Behavioral Neuroscience
Yawning Behavior
Evolution of Yawning
Sensory Afferents to Yawn
Gating the Yawn
Yawning Regulating Yawn Gating
Efferent Yawn Output
Neuromuscular Production of Yawns
Integration of Yawn Circuitry and Behavior
norepinephrine (NE)
Oxytocin (OT)
Yawning figures
Yawn Circuitry
end     Acronyms/Abbreviations

V. Gating the Yawn A. Regions open to modulation 1. Nucleus of the Solitary Tract a. Series of medullary nuclei regulating autonomic and respiratory function b. upstream of NST i. PVN ii. Apneustic Center iii. carotid bodies, aortic bodies, lungs & pharynx stretch receptors c. downstream of NST i. SCG ii. reticular formation, hypothalamus, thalamus 1) feedback
2. PVN a. hypothalamic nucleus regulating stress responses, autonomic function, and appetite i. electrical stimulation of PVN Þ Yawning b. secretes CRF, GABA, OT, AVP, TRH c. upstream of PVN i. SCN 1) biological clock ii. CeA d. downstream of PVN i. brainstem (NST), spinal cord, hypothalamus, limbic brain
2. SCN a. central oscillator - keeps time for other oscillatory nuclei b. secretes AVP, GABA, Glu, VIP, cardiotriphin-like cytokine, prokinectin 2 c. upstream of SCN i. retinal ganglion cells, intergeniculate Leaflet (IGL) of the Thalamic Lateral Geniculate Nucleus ii. median raph 1) secretes serotonin (5-HT, 5-hydroxytryptamine)
3. CeA a. mediates fear, stress, and anxiety output of the amydgala i. amygdala is a cluster of nuclei b. regulates sympathetic autonomic function c. secretes CRF and GABA d. upstream of the CeA i. hippocampus ii. prefrontal cortex (PFC)
B. Circadian Gating 1. modifying the timing or frequency of yawning through phase of SCN activity = entrainment a. D sensory or neurochemical input to SCN i. early night light ÞGlu Þ SCN Þ phase delay 1) later initiation of sleep, later waking 2) late night light ÞGlu Þ SCN NMDAÞ Þ SCN NMDAÞ phase advance ii. 5-HT 1) raph Þ SCN 2) 5-HTÞSCN 5-HT7 receptors Þ phase delay b. D clock output Þ D sleep/wake timing 2. SCN output modifies PVN activity a. CoreSCN ó ShellSCN Þ AVP Þ PVN V1A receptors Þ firing b. possibly:Day/Night transitions Þ SCN FiringÞ AVP Þ PVN firing 3. PVN regulates autonomic sympathetic function a. Þ PVN firing Þ sympathetic output 4. sympathetic activity stimulates yawning a. stimulation of the PVN Þ yawning
D. Limbic Gating 1. modifying the likelihood of yawning through emotion a. e.g. anxiety Þ yawning i. just prior to: parachuting, taking a test, a race... 2. emotional inputs to the yawning circuitry a. inputs from CeA, hippocampus, PFC 3. stimulated by spatial and social cues to anxiety a. e.g. skydiving plane or test room i. activate hippocampal circuits 1) hippocampus modulates spatial memories and spatial relationships 2) temporal and organizational memories spatio-temporal relationships a) yikes! it's a long way to the ground I will be falling a long time 4. stimulated by fearful anticipation of the activity a. activate amygdalar neurons in the CeA b. memory of fear activate neurons in the BLA i. basolateral amygdala connects to CeA c. CeA activity Þ PVN activity 5. electrical stimulation/histamine Þ PVN Þ Yawning
E. PVN-NST-Sympathetic Convergence 1. Yawning is caused by a transient sympathetic arousal a. multiple paths to sympathetic activation 2. Circadian and Emotional pathways converge on the PVN a. stimulation of the PVN Þ yawning 3. PVN directly activates authonomic function in the NST a. NST pathways trigger 3 elements important to yawning i. sympathetic activation ii. muscles of pharynx 1) initial step in the 1st phase of yawning iii. muscles of inspiration
F. Integration of Gating 1. transition of arousal states 2. circadian rhythms are influenced strongly by emotional status a. Þ stress Þ 5-HT release 1) in Hippocampus, Amygdala, PFC, and SCN a) SCN ÞAVP ÞPVN 3. emotional states are influenced by circadian regulation of behavior and physiology a. classic symptoms of depression: i. phase delayed circadian rhythms ii. reduced PVN and Hippocampal feedback responsiveness to stress hormones b. SCN ÞAVP ÞPVN c. SCN core Þ IGL Þ d & m raph Þ 5-HT in PVN, Hippocampus and Amygdala

VI. Norepinephrine (NE)
VII. Oxytocin (OT)
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