Behavioral Neuroscience, lecture on Lordosis Behavior
USD Department of Biology
Behavioral Neuroscience
Sexual Behavior
Sensory Reception - Tactile Receptors
Spinal Synapses
Afferent Spinal Pathways
Hypothalamic Gating
Efferent Motor Cascade
Neuromuscular Production of Lordosis Integrated Story of Lordosis
Substance P
Lordosis figures   Sensory Receptors
Spinal Cord   Lordosis Circuitry
end     Acronyms/Abbreviations
I. Behavior  			

	A. Lordosis is a human medical disorder defined by an
	    excessive inward curve of the spine
		1.  This curve of the spine is also the main characteristic
			of female sexual behavior in many species
			a. rats are the most studied, but most quadripeds
			   and many bipeds show some variation of this
			   sexual position

	B. Female Sexual Behavior
		1. All sexual behavior necessary and sufficient to achieve
		   fertilization of ova by sperm
		2. includes attractive, proceptive, receptive,
		   and copulatory behaviors
			a. attractivity: stimulus value of a female
			   for a given male
			b. proceptivity: extent to which females initiate
				i. reflects overt behavior and 
				   underlying motivational state
				ii. females will not initiate proceptive behavior
				    with males to whom they are not attracted
					(1) castrated males elicit fewer approaches
			c. receptivity: state of responsiveness
			   to sexual initiation
		3. Lordosis is a receptive and copulatory behavior

	C. Proceptive Behaviors precede lordosis

		1. but proceptive and receptive behavior overlaps
		2. Proceptive behavior comprises all appetitve activities
			a. sexually solicitous behavior
			b. high levels of E2 faciliate proceptive behavior
		3. Examples:

			a. affiliative behaviors - maintaining proximity to males
			b. assumption of mating posture
				i. mounting by females (highly proceptive)
					(1) thrusting
						(a) may stimulate ovulation
			c. presentation of genetalia
				i. investigating male's genital region
			d. specialized vocalizations
			e. head bobbing
			f. alternating approaches and withdrawals
		4. Rats - Hopping and Darting
			a. to initiate or maintaing mounting behavior by the male
				i. solicitous behavior that the male finds attractive
					(1) males are motivated to follow and mount
			b. approach the male, then dart away
				i. waiting
				ii. run by

				iii. return, pause in front of the male
			c. hopping a short distance, wait, move back
			d. wiggling the ears

	D. Lordosis is a Reflex - in rats

		1. stimulated by tactile sensory input of
		   male body against female's rump or flanks
			a. female in estrous (heat)
				i. estrous follows the follicular phase
				ii. E2 levels are high,  
				    followed by a short burst of P
				iii. this reflex requires input from the brain
		2. she will arch her back (curve spine)
			a. deflect the tail
			b. head is raised

			c. stands completely immobile

		3. precise postural adjustment
			a. angle of genetalia

		4. in the absence of lordosis, intromission and ejaculation
		   are impossible

	E. Scoring Female responsiveness: Lordosis trials and success
		1. Lordosis Scores (Hardy and Debold, 1971)

			a. unreceptive (score 0: kicking, rearing, or fleeing)
				i. back arched upward
			b. proceptive (score 0.1 - 0.5)
			c. receptive lordosis posture (scores 1-3)
			   with dorsiflexion of the vertebral column 
				i. 0.5 intervals,
				   depending on the degree of curvature of the spine
					(1) 1 point: flat back, tail slightly raised
					(2) 2 pts: back dorsiflexion, head flat
					(3) 3 pts: severe dorsiflexion, head up
				ii. score of 1 or higher considered lordosis response
				    for the calculation of lordosis quotient 

		2. Receptivity scores
			a. average of 10 lordosis scores (0-3)
		3. Lordosis Quotient (LQ)
			a. ratio between male attempts and success
				i. number lordosis/number mounts & intromissions

	F. Reflexive Behaviors like Lordosis may be modified

		1. hormones modify sexual behavior
			a. receptors in the brain

		2. input from limbic brain

			a. enhanced by experience

			b. diminished by stress

II. Reflexes