Amygdala Flashcards
Which are the main nuclei of the amygdala?
Lateral Nucleus: receives direct projections from thalamus, from perirhinal cortex, from association cortex, could be auditory, visive, depending on the modalities of the emotional stimulus. It projects to the central nucleus
Central Nucleus: sends the informations downstream to a lot of structures whome changing activity is the source of different components of the emotional responses
• Bed nucleus of the stria terminalis: stress hormones
• Parabrachial: parasympathetic control
• Central gray: emotional behavior
• Lateral Hypothalamus: sympathetic activation
• Nucleus reticularis pontis caudalis: reflex potentiation
When does the amygdala activates?
The amygdala activates in response to emotional facial expressions, especially (but not exclusively) fear, even when fearful eyes alone are presented subliminally. The amygdala responds not
only when fear is conveyed by facial expression, but also by non-facial, non-visual stimuli,
such as nonverbal vocal sounds (cries, screams) and by whole-body movements that signal fear
What’s Fear conditioning?
• A neutral (conditioned) stimulus (CS), such as a tone, is paired with an aversive unconditioned stimulus (US), such as a mild footshock
• CS-US pairings result in an association of the CS and US, whereby the presentation of the CS alone subsequently elicits a conditioned fear response, such as freezing
Which neural process underlies fear conditioning?
Long-term potentiation (LTP) at synapses transmitting CS information to the LA
Which are the changes caused by fear conditioning?
Prior to fear conditioning, sensory afferents carrying information concerning neutral (to be
conditioned) stimuli (CS+,CS-) converge on principal neurons in the lateral amygdala (LA)
During conditioning, coincident pre- and post-synaptic activity (active synapses and post-
synaptic neurons) leads to input-specific long-term potentiation at sensory afferents carrying CS+
information
After conditioning, potentiated CS+ synapses allow the formerly innocuous CS to drive fear
responses by depolarizing LA principal neurons
Which are the changes caused by fear conditioning?
Prior to fear conditioning, sensory afferents carrying information concerning neutral (to be
conditioned) stimuli (CS+,CS-) converge on principal neurons in the lateral amygdala (LA)
During conditioning, coincident pre- and post-synaptic activity (active synapses and post-
synaptic neurons) leads to input-specific long-term potentiation at sensory afferents carrying CS+
information
After conditioning, potentiated CS+ synapses allow the formerly innocuous CS to drive fear
responses by depolarizing LA principal neurons
Which are the consequences of bilateral lesions of the lateral nucleus of the amygdala?
reduction in the elevation of blood pressure and the duration of freezing evoked by the CS
Which routes involving the amygdala mediate fear conditioning and unconditioned response to fear stimuli?
• direct thalamo-amygdala route (fast & early response)
• thalamo-cortico-amygdala route (slower & complex analysis)
The high and the low transmission routes may have complementary functions, trading off speed of
transmission against accuracy of representation
Both pathways most likely process emotional stimuli unconsciously, with conscious awareness of the stimulus requiring prefrontal areas
Only lesions to both pathways impair fear conditioning
How is the amygdala involved in memory processes?
the amygdala is selectively involved with the formation of enhanced long-term memory of emotionally arousing events
The amygdala is not itself a site of long-term explicit or declarative memory storage, but serves to influence memory-storage processes in other brain regions, such as the hippocampus, neocortex and other
3 processes in which the amygdala plays a key role:
• the processing of emotionally relevant stimuli;
• emotional learning (esp. threat conditioning);
• consolidation of emotional memories
