Limbic System

Question 1

Limbic system

Answer 1

Includes group of cortical and subcortical nuclei found on medial aspect of frontal, parietal + temporal lobe
–> interconnected by cortico-cortical pathways

Question 2

Limbic cortex in frontal + parietal lobe BLOOD SUPPLY

Answer 2

Anterior cerebral artery

Question 3

Limbic cortex in temporal lobe BLOOD SUPPLY

Answer 3

Posterior cerebral artery

Question 4

Limbic cortex in frontal + parietal lobes

Answer 4

Orbito-frontal cortex (sub-callosal area)
Cingulate cortex (anterior + posterior)

Question 5

Limbic cortex in lobe

Answer 5

Parahippocampal cortex

Lies in medial temporal lobe

Question 6

Limbic system function

Answer 6

Mediates sense of reward
Mediates sense of unhappiness or misery
–> for reward or punishment, need to remember experience
–> limbic system involved in memory processes
–> also involved in learning, as to avoid or do an action again

Question 7

Limbic system connections

Answer 7

Olfactory system

–> some smells hard wired to pleasurable or unpleasant emotions

Question 8

Reward circuits

Answer 8

Neuronal circuits that are active when you have the sensation of pleasure, joy, happiness etc.

Question 9

Anterior cingulate cortex

Answer 9

Activated during experience of pain or feelings of misery or depression

Question 10

Pain information

Answer 10

Lateral spinothalamic tract –>

a) parabrachial nucleus –> amygdala
b) anterior thalamic nucleus –> ACC + insula –> PFC

Question 11

Prefrontal cortex activated by ACC to…

Answer 11

“do something” about the pain

Question 12

Cingulotomy

Answer 12

Cutting (anterior) cingulate gyrus to disrupt fibres passing rostro-caudally through it
–> reduces “emotional distress” of pain
V invasive –> not practical

Question 13

Orbitofrontal cortex

Answer 13

Anterior part of cingulate merges into here
Associated with behaviour when threat is anticipated –> actions to avoid pain (or injury)
Prolonged pressure to make impossible choices causes extreme stress –> cortisol + adrenaline release –> sense of hopelessness + clinical depression

Question 14

Obsessive compulsive disorders

Answer 14

Excessive activity in orbito-frontal limbic cortex

Question 15

Posterior cingulate cortex

Answer 15

Emotional significance + memories

Question 16

Parahippocampal Gyrus

Answer 16

Acquisition of new memories

Question 17

Subcortical parts of limbic system

Answer 17

Hippocampus + amygdala

Question 18

Hippocampus

Answer 18

Medial wall of inferior horn of lateral ventricle
Output fibres from fornix which curves upwards and round the over the top of the 3rd ventricle
Fornix- curves forwards and upwards to lie along the midline just under corpus callosum

Question 19

Fornices of hippocampus attached together by

Answer 19

Septum pellucidum

Question 20

Fornix

Answer 20

Anterior end of fornix folds down almost vertically at front of 3rd ventricle + ends up in hypothalamus
Septum reaches down to the anterior pole of hypothalamus
–> group of nuclei known as septal nuclei
Fornix axons end in the septal nuclei + mammillary body of the hypothalamus

Question 21

Neuronal connections between hippocampus + limbic cortex

Answer 21

Info from cingulate cortex –> parahippocampal gyrus
Parahippocampal gyrus –> hippocampus
Info goes from hippocampus along fornix to mammillary bodies in hypothalamus
Info hypothalamus –> anterior thalamus
Anterior thalamus back to cingulate cortex

Question 22

Connections in Limbic system loop is called

Answer 22

Papez’s circuit

Question 23

Hippocampus + memory

Answer 23

Memory’s not stored here

BUT Hippocampus is NEEDED for memory storage

Question 24

Anterograde amnesia

Answer 24

Loss of ability to store new experiences

Question 25

Loss of hippocampal function

Answer 25

Failure to transfer new experiences into long term memories

Question 26

Hippocampus function

Answer 26

Labels new experiences with the place + time they occurred | Enables experience to be properly stored in memory

Question 27

Kluver-Bucy syndrome

Answer 27

Removal of tips of temporal lobes has dramatic effect on animals' responses to fearful situations Abnormalities- psychic blindness, oral tendencies, hypermetamorphesis, altered sexual behaviour, emotional changes --> lost sense of fear --> Bilateral removal of amygdala

Question 28

Amygdala location

Answer 28

Embedded in entorhinal (olfactory) cortex in anterior medial temporal lobe

Question 29

Electrical stimulation of amygdala

Answer 29

Panic, fear and terror responses

Question 30

Loss of fear

Answer 30

Removal of amygdala and adjacent temporal cortex

Question 31

Amygdala function

Answer 31

Activates fight or flight response of symp. NS Sends commands to hypothalamus, which sends commands to reticular formation --> activates reticulospinal tracts + thus Symp. NS Receives input from temporal lobe cortex --> says if new stimulus is pleasurable, painful etc --> labels experience so info stored in memory with experience

Question 32

Amygdala damage

Answer 32

Misinterpretation of hazardous events --> leads to excessive risk taking, odd relations + financial decisions Decreases one's ability to recognise emotion in others --> harder to empathise + conduct normal social relationships

Question 33

Hippocampus vs Amygdala

Answer 33

Hippo- Labels place + date of new experience | Amygdala- Tells us whether pleasant, unpleasant etc.

Question 34

Ventral striatum

Answer 34

Accumbens nucleus- adjacent to septal nuclei Septal nuclei- base of septum pellucidum Basal nucleus (nucleus of Meynert) - just under septal nuclei

Question 35

Accumbens nucleus

Answer 35

Anatomically part of brainstem, but functionally part of limbic system Receives dopaminergic fibres as part of mesolimbic dopamine pathway

Question 36

Mesolimbic pathway

Answer 36

Set of dopamine neurones that project from brainstem regions next to substantia nigra to accumbens nucleus

Question 37

Accumbens nucleus function

Answer 37

Involved in initiation + termination of behaviours (motor actions) that activate reward pathways Dopamine input to accumbens necessary for pleasurable behaviour to take place Blocking dopamine in accumbens --> stop motor actions involved with addictive behaviours

Question 38

Dorsal striatum (caudate and putamen)

Answer 38

Involved in selection of actions to take based on cognitive plans created in dorsal frontal cortex Feeds into motor cortex via globus pallidus + motor thalamus

Question 39

Ventral striatum (nucleus accumbens)

Answer 39

Involved in selection of actions based on threats or rewards | Feeds into motor system via ventral pallidum + globus pallidus

Question 40

Striatum require

Answer 40

Activity in dopamine axons from midbrain