Lecture 35: Parietal Lobe Syndromes

Question 1

What are the functions of the LEFT hemisphere?

Answer 1

• language

- praxis (skilled movement of the hand)

Question 2

What are the functions of the RIGHT hemisphere

Answer 2

• prosody
• spatial representation
• attention

Question 3

Function of Anterior brain (in front of central sulcus)

Answer 3

Action

Question 4

Function of Posterior brain (behind central sulcus)

Answer 4

Perception

Question 5

Function of dorsal brain

Answer 5

Where objects are

Question 6

Function of Ventral brain

Answer 6

What objects are

Question 7

What is the function of the Somatosensory association area (behind S1)?

Answer 7

-integration of visual, tactile and proprioceptive information to represent body in space
Example: treating tools or something you touch/use as an extension of yourself
Example 2: Pinocchio illusion…touching someone elses nose while touching your nose, gives you a feeling of a longer nose

Question 8

What are the functions of the LEFT parietal lobe?

Answer 8

A. Praxis
-Different types of grips
-Example: power grip to open can and precision group to get it off once the cap is loosened
-Example 2: Knowledge of what’s a good tool
-if you want to hammer down a nail and you have a can, banana and a bag of marshmallows, left parietal lesion patients wouldn’t know to pick the can
Example 3: allows you to grasp tools the correct way

B. Numerosity
Counting
Arithmetic

C. Identifying the “what”
-identifying your fingers for example

Question 9

What is the anatomy for praxis?

Answer 9

Ventral parietal lobule on left side
	-codes for actions
	-proprioception
Then sends signals to BOTH
Left and right PRE-motor cortex
	-implements code in motor terms

Question 10

What is the relationship between pre-motor cortex and ventral parietal lobe?

Answer 10

Parietal lobe plans praxic movements
(complex movements)
Pre-motor cortex implements complex movements

Question 11

What is apraxia?

Answer 11

An acquired deficit in learned or skilled movements in the presence of intact strength and sensation

Question 12

In most cases of apraxia, where is the lesion?

Answer 12

The left hemisphere

EVEN IF you have left hand apraxia

Question 13

What is Ideomotor apraxia?

Answer 13

Most common type of apraxia

-opening and closing a can, complex hand movements

Question 14

What are some causes of apraxia?

Answer 14

1. cortico-basilar ganglionic degeneration
2. AD
   
   • when you ask patient to use hand to pantomime nailing in something…patient uses own fist rather than a representation of a hammer
3. focal lesions
4. degenerative disorders

Question 15

When you lesion the LEFT ventral parietal lobe, what symptoms present?

Answer 15

BILATERAL apraxia in limbs

Question 16

What happens when you lesion the left pre-motor cortex?

Answer 16

Right (contralateral) apraxia

Question 17

What are the functions of the RIGHT parietal lobe?

Answer 17

A. prosody (melody of speech)
B. Visual attention, knowledge of environmental position
C. Numerosity
i. Subitizing:
-rapid, confident apprehension of small quantities (<4)…as in if you see 3 sheep, you know that there are three sheep without counting them one by one
-related to target tracking
ii. Estimating

Question 18

What is a common cause of right parietal lesion that leads to neglect?

Answer 18

Right MCA stroke

Question 19

What is MOA of Gerstmann’s syndrome? Symptoms?

Answer 19

MOA: Left parietal lesion (angular gyrus)
Symptoms:
1. agraphia
2. acalculia
3. R/L confusion (as in can’t tell difference between right and left hand)
4. loss of ability to distinguish, name, or recognize the fingers
Better to see Gertsmann as a more general “body schema disturbance” (autopagnosia)

Question 20

What is MOA of right parietal lobe lesion? Symptoms?

Answer 20

MOA: right MCA stroke
Neglect
What is being neglected?
The left side of your body? Vision? Objects? The world?
Answer: All four
	-Anosognosia 
	-Somatophrenia

Question 21

What is Anosognosia?

Answer 21

unilateral unawareness or denial of defects on one side of body

Question 22

What is Somatophrenia?

Answer 22

Patient claims contralateral limbs don’t belong to him/her

Also provides excuses for why they can’t lift their arm…like the arm is tired or someone is holding it down

Question 23

Hemi-space vs. Hemi-object neglect

Answer 23

Patients who neglected left side of objects had lesions that were more VENTRAL
Patients who neglected left side of space = more DORSAL
-hemi-spatial neglect shows simultaneous impairments of eye, head and body centered coordinate spaces

Question 24

Is position encoded with respect to eyes, head or body?

Answer 24

Parietal lobe represent all these frames of reference SIMULTANEOUSLY
Planar gain fields

Question 25

So how do you allow people with neglect to cope?

Answer 25

Tell them to turn sideways when viewing something to view what the leftside would look like
-also if you bring someones left arm to the right side, then they can move that arm

Question 26

Extinction

Answer 26

the phenomenon in which if there is no competing stimulus on the right hand side, the patient can then see what’s on the left (a better chance of detecting that shit)

• as soon as the right offers competing stimuli, the brain will neglect the left hand side
  
  • Furthermore, neglect patients are faster to verify words semantically primed by a picture in their neglected field

Question 27

Why right hemisphere for neglect?

Answer 27

Imbalance in attention due to injury of either hemisphere, but right hemisphere dominance for visuospatial attention makes neglect more frequent and severe after right brain injury

Question 28

Balint’s syndrome

Answer 28

Lesion of BOTH parietal lobes
MOA: prion disease (CJD), AD, CBGD)
Symptoms:
-you can’t represent where anything is in space
-optic ataxia (can’t reach for objects)
-simultagnosia: can only see one object at a time
-ocular apraxia (can’t direct gaze)