Lecture 19: Limbic System Flashcards
1
Q
What led to the limbic system?
A
The search for cortical representation of feeling
2
Q
What is the overall idea behind the limbic system?
A
Emotionally significant stimuli activate sensory pathways that trigger the hypothalamus (controls the ANS) to modulate heart, blood pressure and respiration
3
Q
What are the main structures of the limbic system?
A
- Hippocampal formation
- Amygdala
- Hypothalamus
- Cingulate gyrus
- Anterior, Lateral Dorsal and Dorsal medial nuclei of the thalamus
- Limbic association cortices
4
Q
What makes up the hippocampal formation?
A
Hippocampus, fornix and dentate gyrus
5
Q
What does dysfunction to any structure of the limbic system cause?
A
Psychiatric disorders
6
Q
What is the amygdala involved in?
A
The formation and storage of information related to emotional events, long term memory formation and recognizing danger or fear
7
Q
Which lobe does the amygdala sit in?
A
In the frontal lobe
8
Q
What does the amygdala have a hardwired connection to?
A
The hypothalamus, the hippocampus and the nuclei involved in reward and emotional response
9
Q
What helps us to:
- Form and store information related to emotional events
- Facilitate long term memory formation
- Help us recognize when we are in danger or fearful of something?
A
The amygdala
10
Q
What does the Amygdala do?
A
Helps us to:
- Form and store information related to emotional events
- Facilitate long term memory formation
- Help us recognize when we are in danger or fearful of something?
11
Q
What does injury to the amygdala affect?
A
- Memory formation
- Emotional sensitivity
- Learning and retention
- Depression
- Anxiety
12
Q
Injury to where effects:
- Memory formation
- Emotional sensitivity
- Learning and retention
- Depression
- Anxiety
A
The amygdala
13
Q
What happens when animals have their amygdala’s removed?
A
The animals become very docile
14
Q
A lesion to where can cause animals to become very docile?
A
The amygdala
15
Q
How was the amygdala found to be an emotionally aggressive area of the brain?
A
Animals with their amygdala removed became very docile
16
Q
What does the Amygdala sit anterior to?
A
The hippocampus
17
Q
What sits anterior to the hippocampus?
A
The amygdala
18
Q
What is the Fornix?
A
The connection of the hippocampus to the hypothalamus
19
Q
What is the connection of the hippocampus to the hypothalamus?
A
The Fornix
20
Q
What is the Stria Terminalis?
A
The connection of the amygdala to the hypothalamus
21
Q
What connects the amygdala to the hypothalamus?
A
The stria terminalis
22
Q
What does the limbic system being a circuit allow us to do?
A
Start anywhere
23
Q
What is the Hippocampus?
A
A large nucleus in the parahippocampal gyrus with multiple functions
24
Q
What is the large nucleus in the parahippocampal gyrus known as?
A
The hippocampus
25
What is the main function of the hippocampus?
Converts short term memory to long term memory
26
Where does the hippocampus have its cell bodies?
In the hippocampal formation
27
What has its cell bodies in the hippocampal formation?
The hippocampus
28
Where does the hippocampus extend its axons to?
The hypothalamus
29
What are the two axons of the hippocampus to the hypothalamus?
Fimbriae and fornix
30
What are fimbriae and fornix?
Axons from the hippocampus to the hypothalamus
31
What is the crus?
Where the two fornices from the hippocampus come together
32
What is the body of the fornix?
The midline structure that makes up the lateral ventricle
33
Where does the hippocampus end?
At the mamillary bodies
34
What synapses at the mamillary bodies?
The hippocampal axons
35
In the limbic circuit where does it go from the hippocampus?
The Mamillary bodies
36
In the limbic circuit, where does it go from the mamillary bodies?
The thalamus
37
Where does the tract from the mamillary bodies synapse in the thalamus?
Anterior or lateral dorsal or medial dorsal nuclei of the thalamus
38
What synapses at the anterior, lateral or medial dorsal nuclei of the thalamus?
The mamillary bodies
39
Where do axons from the thalamus project to in the limbic system?
The cingulate gyrus
40
What lobes are part of the cingulate gyrus?
The frontal and parietal lobe
41
Where do axons go from the cingulate gyrus in the limbic system?
To all over the brain
42
What is the order of limbic projects starting with the hippocampus?
1. Hippocampus
2. Mamillary bodies
3. Thalamus
4. Cingulate gyrus
5. Widespread throughout the brain
43
What does the Fornix do?
Connects the hippocampus to the hypothalamus
44
What is the most anterior part of the hippocampus?
The pes hippocampus
45
What is the pes hippocampus?
The most anterior part of the hippocampus
46
What sits underneath the fornix?
The third ventricle
47
What is the Dentate gyrus a part of?
The hippocampus
48
What are the output regions of the dentate gyrus?
CA regions
49
What do the cell bodies of the dentate gyrus communicate with?
Different CA regions
50
Where do CA regions send their axons out as?
The fornix
51
What is the Perforant pathway?
The pathway that the entorhinal cortex used to project to the dentate gyrus of the hippocampus
52
How does the entorhinal cortex project to the dentate gyrus of the hippocampus?
Via the perforant pathway
53
What is the entorhinal cortex?
The region around the hippocampus
54
How is the hippocampus affected in people with Alzheimer's?
People with Alzheimer's have atrophies hippocampi
55
Where is the limbic association cortex located?
On the medial surface of the frontal, parietal and temporal lobes
56
What is located on the medial surface of the frontal, parietal and temporal lboes?
The limbic association cortex
57
What is the limbic association cortex?
The areas that the limbic system is projecting to
58
What did Papez suggest?
The limbic lobe forms a neural circuit that provides the neuroanatomical basis for the elaboration of emotions
59
What did Papez suggest emotion is?
Not a function of any specific brain center but a circuit that involved for basic structures interconnected through several nervous bundles
60
What are the nervous bundles involved in the limbic system suggested by Papez?
- Hypothalamus with mamillary bodies
- Anterior thalamic nucleus
- Cingulate gyrus
- Hippocampus
61
How did Papez propose that the cortex influences the hypothalamus?
Through connections of the cingulate gyrus and hippocampus
62
What is the Limbic circuit of Papez?
A work flow from the cingulate gyrus back to the hippocampus that explains the hippocampus
63
What are the steps in the Papez circuit starting with the hippocampus?
1. Hippocampus goes along the fornix to the hypothalamus and mammillary bodies
2. From the mamillary bodies to the thalamus through the mammillothalamic tract
3. From the thalamus to the cingulate gyrus
4. From the cingulate gyrus to the cortex
5. From the cortex back to the cingulate gyrus and to the hippocampal formation
64
In the circuit of Papez, where does it go after the hippocampus?
From the hippocampus going along the fornix it goes to the hypothalamus and mammillary bodies
65
In the Papez circuit, what happens after reaching the hypothalamus and mammillary bodies?
It goes via the mammillothalamic tract to the thalamus
66
What does the Fornix do?
Carries information from the hippocampus to the hypothalamus and mammillary bodies
67
What carries information from the hippocampus to the hypothalamus and mammillary bodies?
The fornix
68
What does the mammillothalamic tract do?
Carries information from the mamillary bodies to the thalamus
69
What tract carries information from the mamillary bodies to the thalamus?
The mammillothalamic tract
70
Where is information from the thalamus first carried in the circuit of Papez?
It is carried from the thalamus to the cingulate gyrus
71
Where is information from the cingulate gyrus first carried in the circuit of Papez?
It is carried from the cingulate gyrus to the cortex
72
Where is information from the cortex carried in the circuit of Papez?
It is carried back to the cingulate gyrus
73
Where is information from the circuit of Papez carried after returning to the cingulate gyrus?
It is carried via the cingulum to the hippocampus
74
What is the cingulum?
The tract that carries information from the cingulate gyrus to the the hippocampus
75
What tract carries information from the cingulate gyrus to the hippocampal formation?
The cingulum
76
What is the second version of the limbic circuit called?
The Paul Mclean version
77
What was left out in the circuit of Papez?
The amygdala
78
What did the Paul Mclean version of the limbic circuit add?
Amygdala
79
What is the difference between the circuit of Papez and current version?
In the current version, both the hippocampus and the amygdala both talk to the hypothalamus. And the hypothalamus can go straight to the prefrontal cortex or through the cingulate gyrus to the prefrontal cortex
80
Overall what are the differences in the circuit of papez and the current version?
- Hippocampus and amygdala both send inputs to the hypothalamus
- Hypothalamus can go straight to the prefrontal cortex or through the cingulate gyrus to the cortex
81
What neural body did the Paul Mclean circuit (current limbic circuit version) add?
The amygdala
82
What are the bodies in the current limbic circuit starting with the entorhinal cortex?
1. Entorhinal cortex or periamygdaloid
2. Hippocampus
3. Mammillary bodies
4. Thalamus
5. Cingulate gyrus
6. Cortex
7. Cingulate gyrus
8. Hippocampus or entorhinal cortex
83
What is the Periamygdaloid?
Area around the amygdala
84
Starting at the Entorhinal cortex or periamygdaloid where does the current limbic circuit go?
To the amygdala
85
From the amygdala in the current limbic circuit, where does it go?
To the hippocampus
86
What are the two routes to the hippocampus in the current limbic circuit?
- From the entorhinal cortex or periamygdaloid to the hippocampus
- Amygdala to the hippocampus
87
Where does the limbic circuit go after reaching hippocampus in the current system?
To the mammillary bodies
88
Where does the current limbic circuit system go after reaching the Mamillary bodies?
The thalamus
89
What tract connects the mamillary bodies to the thalamus?
The Mammillothalamic tract
90
What does the Mammillothalamic tract do?
Connects the mamillary bodies to the thalamus in the limbic circuit
91
In the current limbic circuit where does it go after the Thalamus?
The cingulate gyrus
92
Where does the cingulate gyrus project to?
The Cortex and back to the hippocampus or entorhinal cortex
93
What does the Cingulum do?
Carries information from the cingulate gyrus to the hippocampus or entorhinal cortex
94
What do the amygdala and hippocampus work together to do?
Store memories with emotional links
95
What is the amygdala responsible for?
Love, anger, fear, sexual desire/arousal, preferences in food, preference in sexual partners
96
What happens if both amygdala are removed?
Animals show extreme docility
97
What is responsible for: Love, anger, fear, sexual desire/arousal, preferences in food, preference in sexual partners?
The amygdala
98
What is the hippocampal formation responsible for?
Learning and memory and storage of making short term to long term memories
99
What is responsible for learning and memory and storage of making short term to long term memories?
The hippocampal formation
100
What happens if the left hippocampus is damaged?
Auditory/vocal memory loss
101
What happens if both hippocampi are removed?
Anterograde amnesia
102
What causes auditory/vocal memory loss?
Damage to the left hippocampus
103
What causes anterograde amnesia?
Both hippocampi being removed
104
What two major limbic function do the hippocampal formation and amygdala mediate?
1. Learning and Memory
2. Emotions
105
What is the Amygdala?
Part of the limbic system most specifically involved with emotional experiences (learned emotion responses) and behavioural expression
106
What does stimulation of the amygdala cause?
Feeling of fear/aprehension
107
What do lesions to the amygdala in animals cause?
Tameness and fearlessness
108
What does the Hippocampal formation have an indirect role in?
Emotion
109
How does the hippocampal formation have an indirect role in emotion?
It is involved in explicit (declarative) memory, memory consolidation and learning from emotional experiences
110
What is the Lateral Amygdala linked to?
The neocortex
111
What is the Anterior Commissure?
The connection between the two amygdala
112
What is the connection between the two amygdala?
The anterior commissure
113
What is the Medial Amygdala linked to?
The striatum
114
What does the medial amygdala connect to?
The Motor and brainstem
115
What does stimulation to the hypothalamus cause?
Extreme pleasure
116
What does the Medial Forebrain bundle connect?
Connects the amygdala to the hypothalamus
117
What is the lateral hypothalamus known as?
The pleasure center
118
What is the Ventromedial hypothalamus known as?
The aversion center
119
Where is the pleasure center?
The lateral hypothalamus
120
Where is the aversion center?
The ventromedial hypothalamus
121
What are the reward centers of the brain?
The septal nuclei and nucleus accumbens
122
What are the septal nuclei and nucleus accumbens together?
The reward center of the brain
123
Where do the Septal Nuclei and Nucleus Accumbens project?
Throughout the hypothalamus and maintain connections with amygdala, hippocampus, cingulum and reticular formation
124
Where in the brain are the septal nuclei found?
In the frontal part of the frontal lobe
125
How do drugs affect the septal nuclei?
The trigger the release of dopamine at these centers
126
What can a bilateral lesion of the frontal gyri cause?
- Difficulties concentration
- Loss of initiative
- Apathy
- Cannot decide
127
What can a bilateral lesion of the orbital cortex cause?
- Unstable emotional behavior
- Loss of inhibition
- Inappropriate social behavior
128
What does bilateral of the temporal pole (amygdala and entorhinal cortex) cause?
- Removal of fearlessness
- But if you stimulate it: Anxiety, fear, panic
129
What does Bilateral lesion of the Parahippocampal gyrus cause?
No new memory
130
Where does the Limbic association cortex receive information from?
Higher order sensory areas, esp. the prefrontal cortex and the parieto-temporal-occipital (PTO) association cortex
131
Where does the limbic association cortex convey information from the cortex and PTO to?
The amygdala and the hippocampus
132
What does the Amygdala do when the limbic association cortex conveys information from higher-order sensory areas to it?
It uses the sensory information to link a particular stimuli with specific emotions
133
What does the Hippocampus do when the limbic association cortex conveys information from higher-order sensory areas to it?
It learns the more complex setting of the environment
134
What are the steps involving the hippocampal formation and amygdala when we have a stimuli?
1. Information will be in the cortex
2. Then will go to the PTO
3. Information will then go to the limbic association cortex
4. Then to the amygdala and hippocampus
135
What are the hippocampal afferents (what projects to the hippocampus)?
1. reward centers
2. Frontal lobe and parietal lobe vis cingulate gyrus
3. Amygdala
136
What are the hippocampal efferents (where does the hippocampus project to)?
1. Cell bodies in the CA region
2. Mamillary bodies
3. Cingulate gyrus and cortex
4. Septal nuclei
5. Amygdala
137
What are the amygdala afferents (what projects to the amygdala)?
1. Higher order center in the temporal lobe and insula
2. Different association cortices
3. Olfacotry bulb
4. Brainstem nuclei (NTS) - stretching of bowels
138
What are the two main Amygdala efferencts?
The Ventral Amygdalofugal pathway and the Stria Terminalis
139
What is the Stria Terminalis?
An axon tract that goes from the amygdala to the hypothalamus or the nucleus accumbens for reward
140
What is the Amygdalofugal pathway?
An axon tract that goes from the amygdala to the hypothalamus and thalamus reward centers of the brain and causes the fear response
141
What disorders is the amygdala strongly implicated in?
Mood disorders, including depression and anxiety and substance abuse
142
What is Kluver-Bucy syndrome?
When lesions to the amygdala cause fearlessness, docileness
143
What can damage to the hippocampus cause?
Severe anterograde amnesia and Alzheimer's disease
144
What are the four major neurotransmitters in the limbic system?
1. Dopamine
2. Serotonin
3. Norepinephrine
4. Acetylcholine
145
Where does the dopamine in the limbic system come from?
The midbrain - substantia nigra, VTA
146
Where does Serotonin in the limbic system come from?
Reticular formation neurons - raphe
147
Where does Norepinephrine of the limbic system come from?
Involved in the reticular activating system – floor of 4th ventricle
148
Where does the Acetycholine in the limbic system come from?
The basal forebrain cholinergic neurons
149
Where are Dopaminergic projections in the limbic system from?
Midbrain Ventral Tegmental Area & SNc
150
What do Dopaminergic projections from from the midbrain VTA travel through to get to the limbic areas?
The medial forebrain bundle
151
Where do Dopaminergic projection in the limbic system go?
Limbic areas, amygdala and Hippocampal formation (involved in emotions, memory & learning)
152
What structures are apart of the Limbic association cortex?
Periamygdaloid cortex, parahippocampal gyrus, entorhinal cortex, cingulate gyrus and frontal region.
153
Where is the VTA?
In the midbrain
154
Where does the VTA project to?
The Medial forebrain bundle
155
Where does the medial forebrain bundle go to?
The nucleus accumbens, and then projects back to the thalamus and reward centers of the brain
156
What do drugs for schizophrenia do?
Block dopamine receptors
157
Where does serotonin in the limbic system come from?
The reticular formation (raphe nuclei)
158
What do serotonergic projections in the limbic system travel via?
The medial forebrain bundle
159
Where do serotonergic projections in the limbic system project to?
Amygdala, hippocampus, striatum & cerebral Cortex
160
What do drugs that block serotonin reuptake mechanisms (SSRIs) do?
Treat depression, anxiety and OCD
161
Where do Noradrenergic projections to the limbic system come from?
The Locus coeruleus
162
What do Noradrenergic projections in the limbic system travel via?
The medial forebrain bundle
163
Where do Noradrenergic projections in the limbic system project to?
Entire cerebral cortex, including limbic association areas, limbic structures
164
Where do Cholinergic projections to the limbic system come from?
Basal forebrain cholinergic neurons (incl. Nucleus Accumbens and Septal Nuclei)
165
What do cholinergic projections in the limbic system travel via?
Diverse pathways
166
Where do cholinergic projections in the limbic system project to?
Entire cerebral cortex, limbic association cortex, amygdala, hippocampal formation
167
What neurotransmitter is lost in Alzheimers disease?
Acetycholine
