23B amygdala, hippocampal and limbic Flashcards
Limbic lobe surrounds….
Limbic System consists of circuits concerned with…
lateral ventricles
Limbic system refers to circuits concerned with emotion (Amygdala- frontal part of temporal lobe) and cognitive function (hippocampus)
Amygdala is located where
Anterior part of temporal lobe
Functions of the amygdala and its nuclei
- olfaction
- emotions
- autonomic
- learning and memory
Three main groups of amygdaloid nuclei
- Corticomedial- The olfactory part
- Central: principal output nucleus; striatum like in structure, important for autonomic control
- Basolateral- principal input nucleus
Major inputs to the corticomedial nuclei are from
olfactory bulb, parabrachial nucleus (taste), Medial dorsal, ventromedial thalamus
Primary output of the corticomedial uceli
hypothalamus
Central nucleus receives its major inputs from where
basolateral nuceli of the amygdala and from the hypothalamus
Principal output of the central nucleus is
brainstem and hypothalamus
Main functions of the central nucleus…KNOW
autonomic control (BP, HR)
arousal
subjective experience
Amygdala is crucial for regulating
emotional and social behavior
Bilateral amygdala lesions=
in a monkey
- hypersexual
- tame
- Hyperphagia if Basolateral nucleus is lesioned, Hypophagia if the central nucleus is lesioned
Central—starve yourself
Animals with bilateral amygdaloid lesions are extremely oral- they put everything in their mouth
ok
Bilateral loss of the anterior temporal lobe (amygdala) is called
Kluver Bucy syndrome
Kluver Bucy symptoms
Rare in human pts
- hypersexual
- hyper oral
- tame
- hyperphagia
- hyperactive
- psychic blindness (don’t recognize the emotional content of facial expressions)
Urbech Wiethe?
Calcifications in neural tissue in the anterior temporal lobes… LIterally cannot recognize fear. Can’t recognize a scared face, can’t draw fear, hav eno idea what it really is. Prevents them from acting appropriately around others
Which part of the brain is the executor of fear?
Amygdala (esp basolateral )
Learning and memories
basolateral nucleus
Principal cell type of the Central Nucleus is
medium spiny GABAergic
Principal cell type in Basolateral
pyramidal cells
Basolateral nucleus of the amygdala receives most of its input from
- Neocortex (association cortex primarily), thalamus, hippocampal formation…..most of it is highly processed sensory info
Major output of the basolateral nucelus is
Back to the central nucleus
Important to realize that the basolateral nucleus is ideally placed between cortical and sensory inputs and outputs to the Central Nucleus and hypothalamus in order to integrate sensory experience and emotional behavior.
BASOLATERAL NUCLEUS IS RESP for emotional component of learning and memories
Hippocampus is derived from what brain region
Telencephalon
Describe hippocampal location
temporal lobe, just behind amygdala
What is the alveus
Collected axons of hippocampal pyramidal cells
Alveus fibers collect and form
fimbria
Fimbria becomes
fornix
Two major input pathways to hippocampal formation
1) Perforant pathway from lateral entorhinal cortex
2) Alvear pathway from medial entorhinal
Describe the tri-synaptic circuit of the hippocampus
Main input to hippocampal formation is excitatory projection from the entorhinal cortex to granule cells in the Dentate Gyrus via the perforant path.
The Dentate gyrus then projects excitatory cells to CA3 pyramidal cells via mossy fibers (very secure)
CA3 then projects to CA1 via schaeffer collaterals.
- Alvear path is ERC to CA1 directly
Almost all inputs to hippocampus come from
Entorhinal complex
Almost all outputs of hippocampal formation are from
subiculum
The Entorhinal complex is fucking important. It receives inputs from where
Cortex, thalamus, brainstem…..thus….the ERC is the gateway to the hippocampus and receives highly processed info about most of our experience
Where does the subiculum project?
widely through the cortex
Principal cells of CA fields and subiculum are
pyramidal neurons….have tons of spines for excitatory inputs
Hippocampal pyramidal neurons (esp CA1) are highly susceptible to what
epilepsy and ischemia
Because of the prevalence of excitatory neurons and their interconnections, the hippocampal formation is highly susceptible to
seizures….thus, GABAergic inhibitory interneurons play an important role in regulating activity
Hippocampal pyramidal cells are especially sensitive to what disease
alzheimers….this loss of hippocampal neurons may be the basis for loss of memory
Hippocampus very important for learnign and memory
especially spatial learnign and memory
place cells
activity related to position of anmal in external environment
To types of memory
Declarative- available to the conscious mind and encoded in language
Procedural: like riding a bike or playing guitar.
Emotional content of memories governed by
amygdala
basal ganglia and cerebellum are crucial for
implicit memory formation
immediate memory
lasts only a few seconds
short term memory
seconds to minutes
working memory
allows us to keep things in mind to allow completion of a task
Long term memories last for days weeks, etc
ok
What is essential for formation and retreiveal of long term memories
hippocampus…..Long term memories stored in neocortex but hippocampus allows us to retrieve them
