Oct11 M2-The Limbic System

Question 1

limbic lobe is what

Answer 1

the cingulate gyrus, ring of cerebral tissue surrounding the corpus callosum (on medial surface of brain)

Question 2

limbic system: structures usually included in it

Answer 2

• cingulate and parahippocampal gyri
• hippocampus and fornix
• amygdala and stria terminalis
• hypothalamus
• prefrontal cortex

Question 3

main limbic system structures seen in medial sagittal cut

Answer 3

• cingulate gyrus
• prefrontal cortex (bottom part of frontal cortex)
• parahippocampal gyrus ant lat to brainstem
• hypothalamus (above parahippocampal gyrus)

Question 4

how to see amygdala and hippocampus in the brain

Answer 4

have to do a coronal anteriorly tilted cut to get both regions
hippocampus
-hippocampus is sup ant to brainstem, medially, on each side
-amygdala is sup ant to hippocampus, medially, on each side

Question 5

what is the fornix

Answer 5

• medial sagitt cut = see corpus callosum under cingulate gyrus. in the bottom, corpus call is closed by another band of white matter = fornix.
• fornix has a U shage and descends to end in the mamillary bodies

Question 6

what is the septal area

Answer 6

part of the pre-frontal cortex that is the most posterior. lying under the fornix

Question 7

hypothalamus relations

Answer 7

• ant sup to brainstem

- inf post to mamillary bodies (coming from fornix)

Question 8

epilepsy relation to limbic system

Answer 8

epilepsy pts often have an abnormality of the hippocampus

Question 9

functions of the limbic system

Answer 9

• emotional reaction to analytical, intellectual and perceptual aspects of conscious experience
• physical manifestations to these things (tachycardia, dry mouth, sweating, etc.)

Question 10

parts of limbic system involved in the emotional reaction and behavior

Answer 10

• cerebral cortex medial and prefrontal cortex
• septal area (most imp)
• amygdala (most imp)
• hippocampus (is a minor player. more involved in learning and memory)

Question 11

parts of limbic system involved in the physical reaction

Answer 11

hypothalamus

Question 12

why limbic system circuitry models are not the best

Answer 12

are a simplistic view of how things work bc show comm between A and B but there is also comm from B to A

Question 13

part of limbic system best understood

Answer 13

hypothalamus (physical reaction. is the operational component or output of the limbic system)

• reciprocal centres (always a centre present doing the opposite of another. heat dissipation and generation. feeding vs satiety) recruit and coordinate motor and ANS activity in response to internal and external demands
• connects to ant pit, brainstem and ANS nuclei of brainstem and spinal cord

Question 14

parts of the limbic system considered to be drivers of the hypothalamus (provide emotional tone and drive hypothalamic responses)

Answer 14

• amygdala (fear and anxiety). lesion BILATERALLY = don’t experience fear in fearful situations
• septal area (pleasure and euphoria)

Question 15

limbic system link to psychiatry

Answer 15

psychiatry = neurology of the limbic system

Question 16

types of studies in psychiatry related to limbic system

Answer 16

• During episodes of depression in familial major depressive disorder pts, it was noticed that the blood flow to the limbic system was altered (possible cause)
• advanced ntrs studies and connections studies

Question 17

main role of the hippocampus

Answer 17

• learning
• memory
• key player in ability to generate a biography of our life continuously (retains ongoing recollection of our life)

Question 18

consequence of bilateral destruction of the hippocampus

Answer 18

• devastating amnestic state in which events, experiences and facts are forgotten as soon as they move from present to past
• can’t learn anything

Question 19

H.M. case

Answer 19

• pt who got neurosurgery in one temporal lobe for temporal lobe epilepsy = no results
• other temporal lobe removed partially = epilepsy improved but lost two hippocampi so was in that constant amnestic state and couldn’t learn anything

Question 20

star mirror drawing test

Answer 20

ask pt to draw in the two borders of a star while looking in a mirror in front of them and not at the real star so have to do opposite of mvmt wanted when look in mirror

• normal person gets better with practice
• HM (no hippocampi) also got better with practice, and he remained as good when redid it days later

Question 21

conclusions from star mirror drawing test in HM

Answer 21

he could do it so

• learning doesn’t mean memory and is another fct
• learning assoc with practice is a function of the basal ganglia AND NOT of the hippocampi. this fct is preserved in pts with hippocampal disorders

Question 22

other brain centers involved in memory than hippocampus (and that will serve for factual learning in part)

Answer 22

long term memory storage is distributed throughout the cortex bilaterally.

• no focal lesions exist producing the loss of everything learned
• loss of long-term memory specifically is a fct of how much cortex was lost

Question 23

2 common problems involving the limbic system

Answer 23

• head injury
• focal (especially temporal lobe) seizures
• cause lesiosn in medial parts of the cerebrum*

Question 24

dementia link to limbic system

Answer 24

dementia is a disorder of limbic system

-caused by impairment of memory and emotion mediated by limbic structures