Behavioral Neuroscience, lecture on amygdala
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Behavioral Neuroscience
Summers
Fear
Afferent Path for Fear
Amygdala
Fear Conditioning
Pavlovian potentiated startle Afferent Shock (US) Pathway
Efferent Output
Neuromuscular Production of Fear Potentiated Startle
Integration of Fear Conditioning
BDNF
Substance P
ACh
Fear figures
Fear Conditioning Circuitry
end     Acronyms/Abbreviations
Fear Conditioning
IV. Amygdala  	

	A. Evolutionarily ancient heterogeneous structure
	
		1. subcortical almond-shaped structure in the rostromedial temporal lobe
		    in front of the hippocampus
		
			a. located just in front of the temporal horn of the lateral ventricle
			    and underneath the parahippocampal gyrus (uncus)
		
		
		2. composed of 4 different functional systems
		
			a. main olfactory + accessory olfactory
			
				i. part of the "nose brain"
			
					(1) heavily connected to the olfactory bulb
			
					(2) expecially the cortical amygdala
			
			b. autonomic
			
			c. cortical
			
				i. especially related to frontal and temporal lobes
			
			
		3. diverged from structures with functions of both striatum and limbic systems
		
			a. consists of phylogenetically new and old divisions
			
				i. multiple developmental origins
			
			b. includes: amygdala and extended amygdala
			
				i. BNST (bed nucleus of the stria terminalis)
			
			c. also includes: striatum and nucleus accumbens
			
				i. striatum - movement
				
				ii. nucleus accumbens - reward, addiction,
				    motivation, salience
	
	B. Nuclei of the Amygdala and extended Amygdala
	
		1. functional systems of the amygdala are defined by their sensory input
		
			a. have functionally specific outputs
			
			b. specifically directional intra-amygdaloid circuitries
	
		
		2. the Basolateral complex (BLA): frontotemporal amygdala  
	
			
			a. Lateral nucleus (LA) is the input region of the amygdala
			
				i. from specific sensory regions of the thalamus
				
				ii. sensory information rapidly transferred
				    to dorsolateral LA
				
					(1) slower to the cortex 
					
					(2) produces primal emotional response
					
					(3) preparation for higher cortex input
				
				ii. cortico-amygdaloid pathways - Glutamatergic
	
				
				iii. BLA complex receives highly processed
				     sensory information
				
					(1) from prefrontal, temporal & insular cortices
					
			b. reciprocal amygdalocortical pathways
			
				i. to limbic, associational and
				   1o visual cortices
				
				ii. Glutamatergic
					
			c. BLA closely related to the cerebral cortex
			
				i. histology, histochemistry and connections
				    are similar to cortex
			
			d. BLA complex projects to the CeA
			
				i. autonomic/somatic signs of fear
			
			e. BLA projects to dorsal striatum and
			   the ventral striatum/nucleus accumbens
			
				i. approach or avoidance
				
				ii. N. accumbens - autonomic extended amygdala
				    continuum
				
					(1) BLA involved in motivational
					    effects of emotion
					
					(2) projects to BNST - autonomic fear, anxiety
				
			f. projects to entorhinal cortex
			
				i. indirectly to the dentate gyrus of the hippocampus 
				
					(1) via the perforant path
					
					(2) influences LTP and hippocampal learning
					
					(3) memory of emotional events
				
				ii. medial BLA receives input from CA1
				    region of hippocampus
				
					(1) and perirhinal cortex
					
					(2) not sensory
			
			g. BLA complex includes basal amygdala
			
				i. basal amygdala: basolateral amygdala
				
					(1) input from the hippocampus
				
				ii. accessory basal nucleus: basomedial amygdala
				
					(1) input from the frontal cortex
		
			
		2. Cortical Amygdala (CoA)
		
			a. surface of the amygdaloid body 
			   adjacent to the temporal cortex and the MeA
			
			b. 1o input to CoA from the olfactory bulb and olfactory cortex
			
				i. olfactory amygdala
				
					(1) also includes piriform cortex - CoA transition
					     and anterior amygdala
						 
				ii. also accessory olfactory amygdala (posteromedial part)
	
			c. projects to the CeA
			
			
		3. Medial Amygdala (MeA)
		
			a. input from accessory olfactory
			
			b. input from the hypothalamus
			
			c. projects to the CeA
		
		
		4. Central Amygdala (CeA)
		
			a. output region of the amygdala
			
				i. GABA projections
				
					(1) connects to extended amygdala - BNST
					
				ii. CRF projections
				
					(1) connections to brainstem
					
						(a) locus ceruleus, raphe
						
				iii. Enkephalin projections
				
					(1) to periaqueductal gray (PAG)
					
					(2) CeA blocks pain via PAG Enk m-opiate-R
					
						(a) also mediated by 5-HT
						
					(3) CeA projections to PAG cause freezing
				
				iv. projects via the stria terminalis
				
					(1) BNST, PVN, nucleus accumbens?
				
				v. projects via the ventral amygdalofugal pathway
				
					(1) brainstem, dorsomedial thalamus,
					    cingulate gyrus, cortex
				
				vi. not to the striatum	
				
				vii. to trigeminal facial motor nucleus
				
					(1) facial expressions of fear
					
				viii. to PnC
				
					(1) enhances startle reflexes
				
			b. CeA controls autonomic nervous system
			
				i. via the PVN in the hypothalamus
				
				ii. and the dorsal motor nucleus of the vagus
				
					(1) HR, BP
				
			c. dual autonomic - limbic association functions
			
			d. input from the BLA, CoA, MeA
			
				i. intra-amygdaloid association fibers
				
			
	C. Intra-Amygdaloid circuitry
	
		1. LA dorsal  LA medial and LA ventral
		
		2. LAm  Basal and Accessory Basal and MeA
		
		3. Accessory Basal  CeA 
		
			a. basal  CeA
			
			b. MeA  CeA
		
		4. CeA  amygdalofugal pathway  (fugal = fleeing)
		                                                          4+5 = efferent projections
		5. CeA  stria terminalis 
	
	
	D. Function of the Amygdala
	
		1. detection of emotional events			
		
			a. production of appropriate responses
			
			b. interpretation of emotional significance
			   of sensory stimuli
			
			c. assigns emotional significance
			
			d. sexually differentiated
			
			e.generation of emotional aspects of dreams
			
		2. facial recognition neurons
		
			a. and produces facial expressions of fear
		
		3. motivational significance
		
		4. attention
		
		5. regulation of the autonomic nervous system
		
		6. perception of body movements
	
		7. memory
	
			a. especially fear memory
	
				i. fear conditioning

V. Fear Conditioning