Limbic System & Prefrontal Cortex Flashcards
major structures that form the limbic system
These form the limbic lobe: Cingulate gyrus Subcallosal gyrus Parahippocampal gyrus Hippocampal formation Uncus Amygdala
These are not part of the limbic lobe but function as part of the limbic system:
Oribitofrontal association area
Hypothalamus
Thalamus
Septal area (rostral end of diencephalon)
Basal ganglia structures
7 functions of limbic system
- Emotions/behavioral expression of emotions
- Learning
- Memory (short term and long term)
- Motivation/drive
- Feeding/drinking
- Defensive behaviors
- Reproduction
interaction between stress, disease, mental health, and recovery
Stress prompts the release of cortisol. Excessive amounts of cortisol remaining in the system for long periods of time (due to increased or ongoing stress) has been linked to the following:
inhibited learning and memory
lower immune system function (i.e. more likely to get sick, stay sick, and/or recover more slowly) and bone density
increased weight gain, blood pressure, cholesterol, and risk of heart disease
increase risk for depression, mental illness, and lower life expectancy
stress-related diseases like colitis, cardiovascular disorders, and adult-onset diabetes
2 types of memory
declarative and procedural memory
declarative memory
Facts, events, etc.
Available for conscious recollection
Easy to form but also easy to forget
(ST and LT memory are subtypes)
procedural memory
Skills, habits, etc.
Require repetition and practice over a longer period but are harder to forget
major factor required to acquire long term memory
CREBs – important for protein synthesis that aids in the metabolic and anatomical changes associated with long-term memory consolidation
Cramming does not work because CREBs are not available in large quantities, but instead rely on persistent enhancement of synaptic transmission via high frequency stimulation
long term potentiation (LTP)
“practice makes perfect”
high frequency activity stimulating a pathway – if this happens long enough a short term memory can be converted into a long term memory
long term depression (LTD)
“use it or lose it”
low frequency activity depresses a pathway and will not keep a memory
retrograde amnesia
memory loss events prior to the trauma
anterograde amnesia
inability to form new memories after the trauma
global transient amnesia
(temporary)
sudden and severe anterograde amnesia in combination with amnesia for recent events immediately leading to some traumatic event/injury – lasts for only a few minutes or days
where are new declarative memories processed and converted to long term mem
Hippocampus in the temporal lobes
However, it is important to note that not all types of memory of formed or stored in the same manner or location. Therefore, damage to the hippocampus will not destroy all memory.
are procedural memories processed in the same place as declarative memories?
No, procedural memories are formed through a complicated interaction of: cerebellum basal ganglia thalamus other areas of cortex and limbic system
clinical manifestations when you lesion the orbitofrontal area
- blunted affect
- decreased emotional drive
- IQ intact except they will perseverate (get hung up on something)
clinical manifestations when you lesion the inferior temporal lobe
Results in anterograde amnesia - will still have LT and procedural memory intact
Lesions due to epilepsy, encephalitis, trauma
clinical manifestations when you lesion the amygdala
(think of AMY as a person) Flat affect/uncontrolled rage Hypersexuality Disinhibited behavior Socially embarrassing Loss of fear Not afraid of much
clinical manifestations when you lesion the septal area
Hypersexuality and rage
TBI - potential cognitive problems
Memory problems (limbic, temporal)
Attention deficits (prefrontal cortex)
Impaired reasoning capabilities/impulsivity (prefrontal cortex)
might be less impulsive or more impulsive
Impaired learning abilities (limbic, temporal)
Orientation/confusion (limbic)
TBI - potential social/emotional problems
Hypersexuality Intimate behavior Agitation/violence Aggressiveness Passive/flat affect/lack of motivation socially inappropriate
prognosis for recovery of cognitive problems vs motor problems after brain injury
The prognosis of TBI for motor return is often better than the prognosis for remediation of cognitive and behavioral problems
cingulate gyrus
above corpus callosum, lots of roles in emotion and memory
subcallosal gyrus
underneath front of corpus callosum, inhibits the amygdala
parahippocampal gyrus
surrounds hippocampus, plays a role in memory formation
hippocampus
largely responsible for formation of memories
uncus
medial component of ventral temporal lobes in front of parahippocampal gyrus, part of entorhinal cortex (olfaction)
amygdala
linked to fear and anxiety
orbitofrontal association cortex
part of frontal lobe
plays a role in social behavior, responding appropriately to social cues, decision making
*one of the least understood areas of the limbic system (emoji reference)
Phineas gage
- working on railroad
- explosion caused iron rod to go through head (eye and frontal lobe)
- affected prefrontal cortex
with personality and executive functioning
hypothalamus
homeostasis, anterior pituitary glands, equilibrium
HM
- part of both temporal lobes removed trying to treat a seizure disorder
- had retrograde amnesia prior to surgery, then permeant anterograde amnesia after surgery
- procedural memory, IQ, and personality all intact
WADA
- a barbiturate called amatol
- injected into carotid artery
- goes to hemispheres of brain
- slows one side down and sees if one side of the brain is more active for a given function (lateralization of brain functioning)
Loop of Papez
- how emotions have such a profound input on decision making
- initial understanding of the limbic system
- It’s a circuit: creates a cycle of communication
- Emotional stimulus activates the thalamus to send signals to hypothalamus and sensory cortex
- Then synapses with cingulate cortex to produce emotional response from the body
- yields a bodily/physical response, and a memory of the emotional response
Stimulus creates a memory of an emotional response, most basic mechanism for habit formation
cortisol
mobilizes energy and surpasses immune responses and serves as an anti-inflammatory agent
