ICL 5.0: The Emotional Brain and The Limbic System Flashcards
what is the limbic system?
a collection of anatomically related structures that vary greatly in function but interact/modulate with one another; this presentation will refer to it as a system
it’s a system that contributes to HOME:
Homeostasis
Olfaction
Memory
Emotion
what are the 5 F’s of the limbic system?
Fleeing
Fighting
Feeding
Feeling
Fornication
how does the limbic system play a role in emotion?
- remembering past events that were both pleasant and traumatic
- perceiving threats from our surroundings
- making choices based on our experiences
- controlling movements based on past learning
- form sensory preferences - likes/dislikes
it doesn’t deal with what makes you happy or sad – if you damage the limbic system it doesn’t make you unhappy but it can increase or decrease your hunger, thirst, sex drive, aggression, fear –> so it has an effect on positive vs. negative emotions but not technically your happiness
what are the functions of the limbic system?
- controlling emotions like anger and fear
- regulating eating, hunger and thirst
- responding to pain and pleasure
- controlling functioning of the autonomic nervous system, including things like pulse, blood pressure, breathing and arousal
- sensing sexual satisfaction
- controlling aggressive or violent behavior
- responding to sensory information, especially sense of smell
what anatomical structures are part of the limbic system?
- hypothalamus
- hippocampus
- amygdala
then there’s also
- septal nuclei
- mammillary bodies
- cingulate gyrus
- periaqueductal grey
- fornix
what is the function of the hypothalamus?
- regulating hormones and maintaining homeostasis –> it feeds information into the limbic system
- controls vegetative, endocrine functions and aspects of emotional behavior
- controls internal conditions such as temperature, osmolality, drive to eat and drink, control body weight, sleep, bowel function, bladder activity, sexual performance
what is the function of the hippocampus?
- memory and focus
- motor control
- forming short-term and long-term memories through consolidating information
- learning new skills from reward, punishment, reinforcement and failure with help from the septal nuclei
- recognition of what’s familiar versus new
- navigation or sense of direction; spatial memory
- involved in olfaction (smelling) and tying together smells with specific memories*
- the hippocampus receives input from and sends output to the amygdala, which plays an important role in the limbic system by creating emotional significance to feelings (positive or negative)
what is the function of the amygdala?
- tied to fear and anxious emotions –> so if there’s damage to the amygdala you won’t have any fear or worry which can actually be bad
ex. anger black out and panic from anxiety disorder that caused panic and then anger - learning and memory of emotional significance of stimuli
- receives neuronal signals from all parts of the limbic cortex
- widespread outputs to cortex, hippocampus, hypothalamus and brainstem
- learns and maintains link between stimulus and its emotional value
what is the function of the septal nuclei?
pleasure and learning through reward and punishment –> it’s very involved in operant conditioning!
it’s involved in the affective nature of sensory sensations so whether the sensations are pleasant or unpleasant aka reward or punishment/satisfaction or aversion
what is the function of the mammillary bodies?
primary function is recollective memory
this is when an individual recalls a specific episode from their past; it could be positive or negative
very active with PTSD
what is the function of the cingulate gyrus?
processing emotions and behavioral regulation
ex. when you come into the lecture hall for a final and you’re anxious, tapping your leg, etc. that’s the cingulate gyrus
what is the function of the periaqueductal grey?
anatomic and functional interface between the forebrain and the lower brainstem and has a major role in integrated behavioral responses to internal (e.g., pain) or external (e.g., threat) stressors –> the PAG is what’s responsible for the fight-or-flight response that will either make you freeze or run away from the situation
not always seen as part of the limbic system but has connects to the system, particularly through the hypothalamus
PAG transforms messages about threat to action: with pain it will elevate or reduce the pain signals returned to injured limb and it takes signals of other threats from hypothalamus and initiates the behavioral responses of fight-or-flight
what is the function of the fornix?
it’s the major tract out of the hippocampus and it’s associated with memory
what structures aren’t officially part of the limbic system but are associated with the septal nuclei?
- ventral tegmental area
releases dopamine in response to rewarding stimuli – so it’s involved with motivation and conditioned responses
- nucleus accumbens
plays a role in the analysis of reward and reinforcing information
these two play a huge role in addiction
what is the Papez circuit?
an anatomical circuit within the limbic system that starts and ends in the hippocampus.
it helps modulate learning and emotional expressions such as sexual desire, pleasure, fear, and anxiety
so it controls emotional expression!!
which structures are involved in the Papez circuit?
hippocampus → fornix → mammillary bodies (hypothalamus) → via the mammillothalamic tract → anterior thalamic nucleus → cingulate gyrus → cingulum → hippocampus
slide 10-12
how do drugs effect the limbic system?
drugs of abuse highjack limbic circuits responsible for processing pleasure and reward
this would include the nucleus accumbens and ventral segmental areas which modulate pleasure and reward and drug seeking
what happens is there’s altered availability/influence of dopamine released by the ventral segmental area onto neurons in the nucleus accumbens
what things can happen when there’s limbic system dysfunction?
- disinhibited behavior: this means someone doesn’t consider the risk of behaviors and ignores social conventions/rules
- increased anger and violence: this is commonly tied to amygdala damage
- hyperarousal: amygdala damage, or damage to parts of the brain connected to the amygdala, can cause increased fear and anxiety
- hypoarousal: this can cause low energy or lack of drive and motivation
- appetite dysregulation: destructive behaviors tied to hyperorality or thalamus dysfunction can include overeating, binge eating or emotional eating
- trouble forming memories: hippocampal damage can include short-term or long-term memory loss
- learning is often greatly impacted by hippocampal damage, since learning depends on memory
- someone with the condition anterograde amnesia loses the ability to form and retain new memories
which 2 disorders are related to limbic system dysfunction?
- Wernicke-Korsakoff syndrome
2. Kluver-Bucy Syndrome
what is Wernicke-Korsakoff syndrome?
a neurological condition effecting the limbic system resulting from thiamine B1 deficiency – almost always related to chronic alcoholism
Wernicke = acute neurological disease with confusion, ataxia, eye abnormalities
Korsakoff = chronic form of dementia, memory loss –> once you start to have dementia symptoms it can’t be reversed
patient will present with pronounced anterograde amnesia, ataxia, impaired declarative memory, and confabulation – procedural/non-declarative motor action memory remains intact
causes problems learning new information, inability to remember recent events and long-term memory gaps. Memory difficulties may be strikingly severe while other thinking and social skills are relatively unaffected
what is Kluver-Bucy Syndrome?
results from bilateral lesions of the amygdala and adjacent temporal lobe structures
results in placidity, decreased aggressive behavior, fearlessness and having little emotional reaction, visual agnosia, hyperorality, hypersexuality
what are the 2 theories of emotion?
- James Lange theory of emotion
2. Schachter-Singer Two-Factor Theory of Emotion
what is the James Lange theory of emotion?
our emotions are felt based directly upon what our body is experiencing as physical sensations
ex. 1st Heart racing, perspiring then 2nd I see a bear; my muscles tense, my heart races. I then” feel afraid due to physiology -evaluated as anxious/stressed
so this is feeling first that then creates a label based on the physiological effect
classical conditioning explains some fear and anxiety disorders by means of James Lange and the Limbic System
what is the Schachter-Singer Two-Factor Theory of Emotion?
emotion is based on two factors: physiological arousal and cognitive label that we give it
ex. 1st - Heart racing, perspiring and then 2nd at a favored concert and having energetic fun – labeled excitement, not fear or anxious and this is because cognitively you’re labeling it differently even though both fear/anxiety and excitement produce a racing heart and perspiration
so how we label the physiological sensation impacts what emotion we have
this cognitive theory can explain despair, anxiety and other disorders by means of Two factor model and Limbic system
