02 Posterior Column Medial Lemniscus

Question 1

stereognosis

Answer 1

-recognizing object by light touch (are you holding coins or keys?)

Question 2

graphesthesia

Answer 2

-recognizing by light touch what is being written on your skin

Question 3

In PCML, vertebral level that divides fasciculus gracilis and cuneatus

Answer 3

T7, above is cuneatus, below is gracilis

Question 4

large Central Cord lesion: what sense is last to be lost and why

Answer 4

Sacral, since sacral anterolateral axons are on the periphery of cord

Question 5

PCML somatotopy orientation at:

• cord
• rostral medulla
• pons

Answer 5

Somatotopy: orientation of dermatomes.

• Cord: legs medial
• Rostral Medulla: legs ventral (standing up)
• Pons: legs lateral, add in head from CN V

Question 6

What region of thalamus does PCML pass through

Answer 6

VPL-ventral posterior lateral

VPM for spinothalamic sense

Question 7

SI cortex regions:

3a, 3b, 1, 2

Answer 7

3a: limb movement
3b: basic tactile (edges etc)
1: motion and direction of movement of objects
2. : limb position

Question 8

SI and SII cortex

-location, function

Answer 8

SI cortex: primary somatosensory cortex

SII cortex: secondary ss cortex, located at parietal operculum along lateral fissure. SI neurons project to SII cortex.

Question 9

parietal association cortices

• location
• function

Answer 9

• located along intraparietal sulcus

- receive sensory info, then project to motor cortex

Question 10

parietal association cortices

-types, and their lesion effects

Answer 10

1. Unimodal. ex. visual, auditory. Lesion–agnosia (unable to recognize object)
2. Multimodal. combine sensation with motivation, relevance. Lesion–contralateral neglect

Question 11

Contralateral neglect

Answer 11

• lesion of parietal association cortex (receive sensory info then project to motor cortex)
• Pt unable to recognize one side of the world (ex cannot draw left sides of objects)