segregation of Gray & White Matter Image removed due to copyright reasons.

19 Segregation of Pathways for Touch & Pain * Dorsal Column-Medial Lemniscus Pathway (DCML) & Anterolateral Pathway (AL) Image removed due to copyright reasons. Please see "Squire, Larry R., ed. Fundamental Neuroscience. 2nd ed. Boston, MA: Academic Press, 2003, Figure 25-11. ISBN: 0126603030."

20 Spinal Cord: Segregation of Pathways for Touch & Pain * Dorsal Column-Medial Lemniscus Pathway (DCML) Image removed due to copyright reasons. Please see "Squire, Larry R., ed. Fundamental Neuroscience. 2nd ed. Boston, MA: Academic Press, 2003, Figure 25-11. ISBN: 0126603030." Image removed due to copyright reasons.

21 Location of DCN & Medial Lemniscus * DC projections synapse in the dorsal column nuclei Images removed due to copyright reasons.

22 Spinal Cord: Segregation of Pathways for Touch & Pain Image removed due to copyright reasons. Please see "Squire, Larry R., ed. Fundamental Neuroscience. 2nd ed. Boston, MA: Academic Press, 2003, Figure 25-11. ISBN: 0126603030."

23 Thalamus: Store Room of Relay & Modulatory Nuclei Image removed due to copyright reasons.

24 Somatosensory Pathways: Thalamic Relay Nuclei * Ventrobasal complex is a collection of somatosensory thalamic nuclei with distinct properties * Tactile inputs from body (DCML) synapse on the ventral posterior lateral nucleus (VPL), facial tactile inputs synapse in VPM Image removed due to copyright reasons.

25 Somatosensory Pathways: Thalamic Relay Nuclei * Ventrobasal complex is a collection of somatosensory thalamic nuclei with distinct properties * Deep/proprioceptive inputs input to regions surrounding the VPL, the shell region, as opposed to the tactile core region Image removed due to copyright reasons. Please see "Squire, Larry R., ed. Fundamental Neuroscience. 2nd ed. Boston, MA: Academic Press, 2003, Figure 25-14. ISBN: 0126603030."

26 Overview I.Peripheral encoding in 2 pathways II. Central Nervous System encoding in 2 pathways III. Cortex: Basic organizational principles Areas, Maps, Columns and Magnification IV.Cortex: Plasticity & its perceptual implications Image removed due to copyright reasons.

27 Somatosensory Pathways: Cortical Areas * Areas 3b and 1 receive VP Nucleus Core input, and 3a and 2 VP Shell input * Convergent intracortical connections predict area 2 rf properties Image removed due to copyright reasons. Please see "Squire, Larry R., ed. Fundamental Neuroscience. 2nd ed. Boston, MA: Academic Press, 2003, Figure 25-14. ISBN: 0126603030."

28 Somatosensory Pathways: Cortical Areas * 4 key distinct areas in the Post-central gyrus: Area 3b = SI -> discrete tactile rf Area 1 -> Similar to 3b, more RA rf Area 3a deep & proprioceptive Area 2 touch + proprioception Please see "Moore, C. I., C. Stern, S. Corkin, B. Fischl, A. Gray, B. Rosen, and A. M. Dale. "Segregation of somatosensory activation in the human hand area using fMRI." Journal of Neurophysiology 84 (2000): 558-569."

29 Somatosensory Cortex: Cortical Maps * Initially motor maps were inferred by Hughlings Jackson (Jacksonian March) Initially motor maps were inferred by Hughlings Jackson (Jacksonian March) * Head (1920), tactile maps Inferred from crude lesion patients Penfield, electrical stimulation and in surgery patient reports * Penfield and S. Corkin, well- described lesions post-surgery Image removed due to copyright reasons. Please see "Squire, Larry R., ed. Fundamental Neuroscience. 2nd ed. Boston, MA:Academic Press, 2003, Figure 25-15. ISBN: 0126603030."

30 Visual Cortex: Cortical Columns Discovered & explicated by Mountcastle: Cells in a vertical dimension across the layers of the neocortex tend to have the same rf properties Images removed due to copyright reasons.

31 Somatosensory Cortex: Cortical Columns * Orientation columns in V1 Image removed due to copyright reasons. Please see "Squire, Larry R., ed. Fundamental Neuroscience. 2nd ed. Boston, MA: Academic Press, 2003. ISBN: 0126603030."

32 Cortical Isofrequency Columns Auditory Cortex Image removed due to copyright reasons. Please see "Kilgard, M.P., and M. M. Merzenich. "Distributed representation of spectral and temporal information in rat primary auditory cortex." Hearing Research 134 (1999), 16-28."

33 Somatosensory Cortex: Cortical Magnification * Cortical Magnification Rule: Space devoted to a skin surface is inversely proportional to the size of the receptive field in that area (Sur et al., 1980) Image removed due to copyright reasons. Please see "Squire, Larry R., ed. Fundamental Neuroscience. 2nd ed. Boston, MA: Academic Press, 2003, Figure 25-15. ISBN: 0126603030." Image removed due to copyright reasons. Please see "Sur, M, M. M. Merzenich, and J. H. Kaas. "Magnification, receptive-field area, and "hypercolumn" size in areas 3b and 1 of somatosensory cortex in owl monkeys." Journal of Neurophysiology 44 (1980): 295-311."

34 Overview I.Peripheral encoding in 2 pathways II. Central Nervous System encoding in 2 pathways III. Cortex: Basic organizational principles Areas, Maps, Columns and Magnification IV.Cortex: Plasticity & its perceptual implications Image removed due to copyright reasons.

35 Somatosensory Cortex: Adult Cortical Plasticity Images removed due to copyright reasons.

36 Somatosensory Cortex: Adult Cortical Plasticity Images removed due to copyright reasons.

37 Perceptual Consequences * Phantom Limbs, reference zones Image removed due to copyright reasons

38 Perceptual Consequences Beyond Phantom Limb? * Increased spatial tactile resolution in reference zones. First discovered By Teuber (founder of the Department) * Possible cause? Image removed due to copyright reasons.

39 Effect of Massive Deafferentation: Spinal-Cord Injury * Phantom body sensations

40 Effect of Massive Deafferentation: Cortical Plasticity * Cortical activation maps to the phantom percept, but whats the problem here? Whats the answer? mage removed due to copyright reasons. Please see "Moore, C. I., C. E., Stern, C., Dunbar, S., Kostyk, A., Gehi, and S., Corkin. "Referred Phantom Sensations and Cortical Reorganization After Spinal Cord Injury in Humans." PNAS USA 97 (2000): 14703-14708."

41 Effect of Massive Deafferentation: Cortical Plasticity * Cortical activation maps to the phantom percept,Cortical Plasticity:Adaptive Effects * Wang et al: Trained skin regions develop but whats the problem here? Whats the answer? Image removed due to copyright reasons. Please see "Moore, C. I., C. E., Stern, C., Dunbar, S., Kostyk, A., Gehl, and S., Corkin. "Referred Phantom Sensations and Cortical Reorganization After Spinal Cord Injury in Humans." PNAS USA 97 (2000): 14703- 14708." Image removed due to copyright reasons.

42 Cortical Plasticity: Adaptive Effects Wang et al: Trained skin regions develop overlapping rf. * String instrument players have expanded representations of the picking hand Image removed due to copyright reasons. Please see "Wang, X., M. M. Merzenich, K. Sameshima, and W. M. Jenkins. "Remodeling of hand representation in adult cortex determined by timing of tactile stimulation." Nature 378 (1995): 71-75."

43 Overview I.Peripheral encoding in 2 pathways II. Central Nervous System encoding in 2 pathways III. Cortex: Basic organizational principles Areas, Maps, Columns and Magnification IV.Cortex: Plasticity & its perceptual implications Image removed due to copyright reasons.


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