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
IX. Integration of Fear Conditioning  

	A. Acoustic Startle Circuit 

		1. Loud sudden Sound
        
		2. Ear

			a. Cochlear Root Neurons (CRN) in VIIIth nerve

				i. Glu: Carry Acoustic information  						       

					(1) not for hearing purposes

						(a) hearing: uniportant for startle response						        

							(i) not missing, just unimportant	  	   

		3. Reticular caudal Pontine nucleus (PnC = pontis caudalis reticularis)

			a. AMPA/NMDA
            
			b. potentiated by additional Glu inputs
            
				i. from CeA, Deep SC, reticular nucleus, and PAG
        
		4. Spinal motor neurons
        
			a. ACh
        
		5. muscles
        
			a. Nicotinic Receptors

		6. Jump

	B. Fast Fear Circuit 

		1. Foot Shock
        
		2. Nociceptors
		
			a. bare sensory receptors in the skin of the foot
            
				i, soma in DRG (dorsal root ganglion)
            
			b. terminals in the dorsal horn (gray) of the spinal cord

				i. Glu Þ AMPA/NMDA
                
				ii. some may colocalize SP
            
		2. Nociceptive information to Posterior Intralaminar Nucleus (PIN)
        
			a. Glu Þ AMPA/NMDA 

		3. Basolateral Amygdala
        
		4. BLA Glu Þ AMPA/NMDA Central Amygdala

		5. CeA Glu Þ AMPA/NMDA PnC
        
			a. CRF too? 
 
       
	C. Slower Fear Cicuit - modulated
    
		1. Foot shock Þ Nociceptors Þ Spinal Dorsal horn Þ 

		2. decussation Þ spinothalamic tract in anteriolateral column Þ Thalamus
        
		3. Thalamic PIN + VPNGluÞ AMPA/NMDAPosterior Insular Cortex (PIC)
        
			a. Thalamic nociceptive neurons: 
			   VPNGlu Þ AMPA/NMDASomatosensory CortexGlu Þ AMPA/NMDAPIC
        
		4. PIC GluÞ AMPA/NMDA LA Þ BLA    
 
   

	D. Visual Conditioned Stimulus Circuit
    
		1. light presented just before/during foot shock
        
		2. Eye
 
 			a. Retina Glu Þ AMPA/NMDA thalamic LGN
            
			b. LGNGlu Þ AMPA/NMDAvisual 1o ctx Þ temporal ctx Þ perirhinal ctx
            
				i. temporal ctxGlu Þ AMPA/NMDALAGlu Þ AMPA/NMDABLA
                
				ii. perirhinal ctxGlu Þ AMPA/NMDALA Þ AMPA/NMDABLA 
            
			c.  Retina Glu Þ AMPA/NMDA thalamic LPN
            
				i. LPNGlu Þ AMPA/NMDAvisual 1o ctx / temporal ctx 
				  / perirhinal ctx and LA

    
	E. Fear Learning Circuit 

		1. light (1. temporal cortex/ 2. perirhinal cortex/ 3. LPN)
		   + shock (4. PIN / 5. PIC) Þ LA
        
		2. light LAGlu signals + painGlu siganals converge LAÞ BLA neuroplasticity


			a. Acquisition

				i. Glu potentiation
                
					(1) Glu Þ NMDA with NR2Bsub> Þ MEK/ERK
                    
					(2) BDNF - TrKB Þ PI3K; ERK Þ nucleus
                    
						(a) CREB Þ CRE
                        
		       

			b. Consolidation
            
				i. ò BLA gephyrin Þ ò GABAA
                
					(1) ò GABAA Þ ñ LTP

						(a) ñ BDNF - TrKB					        



	F. Expression  (Light + Loud sudden Sound = Conditioned Fear + Startle)
            
		1. Þ ñ BLA AMPA Þ ñ NMDA with NR2A
        
		2. BLA Þ ñ MeA AMPA Þ ñ NMDA with NR2A
        
			a. MeAGlu/Enk/SP Þ ñ AMPA/NMDA/m/NK1VMHEnk/SP Þ ñ m/NK1PAG
        
		3. BLA Þ ñ CeA AMPA Þ ñ NMDA with NR2A
        
			a. CeA Glu Þ ñ PnC AMPA/NMDA
            
		4. Convergence of CRN, PAG, CeA Þ PnC
        
			a. Glu potentiation
            
				i. CRF from longer term stress Þ ñ PnC Glu potentiation
                
				ii. Þ ñ#neurons firing + rate
                
			b. ñññ PnC Þ ñññspinal cord ventral horn
			   motor neuron ACh
            
			c. Þ ñ ñ ñ quadriceps femoris + gastrocnemius muscles
            
			d. ñ ñ ñ  jump

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