NB11-1 - Emotions and DLA Flashcards
Describe what classical fear learning/threat prediction is? Provide an example using proper terminology.
Classical fear learning is learning to fear a stimulus based upon past experiences. The classic example is of a mouse that receives a shock, the unconditioned stimulus, right after a sound, the conditioned stimulus, is played. Eventually the mouse learns to fear (the conditioned response) the sound even when there is no shock.
Explain what extinction memory using the mouse trial. How does extinction memory relate to fear conditioning? What is the significance of this relationship?
After the mouse has learned to fear the sound, the sound will repetitively be played without a shock. Eventually, the mouse will stop fearing the sound. This is extinction memory. The extinction memory does not erase/reverse the original fear conditioning but rather competes with it. Because of this, it is possible to see a spontaneous return of fear
Explain what contextual fear conditioning is using the mouse experiment. Why are these types of experiments useful on humans?
This type of fear conditioning is dependent upon another context (usually an environment). For example, if the mouse experiment was carried out so that the mouse only received the shock after the sound was played in a blue cage and never recived the shock in the red cage, the mouse would learn to only fear the sound in the blue cage.
If the subject was to begin fearing the stimulus in the safe environment, this could indicate issues with the fear learning system that would predispose the subject to an anxiety disorder.
Describe the neural pathway that least to classical fear conditioning. Use the mouse experiment as an example.
- Sound information is transmitted to the auditory cortex
- The shock is routed through the pain pathway to the somatosensory cortex
- Both signals are then routed to the basolateral nucleus of the amygdala where plasticity is developed between cells that store the fear of the stimulus and cells that trigger the fear response
- When fear is triggered, that information is sent to the central amygdala where a cascade of conditioned responses is initiated
List the major structures the central amygdala could stimulate in order to elicit a fear response. Describe what the fear response is in each of these cases.
- Stimulation of the central gray center (aka periaqueductal gray) would facilitate cessation of movement (freezing)
- Stimulation of the lateral hypothalamus would lead to an increase in SNS activity
- Stimulation of the bed nucleus of the stria terminals activated the hypothalamic pituitary adrenal axis which leads to an increase in the release of stress hormones
Describe the neural pathway that leads to the formation of extinction memory.
Mechanism is not well understood but it is known that the ventromedial prefrontal cortex down regulates amygdala firing and the vmPFC is inhibited during classical fear conditioning when the unconditioned stimulus is applied. Therefore, it is thought that the increased activity of the vmPFC (due to the absence of the unconditioned stimulus) has to do with the formation of extinction memory.
Describe the neural pathways that lead to developing contextual fear memory.
During classical fear conditioning, stimulus information is also being processed by the hippocampus, in addition to the amygdala. The hippocampus is able to upregulate or downregulate amygdala firing. Contextual fear conditioning has taken place when the hippocampus down regulates the amygdala in safe contexts and up regulates it in threat contexts.
What is believed to be the cause of over generalized fear responses and why?
Hippocampal Damage
The hippocampus is crucial to contextualizing fear responses.
What region of the brain has been found to be responsible for long term fear memory?
The orbitofrontal cortex
amygdala
List the three psychological theories of emotion we need to know in chronological order.
- James-Lange theorized that emotional stimuli cause physical response which drives subjective feelings
- Cannon-Bard theorized that emotional stimuli cause simultaneous physical response and subjective feeling
- Schachter-Singer developed a two-factor theory that cognitive appraisal (a personal interpretation of a situation) and physiological state interact to give rise to subjective feeling.
Describe Broca’s contribution to the conceptual evolution of the limbic system.
He discovered that as species became evolutionarily closer to humans, their olfactory cortices shrunk and their prefrontal cortices expanded. He also noted that the sense of smell had to do with more than the olfactory bulb and that a ring of structures in the center of the brain were involved. He named this ring of structures the limbic lobe
What structures does the limbic lobe consist of, according to Broca?
subcallosal gyrus, cingulate gyrus, isthmus, parahippocampal gyrus and uncus
These are still considered to be part of the limbic lobe
Describe Papez’s contrinution to the conceptual evolution of the limbic system.
Papez noticed that his patients who had lesions to limbic structures were prone to emotional outbursts. He therefore correctly theorized that the limbic circuitry had something to do with emotion. He incorrectly theorized that the circuit was “thalamus-hippocampus-hypothalamus-cingulate” and that the cingulate was the main structure supporting emotional experience.
Describe MacClean’s contrinution to the conceptual evolution of the limbic system.
MacClean was the first to develop EEG probes that could be used to measure activity in limbic structures. He would used these probes to measure activity during his patient’s auras (often involving fear) before a seizure. He discovered that there were more structures involved with processing emotion than what Broca first postulated. He added the hippocampus, thalamus, hypothalamus, cingulate, amygdala, and septal region to the list of structures that process emotions. He also put forth the model of the triune brain which, based on evolution, separates the forebrain into three primary areas: reptilian brain (basal ganglia), paleomammalian complex (limbic system), and neomammalian complex (neocortex). He claimed that these brain regions could not communicate with each other and that, therefore, emotions were separated from intellect and could not be controlled.
A
IMPORTANT - These responses can be elicited even though the patient has psychic blindness
B
The hippocampus is important for storing regular, non-emotional, memory but the amygdala is where emotional memory is stored.
D
C
E
Amygdala is hyperactive
