As a phenomenon worthy of neurobiological research, orgasm has
received less attention than its impact on human perceptual experience
would predict, likely, at least in part, because of its inherently sensitive
(inter)personal properties and historically limited research funding. We
investigate orgasm for two reasons: first, to explore further its intrigu-
ing neurobiological reality; second, to validate the experiences of certain
groups of women who report that they feel orgasms (a) despite their
health professionals denying the possibility due to the women’s neuro-
logical condition, for example, complete spinal cord injury; (b) in
Functional MRI of the Brain
During Orgasm In Women
Barry R. Komisaruk
Rutgers, The State University of New Jersey
Women diagnosed with complete spinal cord injury (SCI) at T10 or higher
report sensations generated by vaginal-cervical mechanical self-stimulation
(VCSS). In this paper we review brain response to sexual arousal and
orgasm in such women, and further hypothesize that the afferent pathway
for this unexpected perception is provided by Vagus nerves, which bypass the
spinal cord. Using functional magnetic resonance imaging (fMRI), we ascer-
tained that the region of the medulla oblongata to which the vagus nerves
project (the Nucleus of the Solitary Tract or NTS) is activated by VCSS. We
also used an objective measure, VCSS-induced analgesia response to experi-
mentally-induced finger pain, to ascertain the functionality of this pathway.
During VCSS, several women experienced orgasms. Brain regions activated
during orgasm included the hypothalamic paraventricular nucleus, amyg-
dala, accumbens-bed nucleus of the stria terminalis-preoptic area, hippocam-
pus, basal ganglia (especially putamen), cerebellum, and anterior cingulate,
insular, parietal and frontal cortices, and lower brainstem (central gray, mes-
encephalic reticular formation, and NTS). We conclude that the vagus nerves
provide a spinal cord-bypass pathway for vaginal-cervical sensibility and
that activation of this pathway can produce analgesia and orgasm.
Key Words: brain imaging. fMRI, orgasm, spinal cord, vagina, Vagus nerves.
Barry R. Komisaruk, PhD, is a Professor II in the Department of Psychology, and
Beverly Whipple, Ph D, RN, FAAN, is Professor Emerita of the College of Nursing, Rut-
gers, The State University of New Jersey, Newark, NJ. The authors gratefully acknowl-
edge the following funding support: The Christopher Reeve Paralysis Foundation (BRK
and BW), NIH-R25GM60826 (BRK), and the Charles and Johanna Busch Foundation,
Rutgers, The State University of New Jersey (BRK and BW). Figures 1, 2, 4, and 6-9 are
reprinted from Komisaruk et al. (2004) with permission from Elsevier. Correspondence
concerning this article should be address to Barry R. Komisaruk, Department of Psychol-
ogy, Rutgers, The State University of New Jersey, Newark, NJ 07102.
response to vaginal (“G spot”) stimulation; (c) in response to cervical
stimulation; and/or (d) by thought alone, without physical stimulation.
Orgasms–Genital and Nongenital
Although orgasm is characteristically a response to genital stimula-
tion, there are many reports that other types of sensory stimulation also
generate orgasms, some perceived as feeling “genital” but others as
“nongenital.” For example, we have documented cases of women who
claim that they can experience orgasms just by thinking, without any
physical stimulation; their bodily reactions—doubling of heart rate,
blood pressure, pupil dilation, and pain threshold—bear out their claim
(Whipple, Ogden, & Komisaruk, 1992). Men and women who have
spinal cord injury have described to us that the skin near their injury
feels hypersensitive to touch. Painful and intensely aversive if acciden-
tally brushed, when stimulated in the right way and/or by the right per-
son, touch can produce orgasmic feelings that may or may not be
perceived as emanating from the genitalia. One woman with complete
spinal cord injury at the upper thoracic level experienced an area of
hypersensitivity at the neck and shoulder and claimed to have orgasms
from stimulation of the skin of her neck. In the laboratory, her heart
rate and blood pressure increased markedly during self-application of a
vibrator to her neck-shoulder junction, and she described experiencing
an orgasm accompanied by a “tingling” sensation in her vagina (Sipski,
Komisaruk, Whipple, & Alexander, 1993). Kinsey, Pomeroy, and Martin
(1948), Masters and Johnson (1966), and Paget (2001) each reported
women who stated that they experience orgasms from breast or nipple
stimulation; in addition, Paget (2001) described orgasms produced by
stimulation of mouth or anus in women and men. The heroine in the
novel Kinflicks, realizing that she had had an orgasm when her lover
held her hand, says that she can experience orgasms from stimulation
anywhere on her body (Alther, 1975).
Consideration of the sensory pathways likely activated in some of the
above examples can suggest the bases for these experiences of orgasm.
The pelvic nerve provides afferent innervation of the vagina, cervix, and
rectum (Berkley, Hotta, Robbins, & Sato, 1990; Komisaruk, Adler, &
Hutchison, 1972; Peters, Kristal, & Komisaruk, 1987). Because activa-
tion of this nerve through vaginal stimulation can generate orgasm, it is
not surprising that when activated nongenitally (i.e., rectally) it can
also generate orgasm. Indeed, women have described feeling the need to
defecate during uterine contractions at parturition, indicating a second
context in which “cross-talk” exists between at least two organs inner-
vated by the same (pelvic) nerve, leading to a form of referred sensation.
2B. KOMISARUK & B. WHIPPLE
BRAIN MRI OF WOMEN DURING ORGASM3
In men, afferent activity from the prostate (via the hypogastric
nerve) during ejaculation contributes to the pleasurable sensation of
orgasm, on the basis that prostatectomy is reported to diminish this
feeling (Koeman, Van Driel, Schultz, & Mensink, 1996). The orgasm-
producing role of this afferent activity could help account for the experi-
ence of orgasm in men receiving mechanostimulation of the prostate
during anal intercourse, which would add to the afferent activity gener-
ated via the pelvic nerve anal afferents. The hypogastric nerve also con-
veys afferent activity from the uterus and cervix (Berkley et al., 1990;
Bonica, 1967; Peters et al., 1987). The orgasmic role of afferent activity
via this nerve in men may help to account for the parallel drawn
between the feelings generated through uterine and vaginal stimulation
during childbirth and during orgasm (Newton, 1955).
The orgasm-inducing effect of breast or nipple stimulation may be
related to the functional convergence in the central nervous system of
their afferent (spinal nerve) pathways with vaginal and cervical affer-
ents (for a review see Komisaruk & Whipple, 2000). The evidence of
such convergence is that, in women, oxytocin is secreted from the poste-
rior pituitary into the systemic circulation in response to either of these
two sources of stimulation, in the “milk-ejection” reflex and the Fergu-
son reflex, respectively. The oxytocin released by suckling stimulates
the contraction of myoepithelial cells that envelop the milk-secreting
glands in the breast, forcibly expelling milk. The released oxytocin can
concurrently stimulate the uterine smooth muscle to contract. Con-
versely, intrauterine pressure and the consequent mechanical stimulus
against the cervix exerted by the fetus at parturition stimulates pelvic
nerve afferents that lead to release of oxytocin in a positive feedback
mechanism, the Ferguson reflex (Ferguson, 1941). The oxytocin thus
released can also produce expulsion of milk from the breast in women
who are lactating at term. Because the final common pathway for oxy-
tocin secretion is primarily the paraventricular nucleus of the hypothal-
amus (and secondarily the supraoptic nucleus of the hypothalamus;
Cross & Wakerly, 1977), breast, nipple, cervical, and vaginal afferent
activity each evidently converge on these nuclei.
Oxytocin is released into the systemic circulation during orgasm in
women and men (Carmichael et al., 1987; Carmichael, Warburton,
Dixen, & Davidson, 1994; Blaicher et al., 1999). We have reported that
the paraventricular nucleus of the hypothalamus is activated during
orgasm in women (Komisaruk et al., 2004, and this article). The percep-
tion of orgasm is most likely not produced by oxytocin, for injection of
oxytocin neither induced nor intensified orgasm (Gooren, 1991). (How-
ever, there is a report based on a single case of a woman who described
4 B. KOMISARUK & B. WHIPPLE
heightened subjective pleasure related to intensified uterine and vaginal
contractions upon self-treatment with intranasal oxytocin [Anderson-
Hunt & Dennerstein, 1994]). Although a direct action of oxytocin on the
brain to modulate orgasm cannot be ruled out, it seems more likely that
oxytocin has an augmenting action via the uterine and vaginal afferent
activity it generates by oxytocin, stimulating the contraction of smooth
muscle of the vagina, cervix and/or uterus. A sexually activating effect of
oxytocin, via its stimulating contraction of genital muscular organs that
in turn generate sensory input, is supported by findings in the labora-
tory rat. Although the female rat shows no evidence of orgasm, oxytocin
injected subcutaneously increased the rats’ sexual receptivity; cutting
the sensory nerves from the vagina, cervix, and uterus abolished that
effect (Moody, Steinman, Komisaruk, & Adler, 1994).
We speculate that another factor is more significant for orgasm than
the action of oxytocin alone. The two sources of sensation (breast-nipple
and cervix-vagina) that converge on the paraventricular nucleus may
interact with each other there (e.g., breast stimulation altering the sen-
sory quality of concurrent vaginal stimulation) and activate the par-
aventricular nucleus, which in turn projects to, and activates, a neural
system that generates the perceptual experience of orgasm. We do not
rule out, however, that oxytocin could influence this system via a direct
effect on the brain.
Evidence of a Spinal Cord-Bypass Pathway: The Vagus Nerves
Although we had already convinced ourselves of the need to extend
the concept of orgasm beyond the genital, we were further intrigued by
anecdotal reports in the literature that women with complete spinal
cord injury experience orgasms (Whipple, 1990). We were even more
encouraged to try to understand this phenomenon when women with
complete spinal cord injury in our own research studies reported to us
that they were responding to vaginal and/or cervical self-stimulation
(CSS). Some could perceive it, and some experienced orgasms in
response to it.
In earlier reports, women diagnosed with “complete” spinal cord
injury had claimed they could perceive genital sensations, including
orgasm (Cole, 1975; Kettl et al., 1991; Whipple, 1990), which we (Komis-
aruk & Whipple, 1994; Whipple & Komisaruk, 1997; Whipple, Gerdes,
& Komisaruk, 1996; Komisaruk, Gerdes, & Whipple, 1997) and others
(Sipski & Alexander, 1995; Sipski, Alexander, & Rosen, 1995) con-
firmed. In addition, Berard (1989) reported that pregnant women with
spinal cord injury below T12 could feel uterine contractions and move-
ment of their fetus in utero.
BRAIN MRI OF WOMEN DURING ORGASM5
We hypothesized that some genital sensation could occur if the com-
plete spinal cord injury extended as high as spinal cord level Thoracic
11. This choice was based on evidence of the peripheral distribution and
level of entry into the spinal cord of the genital sensory nerves in women
(Bonica, 1967), as well as our and others’ mapping of the sensory fields
and zones of entry into the spinal cord of the genital sensory nerves in
the female rat (Berkley et al., 1990; Cunningham, Steinman, Whipple,
Mayer. & Komisaruk, 1991; Komisaruk et al., 1972; Kow & Pfaff, 1973-
1974; Peters et al., 1987). We formulated this hypothesis on the basis
that the hypogastric nerves ascend in the sympathetic chain and enter
the spinal cord at thoracic levels 10-12 (Bonica, 1967; Netter, 1986).
Consistent with this nerve distribution, we found that a group of 10
women (“lower-injury” group), whose complete spinal cord injury was
below T10 (thus presumably allowing some genitospinal input to enter
the brain at T10), could indeed feel the CSS. They also could feel the
application of the stimulator by one of the investigators, and they
showed significant analgesia (an objective measure of response) at the
fingertips during CSS (Whipple & Komisaruk, 1985, 1988). Further-
more, two of the women experienced orgasms to the self-stimulation
(Komisaruk, Gerdes, et al., 1997; Komisaruk & Whipple, 1994; Whipple
et al., 1996; Whipple & Komisaruk, 1997). Of greater interest, a group
of six women with complete spinal cord injury at or above T10 (as high
as T 7, the“upper-injury” group) had perceptual responses comparable
to the other, lower-injury group. Specifically, four of the six had percep-
tual responses to the cervical stimulation by the investigator and could
feel the CSS; all experienced analgesia measured at the fingertips (a
significant group effect); and one of the women experienced orgasms in
the laboratory. In addition, in both groups of women, all but one (in the
lower-injury group) reported that they commonly experience menstrual
Based on these unexpected and surprising findings, we proposed that
the women with the higher level of complete spinal cord injury (i.e., the
upper injury group) experience the vaginocervical stimulation via the
Vagus nerves (i.e., Cranial Nerve 10), which bypasses the spinal cord in
its course to the brain (Komisaruk, Gerdes, et al., 1997; Komisaruk &
Whipple, 1994; Komisaruk, Whipple, Gerdes, Harkness, & Keyes, 1997;
Whipple et al., 1996; Whipple & Komisaruk, 1997).
To provide some perspective on our conjecture, the traditional view
of the pathway by which genital stimulation reaches the brain is via
the spinothalamic tract. In cases of traumatic spinal cord injury, if this
tract is interrupted, genital stimulation-induced orgasm is blocked in
women and men (Beric & Light, 1993). Curiously, this pathway also
6 B. KOMISARUK & B. WHIPPLE
contains axons that convey pain impulses to the brain. In such cases as
the intractable pain of cancer, the spinothalamic tract may be thera-
peutically transected by surgery. For one noninjured male patient, this
procedure has been reported to block genitally stimulated orgasm
along with blocking the pain. His pain blockage persisted for several
months; when the pain reappeared, so did his genital orgasmic
response (Elliott, 1969).
Our hypothesis that the Vagus nerves provide an additional genital
sensory pathway in women is plausible as follows. Evidence for a
vaginocervical sensory role for the Vagus was first presented by Gue-
vara-Guzman and colleagues, based on their studies in the laboratory
rat (Ortega-Villalobos et al., 1990). They reported that the neural tracer,
horseradish peroxidase, when injected into the cervix, produced labeling
of neurons in the nodose ganglion, which is the dorsal root (i.e., sensory)
ganglion of the Vagus nerves. More recently, the innervation of the
uterus and cervix by the Vagus nerves in the rat was confirmed by
Papka and colleagues (Collins, Lin, Berthoud, & Papka, 1999).
Support for a vaginocervical sensory role for the Vagus nerves in the
rat was also provided by functional studies. Vagal electrical stimulation
has been shown to produce analgesia in rats (Maixner & Randich, 1984;
Ness, Randich, Fillingim, Faught, & Backensto, 2001; Randich & Geb-
hart, 1992) and in humans (Kirchner, Birklein, Stefan, & Handwerker,
2000), and we reported that vaginocervical probing in rats produces
analgesia even after combined bilateral transection of the known geni-
tospinal nerves (pudendal, pelvic, and hypogastric; Cueva-Rolon et al.,
1996). In the same individual rats (Cueva-Rolon et al., 1994), the anal-
gesia was abolished after subsequent bilateral transection of the Vagus
nerves. Furthermore, in a separate study in rats, we found that signifi-
cant pupil dilatation in response to vaginocervical stimulation per-
sisted, although at a diminished magnitude, after total surgical ablation
of the spinal cord at the midthoracic level (T7); subsequent bilateral
transection of the Vagus nerves at the subdiaphragmatic level abolished
that pupil dilatation response (Komisaruk, Bianca, et al.1996). Further-
more, electrical stimulation of the central end of the transected Vagus
nerves produced marked and immediate pupil dilatation (Bianca et al.,
1994; Komisaruk et al., 1995). In addition, Hubscher and Berkley (1994,
1995) reported that neurons of the Nucleus of the Solitary Tract (NTS)
in the medulla oblongata) in rats responded to mechanical stimulation
of the vagina, cervix, uterus, or rectum, and that vagotomy altered
these responses. Thus, various lines of evidence, both anatomical and
functional, support a genital sensory role for the Vagus nerves, at least
in the laboratory rat.
BRAIN MRI OF WOMEN DURING ORGASM7
Evidence That the Vagus Nerves Are Genital-Sensory in Women
To ascertain whether the Vagus nerves function comparably in
women, we used functional magnetic resonance imaging (fMRI) to
observe whether vaginocervical self-stimulation (VCSS) produces activa-
tion of the region of the brain to which the sensory vagus projects (i.e.,
the NTS). For this study, we identified women whose complete spinal
cord injury above T10 was due to mechanical interruption (gunshot
wound) rather than to compressive injury, in order to reduce the possibil-
ity of undetected residual spinal cord pathways. The region of the NTS
was identified in a prior fMRI study in which the participants tasted a
sweet-salty-sour-bitter liquid mixture (Komisaruk, Mosier, et al., 2002)
in order to activate the superior region of the NTS, which conveys gusta-
tory afference (Travers & Norgren, 1995). We determined whether this
region was activated in our participants by squirting a 1 ml sample of
our tasting mixture into the mouth of the women and recording the fMRI
activation pattern. The women then performed VCSS.
In humans, the NTS is a long tubular nucleus that is situated verti-
cally in the medulla oblongata of the brainstem, which itself is situated
vertically as an extension of the spinal cord. In the rat, the NTS has
been shown to have a viscerotopic organization which, if extrapolated
to humans, would place oral input at the uppermost region, followed
sequentially by input from esophageal, gastric, and intestinal stimula-
tion, respectively, in descending order toward the lowermost region of
the NTS (Altschuler, Rinaman, & Miselis, 1992). Because of this, we
hypothesized that responses to CSS would occur at the lowermost
region of the NTS (i.e., at the NTS pole opposite and below that acti-
vated by the tasting mixture). The fMRI of woman #1 shows the
anatomical location of the NTS based on histological atlases; it also
shows, in sagittal (top) and coronal (bottom) views, the regions acti-
vated by taste and by CSS, respectively (Figure 1). The results support
our hypothesis. This woman reported that she experienced orgasms
during the CSS.
Figure 2 is a composite of five different women with spinal cord
injury, in coronal view, showing the individual location of activation of
the NTS during VCSS. Note the similarity of location of the responses.
Each of these women could feel the stimulator in the vagina or
against the cervix. When it was inserted against the cervix, one woman,
AN, described a feeling of changing pressure as the stimulator was
moved, and another woman, VA, described a feeling of a “chill inside,”
which increased if increasing pressure was exerted against the cervix.
The perceptual responses to VCSS reported by these two women were
8 B. KOMISARUK & B. WHIPPLE
consistent with our earlier findings in other women with comparable
completeness and dermatomal levels of spinal cord injury (Komisaruk,
Gerdes, et al., 1997). Participant AP described a feeling of “touch inside”
when the stimulator was inserted against the cervix. She showed a
93.5% increase in pain detection threshold during the VCSS. Partici-
pant ED had normal sensibility at T10 but none below that level. She
stated that she could feel stimulation of the anterior vaginal wall, and
she showed the greatest magnitude of elevation of pain detection
Each of the above four women fulfilled the American Spinal Injury
Association (ASIA; 1992) criterion of “complete” spinal cord injury in
that they reported no sensory awareness of digital anal stimulation.
Participant EL had no cutaneous sensibility below T9; however, she did
have awareness of digital anal stimulation and was consequently diag-
nosed as having an “incomplete” spinal cord injury. The spinal cord MRI
of EL showed spinal cord injury in the form of a syrinx (i.e., a pathologic
tubular cavity in the spinal cord) at T 7-8, although it is not clear
whether the spinal cord was completely interrupted (Figure 2, EL). She
Figure 1. Brain regions activated by cervical self-stimulation and by a strong taste in a
woman with complete spinal cord injury that would block genital sensory pathways
through the spinal cord. Activation regions correspond to the lower and upper limits of
the Nucleus of the Solitary Tract (NTS), which is the sensory nucleus of the Vagus nerves
in the brainstem medulla oblongata.
BRAIN MRI OF WOMEN DURING ORGASM9
stated that she had a sensation of “touch inside” and of vaginal muscle
contraction when the stimulator was inserted. EL showed an increase
in pain detection threshold of 39.6%. As indicated in Figure 2, some of
these women also experienced orgasms during VCSS while we were
recording their fMRI activity. This enabled us to observe regional brain
activity during VCSS prior to, during, and after the occurrence of
orgasm. Figure 3 provides an overall view of the brain at the beginning
of CSS compared with the activity at orgasm. Note the much greater
and widespread activation in the lower brainstem, forebrain, and cere-
bellum during orgasm. This pattern of widespread activation of the
brain during orgasm was a common observation in the women.
Figure 4 shows, at two different threshold imaging criteria (p < 0.05
and p < 0.01), that brain regions activated during orgasm included
Figure 2. Activation of the NTS by cervical self-stimulation in five women with spinal
cord injury. (In this and the following figures, for clarity, the regions of interest have been
highlighted with outlining and/or arrows.) The level and completeness of the spinal cord
injury are specified below each image. The ASIA criteria signify the lowest dermatomal
level at which normal bilateral cutaneous (pinprick and/or cotton wisp) sensibility exists.
“A” signifies “complete” spinal cord injury (i.e., no sensation or voluntary movement below
that level, and no awareness of digital anal stimulation); “B” signifies “incomplete”
injury; in this case, there was no sensation or voluntary movement below the level of
injury, but there was awareness of digital anal stimulation. The label Neur is the more
stringent categorization of the injury that we used in our earlier study of women with
spinal cord injury (Komisaruk, Gerdes, et al., 1997)— that is, the lowest level at which
there was any sensation at all, rather than the ASIA criterion of the lowest level of “nor-
mal” sensation. In addition, the numbers “1” and “2” represent impaired and normal sen-
sibility, respectively. Thus, “1@T7” in the case of woman AN signifies that there was
impaired sensibility at T7, but no sensibility below T7, and “2@T7” in the case of partici-
pant VA signifies that there was normal sensibility at T7, but no sensibility below T7.
Both these women experienced an increase in pain detection threshold measured at the
fingers in response to VCSS — by 21.4% and 45.3%, respectively, over resting control lev-
els. Concurrently, tactile thresholds, measured at the hand using von Frey fibers,
10 B. KOMISARUK & B. WHIPPLE
hypothalamus, amygdala, cingulate cortex, and insular cortex. The
images at the left of this figure show the MRI anatomical image of the
same brain on which the activity is superimposed.
Figure 3. Activity at sequential levels of the brain (“sections” in the frontal plane) during
cervical self-stimulation before, compared to during, orgasm.
Figure 4. Some regions of the forebrain activated during orgasm.
BRAIN MRI OF WOMEN DURING ORGASM11
The involvement of the amygdala in orgasm per se, more than its “sim-
ply” showing a sensory response to CSS, is evidenced in Figure 5. In this
case, CSS was applied continuously, generating multiple orgasms that
occurred during only the first 3 of the 5 min shown. The CSS was main-
tained during the entire 5 min. In this case, activation of the amygdala
occurred only during the 3 min when orgasms were occurring. During the
last 2 min, although CSS continued, both the activation of the amygdala
and the orgasms ceased. We concluded that the amygdala does not simply
respond sensorially to CSS, but instead its activation is concomitant with
vaginocervical-induced orgasm per se. It is not possible to discern from
this finding whether activation of amygdala is a cause or an effect of
orgasm, but it is possible to conclude that the amygdala is not simply a
sensory target region for genital afferent activity.
Figure 6 shows fMRI images at two different brain regions, the hypo-
thalamus (upper and lower images on the right) and anterior to that,
the preoptic and/or bed nucleus of the stria terminalis region (upper
and lower images on the left). The upper images show the fMRI activity
at orgasm; the lower images show the same activity superimposed on
the corresponding brain anatomy. Note the activation in the region of
the paraventricular nucleus of the hypothalamus, amygdala, cingulate
cortex, insular cortex, and region of the nucleus accumbens.
Figure 7 shows fMRI activity in the region of the paraventricular
nucleus of the hypothalamus during orgasm. The schematic view on the
right shows an artist’s diagram (Netter, 1986) of this region, locating
the paraventricular nucleus to the left and slightly below the anterior
commissure. The anatomical MRI image shows the comparable region,
Figure 5. Repeated “snapshots” of amygdala activity in a woman with spinal cord injury.
Note that the amygdala was activated only while orgasm was occurring, despite continu-
ous cervical self-stimulation.
12 B. KOMISARUK & B. WHIPPLE
Figure 6. Additional regions of the forebrain activated during orgasm.
Figure 7. Activation of the paraventricular nucleus of the hypothalamus, which produces
oxytocin, during, but not before, orgasm. Cervical self-stimulation was applied before and
BRAIN MRI OF WOMEN DURING ORGASM13
the crosshairs identifying the anterior commissure. The image to the
right shows the fMRI activity at orgasm superimposed on this anatomi-
cal image. The two lower images show the fMRI at the beginning of CSS
(left) and at orgasm (right). Note the activation in the region of the par-
aventricular nucleus only at orgasm.
Figure 8 shows a greater activation of the hippocampus at orgasm
than at the onset of CSS.
Figure 9 shows a sequence of activation of forebrain components as
orgasm developed in one of the women (EL) during continuous CSS over
an 8-min period. Initially, none of the seven brain regions was activated.
But, over the course of the 8-min period leading up to orgasm, the
medial amygdala, basal ganglia, and insula showed the earliest activa-
tion; then the cingulate cortex entered into activation, and, at orgasm,
the nucleus accumbens, paraventricular nucleus of the hypothalamus,
and hippocampus became activated. In addition, the activation of insula
and basal ganglia became more extensive.
The brain activity observed during VCSS necessarily includes that
which generates the arm and hand movement producing the VCSS, as
well as that indicating the sensory response to that stimulation. Rather
than trying to discount such motor and sensory representation from the
orgasm records, and in order to clarify which brain activity relates
directly to orgasm, we studied (or selected) women who can experience
Figure 8. Activation of the hippocampus during orgasm
14 B. KOMISARUK & B. WHIPPLE
orgasm by thought alone, without any physical self- or other- stimula-
tion. We previously reported autonomic responses during orgasm in 10
women who claimed that they could generate orgasms by thought alone
(Whipple et al., 1992). Initially skeptical of their claims, we compared
the autonomic responses under two conditions in each woman: one dur-
ing genital self-stimulation-induced orgasm and the other during
thought-induced orgasm. We found to our surprise that each of the
parameters measured in a counterbalanced design (i.e., heart rate,
blood pressure, pupil dilatation, and pain threshold) approximately dou-
bled during orgasm compared to initial resting baseline under both the
conditions. The women described the imagery they experienced during
the thought-induced orgasms variously: in some cases, erotic; others,
pastoral; and still others, abstract (e.g., as “energy flow” repeatedly
ascending and descending the body axis).
Preliminary findings from our fMRI study of other women who can
generate thought orgasms indicate that, similar to the case of VCSS-
induced orgasms, regions of the nucleus accumbens, paraventricular
nucleus of the hypothalamus, hippocampus, and anterior cingulate cor-
tex are activated during thought-induced orgasm (Figure 10). This sug-
gests that activation of these brain regions is rather specifically related
to orgasm, in the sense that they are not related to the brain control of
the efferent and the consequent “re-afferent” activity that generates
orgasm via hand movement in response to genital self-stimulation. We
noted that the amygdala was not activated during the thought orgasms,
leading us to speculate that the amygdala may have a genital sensory
role in orgasm, whereas the other regions activated may have a more
Figure 9. Sequential “snapshots,” in a selected brain “section,” of activation of different
brain regions as orgasm developed in response to continuous cervical self-stimulation.
BRAIN MRI OF WOMEN DURING ORGASM15
Brain Regions Activated During Genital Self-Stimulation and Orgasm
The brain regions that we found to be activated during CSS-induced
orgasms include hypothalamus, limbic system (including amygdala, hip-
pocampus, cingulate cortex and insular cortex, and the region of the
accumbens-bed nucleus of the stria terminalis-preoptic area), neocortex
(including parietal and frontal cortices), basal ganglia (especially puta-
men), and cerebellum, in addition to lower brainstem (central gray, mes-
encephalic reticular formation, and NTS). Differences between regional
activation during, versus before or after, orgasm suggest that areas
more directly related to orgasm include the paraventricular area of the
hypothalamus, amygdala, anterior cingulate region of the limbic cortex,
and region of the nucleus accumbens.
Although there is no evidence of orgasm in female rats, a number of
researchers have reported that some of the same-named brain regions
become activated during mating or vaginocervical stimulation. Thus,
using the c-fos immunocytochemical method in rats, activation was
reported in amygdala (Erskine & Hanrahan, 1997; Pfaus & Heeb, 1997;
Rowe & Erskine, 1993; Tetel, Getzinger, & Blaustein, 1993; Veening &
Coolen, 1998; Wersinger, Baum, & Erskine, 1993); paraventricular
nucleus of the hypothalamus (Pfaus & Heeb, 1997; Rowe & Erskine,
1993); medial preoptic area (Erskine & Hanrahan, 1997; Reyna-Neyra,
Camacho-Arroyo, Cerbon, & Gonzalez-Mariscal, 2000: Tetel et al., 1993;
Wersinger et al., 1993); midbrain central gray (Pfaus & Heeb, 1997;
Figure 10. Brain regions activated during orgasm generated by thought alone, without
16 B. KOMISARUK & B. WHIPPLE
Tetel et al., 1993); and, based on local release of dopamine, the nucleus
accumbens (Pfaus, Damsma, Wenkstern, & Fibiger, 1995).
To our knowledge, we are the first to report activation of hypothala-
mus during orgasm in men or women. An earlier study of orgasm in
men, based on positron emission tomography (PET), reported activation
in prefrontal cortex, but not subcortical structures (Tiihonen, et al.,
1994). Also in men, using PET, Holstege and colleagues (Georgiadis et
al., 2002; Holstege et al., 2003) reported that the mesodiencephalic
area, cerebellum pontine reticular formation, basal ganglia (putamen
and claustrum), and several cortical regions, including the lateral pre-
frontal cortex but not the hypothalamus, were activated during orgasm.
In men during sexual arousal (but not orgasm) elicited by their viewing
photographs, Wallen and colleagues (Hamann, Herman, Nolan, & Wallen,
2002) reported that fMRI activity was increased relative to the activity in
women in the amygdala, hippocampus, and hypothalamus. Striatal
regions (caudate and nucleus accumbens) were activated in both men and
women. In a separate study (Karama et al., 2002), when the fMRI of men
and women were compared while they watched erotic film segments, the
men showed greater activity than the women in the hypothalamus and
thalamus. The level of hypothalamic activity correlated with the subjective
level of sexual arousal reported by the men. Brain regions activated in
both the men and women were the amygdala, ventral striatum, and the
following cortices: anterior cingulate, insular, orbitofrontal, medial pre-
frontal, and occipitotemporal. In an fMRI study of women observing erotic
visual stimuli (Park et al., 2001), activation was found in the thalamus,
striatum (caudate and globus pallidus), and the following cortical regions:
cingulate, insular, inferior temporal, inferior frontal, occipital, and corpus
callosum. The occipital cortex (visual cortex) was much more highly acti-
vated by the erotic than the nonerotic films.
There does not seem to be a simple means of accounting for the dif-
ferences in brain area activation reported among the various studies
summarized above. Although one could generate some “just-so” cogni-
tive neuroscience stories (e.g., different brain areas independently found
in other studies to be related to “emotional,” “expectancy,” “initiative,”
etc. responses), it seems more prudent to postpone such speculation
pending information generated by “differential diagnostic” types of
studies. We, however, not heeding this caveat, throw caution to the
winds and make the following speculations.
Suggested Role of Some Brain Regions in Orgasm
Activation in the region of the paraventricular nucleus (PVN) of the
hypothalamus is consistent with reports of oxytocin release during
BRAIN MRI OF WOMEN DURING ORGASM17
orgasm. This process occurs in three stages: The PVN neurons secrete
oxytocin, which is stored in the posterior pituitary gland (Cross & Wak-
erley, 1977); vaginal or cervical stimulation releases the oxytocin from
the posterior pituitary gland into the bloodstream, in the Ferguson
Reflex (Ferguson, 1941); orgasm releases the oxytocin into the blood-
stream (Blaicher et al., 1999; Carmichael, et al., 1987, 1994). Thus, it is
probable that this release of oxytocin is due to the activation of the PVN
observed at orgasm.
During orgasm, the insular cortex and anterior cingulate cortices are
active, as they have been reported to be during response to pain (Born-
hovd et al., 2002; Casey, Morrow, Lorenz, & Minoshima, 2001; Ploner,
Gross, Timmermann, & Schnitzler, 2002). These reports suggest an
interesting local interaction between regions of the brain. Further
research is needed to compare, within the same individual, brain
regions activated during pleasure with those activated during pain (i.e.,
a “differential diagnosis” study). The region of the nucleus accumbens
also showed activation during orgasm in the present study, suggesting
it has a role in mediating orgasmic pleasure in women. This brain
region has also been reported to show fMRI activation during the “rush”
induced by an intravenous injection of nicotine (Stein et al., 1998).
Reliably, the cerebellum was activated during orgasm. The cerebel-
lum modulates muscle tension via the gamma efferent system, and it
receives proprioceptive information (Netter, 1986). Muscle tension can
reach peak levels during orgasm (Masters & Johnson, 1966) and con-
tribute to the sensory pleasure of orgasm (Komisaruk & Whipple,
1998, 2000). It is likely that the cerebellum thereby plays a significant
motoric role in orgasm; our present research makes it tempting to
speculate that it has a significant perceptual/cognitive-hedonic role in
Previous Studies of Brain Regions Involved in Orgasm: Epilepsy
Much of what is known about how the brain produces orgasms is based
on studies of epileptic seizures. In numerous reports, men and women
describe orgasmic feelings just prior to the onset of an epileptic seizure, a
condition called an “orgasmic aura” (Calleja, Carpizo, & Berciano, 1988;
Janszky et al., 2002, 2004; Reading & Will, 1997). Electroencephalo-
graphs show that the most common brain region from which these orgas-
mic auras originate is the right temporal lobe, which contains the
hippocampus and the amygdala. The aura may have a spontaneous onset
or may be triggered by some specific stimulus, for example in one woman,
brushing her teeth (Chuang, Lin, Lui, Chen, & Chang, 2004). Although
seizure-related orgasms may be described as “unwelcome” (e.g., Reading
18B. KOMISARUK & B. WHIPPLE
& Will, 1997), in other cases they have been described as pleasurable.
One woman was reported to have refused anti-epileptic medication or
brain surgery because she enjoyed her orgasmic auras and did not want
them eliminated (Janszky et al., 2004).
An interesting and instructive observation in the case of these orgas-
mic auras is that they are not necessarily experienced as involving geni-
tal sensation. In contrast, other reports document epileptic seizures
originating in the sensory cortex, the region to which the genitalia pro-
ject. In the latter cases, the individuals reported an experience of geni-
tal sensation developing into an orgasm that feels as if it were indeed
generated by genital stimulation (e.g., Calleja et al., 1988).
Some Methodological Considerations
It is evident from the above discussion that different methodologies
provide different types of insights into the neural basis of orgasm and
that each methodology has its unique advantages and limitations. In
the context of the present findings it is most germane to address fMRI
and PET methodologies. Both of these methods work in awake humans
to provide a three-dimensional map of brain regions active during the
condition of interest (e.g., VCSS orgasm) relative to control conditions
(e.g., unstimulated resting, or VCSS prior or subsequent to orgasm).
These two methods have an advantage over the EEG (electroencephalo-
gram) in that the latter does not provide information on localized acti-
vation that occurs deep in the brain. They also have an advantage over
implanted electrode recording of multi-neuronal activity in that neither
fMRI nor PET is invasive, in contrast with methods that utilize acutely
or chronically inserted electrodes. The major limitation of the fMRI and
PET methods is that, rather than providing a measure of neural activ-
ity per se, they both make use of a hemodynamic response that indi-
rectly measures neural activity. That is, typically in PET methodology,
water is first synthesized in a biochemistry laboratory close to the par-
ticipant and radioactively labeled with Oxygen15, which has a half-life of
only 2 min; then, after its intravenous injection, the distribution of the
radioactivity in the brain is mapped in three dimensions. Blood flow
normally increases locally in regions of increased neuronal activity, cre-
ating a relative increase in the amount of radioactivity per unit time in
those regions. This relative change provides the data in PET. Because of
the 2-min half-life, subsequent injections of the labeled water are typi-
cally administered at 15-min intervals (i.e., alternating control and
experimental stimulus conditions). The limitations of the PET method
include its invasive intravenous injections of radioactivity, as well as its
complexity and temporal constraints: coordinating the on-site produc-
BRAIN MRI OF WOMEN DURING ORGASM19
tion of radioactive oxygen using a cyclotron, immediate utilization of the
oxygen in the synthesis of water, immediate injection of the water intra-
venously, time lag waiting for the water to be distributed to the brain,
and difficulty of timing the pulse of radioactivity to concur with the
orgasm–a rather heroic effort (e.g., Komisaruk, Whipple, et al., 2002;
Whipple & Komisaruk, 2002). Furthermore, because the region of
increased radioactivity is relatively diffuse, the method is better suited
to experimental paradigms in which a relatively large brain region (neo-
cortex or basal ganglia) is expected to be involved, rather than rela-
tively small regions such as specific brain stem nuclei.
The fMRI method is also based on the increased blood flow to acti-
vated neurons. When the neurons become more active, they use more
oxygen. Two processes result: First, oxygen is removed from the hemo-
globin of the blood originally supplying the neurons; second, to compen-
sate, more oxygenated blood flows to the region. Because the magnetic
property of the iron in the hemoglobin of the blood is affected by
whether it is combined with oxygen or depleted of oxygen, these two
processes create a perturbation in the local magnetic environment that
is mapped in three dimensions, providing the data for the fMRI method
(Ogawa, Lee, Kay, & Tank, 1990). The resolution of the fMRI method is
sharper than that of the PET method, to the extent that it can map the
brainstem location of different specific motor and sensory clusters of
neurons (i.e., specific cranial nerve nuclei) activated by specific motor or
sensory tasks (Komisaruk, Mosier, et al., 2002).
Researchers use various strategies for analyzing fMRI or PET data,
comparing the observed activity, for example, either to other regions con-
currently in the same brain “slice” and/or to activity in the absence of sen-
sory stimulation. Another consideration is whether to use an inductive
strategy, with no prior hypothesis, that analyzes where regional activity
differs significantly from other regional activity, or whether to make an a
priori selection for analysis of specific “regions of interest,” comparing
their activity in stimulation and no-stimulation conditions. Still another
consideration is how to establish the threshold at which activation will be
considered significantly greater than at selected controls; if the threshold
is too stringent, areas of activation will be missed; if it is too low, activity
in the “background” will obscure activity in specific regions (e.g., Poline,
Holmes, Worsley, & Friston, 1997).
In general in our studies, the highest thresholds that showed activa-
tion of specific brain regions at orgasm were selected and maintained
constant when compared with the same brain regions prior to orgasm.
In that way, we observed changes related specifically to orgasm. This
strategy could, theoretically, lead to the conclusion that some brain
20 B. KOMISARUK & B. WHIPPLE
regions were not active until orgasm, but, practically, it enables us to
ascertain those brain regions that are differentially activated during
orgasm. We have been careful to interpret our findings as indicating rel-
ative, rather than absolute, changes in brain activity related to orgasm.
With the exception of the brain images shown Figures 5 and 10, the
images have been published previously. The specific selection criteria
are presented in that publication (Komisaruk et al., 2004).
Which Brain Regions Generate the Feeling of Orgasm?
It is tempting to speculate that activity of one or more of the above-
cited regions activated during orgasm produces the voluptuous sensa-
tion of orgasm. This consideration raises one of the ultimate questions
in neuroscience (indeed, the reason many of us entered the field): which
brain regions generate conscious awareness and by what mechanism?
Are we aware of the activity of the nucleus accumbens? Does it generate
feelings of craving and/or pleasure? The cingulate cortex? Insula? Par-
aventricular nucleus of the hypothalamus? Does activation of any of
these brain regions give rise to awareness? What makes some activated
neurons produce feelings of pleasure and others, feelings of pain?
How does one bridge the gap between locating the brain correlates of
orgasm and understanding how that brain activity generates the plea-
surable feeling of orgasm? In a new study. Dunn, Cherkas, and Spector
(2005) suggested another dimension to take into account. In a large sur-
vey of the relative frequency of orgasm during intercourse or during
masturbation they found a higher correlation among identical twins
(31% and 39%, respectively) than among fraternal twins (10% and 17%,
respectively). These findings indicate a possible genetic component to
mechanisms underlying orgasm. Thus, the study adds another element
to the perennially intriguing question: what factors mediate orgasm?
These are fundamental questions, unanswered but perhaps not unan-
swerable. If orgasm is a phenomenon of the brain that is somehow more
than the sum of the reafferent sensory activity generated from the smooth
and striated muscles, we are again led to ask the linked questions: Which
neurons generate our experience of pleasure and how do they do so? The
answer must lie in developing a concept of orgasm that includes but tran-
scends the understandings available through PET and fMRI.
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