Neuro: 4.5 - Limbic System

Front 1

What are the functions of the limbic system?

Back 1

- Cortical information and hypothalamic impulses are integrated
- Homeostasis (autonomic regulation), Olfaction, Memory, Emotion = HOME

Front 2

What does "limbus" mean?

Back 2

Border or hem between the new (neocortex) and the old (brainstem) brain

Front 3

Why was the limbic lobe referred to as the rhinencephalon? Correct?

Back 3

- Anatomists thought interconnections between the olfactory system and the limbic lobe indicated that this area had olfactory function
- Limbic system is not the "smell brain" rather it is just one of several sensory inputs

Front 4

What was Papez's understanding of the limbic lobe?

Back 4

- Emotion is the product of the limbic circuit
- Input enters from other structures to be elaborated as emotion
- Ultimately influences the hypothalamus to release appropriate hormones

Front 5

What are the structures that form Papez's Limbic Circuit?

Back 5

Cingulate --> Hippocampus --> Fornix --> Mamillary Bodies --> Anterior Thalamus --> Cingulate

Front 6

How was Papez's circuit modified by McLean?

Back 6

- Expanded to include hypothalamus, septal area, orbitofrontal cortex, nucleus accumbens (part of striatum), and amygdala
- Basic circuit is still there but with additional inputs and outputs

Front 7

What justifies the concept of the "limbic system"?

Back 7

- Common physiologic and neurochemical properties
- Intricate anatomic connections
- Common behavioral associations

Front 8

How was it established that the limbic system had common physiologic and neurochemical properties?

Back 8

- Herpes virus has a special affinity for these regions (leads to severe memory and behavioral disturbance)
- Susceptible to kindling (process by which a seizure is initiated and its recurrence made more likely) and development of seizure foci
- High density of cholinergic innervation and opiate receptors (involved in memory and perception of pain and pleasure)

Front 9

The limbic system is characterized by what kind of innervation and receptors? Functions?

Back 9

- High density of cholinergic innervation and opiate receptors
- Mechanism for involvement of limbic system in memory and perception of pain and pleasure

Front 10

What provides the cholinergic input for the brain (memory)?

Back 10

Septal nuclei and nucleus basilis of Meynert

Front 11

What system is critical for positive reinforcing brain mechanisms?

Back 11

Mesocorticolimbic Dopamine system

Front 12

What does the fornix connect?

Back 12

- Hippocampus
- Mammillary and Septal Nuclei

Front 13

What does the mammillothalamic tract connect?

Back 13

- Mammillary bodies
- Anterior Thalamus

Front 14

What does the Perforant Path connect?

Back 14

- Entorhinal cortex
- Dentate (Hippocampus)

Front 15

What are the efferent projections from the amygdala?

Back 15

- Stria Terminalis (to septal nuclei and hypothalamus)
- Ventral Amygdalofugal Pathway (to hypothalamus and brainstem nuclei)
- Directly to hippocampus, entorhinal cortex, and temporal and other neocortical areas

Front 16

What are the afferent projections to the amygdala?

Back 16

- Stria Terminalis (from septal nuclei and hypothalamus)
- Ventral Amygdalofugal Pathway (from hypothalamus and brainstem nuclei
- Lateral Olfactory Tract (from olfactory bulb and olfactory cortex)
- Direct from Temporal Lobe (neocortical areas and hippocampus)

Front 17

What are the cortical structures of the "Outer Core"?

Back 17

- Cingulate Gyrus
- Orbital Frontal Lobe
- Subcallosal Area
- Parts of Temporal Lobe (Hippocampus, Parahippocampal Gyrus, Uncus)

Front 18

What are the functions of the Cingulate Gyrus? Component of what?

Back 18

- Rostral - emotions and motor
- Caudal - visual spatial and memory
- Outer Core

Front 19

What are the functions of the Orbital Frontal Lobe? Component of what?

Back 19

- Personality
- Behavioral Control
- Self awareness
- Outer Core

Front 20

What are the functions of the Temporal Lobe (Hippocampus, Parahippocampus, and Entorhinal Cortex)? Component of what?

Back 20

- Memory
- Outer Core

Front 21

What are the cortical structures of the "Inner Core"?

Back 21

- Anterior Thalamic Nucleus
- Mammillary Body
- Hypothalamic Nuclei
- Septal Nuclei

Front 22

What are the functions of the Hypothalamic Nuclei? Component of what?

Back 22

- Pleasure Center
- Autonomic regulation - involved in BP, feeding, temperature regulation, and immune response
- Endocrine integration (ACTH and TSH secretion regulation from pituitary)
- Also involved in maternal behavior
* Inner Core

Front 23

Where do neurons in the hypothalamus project to? Functions?

Back 23

Pituitary Gland

Front 24

What are the functions of the Amygdala? Component of what?

Back 24

- Preservation of self behaviors
- Emotion
- Social behavior
- Aggression and defense response
- Sexual behavior
- Affective significance of visual stimuli
- Affect of faces
- Affective regulation
* Inner Core

Front 25

What are the functions of the Septal Nuclei? Component of what?

Back 25

- Preservation of species behaviors
- Sexual behavior
- Emotionality
* Inner Core

Front 26

What is Structure 3 (light pink)?

Back 26

Fornix (3)

Front 27

What is Structure 11 (small purple)?

Back 27

Mammillary Body (11)

Front 28

What is Structure 13 (light purple)?

Back 28

Amygdala (13)

Front 29

What is Structure 10 (blue/purple)?

Back 29

Hypothalamus (10)

Front 30

What is Structure 12 (hot pink)?

Back 30

Hippocampus (12)

Front 31

What does the Medial Forebrain bundle connect?

Back 31

Hypothalamic nuclei with amygdala and brainstem nuclei

Front 32

What causes the symptoms of Kluver-Bucy Syndrome in rhesus monkeys?

Back 32

Bilateral large temporal lesions including amygdala, hippocampus, and uncus

Front 33

What are the symptoms of Kluver-Bucy Syndrome in rhesus monkeys?

Back 33

- Psychic blindness (lose ability to detect meaning of objects = visual agnosia)
- Oral tendencies (examine all objects by mouth)
- Hypermetamorphosis (notice and react to every visual stimulus)
- Tameness (no motor or vocal reactions w/ fear or anger)
- Hypersexuality

Front 34

What are the symptoms of Kluver-Bucy Syndrome?

Back 34

- Visual agnosia (loss of recognition of simple familiar objects or people)
- Increased oral activity
- Hypermetamorphosis (attend and react to every visual stimulus within visual field - subsequent compulsive handling of object)
- Placidity (flat affect, lack of aggressive behavior, absence of fear)
- Hypersexuality (indiscriminate sexual advances)
- Bulimia

Front 35

What can cause Human Kluver-Bucy Syndrome?

Back 35

- Post traumatic encephalopathy
- Herpetic viral encephalitis (most common)
- Anoxia
- Subarachnoic hemorrhage
- Pick's disease
- Alzheimer's Disease
- Bilateral temporal infarction
- Focal status epilepticus
* All have extensive lesions involving bilateral temporal cortex and amygdala *

Front 36

What causes the symptoms of Geschwind Syndrome?

Back 36

- Sensory limbic hyperconnection - strengthening of synaptic connections
- Interictal (between seizures) personality in temporal lobe epilepsy

Front 37

What are the symptoms of Geschwind Syndrome?

Back 37

- Increased concern w/ philosophical, cosmic, or religious issues
- Altered sexual behavior (usually hyposexual)
- Hypergraphia (extensive writing - religious or philosophical in nature)
- Viscosity (tendency towards interpersonal stickiness, difficulty breaking off conversation)
- Interictal personality in temporal lobe epilepsy

Front 38

How are interictal personality (Geschwind syndrome) and Kluver-Bucy Syndrome related?

Back 38

- Interictal personality - HYPER-connection
- Kluver-Bucy Syndrome - DIS-connection

Front 39

What are the most pleasurable regions of the brain as determined by electrode stimulation of the brain?

Back 39

- Lateral Hypothalamus
- Medial Forebrain Bundle (connects hypothalamus and septum)
- Nucleus Accumbens

Front 40

How was it determined that the lateral hypothalamus and the medial forebrain bundle were the "most pleasurable" regions of the brain?

Back 40

Implanted an electrode into the hypothalamic and septal regions of a rat and found that rats would forfeit food and water, forget about sex, and even accept pain for an opportunity to self-stimulate

Front 41

What NT systems are implicated in the pleasure from self-stimulation of the lateral hypothalamus and medial forebrain bundle?

Back 41

- Catecholamines
- Dopaminergic systems (blocking dopamine caused transitory reductions in self-stimulation)

Front 42

How do addictive drugs affect the limbic system?

Back 42

- Produce potent effects on behavior by enhancing mesolimbic dopamine activity
- E.g., heroin increases neuronal firing rate of dopamine cells
- E.g., cocaine inhibits reuptake of dopamine

Front 43

Lesions to what area can produce pain, rage, or strong aversive reactions and long lasting hyperemotionality?

Back 43

Lesions to ventromedial nucleus of hypothalamus

Front 44

What happens if there are lesions to the ventromedial nucleus of hypothalamus?

Back 44

Can produce pain, rage, or strong aversive reactions and long lasting hyperemotionality

Front 45

What happens if there are lesions to the amygdala?

Back 45

- Leads to tameness or reduced emotional excitability
- Monkeys become social isolates (important for normal social interactions); indiscriminate hypersexuality; devestating effect on maternal behavior

Front 46

What is the amygdala tied to?

Back 46

Sensory association areas which participate in the modulation of emotional reactions

Front 47

Discharges in the amygdala are most frequently associated with what?

Back 47

Affective phenomena in patients with epilepsy

Front 48

What brain structure plays a role in PTSD?

Back 48

Amygdala - supports a classical fear conditioning; characterized by inability to extinguish fear memories

Front 49

What affects the amount of activity in the amygdala during a social interaction?

Back 49

- Emotional significance
- Degree of ambiguity

Front 50

Where are there cells that respond selectively to faces?

Back 50

In the amygdala

Front 51

The amygdala of humans plays a role in what?

Back 51

Integration of emotions, fear and memory

Front 52

What are the roles of the septal nuclei (septal region)?

Back 52

- Positive control for sexual behavior (lesions to septal region abolish hypersexuality)
- Stimulation leads to 400% increase in sexual drive
- Emotionality (lesions lead to rage and irritability)

Front 53

What are the implications of septal region lesions?

Back 53

- Abolishes hypersexuality
- Enhancement of social contacts
- Tumors result in rage-like attacks and increased irritability

Front 54

What are the implications of hippocampal lesions?

Back 54

Amnesia (inability to form new memories, but still can remember past memories)

Front 55

If someone loses their old memories but can still form new memories, what is the cause?

Back 55

Psychogenic Amnesia (not hippocampus)

Front 56

If someone loses their new memories but can still form old memories, what is the cause?

Back 56

Lesions to hippocampus, dorsal medial nucleus of thalamus, mammillary nuclei alone or in combination (necessary for declarative memory - acquisition of new facts and events)

Front 57

What are the two forms of long-term memory?

Back 57

- Explicit (Declarative) - for facts and events
- Implicit (Non-declarative) - for priming, procedural skills, classical and operant conditioning, and habituation and sensitization

Front 58

What are the two forms of Explicit (Declarative) Memory?

Back 58

- Episodic - personal events in one's life, actively remembered, embedded in time and place
- Semantic - facts known rather than actively remembered

Front 59

What does the hippocampal formation consist of?

Back 59

- Hippocampus
- Dentate Gyrus
- Subiculum

Front 60

What structure has extensive connections with the hippocampus and amygdala?

Back 60

Neocortex

Front 61

What is the major efferent to the hippocampal formation? Afferent?

Back 61

- Efferent - fornix
- Afferent - perforant path

Front 62

The hippocampus is important for what kind of memory?

Back 62

Formation of episodic memories (personal events in one's life, actively remembered, embedded in time and place)

Front 63

How does temporal lobe epilepsy affect the hippocampus?

Back 63

Can lead to hippocampal sclerosis and atrophy (lose episodic memory)

Front 64

What are some other causes of memory disorders besides lesions to the hippocampus?

Back 64

- Dementia
- Head trauma
- Stroke (less common because usually strokes are on one side)
- Wernicke Korsakoff's

Front 65

What causes the symptoms of Wernicke Korsakoff's Syndrome?

Back 65

- Chronic alcoholism and nutritional deficiency (thiamine)
- Lesions to mammillary bodies and thalamus

Front 66

What are the symptoms of Wernicke Korsakoff's Syndrome?

Back 66

- Acute: confusion, disorientation, oculomotor dysfunction, ataxia
- Chronic: anterograde and temporally-graded retrograde amnesia

Front 67

What are the divisions of the Cingulate Gyrus and their functions?

Back 67

- Anterior Cingulate - emotion and motor functions
- Posterior Cingulate - visuospatial and memory functions

Front 68

What are the changes after lesions to the anterior cingulate?

Back 68

- Emotional blunting, decreased motivation, disruption of mating behavior, impaired maternal infant interactions, impatience, lowered threshold for fear or startle
- Abolish conditioned emotional vocalizations
- Decreased pain
** Apathy, disinhibition, placidity (not easily upset or excited), depression, anxiety, obsessive-compulsive behaviors, heightened sexuality, bulimia

Front 69

What procedure can successfully treat OCD?

Back 69

Cingulotomy

Front 70

What can cause akinetic mutism (no desire or need to talk)?

Back 70

Bilateral anterior cingulate cortex lesions

Front 71

What causes the symptoms of Gilles de la Tourette Syndrome? Therapy?

Back 71

- Abnormalities in Anterior Cingulate
- Lesions of AC can relieve OCD behaviors
- Disconnection of AC from thalamus can reduce other Tourette's symptoms

Front 72

What are the symptoms of Gilles de la Tourette Syndrome?

Back 72

- Complex coordinated movement patterns
- Obsessive compulsive behaviors
- Tics, impulsive behavior

Front 73

What are the functions of the anterior cingulate?

Back 73

Integration of thought, motivation, and emotion w/ movement

Front 74

Excessive amplification of signals from the Anterior Cingulate can cause what?

Back 74

- Excessive emotional signals --> anxiety and obsessive compulsive behaviors
- Excessive motor behavior --> tics and impulsive behavior
- Excessive filtering of emotions --> apathy, akinesis, mutism

Front 75

What are the symptoms of Orbital Frontal Lobe Syndrome?

Back 75

- Disinhibited
- Tactless
- Bawdy
- Boastful
- Grandiose
- Restless
- Impulsive
- Inattentive
- Perseverative
- Tendency to dress carelessly and eat gluttonously

Front 76

What are the symptoms of Frontal/Convexity or Dorsolateral - Frontal Lobe Syndrome?

Back 76

- Apathetic
- Slow
- Demonstrating little initiative or spontaneity
- Responding in an automaton like manner
- Vacancy of expression

Front 77

What are the symptoms of Medial Frontal Lobe Syndrome?

Back 77

- Akinetic mutism
- Inert
- Speechless
- Intact sleep wake cycle
- "motionless, mindless, wakefulness"
- Loss of drive to move or speak