Behavioral Neuroscience, lecture on Afferent US pathways for Shock
Behavioral Neuroscience
Afferent Path for Fear
Fear Conditioning
Pavlovian potentiated startle Afferent Shock (US) Pathway
Efferent Output
Neuromuscular Production of Fear Potentiated Startle
Integration of Fear Conditioning
Substance P
Fear figures
Fear Conditioning Circuitry
end     Acronyms/Abbreviations
Fear Conditioning
VI. Afferent Pathways for Fear: Foot Shock US			back to  Conditioning of Fear Responses 

	A. Foot Shock triggers tactile receptors
		1. Somatosensory (touch) receptors
			a. stretch receptors
				i. Merkel cells - pressure (touch domes)
				ii. medium fast - 42-72 m/s
					 golgi tendon organs up to 120 m/s
		2. Nociceptors
			a. pain receptors
				i. bare nerve endings
					(1) small, myelinated - sharp pain
						(a) slower velocity 12-36 m/s
						(b) similar to thermorecptors for cold
					(2) unmyelinated - burning pain
						(a) very slow velocity 0.5-1.2 m/s
						(b) similar to thermorecptors for warmth
		3. both kinds of receptors at the skin
			a. cell bodies in dorsal root ganglion
			b. terminals in the dorsal horn (gray) of the spinal cord
				i. separately for pressure and nociception
					(1) pain - via Lissauer's tract to
					    layers I and II of dorsal horn also V, VI, X
					(2) pressure - layers III - VI of dorsal horn
	B. Spinal Cord
		1. spinal cord somatosensory cells ascending projections
			a. pressure in the dorsal columns
			    gracile fasciculus for feet
				 cuneate fasciculus for paws
				 to dorsal column nuclei in medulla
			b. axons from dorsal column decussate
				then via medial lemniscus to Thalamus
		2. spinal pain neurons decussate
			a. ascend as anterolateral system
			b. spinothalamic tract
	C. Thalamus
		1. Somatosensory information to Ventroposterior Nucleus (VPN)
			a. also some nociceptive neurons
		2. Nociceptive informatin to Posterior Intralaminar Nucleus (PIN)
			a. also to reticular formation for arousal
				i. remember PnC
		3. but information about the shock US is also transmitted from other sources
		   that (send fibers through, but) do not form synapses in the thalamus
	D. Thalamic VPN projects to Somatosensory Cortex
		1. Parietal lobe just posterior to central sulcus
		2. Somatosensory Cortex processes of information about touch
			a. connects to association corticies
			b. and connects to motor cortex
		3. Somatosensory Ctx projects to Posterior Insular Cortex
	E. Posterior Insular Cortex
		1. input from Posterior Intralaminar Nucleus
		2. input from Somatosensory Cortex
		3. Insular cortex includes both 1o olfactory,
		   accessory olfactory and auditory corticies
			a. insula processes convergent information to produce
			   an emotionally relevant context for sensory experience
			b. posterior insula is for Somatosensory-auditory-skeletomotor
				i. anterior insula is olfactory, gustatory,
				   viceral, autonomic, and limbic function
	F. Lateral Amygdala - input region of the amygdala
		1. input from Posterior Insular Cortex
		2. input from Thalamic PIN
		3. doubly processed foot shock information to BLA
	G. Basolateral Amygdala - confluence of CS (light) with US (shock)
		1. site of learning association between CS and US
		2. for expression (motor output due to memory)
			a. processed CS + US signal
			b. passes through MeA and CeA
				i. projection to MeA contains Substance P, Glu, Enk 
			c. to next confluence at caudal pontine reticular nucleus (PnC)
				i. CS/US learning = acoustic startle signal

VI.V Substance P

VII. Motor Efferent Pathways for Fear Conditioning Responses