Sex, Drugs and Love: A Few Good

Altered StatesGroup 10:

Keren Alon, Alexander Fields, Dean Martinez and Hayden

Rausch

Group 10:Keren Alon, Alexander Fields, Dean Martinez and Hayden

Rausch

The Neural Basis of Sex as an Altered State

The Neural Basis of Sex as an Altered State

HormonesHormones

HormonesHormones

Testosterone: plays a role in desire and arousal.

Estrogens: no apparent direct role in arousal. However, loss of estrogens impairs physiological arousal response in females.

Prolactin: high or low levels inhibit sexual response.

Testosterone: plays a role in desire and arousal.

Estrogens: no apparent direct role in arousal. However, loss of estrogens impairs physiological arousal response in females.

Prolactin: high or low levels inhibit sexual response.

Hormones ContinuedHormones Continued

Oxytocin: Plays a role in maternal behaviors. Facilitates physiological and psychological sexual arousal.

Pheromones: volatile signaling substances secreted from glands. Thought to be sensed in the Vomeronasal organ. May have role in female reproductive cycle synchrony. May also facilitate sexual behavior.

Oxytocin: Plays a role in maternal behaviors. Facilitates physiological and psychological sexual arousal.

Pheromones: volatile signaling substances secreted from glands. Thought to be sensed in the Vomeronasal organ. May have role in female reproductive cycle synchrony. May also facilitate sexual behavior.

Begin NeurotransmissionBegin Neurotransmission

End NeurotransmissionEnd Neurotransmission

NeurotransmittersNeurotransmitters

Nitric Oxide (NO) Key player in clitoral and penile erection through the

NO/guanylate cyclase/GTP/cGMP pathway (Viagra works on the cGMP component).

Serotonin Depending on receptor type can facilitate or inhibit

sexual behavior. Approximately 95% of 5-HT receptors are peripheral

(including the vascular smooth muscle of the genitals).

Possible locus for the sexual side effects brought on by SSRIs.

Nitric Oxide (NO) Key player in clitoral and penile erection through the

NO/guanylate cyclase/GTP/cGMP pathway (Viagra works on the cGMP component).

Serotonin Depending on receptor type can facilitate or inhibit

sexual behavior. Approximately 95% of 5-HT receptors are peripheral

(including the vascular smooth muscle of the genitals).

Possible locus for the sexual side effects brought on by SSRIs.

More NeurotransmissionMore Neurotransmission

Dopamine Seems to facilitate sexual feelings

and behaviors Cocaine often reported to increase

sexual enjoyment. Chronic use impairs sexual function.

Dopamine Seems to facilitate sexual feelings

and behaviors Cocaine often reported to increase

sexual enjoyment. Chronic use impairs sexual function.

Still NeurotransmittingStill Neurotransmitting

Epinephrine Plays a role in the maintaining

detumescence in males Plasma levels have been shown to increase

with arousal, peak at orgasm, and return to baseline within a few minutes post-climax (in females).

Norepinephrine has similar effects.

Epinephrine Plays a role in the maintaining

detumescence in males Plasma levels have been shown to increase

with arousal, peak at orgasm, and return to baseline within a few minutes post-climax (in females).

Norepinephrine has similar effects.

End NeurotransmissionEnd Neurotransmission

Opioids May modulate levels of hormones

released, leading to changes in arousal.

In male animals opioid levels increase during sexual activity.

Chronic opiate use causes sexual dysfunction.

Opioids May modulate levels of hormones

released, leading to changes in arousal.

In male animals opioid levels increase during sexual activity.

Chronic opiate use causes sexual dysfunction.

Spinal Control of SexSpinal Control of Sex Some sexual functions are

under spinal control. Women with spinal injury are

still able to achieve orgasm. Ejaculation is controlled

through the Spinal Ejaculation Generator. Located in the

lumbosacral spine. Receives sensory input

from the penis, and some input from supraspinal nuclei.

Ejaculation reflex present even in men with spinal injury.

Some sexual functions are under spinal control.

Women with spinal injury are still able to achieve orgasm.

Ejaculation is controlled through the Spinal Ejaculation Generator. Located in the

lumbosacral spine. Receives sensory input

from the penis, and some input from supraspinal nuclei.

Ejaculation reflex present even in men with spinal injury.

Sex and Supraspinal AreasSex and Supraspinal Areas

Nucleus Paragigantocellul-aris in the Locus Coereleus. Serotonergic

projections to spinal efferents

May be responsible for inhibiting sexual response.

Nucleus Paragigantocellul-aris in the Locus Coereleus. Serotonergic

projections to spinal efferents

May be responsible for inhibiting sexual response.

Sex and Supraspinal AreasSex and Supraspinal Areas

Hypothalamus Medial Preoptic Area: involved in mate

selection and recognition. Lesions abolish only copulatory behavior.

Paraventricular Nucleus: Causes release of oxytocin during sexual activity. Also has projections to pelvic autonomic and somatic efferents. Heavily connected with medial preoptic.

Hypothalamus Medial Preoptic Area: involved in mate

selection and recognition. Lesions abolish only copulatory behavior.

Paraventricular Nucleus: Causes release of oxytocin during sexual activity. Also has projections to pelvic autonomic and somatic efferents. Heavily connected with medial preoptic.

Sex and the Supraspinal Regions

Sex and the Supraspinal Regions

Forebrain Regions: Medial Amygdala and Bed Nucleus of Stria Terminalis Strongly activated during copulation. May control sexual motivation.

Forebrain Regions: Medial Amygdala and Bed Nucleus of Stria Terminalis Strongly activated during copulation. May control sexual motivation.

rCBF Changes Associated with Clitorally Induced Orgasm in Healthy

Women

rCBF Changes Associated with Clitorally Induced Orgasm in Healthy

Women Georgiadis, et al. 2006. PET study, scans performed under four

conditions: rest, clitoral stimulation or arousal, orgasm imitations (motor control), and orgasm.

Decreased activity in prefrontal cortex as arousal increases and peaks with orgasm.

Georgiadis, et al. 2006. PET study, scans performed under four

conditions: rest, clitoral stimulation or arousal, orgasm imitations (motor control), and orgasm.

Decreased activity in prefrontal cortex as arousal increases and peaks with orgasm.

Sex and ConsciousnessSex and Consciousness

Is sex an altered state? There’s a good chance Prefrontal deactivation during orgasm

Dietrich’s ladder model.

Is sex an altered state? There’s a good chance Prefrontal deactivation during orgasm

Dietrich’s ladder model.

The Rewards of “Healthy” Drug

Addiction

IntroductionIntroduction

Drug addiction is one of the most costly diseases in modern society

Passionate love closely imitates substance abuse

Uses the same reward system in the brain

Drug addiction is one of the most costly diseases in modern society

Passionate love closely imitates substance abuse

Uses the same reward system in the brain

Introduction Cont’dIntroduction Cont’d

Consciousness altering drugs have multiple effects

The effect of the drug depends on the amount of dosage the individual has taken

Also the effects of a psychoactive drug depends on the user’s history and expectations

Consciousness altering drugs have multiple effects

The effect of the drug depends on the amount of dosage the individual has taken

Also the effects of a psychoactive drug depends on the user’s history and expectations

Effects on ConsciousnessEffects on Consciousness Drugs vary in how they

affect behavior and consciousness

Different types such as stimulants, depressants, hallucinogens, and other types of drugs such as marijuana and morphine

Psychoactive drugs have a variety of effects in various functions, also they do not create new responses, just modify behavioral and physiological responses

Drugs vary in how they affect behavior and consciousness

Different types such as stimulants, depressants, hallucinogens, and other types of drugs such as marijuana and morphine

Psychoactive drugs have a variety of effects in various functions, also they do not create new responses, just modify behavioral and physiological responses

DrugsDrugs

Drugs are used to induce feeling of euphoria, a “high”

The neurotransmitter associated with drug addiction and abuse is dopamine, along with other NTs such as serotonin, and GABA

Drugs are used to induce feeling of euphoria, a “high”

The neurotransmitter associated with drug addiction and abuse is dopamine, along with other NTs such as serotonin, and GABA

The Drug Reward SystemThe Drug Reward System

Activated by rewarding stimulus i.e. sex

Coe structures of the reward system is located in the limbic system

Consists of several brain structures: VTA, nucleus accumbens, and the prefrontal cortex

VTA -> Nuc Accumbens -> PFC

Activated by rewarding stimulus i.e. sex

Coe structures of the reward system is located in the limbic system

Consists of several brain structures: VTA, nucleus accumbens, and the prefrontal cortex

VTA -> Nuc Accumbens -> PFC

DopamineDopamine

Dopamine- Most directly implicated in positive

reinforcement, i.e. rewarding and pleasurable effects of the drug

- Many addictive drugs enhance dopamine transmission, specifically in the mesocorticolimbic system

- One of the main forces driving the reward system

Dopamine- Most directly implicated in positive

reinforcement, i.e. rewarding and pleasurable effects of the drug

- Many addictive drugs enhance dopamine transmission, specifically in the mesocorticolimbic system

- One of the main forces driving the reward system

Other NeurotransmittersOther Neurotransmitters

Serotonin Involved in the modulation of both drug

self-administration and dopamine levels May be important in modulating

motivational factors of obtaining a drug Serotonin projects to the NA and the VTA to

regulate release of dopamine It also modulates the reward pathway

through various mechanisms by interacting with different receptors in the brain

Serotonin Involved in the modulation of both drug

self-administration and dopamine levels May be important in modulating

motivational factors of obtaining a drug Serotonin projects to the NA and the VTA to

regulate release of dopamine It also modulates the reward pathway

through various mechanisms by interacting with different receptors in the brain

Other Neurotransmitters cont’d

Other Neurotransmitters cont’d

GABA Involved in modulation of the dopaminergic reward

system Disinhibits dopaminergic neurons making them fire

more rapidly and releasing more dopamine in the reward system to induce euphoria

Endorphins Also motivate behavior Place preference is elicited when applied in the NA Also increases dopamine in the reward pathway

GABA Involved in modulation of the dopaminergic reward

system Disinhibits dopaminergic neurons making them fire

more rapidly and releasing more dopamine in the reward system to induce euphoria

Endorphins Also motivate behavior Place preference is elicited when applied in the NA Also increases dopamine in the reward pathway

Love as an ASC

Helen Fisher’s Recent Study Journal of Neuroscience

Helen Fisher’s Recent Study Journal of Neuroscience

-Analyzed about 2,500 brain images from 17 college students who were in first weeks/months of new love

-Students looked at a picture of their beloved while an M.R.I machine scanned their brains.

-Researchers then compared the images with others taken while the students looked at a picture of an acquaintance.

-Analyzed about 2,500 brain images from 17 college students who were in first weeks/months of new love

-Students looked at a picture of their beloved while an M.R.I machine scanned their brains.

-Researchers then compared the images with others taken while the students looked at a picture of an acquaintance.

-The images showed hot spots in the brain, below conscious awareness.

-Areas called the caudate nucleus and the ventral tegmental area

-These areas are dense with cells that produce or receive the brain chemical Dopamine.

-The images showed hot spots in the brain, below conscious awareness.

-Areas called the caudate nucleus and the ventral tegmental area

-These areas are dense with cells that produce or receive the brain chemical Dopamine.

Dopamine and LoveDopamine and Love

-When a person feels in love, they activate their pleasure centers in the brain which are rich in dopamine

-Dopamine causes a person’s heart to race, pupils to dilate and a slight perspire.

-Since it is a natural endorphin (acts like heroin or morphine) it causes the body to respond by relaxing the body and kills pain in high doses.

-Also a hormone involved with addictive behavior and OCD

-It is the hormone that makes a person feel an “erotic high” when they see their lover, eventually the person will become addicted to feeling that “erotic high”

-Also, when there is a continued presence of a lover, there is a gradual increase of dopamine

-When a person feels in love, they activate their pleasure centers in the brain which are rich in dopamine

-Dopamine causes a person’s heart to race, pupils to dilate and a slight perspire.

-Since it is a natural endorphin (acts like heroin or morphine) it causes the body to respond by relaxing the body and kills pain in high doses.

-Also a hormone involved with addictive behavior and OCD

-It is the hormone that makes a person feel an “erotic high” when they see their lover, eventually the person will become addicted to feeling that “erotic high”

-Also, when there is a continued presence of a lover, there is a gradual increase of dopamine

b-Phenylethylamine (PEA) or the "love chemical"

b-Phenylethylamine (PEA) or the "love chemical"

-Falling in love involves the enhanced secretion of PEA in the first 2-4 years of the relationship

-This natural drug creates a euphoric high and helps obscure the failings and shortcomings of the potential mate.

-High levels of PEA increases sex drive and is thought to be the hormone of libido.

-The body as becomes tolerant of PEA like dopamine once the body has been exposed to it for long periods of time.

-Falling in love involves the enhanced secretion of PEA in the first 2-4 years of the relationship

-This natural drug creates a euphoric high and helps obscure the failings and shortcomings of the potential mate.

-High levels of PEA increases sex drive and is thought to be the hormone of libido.

-The body as becomes tolerant of PEA like dopamine once the body has been exposed to it for long periods of time.

Oxytocin, the “cuddling chemical”

Oxytocin, the “cuddling chemical”

-Hormone involved with love, also an endorphin and has an opiate-like effect

“Produced by the brain, it sensitized nerves and stimulates muscle contraction. Scientists speculate that oxytocin might encourage cuddling between adult women and men.”

-Acts as a natural tranquilizer, allows for women to become more sensitive to other’s feelings.

-Released during sexual experiences as well as when lovers touch because it activates cell-surface proteins in the nucleus accumbens, which causes release of dopamine---> Euphoric high

-Hormone involved with love, also an endorphin and has an opiate-like effect

“Produced by the brain, it sensitized nerves and stimulates muscle contraction. Scientists speculate that oxytocin might encourage cuddling between adult women and men.”

-Acts as a natural tranquilizer, allows for women to become more sensitive to other’s feelings.

-Released during sexual experiences as well as when lovers touch because it activates cell-surface proteins in the nucleus accumbens, which causes release of dopamine---> Euphoric high

Behavior Changes Associated with Love

Behavior Changes Associated with Love

-Love allows for companionship, which gives a person gratification and a feeling of purpose in life

-When people first fall in love, they experience feeling giddy, playful, and are preoccupied with thoughts of the one they love

-Disinhibition: physical and intimate

(-->Lack of normal conc) -Love creates and reinforces

the self. People's sense of who they are is strongly affected by whom they love and whom they perceive as loving them.”

-Love allows for companionship, which gives a person gratification and a feeling of purpose in life

-When people first fall in love, they experience feeling giddy, playful, and are preoccupied with thoughts of the one they love

-Disinhibition: physical and intimate

(-->Lack of normal conc) -Love creates and reinforces

the self. People's sense of who they are is strongly affected by whom they love and whom they perceive as loving them.”

More Behavioral Changes…

More Behavioral Changes…

-When people are in love they feel that they must protect the one they love and will do anything for the one they love.

-Priorities shift and motivation is centered around that person versus other responsibilities

-Obsessive thoughts regarding the loved one and compulsive acts are common. (similar to behaviors of drug addicts)

-Lover becomes salient in everyday occurrences

-Primed to think of that person, things that you ordinarily wouldn’t pay attention to suddenly make you think of your loved one (similar t-shirt, etc.)

-When people are in love they feel that they must protect the one they love and will do anything for the one they love.

-Priorities shift and motivation is centered around that person versus other responsibilities

-Obsessive thoughts regarding the loved one and compulsive acts are common. (similar to behaviors of drug addicts)

-Lover becomes salient in everyday occurrences

-Primed to think of that person, things that you ordinarily wouldn’t pay attention to suddenly make you think of your loved one (similar t-shirt, etc.)

Is Love an Addiction? Is Love an Addiction? -When one is in love, the

pleasure parts of the brain are activated by hormones (dopamine, PEA and oxytocin) which act as natural endorphins. They act like amphetamines do on the brain.

-The longer a couple is together their brains become tolerant to the hormones being released, which causes the euphoric feeling not to be felt as strongly.

-Allostasis: body adjusts to new state

-Similar to tolerating drugs

-When one is in love, the pleasure parts of the brain are activated by hormones (dopamine, PEA and oxytocin) which act as natural endorphins. They act like amphetamines do on the brain.

-The longer a couple is together their brains become tolerant to the hormones being released, which causes the euphoric feeling not to be felt as strongly.

-Allostasis: body adjusts to new state

-Similar to tolerating drugs

Withdrawal PhaseWithdrawal Phase -Because of this acquired tolerance,

when the couple breaks up, there must be a withdrawal period.

-The withdrawal of romantic love has serious mental health repercussions.

-A study revealed that breakups often lead to depression and anxiety. fMRI-based studies demonstrated how the insular cortex, in charge of experiencing pain, became active when subjects viewed photos of former loved ones.

-Symptoms similar to to being addicted to drugs, so people who think they are addicted to love, might really be addicted to the feelings and hormones released during love.

-Because of this acquired tolerance, when the couple breaks up, there must be a withdrawal period.

-The withdrawal of romantic love has serious mental health repercussions.

-A study revealed that breakups often lead to depression and anxiety. fMRI-based studies demonstrated how the insular cortex, in charge of experiencing pain, became active when subjects viewed photos of former loved ones.

-Symptoms similar to to being addicted to drugs, so people who think they are addicted to love, might really be addicted to the feelings and hormones released during love.

So is love an ASC? Yes!

So is love an ASC? Yes!

-The combination of hormonal and behavioral changes, along with the overall change of one’s perception results in a divergence from normal consciousness.

-Body adjusts to new state and becomes dependent on their lover.

-Areas of the brain undergo change similar to exposure to drugs.

-Hence, if being addicted to drugs is considered an ASC, so should being in love.

-The combination of hormonal and behavioral changes, along with the overall change of one’s perception results in a divergence from normal consciousness.

-Body adjusts to new state and becomes dependent on their lover.

-Areas of the brain undergo change similar to exposure to drugs.

-Hence, if being addicted to drugs is considered an ASC, so should being in love.

Behavioral Correlations Between Sex, Love & Drugs

Behavioral Correlations Between Sex, Love & Drugs

Attentional/Focus Shift Searching/Wanting Preoccupation Restlessness Excessive Wakefulness/Sleepiness Climactic Arousal Ignoring Negative Effects/Behaviors Withdrawal: Depression/Angst/Anxiety Fantasy Stress

Attentional/Focus Shift Searching/Wanting Preoccupation Restlessness Excessive Wakefulness/Sleepiness Climactic Arousal Ignoring Negative Effects/Behaviors Withdrawal: Depression/Angst/Anxiety Fantasy Stress

SimilaritiesSimilarities

Neuroimaging shows the PFC, VTA, and the caudate are active when in love and using drugs

Dopamine and Norepinephrine are very much involved in both processes

Neuroimaging shows the PFC, VTA, and the caudate are active when in love and using drugs

Dopamine and Norepinephrine are very much involved in both processes

Pleasure and Reward Systems

Pleasure and Reward Systems

Control our sexual behavior Reward system may have evolved

to get animals interested in sex Sex around longer than drugs Limbic area VTA Caudate Nucleus DA system

Control our sexual behavior Reward system may have evolved

to get animals interested in sex Sex around longer than drugs Limbic area VTA Caudate Nucleus DA system

Drug Highs Can Be Like Sex Highs

“Stimulants like cocaine act on the brain's dopamine system, and so mimic the thrill of desire and anticipation. Depressant drugs like heroin, on the other hand, produce the

opposite kind of pleasure - a dreamy satiation and freedom from pain, caused by their action on the brain's opioid system.

A speedball, a cocktail of cocaine and heroin, can be

likened to a rapid, hyped-up sex simulation, moving rapidly from desire to climax.”-

Maia Szalavitz, “Love is the drug”, 23

November 2002 , New Scientist Magazine

“Stimulants like cocaine act on the brain's dopamine system, and so mimic the thrill of desire and anticipation. Depressant drugs like heroin, on the other hand, produce the

opposite kind of pleasure - a dreamy satiation and freedom from pain, caused by their action on the brain's opioid system.

A speedball, a cocktail of cocaine and heroin, can be

likened to a rapid, hyped-up sex simulation, moving rapidly from desire to climax.”-

Maia Szalavitz, “Love is the drug”, 23

November 2002 , New Scientist Magazine

Is love an equal state as sex or lust?

Is love an equal state as sex or lust?

Brains in love and brains in lust don't look too much alike.

when researchers showed erotic photos to people as they underwent brain scans, they found activity in the hypothalamus and amygdala areas of the brain

Different areas than “in love’s” reward center

the two do become linked. People in love have elevated levels of dopamine. Lots of dopamine, in turn, triggers the production of testosterone

Brains in love and brains in lust don't look too much alike.

when researchers showed erotic photos to people as they underwent brain scans, they found activity in the hypothalamus and amygdala areas of the brain

Different areas than “in love’s” reward center

the two do become linked. People in love have elevated levels of dopamine. Lots of dopamine, in turn, triggers the production of testosterone

Is love a continuous state over time? No.

Is love a continuous state over time? No.

Over time, love related activity in the reward center returns to normal

Meanwhile, other areas become active Emotion areas, like insula and anterior

cingulate cortex, where sown to be active in similar studies with long-term (2+ years) relationship subjects

Changing state?

Over time, love related activity in the reward center returns to normal

Meanwhile, other areas become active Emotion areas, like insula and anterior

cingulate cortex, where sown to be active in similar studies with long-term (2+ years) relationship subjects

Changing state?

Final ThoughtsFinal Thoughts

PFC is shut down during peak of sex disabling the highest level of Dietrich's hierarchy of consciousness.

When you fall in love, the same system becomes active as when you take cocaine

The systems that are built into us to find food and water are the things that were also active when kings renounced their thrones or people turn their backs on their friends and family all in the name of love

PFC is shut down during peak of sex disabling the highest level of Dietrich's hierarchy of consciousness.

When you fall in love, the same system becomes active as when you take cocaine

The systems that are built into us to find food and water are the things that were also active when kings renounced their thrones or people turn their backs on their friends and family all in the name of love

ReferencesReferences Esch, Tobias and Stefano, George. The Neurobiology of Love.

Neuroendocrinology Letters. 2005; 26 (3): 175-192. Fisher, Helen, et al. Defining the Brain Systems of Lust, Romantic

Attraction, and Attachment. Archives of Sexual Behavior. 2002 (31, 5): 413-419.

Bartels, Andreas and Zeki, Semir. The Neural Correlates of Maternal and Romantic Love. NeuroImage 21 (2004) 1155-1166.

Aron, Arthur, et al. Reward, Motivation, and Emotion Systems Associated With Early-Stage Intense Romantic Love. Journal of Neurophysiology. 2005 (94): 327-337.

Chiba, Andrea. “Reward and Drug Addiction.” University of California, San Diego. 8 May 2007.

Wallace, Ben, et al. Consciousness and Behavior. (Prospect Heights, Illinois: Waveland Press, 2003), 44-50.

Neuroanatomy and Physiology of Brain Reward II. http://ibgwww.colorado.edu/cadd/a_drug/essays/essay4.htm. Accessed 1 June 2007.

Esch, Tobias and Stefano, George. The Neurobiology of Love. Neuroendocrinology Letters. 2005; 26 (3): 175-192.

Fisher, Helen, et al. Defining the Brain Systems of Lust, Romantic Attraction, and Attachment. Archives of Sexual Behavior. 2002 (31, 5): 413-419.

Bartels, Andreas and Zeki, Semir. The Neural Correlates of Maternal and Romantic Love. NeuroImage 21 (2004) 1155-1166.

Aron, Arthur, et al. Reward, Motivation, and Emotion Systems Associated With Early-Stage Intense Romantic Love. Journal of Neurophysiology. 2005 (94): 327-337.

Chiba, Andrea. “Reward and Drug Addiction.” University of California, San Diego. 8 May 2007.

Wallace, Ben, et al. Consciousness and Behavior. (Prospect Heights, Illinois: Waveland Press, 2003), 44-50.

Neuroanatomy and Physiology of Brain Reward II. http://ibgwww.colorado.edu/cadd/a_drug/essays/essay4.htm. Accessed 1 June 2007.

References ContinuedReferences Continued Georgiadis, Janniko, et al. Regional Cerebral Blood Flow Changes

Associated with Clitorally Induced Orgasm in Healthy Women. European Journal of Neuroscience. 2006 (24): 3305-3316.

Allard, Julen, et al. Spinal Cord Control of Ejaculation. World Journal of Urology. 2005 (23): 119-126.

McKenna, Kevin. The Neurophysiology of Female Sexual Function. World Journal of Urology. 2002 (20): 93-100.

Pfaus, James. Neurobiology of Sexual Behavior. Current Opinion in Neurobiology. 1999 (9): 751-758.

Meston, Cindy, and Frohlich, Penny. The Neurobiology of Sexual Function. Archives of General Psychiatry. 2000 (57): 1012-1030.

Georgiadis, Janniko, et al. Regional Cerebral Blood Flow Changes Associated with Clitorally Induced Orgasm in Healthy Women. European Journal of Neuroscience. 2006 (24): 3305-3316.

Allard, Julen, et al. Spinal Cord Control of Ejaculation. World Journal of Urology. 2005 (23): 119-126.

McKenna, Kevin. The Neurophysiology of Female Sexual Function. World Journal of Urology. 2002 (20): 93-100.

Pfaus, James. Neurobiology of Sexual Behavior. Current Opinion in Neurobiology. 1999 (9): 751-758.

Meston, Cindy, and Frohlich, Penny. The Neurobiology of Sexual Function. Archives of General Psychiatry. 2000 (57): 1012-1030.