unit 3b

Question 1

Posterior parietal cortex (PPC)

Answer 1

located posterior to sensorimotor cortex

-Integrates sensory & motor portions of the brain
- processes position of body & objects in space
-controls eye mvmts

Lesions: Problems w/ visual-spatial coordination. problems w/ attention, neglect syndromes

Question 2

Premotor cortex (PMA)

Answer 2

Located anterior to M1 & inferior to SMA

-Controls postural/trunk & lrg limb muscles
-planning of actions based on sensory cues
-refinement of mvmts based on sensory input w/ cerebellum

Lesions: disruption of learned responses to visual cues

Question 3

Supplementary Motor area (SMA)

Answer 3

located just anterior to M1 & superior to PMA

-involved in planning learned sequences of mvmts
-activity prior to mvmt
- strong connections w/ subcortical structures

Unilateral Lesions:
~disruption of learned sequence of mvmt

Bilateral lesions:
-blocks all mvmt.

Stimulation:
-creates strong urge to move

Question 4

Primary motor cortex (M1)

Answer 4

Strip of cortex just anterior to central sulcus (in frontal lobes) where primary control of motor mvmt occurs

M1 contains a body-based motor map similar to somatotopic representation in S1

M1 controls execution of mvmt

Lesions: spastic paralysis
Stimulation: executes a mvmt

Question 5

Corticospinal (C.S.) tract

Answer 5

the fiber that connect motor cortex thru spinal cord to motor neurons thru-out body

split into 2: Lateral & anterior

Question 6

Lateral corticospinal tract

Answer 6

80% of the C.S axons cross to other side
- generally go to limbs

Question 7

Anterior corticospinal tract

Answer 7

20% of C.S. axons DONT cross
- generally go to the trunk

Question 8

Upper motor neurons

Answer 8

originate in the M1 motor region of the cerebral cortex & carry motor info down to specific spinal cord lvl

the cell bodies of upper motor neurons are in M1 & their axons make up the C.S. tract

Damage: (to cell bodies in M1 or axons along spinal cord) ‘function goes up’ b/c rest of cortex sends inhibitory signal s to lower motor neurons

When a mvmt is made, upper motor neurons stop inhibitory signals to allow lower motor neurons to fire & produce a mvmt

W/ damage to upper motor neurons, baseline inhibitory inputs f/ cortex is lost & lower motor neurons are hyper-active, causing spastic muscles

Question 9

Lower motor neurons

Answer 9

Bring nerve impulses f/ upper motor neurons out to the muscles

Cell bodies are in spinal cord & send axons to innervate sets of muscles fibers

When damaged : ‘function goes down’

When they dont work, there is no way to send signal to muscles to tell them to contract
- muscles are flaccid (loose + floppy) & eventually atrophy due to loss of neurotrophic (feeding) factors that lower motor neurons also deliver to muscles fibers

Question 10

Somatotopic organization

Answer 10

organization that follows a map of the body
- ex: neighboring body parts have neighboring representations in cortex

Question 11

Hemiplegia

Answer 11

total paralysis of arm, leg, & trunk on the same side of body
-usually from lesions to M1

Question 12

Hemiparesis

Answer 12

weakness on 1 side of the body

Question 13

Anosognosia

Answer 13

a disorder where the patient is unaware & denies their disability
- often assoc. w/ paralysis & right dorsal parietal damage (also seen in Anton’s syndrome, eating disorders)

Patients typically use confabulations to ‘explain’ why they have the symptoms

Question 14

Confabulation

Answer 14

Lying unintentionally

A disturbance of memory, defined as production of fabricated, distorted, or misinterpreted memories abt oneself or world, w/o conscious intention to deceive

Certain types of damage to parietal lobes can cause neglect syndromes that are assoc. w/ confabulation

The patient has anosognosia- thus is not aware that they have a deficit (ex: paralysis) & instead come up w/ random/untrue reasons for why they dont have an issue

Question 15

Anton’s syndrome

Answer 15

blindness & anosognosia f/ dorsal occipital damage

Question 16

Hemispatial neglect

Answer 16

syndrome where patients are unaware of world/themselves/objects/ visual scene/etc on 1 side of space
- usually the left side f/ damage to right posterior parietal cortex

Question 17

Gerstmann’s syndrome

Answer 17

syndrome where patients have finger agnosia (can’t identify what their fingers are)

problems w/ left/right differentiation & calculation & writing

Usually cause by damage to inferior part of dominant parietal cortex or can be developmental

Question 18

Apraxia

Answer 18

disorder of motor planning involving loss of ability to carry out learned purposeful mvmts, despite having desire & physical ability to perform the mvmts

Several sub-types: [Verbal apraxia-apraxia of speech in childhood]

Question 19

Basal Ganglia

Answer 19

gap of cell bodies below cortex interconnected w/ cortex, thalamus, & brainstem
- involved in motor control * cognition, emotions, + learning

Circuitry includes ‘direct’/excitatory & ‘indirect’/inhibitory pathways

Question 20

Dopamine

Answer 20

neurotransmitter that plays key role in basal ganglia motor circuit + inhibitory & exhibitory pathways
- also key neurotrans. in arousal + reward syst.

Question 21

Hypokinetic

Answer 21

characterized by DECREASED mvmt

Question 22

Hyperkinetic

Answer 22

characterized by INCREASED mvmt

Question 23

Parkinsons’s disease

Answer 23

A hypo kinetic disease characterized by
- slowing or loss of mvmt (akinesia)
- muscle rigidity
-‘pill-rolling’ tremor at rest

Cause:
- due to loss of dopamine neurons in basal ganglia that cause decrease in activity in basal ganglia’s excitatory ‘direct pathway

Treatments:
- medication (L-Dopa), fetal neural tissue graft, deep brain stimulation (DBS)

Question 24

Huntington’s chorea

Answer 24

a hyperkinetic disease characterized by:

Cause: autosomal dominant genetic mutation that causes proteins to build up in & ultimately. kill cortical neurons (esp in the inhibitory ‘indirect’ pathway of basal ganglia)
- Cell death is progressive & causes a decline in mental abilities [personality changes, memory issues, dementia] & uncoordinated jerky mvmts (chorea) → eventually leads to death {usually f/ malnutrition due to constant mvmt & or other complications}

Question 25

Hemiballismus

Answer 25

Relatively rare hyperkinetic disorder characterized by involuntary flinging motions of the extremities - that incr. w/ increased activity
- Symptoms stop during sleep

Causes:
Damage to inhibitory pathway of the motor loop, esp. f/ damage to sub-thalamic nucleus

Treatments: deep brain stimulation, surgery to remove more basal ganglia, drugs that reduce neural signaling