Limbic System & Prefrontal Cortex

Question 1

major structures that form the limbic system

Answer 1

These form the limbic lobe:
Cingulate gyrus
Subcallosal gyrus 
Parahippocampal gyrus 
Hippocampal formation
Uncus
Amygdala 

These are not part of the limbic lobe but function as part of the limbic system:
Oribitofrontal association area
Hypothalamus
Thalamus
Septal area (rostral end of diencephalon)
Basal ganglia structures

Question 2

7 functions of limbic system

Answer 2

1. Emotions/behavioral expression of emotions
2. Learning
3. Memory (short term and long term)
4. Motivation/drive
5. Feeding/drinking
6. Defensive behaviors
7. Reproduction

Question 3

interaction between stress, disease, mental health, and recovery

Answer 3

Stress prompts the release of cortisol. Excessive amounts of cortisol remaining in the system for long periods of time (due to increased or ongoing stress) has been linked to the following:
inhibited learning and memory
lower immune system function (i.e. more likely to get sick, stay sick, and/or recover more slowly) and bone density
increased weight gain, blood pressure, cholesterol, and risk of heart disease
increase risk for depression, mental illness, and lower life expectancy
stress-related diseases like colitis, cardiovascular disorders, and adult-onset diabetes

Question 4

2 types of memory

Answer 4

declarative and procedural memory

Question 5

declarative memory

Answer 5

Facts, events, etc.
Available for conscious recollection
Easy to form but also easy to forget
(ST and LT memory are subtypes)

Question 6

procedural memory

Answer 6

Skills, habits, etc.

Require repetition and practice over a longer period but are harder to forget

Question 7

major factor required to acquire long term memory

Answer 7

CREBs – important for protein synthesis that aids in the metabolic and anatomical changes associated with long-term memory consolidation
Cramming does not work because CREBs are not available in large quantities, but instead rely on persistent enhancement of synaptic transmission via high frequency stimulation

Question 8

long term potentiation (LTP)

Answer 8

“practice makes perfect”

high frequency activity stimulating a pathway – if this happens long enough a short term memory can be converted into a long term memory

Question 9

long term depression (LTD)

Answer 9

“use it or lose it”

low frequency activity depresses a pathway and will not keep a memory

Question 10

retrograde amnesia

Answer 10

memory loss events prior to the trauma

Question 11

anterograde amnesia

Answer 11

inability to form new memories after the trauma

Question 12

global transient amnesia

Answer 12

(temporary)
sudden and severe anterograde amnesia in combination with amnesia for recent events immediately leading to some traumatic event/injury – lasts for only a few minutes or days

Question 13

where are new declarative memories processed and converted to long term mem

Answer 13

Hippocampus in the temporal lobes
However, it is important to note that not all types of memory of formed or stored in the same manner or location. Therefore, damage to the hippocampus will not destroy all memory.

Question 14

are procedural memories processed in the same place as declarative memories?

Answer 14

No, procedural memories are formed through a complicated interaction of:
cerebellum
basal ganglia
thalamus
other areas of cortex and limbic system

Question 15

clinical manifestations when you lesion the orbitofrontal area

Answer 15

• blunted affect
• decreased emotional drive
• IQ intact except they will perseverate (get hung up on something)

Question 16

clinical manifestations when you lesion the inferior temporal lobe

Answer 16

Results in anterograde amnesia - will still have LT and procedural memory intact
Lesions due to epilepsy, encephalitis, trauma

Question 17

clinical manifestations when you lesion the amygdala

Answer 17

(think of AMY as a person)
Flat affect/uncontrolled rage 
Hypersexuality 
Disinhibited behavior 
Socially embarrassing 
Loss of fear
Not afraid of much

Question 18

clinical manifestations when you lesion the septal area

Answer 18

Hypersexuality and rage

Question 19

TBI - potential cognitive problems

Answer 19

Memory problems (limbic, temporal)
Attention deficits (prefrontal cortex)
Impaired reasoning capabilities/impulsivity (prefrontal cortex)
might be less impulsive or more impulsive
Impaired learning abilities (limbic, temporal)
Orientation/confusion (limbic)

Question 20

TBI - potential social/emotional problems

Answer 20

Hypersexuality 
Intimate behavior
Agitation/violence 
Aggressiveness 
Passive/flat affect/lack of motivation socially inappropriate

Question 21

prognosis for recovery of cognitive problems vs motor problems after brain injury

Answer 21

The prognosis of TBI for motor return is often better than the prognosis for remediation of cognitive and behavioral problems

Question 22

cingulate gyrus

Answer 22

above corpus callosum, lots of roles in emotion and memory

Question 23

subcallosal gyrus

Answer 23

underneath front of corpus callosum, inhibits the amygdala

Question 24

parahippocampal gyrus

Answer 24

surrounds hippocampus, plays a role in memory formation

Question 25

hippocampus

Answer 25

largely responsible for formation of memories

Question 26

uncus

Answer 26

medial component of ventral temporal lobes in front of parahippocampal gyrus, part of entorhinal cortex (olfaction)

Question 27

amygdala

Answer 27

linked to fear and anxiety

Question 28

orbitofrontal association cortex

Answer 28

part of frontal lobe
plays a role in social behavior, responding appropriately to social cues, decision making
*one of the least understood areas of the limbic system (emoji reference)

Question 29

Phineas gage

Answer 29

• working on railroad
• explosion caused iron rod to go through head (eye and frontal lobe)
• affected prefrontal cortex
  with personality and executive functioning

Question 30

hypothalamus

Answer 30

homeostasis, anterior pituitary glands, equilibrium

Question 31

HM

Answer 31

• part of both temporal lobes removed trying to treat a seizure disorder
• had retrograde amnesia prior to surgery, then permeant anterograde amnesia after surgery
• procedural memory, IQ, and personality all intact

Question 32

WADA

Answer 32

• a barbiturate called amatol
• injected into carotid artery
• goes to hemispheres of brain
• slows one side down and sees if one side of the brain is more active for a given function (lateralization of brain functioning)

Question 33

Loop of Papez

Answer 33

• how emotions have such a profound input on decision making
• initial understanding of the limbic system
• It’s a circuit: creates a cycle of communication
• Emotional stimulus activates the thalamus to send signals to hypothalamus and sensory cortex
• Then synapses with cingulate cortex to produce emotional response from the body
• yields a bodily/physical response, and a memory of the emotional response
  Stimulus creates a memory of an emotional response, most basic mechanism for habit formation

Question 34

cortisol

Answer 34

mobilizes energy and surpasses immune responses and serves as an anti-inflammatory agent