Lecture 11 - Limbic system Flashcards
The hippocampal formation consists of
Dentate gyrus
Entorhinal cortex
Subiculum
Hippocampus proper
The hippocampus consists of
Hippocampus proper + Dentate gyrus
Broca’s Limbic LOBE is purely an ___ term and is composed of _____ , and does not contain any ___structures
- anatomical
- Fornicate gyrus (cingulate + parahippocampal)
- subcortical
describe Maclean’s Limbic SYSTEM
- the TRIUNE BRAIN THEORY
- consists of 3 distinct brain layers:
1. Primitive brain (archipallium) - survival, action brain
2. Intermediate brain (paleopallium, limbic brain) - emotional brain
3. Rational brain (neopallium) - the logical/thinking brain
what are the functions of the Limbic System?
- learning & memory
- control of emotion & instinctive behaviour
What are widely accepted concepts of the Limbic system? (x3)
- analyses sensory stimuli for emotional significance
- stores emotionally significant memory
- impacts cognitive responses required for normal social behaviour/survival
What are the major cortices involved in the LIMBIC SYSTEM? (x5)
- hippocampal formation (D.E.S.H)
- Parahippocampal gyrus
- Cingulate Gyrus
- Oribto-frontal cortex
- subcallosal area
What are the nuclei involved in the LIMBIC SYSTEM? (x3)
- Amygdala
- hypothalamus
- anterior nucleus of Thalamus
What are the fibre tracts involved in the LIMBIC SYSTEM? (x4)
- fornix
- fornical commissure
- cingulum
- uncinate fascicle
The cingulum connects ____
the uncinate fascicle connects ____
- cingulate and parahippocampal gyri
- temporal and frontal lobes (orbitofrontal cortex)
memory is defined as (x3)
- acquisition
- storage
- retrieval
of information
Short-term memory is also know as? it is important for ___
- working, transient, online memory
- performing daily acitivities
Describe the mechanisms of Short-term memory
- > sensory stimulus = < 1s
- > forget stimulus
- > attention + sensory stimulus = few seconds
- > peformance in daily activity
- > forget stimulus
Short-term memory is mediated by
the PFC
short-term memory is encoded into long-term memory by
the hippocampus
Long-term memory can be divided into (x2)
- Explicit memory
- declarative
- conscious processing
- Implicit memory
- non-declarative
- unconscious processing
Explicit memory is divided into __and stored in __
- semantic (Basic knowledge)
- episodic (personal events)
- most higher association cortices
Implicit memory is divided into ___ and stored in (respectively)
- memories of skills and habits (stored in Basal ganglia, cerebellum, motor cortex)
- emotional memories (stored in amygdala)
Which cortical structure is the “door/gate” to the Limbic Loop?
the entorhinal cortex
Describe the features and functions of the Entorhinal cortex (x5)
- rostral most part of parahippocampal gyrus
- door to limbic loop
- contains grid cells for spatial navigation
- first site to be affected in Alzheimer’s disease
- important for learning, memory and spatial nav.
Describe the functions and features of the hippocampus (x4)
- contains TIME NEURONS (for order of events)
- contains PLACE NEURONS (spatial navigation)
- deals with EXPLICIT memory
- converts short-term into long-term memory (specifically “where” & “when” of events)
What is retrograde and anterograde amnesia?
retrograde - unable to retrieve information from long-term memory
anterograde - unable to encode/store new information to long-term memory
What type of amnesia will result from a lesion of the hippocampus?
profound anterograde amnesia where one is unable to store new information into long-term memory and is unable to spatially navigate, but skilled memory and short-term memory are still intact.
The hippocampus Proper is also know as ___. It is divided into ____.
- cornu ammonis
- CA1
- CA2
- CA3
- CA4
Which hippocampal portion is sensitive to low levels of oxygen (Hypoxia)?
CA1
Which hippocampal portion is involved in seizure generation?
CA2
What is the name of the fibre tract within the hippocampus?
Alveus
Fibres of the alveus become the ___ which become the __.
- fimbria of the hippocampus
- fornix
Where in the cortex does adult neurogenesis occur?
dentate gyrus
The limbic/Papez Circuit is believed to
underlie the connection between emotion and memory
The papez ciruit involves
Entorhinal cortex -> dentate gyrus -> hippocampus -> mammillary bodies –> ant. nucleus of Thalamus -> cingulate gyrus - - - - - -> (back to entorhinal cortex via cingulum)
The amygdala is contained within the ___ gyrus of the ___
semilunar
uncus
What causes Wernicke-Korsakoff Syndrome ?
What are the symptoms?
- damage to the mamillary bodies caused by Vitamin B1 deficiency caused by severe malnutrition or chronic alcoholism
- Memory loss, disturbance of Papez circuit
What are the functions of the amygdala? (x3)
- stores emotional memories of fear
- analyses environmental stimuli for emotional significance (hostility/friendliness)
- initiates attachment (if friendly) or fear response (fight or flight response via hypothalamus) (if hostile)
