The Limbic System Flashcards
What is the limbic system?
A set of interconnected cortical and subcortical structures forming a border around the brainstem.
What are the main functions of the limbic system? (HOME)
Homeostasis (autonomic and endocrine control), olfaction, memory, and emotions/drives.
What structure forms the “limbic lobe”?
A rim of the cerebral cortex (grey matter) adjacent to the corpus callosum and diencephalon.
What was the original Papez Circuit and who developed it?
James Papez (1937) proposed the circuit involving four basic structures for emotional experience: Gyrus cinguli, Hippocampal formation, Mamillary body and the Anterior nucleus of the thalamus
How did Paul McLean revise the Papez circuit in 1970?
McLean added more structures to the circuit and coined it the “limbic system,” incorporating the prefrontal cortex, parahippocampal gyrus, amygdala, thalamus, and septal nuclei.
Which areas are included in the limbic cortex?
Parahippocampal gyrus, cingulate gyrus, and medial orbitofrontal cortex.
What is the function of the hippocampal formation?
Memory formation and consolidation from short-term to long-term memory
What are the main components of the hippocampal formation?
Dentate gyrus and hippocampus, Indusium griseum
What are the main components of the Limbic system?
Limbic cortex
– Parahippocampal gyrus, cingulate gyrus,
Medial Orbitofrontal cortex
* Hippocampal formation
– Dentate gyrus, hippocampus
* Amygdala
* Olfactory cortex
* Diencephalon
– Hypothalamus, thalamus (anterior nucleus,
mediodorsal nucleus)
* Basal Ganglia
– Ventral striatum (Nucleus Accumbens, Caudate,
Putamen)
* Basal forebrain
* Septal nuclei
* Also includes the tracts that link these
structures: fornix, mammillothalamic,
stria terminalis, etc
Which areas are included in the limbic cortex?
Parahippocampal gyrus, cingulate gyrus, and medial orbitofrontal cortex.
What is the function of the hippocampal formation?
Memory formation and consolidation from short-term to long-term memory.
Where is the amygdala located, and what is its primary function?
Located in the roof of the inferior horn of the lateral ventricle, and it regulates emotions like fear, rage, affection, and aggression.
What is the role of the fornix in the limbic system?
The fornix carries efferent projections from the hippocampus, connecting it to structures like the septal area, mammillary bodies, and anterior nucleus of the thalamus.
What is the role of the alveus and fimbrae in the limbic system?
The alveus is a collection of efferent fibers originating from the pyramidal cells of the hippocampus. Its primary function is to transmit signals away from the hippocampus towards the fimbria, which is a key pathway for communication between the hippocampus and other parts of the limbic system.
What is the relationship between the alveus and the fimbria?
The alveus serves as the initial efferent pathway that carries fibers from the hippocampus. These fibers then pass medially on the hippocampus’ surface and continue as the fimbria, which is the next major structure in the pathway leading to the fornix.
What is the function of the fimbria in the limbic system?
The fimbria carries the efferent fibers from the hippocampus (originating from the alveus) and transmits them to structures such as the septal area, mammillary bodies, and the anterior nucleus of the thalamus. These structures are important for functions like memory processing, emotional regulation, and overall limbic system communication.
How does the fimbria contribute to memory processing?
The fimbria helps transmit hippocampal output to key structures like the mammillary bodies and thalamus, which are involved in memory consolidation and emotional regulation. This makes the fimbria essential for the processing and retention of long-term memory.
What are the main connections of the limbic system?
The main connections of the limbic system include:
Stria terminalis: A major pathway that connects the amygdala with the hypothalamus and other limbic structures.
Medial forebrain bundle: A collection of fibers that connects several limbic structures, playing a role in emotional and motivational behavior.
Mammillothalamic tract: A pathway that connects the mammillary bodies to the anterior nucleus of the thalamus, involved in memory and emotional processing
What nuclei are involved in the limbic system?
The key nuclei in the limbic system include:
Amygdala: Central to emotional processing, particularly fear and aggression.
Septal nuclei: Involved in the regulation of emotional responses and reward.
Mammillary bodies: Important for memory processing, particularly within the Papez circuit.
Anterior nucleus of the thalamus: A critical relay station in the Papez circuit, involved in emotional processing and memory consolidation
How do the stria terminalis and medial forebrain bundle contribute to limbic system functions?
Stria terminalis connects the amygdala with the hypothalamus and other limbic structures, facilitating emotional processing, particularly in relation to fear and stress responses.
The medial forebrain bundle connects various limbic structures and is crucial for regulating emotions, motivation, and reward-seeking behavior.
What is the function of the mammillothalamic tract?
The mammillothalamic tract connects the mammillary bodies to the anterior nucleus of the thalamus. This tract is important in the Papez circuit, which is involved in memory consolidation and emotional regulation.
What would happen if there was damage to the nuclei of the limbic system, such as the amygdala or mammillary bodies?
Damage to these nuclei could result in various impairments:
- Amygdala damage could impair emotional responses, particularly those related to fear, aggression, and anxiety.
- Septal nuclei damage could affect emotional regulation, leading to behaviors like heightened aggression or reduced motivation.
- Mammillary bodies damage is linked to memory deficits, particularly those related to memory consolidation and recall.
- Anterior nucleus of the thalamus damage could lead to disturbances in emotional processing and memory functions.
What are the primary functions of the cingulate gyrus?
The cingulate gyrus is involved in:
Mediating emotional responses to pain.
Assigning emotion to internal and external stimuli.
Vocalizing internal states, which allows us to express our emotions verbally.
What happens if the cingulate gyrus is damaged?
Damage to the cingulate gyrus can lead to:
The autonomic system losing its ability to respond to conditioned stimuli.
Behavioral changes such as aggression, shyness, and a reduced affect (emotional expression).
How does the cingulate gyrus contribute to emotional expression?
The cingulate gyrus plays a key role in vocalizing internal states, meaning it helps us express our emotions out loud, which is essential for emotional communication.
What behavioral changes might occur due to dysfunction in the cingulate gyrus?
Dysfunction in the cingulate gyrus can cause behaviors such as:
Aggression.
Shyness or social withdrawal.
Reduced emotional affect or a flattening of emotional expression.
How does the cingulate gyrus relate to the autonomic system?
The cingulate gyrus is involved in processing emotions and is linked to the autonomic system, which controls bodily responses to emotions. If the cingulate gyrus is damaged, the autonomic system may lose its ability to properly respond to conditioned stimuli, affecting emotional regulation and behavior.
What mental health conditions have been linked to damage in the cingulate cortex?
Damage to the cingulate cortex has been associated with:
Early Alzheimer’s disease.
Schizophrenia.
Obsessive-compulsive disorder (OCD).
Depression.
Bipolar disorder.
Addiction.
How is damage to the cingulate cortex related to early Alzheimer’s disease?
In early Alzheimer’s disease, damage to the cingulate cortex can impair emotional processing and memory, contributing to cognitive decline and difficulty in managing emotional responses.
What is the Indusium Griseum?
The Indusium Griseum is a thin sheet of grey matter that extends along the medial and lateral longitudinal striae from the paraterminal gyrus via the gyrus fasciolaris to the dentate gyrus.
Which structures are connected by the Indusium Griseum?
The Indusium Griseum connects the paraterminal gyrus, gyrus fasciolaris, and dentate gyrus
What is the Dentate Gyrus?
The Dentate Gyrus is a notched band of grey matter located between the fimbria of the hippocampus and the parahippocampal gyrus, separated by the hippocampal sulcus.
What is the relationship between the Dentate Gyrus and the hippocampus?
The Dentate Gyrus lies between the fimbria of the hippocampus and the parahippocampal gyrus, playing a key role in the hippocampal formation and memory processing.
Where is the Hippocampus located?
The Hippocampus is an elongated, prominent elevation situated along the floor of the inferior horn of the lateral ventricle, positioned above the Dentate Gyrus.
What is the ‘pes hippocampi’?
The ‘pes hippocampi’ is the bulbous extremity at the anterior end of the hippocampus, marked by ridges.
What are the main connections of the Hippocampus?
The Hippocampus has important connections through the fimbria (which continues as the fornix), linking the hippocampal formation with other structures in the limbic system, including the mamillary bodies and anterior nucleus of the thalamus.
What are the main functions of the hippocampal formation?
Making new memories.
Consolidating information from short-term to long-term memory.
What mental conditions are associated with damage to the hippocampal formation?
Damage to the hippocampal formation has been linked to:
Reduced volume in conditions like schizophrenia, PTSD, and depression.
Alzheimer’s disease significantly affects the hippocampal formation, leading to memory impairment.
What is the role of the fornix in the hippocampus?
The fornix is the sole efferent projection fiber of the hippocampus, which carries information from the hippocampus to other structures in the brain. It begins as the alveus, the efferent fibers from the pyramidal cells of the hippocampus.
How does the fornix develop from the alveus?
The fibers of the alveus pass medially on the surface of the hippocampus to form the fimbria, which then continue as the crura. The crura fuse to form the body of the fornix, which then splits into columns of the fornix.
What are the main pathways of the fornix?
The fornix has two main fiber pathways:
Pre-commissural fibers → septal area.
Post-commissural fibers → mamillary body and the anterior nucleus of the thalamus.
Where is the amygdala located?
The amygdala is an ovoid mass of grey matter situated in the roof of the inferior horn of the lateral ventricle.
What functions is the amygdala essential for?
The amygdala is crucial in the regulation of:
Emotions like love, friendliness, affection, fear, rage, and aggression.
What are the major connections of the amygdala?
Input: The amygdala receives input from the lateral olfactory stria and parahippocampal gyrus, as well as sensory inputs (visual, auditory, tactile, taste).
Output: The amygdala sends output through the stria terminalis, with supracommissural fibers targeting the septal nuclei, and commissural fibers to the hypothalamus (including the preoptic and anterior nuclei).
What are the effects of damage or stimulation to the amygdala?
Electrical stimulation of the amygdala can induce emotional attacks (e.g., rage).
Rabies virus can affect the amygdala, leading to violent behavior, especially when it attacks the temporal lobe.
Lesions in the amygdala reduce the ability to identify the motivational and emotional significance of events, affecting emotional processing.
