Behavioral Neuroscience Summers

Fear Afferent Path for Fear Amygdala Fear Conditioning

Afferent Shock (US) Pathway Efferent Output Neuromuscular Production of Fear Potentiated Startle Integration of Fear Conditioning

ACh BDNF Gephyrin Enkephalin

Substance P Fear figures Fear Conditioning Circuitry end     Acronyms/Abbreviations

Fear Conditioning
VII. Efferent Motor output: Fear Potentiated Startle			

	A. Efferent response begins with processed CS + US signal in BLA
	
		
	B. BLA projects to MeA
	
		1. synapes include Glutamate, Enkephalin, Substance P
		
			a. Glu binding AMPA 
			   Enkephalin (Enk) to m-opiate-R
			   Substance P (SP) binding to NK1 receptors
		
		2.MeA outputs to the ventromedial hypothalamus (VMH)
		
			a. from there to the periaqueductal gray (PAG)
			
			b. PAG to PnC
			
		3. MeA to CeA
	
	
	C. BLA projects to CeA
	
		1. BLA 1o source of afferent innervation for CeA
		
		2. CeA projects to deep white layers of the superior colliculus
		and
		3. deep mesencephalic reticular nucleus
		
		4. and directly to the caudal pontine reticular nucleus
		
			a. merges with the startle pathway
	
	
	D. Pontis caudalis reticularis (PnC)
	
		1. input from Startle Pathway
		
			a. Ear Þ Cochlear Root Neurons Þ PnC
			
			b. Glu binding AMPA and NMDA receptors
			
		2. input from medial division of the CeA
		
			a. directly
			
				i. CeA has Glu projections; to PnC?
				
				ii. CRF binds to CRF1 receptors
				
					(1) enhances startle (only 50%) 
					
					(2) may be from the BNST
			
			b. CeA Þ Deep SC/ME Þ PnC
			
				i. CeA Þ Deep SC/ME is a Glu synapse with AMPA-R
				
				ii. Deep SC/ME Þ PnC also Glu synapse with AMPA-R
		
		3. input from MeA
		
			a. MeA Þ VMH Þ PAG Þ PnC
			
				i. MeA Þ VMH are Glu/Enk/SP synapses
				
					(1) Glu-AMPA, Enk-m, SP-NK1
		
				ii. VMH Þ PAG are Enk-m/SP-NK1 synapses
				
					(1) but not Glu
					
		4. Convergence potentiates startle output
		
			a. bigger jump in response to sharp sound
			
			b. due to potentiated PnC output
			
				i. Glu binding AMPA receptors on motor neurons
	
			
	E. PnC Potentiated Startle on spinal motor neurons
	
		1. more motor neurons recruited
		
			a. ACh-Nicotinic R causes...
		
		2. more muscle fibers contract
		
		3. bigger startle response to sharp sound