Limbic System

Question 1

limbic lobe forms rim of cortex at junction between _______ and ________

Answer 1

limbic lobe forms rim of cortex at junction between DIENCEPHALON and CEREBRAL CORTEX

Question 2

papez circuit original proposed pathway

Answer 2

hippocampal fibers –> mammillary bodies –> anterior nucleus –> cingulate gyrus –> hippocampal formation

Question 3

Kluver-Bucy syndrome

Answer 3

• behavioral syndrome
• due to bilateral removal of medial temporal lobes in monkeys
• fearless/placid
• hypersexuality
• excessive sniffing/oral examination

SHOWED IMPORTANCE OF INTACT LIMBIC STRUCTURES AND CONNECTIONS TO APPROPRIATE BEHAVIORAL PATTERNS
(note: amygdala was also taken)

Question 4

Papez circuit - updated structures

Answer 4

addition of:

• prefrontal cortex
• association cortex
• amydala
• DMN thalamus
• hypothalamus

hippocampal fibers –> mammillary bodies –> anterior nucleus –> cingulate gyrus –> hippocampal formation

Question 5

limbic structures include:

Answer 5

• orbital/medial prefrontal cortex (plan/choose appropriate responses to life situations
• amygdala
• septal nuclei (pleasure center)
• dorsomedial nucleus of thalamus (limbic nucleus)
• ventral basal ganglia (nucleus accumbens, ventral pallidum :: reward circuit)
• hypothalamus

Question 6

function of orbital and medial prefrontal cortex

Answer 6

planning and choosing appropriate responses to life situations

Question 7

septal nuclei

Answer 7

• pleasure center
• cholinergic input to hippocampus

lesion = rage

Question 8

septum pellucidum

Answer 8

separates 2 lateral ventricles

-thin membrane

Question 9

hippocampus has been implicated in:

Answer 9

• memory function
• Alzheimer’s disease
• schizophrenia
• hippocampal sclerosis and epilepsy
• autism
• depression
• modulating endocrine functions (via input to hypothalamus)
• modulation of aggressive behaviors

Question 10

T/F: depression can decrease the size of the hippocampus

Answer 10

T

-and antidepressants MAY be able to restore it to its original size

Question 11

role of hipppocampus in emotion

Answer 11

• INDIRECT role in emotion

- via connections to limbic cortex, amygdala, septal nuclei, and regulation of stress axis

Question 12

hippocampus is essential for _________

Answer 12

hippocampus is essential for FACTUAL/DECLARATIVE MEMORY

Question 13

structures of the hippocampal formation

Answer 13

• dentate gyrus (stem cells)
• hippocampus proper
• subiculum

Question 14

which part of the limbic system contains stem cells?

Answer 14

DENTATE gyrus

• part of hippocampal formation
• everyone (except Alz pts) have v prolific stem cells

Question 15

T/F: information in hippocampus flows in two directions

Answer 15

FALSE: it is a ONE WAY circuit

Question 16

HM research patient

Answer 16

• seizures
• experimental surgery to take out MEDIAL TEMPORAL structures, hippocampus (and surrounding cortex) bilaterally

After

• few seizures
• unable to form NEW long-term memories
• profound retrograde amnesia

Question 17

functional elements of declarative memory

Answer 17

experience –> short term memory –> consolidation process –> long term storage

• consolidation process requires hippocampal formation
• formation of long term memory requires sleep

Question 18

which limbic structure is most specifically involved in emotions?

Answer 18

amygdala

hippocampus is only indirectly involved

Question 19

amygdala is implicated in:

Answer 19

• temporal lobe epilepsy
• schizophrenia
• Alzheimer’s
• autism
• anxiety states/PTSD
• affective disorders
• panic disorders
• emotional memory

Question 20

functions of amygdala

Answer 20

• determining affective perception of sensory stimuli
• attaches emotional significance to various stimuli perceived by association cortex
• plays central role in fear and fear conditioning

Question 21

“low road” to amygdala

Answer 21

emotional stimulus –> sensory thalamus –> amygdala –> emotional responses

• reflexive
• keeps us alive in dangerous situations
• problematic in police force

Question 22

“high road” to amygdala

Answer 22

emotional stimulus –> sensory thalamus –> SENSORY CORTEX –> amygdala –> emotional responses

-normal route

Question 23

effect of chronic stress on amygdala

Answer 23

• no feedback to stop stress response

- cannot protect from damage

Question 24

missing amygdala

Answer 24

SM

• has no fear
• cannot recognize fear
• cannot draw fear

Question 25

role of amygdala in memory

Answer 25

EMOTIONAL MEMORY
Amnesic patient:
-Dr shook hands w/ thumbtack
-pt never shook hand w/ Dr again
-did not recognize Dr

David (pt)

• could not recognize anyone
• drawn to those who were nice to him

Question 26

implicit vs explicit emotional memory

Answer 26

IMPLICIT

• amygdala
• emotional response (panic, fear)

EXPLICIT

• hippocampus
• facts, details

Question 27

role of noradrenaline

Answer 27

• released during stress

- thought to stabilize/strengthen memories

Question 28

effect of stress on memory

Answer 28

• mild stress enhances memory

- chronic stress interferes w/ memory (via hippocampus)

Question 29

CA1 neurons

Answer 29

(of hippocampal formation)

• highly susceptible to anoxia
• can be damaged in near drowning incidents, epileptic seizures, brief loss of O2 during surgical procedure