Interdisciplinary Program in NeuroscienceEye Movement & Vision Research LAB

Hwang, Jae Won

Somatosensory Sensation & Motor Functions

Somatosensory Sensation

Somatosensory Sensation– Modalities– Receptors– Somatosensory Pathways– Somatosensory Cortex

Motor Functions Disorders

Somatosensory Modalities

Touch Proprioception Nociception Temperature Sense

Morphology of DRG Cell

Ref. 1. Ch 22 p. 431

Mechanoreceptors (touch)

Ref. 1. Ch 22 p. 433

Mechanoreceptors (proprioception)

Ref. 1. Ch 21 p. 415

Receptor Types

Ref. 1. Ch 22 p. 432

Receptive Field (touch)

Ref. 1. Ch 22 p. 434

Two Point Discrimination

Ref. 1. Ch 22 p. 436

Distribution of DermatomesRef. 1. Ch 22 p.

445

Spinal CordRef. 1. Ch 18 p. 339 & Ref. 2. Ch 3

p.76

Touch & Proprioception(joint) PathwayRef. 3. http://thalamus.wustl.edu/course/

bassens.html

Decussation of Medial Lemnisci

Ref. 2. Ch 5 p. 195

Proprioception(muscle & tendon) Pathway

Ref. 3. http://thalamus.wustl.edu/course/body.html

Nociceptive Afferent Fibers

Ref. 1. Ch 24 p. 473-474

Pain & Temperature Pathway

Ref. 3. http://thalamus.wustl.edu/course/body.html

Sensory Pathways (summary)

Ref. 1. Ch 22 p. 447

Sensory Pathways (summary)

Ref. 1. Ch 22 p. 447

Comparison of sensory pathway description among the references

Decussation of Medial Lemnisci Spinocerebellar Anterolater

(spinothalamic)

Ref. 1 Touch &Proprioception

Pain &Temperature

Ref. 2Discriminative touch, Vibration, & Prop

rioception

Light Touch &Pressure

Pain &Temperature

Ref. 3 Discriminative touch

Proprioception Pain &Temperature

Ascending & Descending Tracts

Ref. 2. Ch 4 p. 145

Segmental Organization of SC

Ref. 2. Ch 4 p. 168

Thalamus

Ref. 1. Ch 18 p. 343

Somatosensory Cortex

Ref. 1. Ch 23 p. 453

RF of Cell in a Column in SSC

Ref. 1. Ch 23 p. 456

Receptive Fields of Neurons in SSC

Ref. 1. Ch 23 p. 455

Columnar Organization of Sensory Input

Ref. 1. Ch 23 p. 459

Sensory Homunculus

Ref. 1. Ch 18 p. 344

Processing of Sensory Information

Ref. 1. Ch 18 p. 345

Motor Functions

Somatosensory Sensation Motor Functions

– Brain Structures Involved in Motor Control– Motor Pathways– Motor Neurons– Neuromuscular Junction

Disorders

Motor Cortices

Ref. 4. Ch 4 p. 144 & Ref. 1. Ch 38 p. 760

Flow of Motor Information

Ref. 1. Ch 19 p. 356

Supplementary & Premotor Areas

Ref. 1. Ch 38 p. 773

Parietal Cortex

Ref. 4. Ch 4 p.148 & Ref. 1. Ch 28 p. 567

Command Flow of Left PL

Ref. 5. Ch 8 p. 216

Cerebellum

Ref. 1. Ch 42 p. 835

Basal Ganglia

Ref. 1. Ch 43 p. 856

Corticospinal Tract

Ref. 3. http://thalamus.wustl.edu/course/basmot.html

anterior corticospinal tract (about 10%) lateral corticospinal tract

Pyramidal Decussation

Ref. 2. Ch 5 p. 195

Corticospinal Tract

Ref. 1. Ch 18 p. 346

Corticospinal Tract

Ref. 1. Ch 18 p. 346

Corticobulbar & Rubrospinal Tracts

Ref. 5. Ch 8 p. 212

Ventromedial Pathways

Ref. 5. Ch 8 p. 213

Motor Neurons

Ref. 2. Ch 4 p. 165

Neuromuscular Junction

Ref. 1. Ch 11 p. 188

Disorders

Somatosensory Sensation Motor Functions Disorders

– Spinal Cord Syndromes– Phantom Limb– Agnosia & Apraxia– Subcortical Motor Disorders– Neurogenic Diseases of Motor Unit

Spinal Cord Syndromes

Ref. 2. Ch 4 p. 173

Phantom Limb

Ref. 1. Ch 20 p. 393

MEG of Amputee

Ref. 6. Ch 2 p. 32 & Ref. 7. p. 1610

Agnosia

The Inability to perceive or identify a stimulus by means of a particular sensory modality, even though its details can be detected by means of that modality and the person retains relatively normal intellectual capacity– Apperceptive visual agnosia

People with apperceptive visual agnosia may have normal visual acuity, but they cannot successfully recognize objects visually by their shape.

Prosopagnosia (Prosopon means “face”)– Associative visual agnosia

People with associative visual agnosia appear to be able to perceive normally but cannot name what they have seen.

Example of Agnosia

Ref. 1. Ch 62 p. 1235

Apraxia

The inability to properly execute a learned skilled movement– Limb apraxia– Constructional apraxia– Oral apraxia– Apraxic agraphia

Limb Apraxias Limb apraxia is character-i

zed by movement of the wrong part of the limb, incorrect movement of the correct part, or correct mevements but in the incorrect sequence.

Ref. 5. Ch 8 p. 215

Constructional Apraxia The primary deficit in c

onstructional apraxia appears to involve the ability to perceive and imagine geometrical relations.

Dressing Apraxia

Ref. 5. Ch 8 p. 216

Balint’s syndrome

Balint’s syndrome occurs in people with bilateral damage to posterior parietal and prestriate cortex.

Balint’s syndrome consists of three major symptoms.– Optic ataxia (ataxia comes from the Greek word for “disorderly”)

A person with BS might be able to perceive and recognize a particular object, but when he or she tries to reach for it, the movement is often misdirected.

– Ocular apraxia (“without visual action”) If an object moves, or if a light flashes, the person with BS may report se

eing something but will not be able to make an eye movement that directs the gaze toward the target.

– Simultanagnosia If the gaze of a person with BS happens to fall on an object, he or she wil

l perceive it. But only one object will be perceived at a time.

Ref. 5. Ch 6 p. 163

Hemineglect

Ref. 1. Ch 20 p. 394-396

Parkinson’s Disease

Ref. 1. Ch 43 p. 860

Huntington’s DiseaseRef. 1. Ch 43 p.

860

Diseases of the Motor Unit

Ref. 1. Ch 35 p. 697

Myasthenia Gravis

Ref. 1. Ch 16 p. 299

References1. Eric R. Kandel, James H. Schwartz, Thomas M. Jessell (2000) Principles of Neural Science, 4th ed. New York, NY: McGraw-Hill

2. Richard S. Snell (2001) Clinical neuroanatomy for medical students, 5th ed. Baltimore, MD: Lippincott Williams & Wilkins

3. Diani W. Molavi (1997) Neuroscience tutorial Retrieved from WWW April 19, 2003. http://thalamus.wustl.edu/course/

4. Marie T. Banich (1997) Neuropsychology Boston, MA: Houghton Miffin

5. Neil R. Carson (1995) Foundations of physiological psychology, 3rd ed. Needham, MA: Allyn & Bacon

6. V.S. Ramachandran, Sandra Blakeslee (1998) Phantoms in the brain New York, NY: HarperCollins

7. Ramachandran VS, Hirstein W. (1998) The perception of phantom limbs. The D. O. Hebb lecture Brain, 121, 1603-1630