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, 8 (10), 2822-30

Women's Clitoris, Vagina, and Cervix Mapped on the Sensory Cortex: fMRI Evidence

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Women's Clitoris, Vagina, and Cervix Mapped on the Sensory Cortex: fMRI Evidence

Barry R Komisaruk et al. J Sex Med.

Abstract

Introduction: The projection of vagina, uterine cervix, and nipple to the sensory cortex in humans has not been reported.

Aims: The aim of this study was to map the sensory cortical fields of the clitoris, vagina, cervix, and nipple, toward an elucidation of the neural systems underlying sexual response.

Methods: Using functional magnetic resonance imaging (fMRI), we mapped sensory cortical responses to clitoral, vaginal, cervical, and nipple self-stimulation. For points of reference on the homunculus, we also mapped responses to the thumb and great toe (hallux) stimulation.

Main outcome measures: The main outcome measures used for this study were the fMRI of brain regions activated by the various sensory stimuli.

Results: Clitoral, vaginal, and cervical self-stimulation activated differentiable sensory cortical regions, all clustered in the medial cortex (medial paracentral lobule). Nipple self-stimulation activated the genital sensory cortex (as well as the thoracic) region of the homuncular map.

Conclusion: The genital sensory cortex, identified in the classical Penfield homunculus based on electrical stimulation of the brain only in men, was confirmed for the first time in the literature by the present study in women applying clitoral, vaginal, and cervical self-stimulation, and observing their regional brain responses using fMRI. Vaginal, clitoral, and cervical regions of activation were differentiable, consistent with innervation by different afferent nerves and different behavioral correlates. Activation of the genital sensory cortex by nipple self-stimulation was unexpected, but suggests a neurological basis for women's reports of its erotogenic quality.

Conflict of interest statement

Conflict of Interest:

None

Figures

Figure 1
Figure 1
Three views of the paracentral lobule, showing its relation to adjacent cortical regions (adapted from [32]). The relation of the paracentral lobule to the sensory cortical homunculus of Penfield and Rasmussen [3] is shown by the lines connecting the corresponding regions.
Figure 2
Figure 2
Three-axis (columns: coronal, sagittal and transaxial) views of the group-based responses to experimenter-applied (finger and toe) or participant self-applied (clitoris, vagina, or cervix) stimulation in relation to the homuncular map (adapted) generated by Penfield and Rasmussen [3]. The arrows indicate the sensory cortical regions activated by the various stimulated body regions. Finger stimulation activated the postcentral (sensory) gyrus. Hallux (large toe) stimulation activated the medial paracentral lobule. Clitoral, vaginal, cervical, and nipple self-stimulation also activated the medial paracentral lobule. Note that the perineal (groin) region just lateral to the midline in the paracentral lobule was also activated by clitoral, vaginal, and cervical self-stimulation. There was marked hand-related activation in the postcentral gyrus, and continuation of activation into the supplementary motor area immediately rostral to the sensory cortical responses, in the self-stimulation conditions. The secondary sensory cortex (SII; at the base of the homunculus) was activated under all the stimulus conditions (not evident in these images in the thumb stimulation condition). The “hot-metal” calibrations show the range of Z-scores for the intensity of the fMRI responses.
Figure 3
Figure 3
a: Group-based composite view of the clitoral, vaginal and cervical activation sites, all in the medial paracentral lobule, but regionally differentiated. We interpret this as due to the differential sensory innervation of these genital structures, i.e., clitoris: pudendal nerve, vagina: pelvic nerve, and cervix: hypogastric and vagus nerves (e.g., [14]). b: Nipple self-stimulation activated not only the thoracic region, but also unexpectedly, the genital region of the medial paracentral lobule. Shown are superimposed responses to nipple and genital self-stimulation in three participants. Note the congruence between activation produced by stimulation of nipple and cervix (left panel), nipple, cervix and clitoris (center panel), and nipple, vagina, cervix and clitoris (right panel). Not unexpectedly, cervical self-stimulation activated the groin region (center panel). However, it is surprising that vaginal self-stimulation activated the thoracic nipple region (center panel), and nipple self-stimulation activated the groin sensory region (left panel). Color coding: nipple (white), cervix (yellow), clitoris (green), vagina (red, or when congruent with nipple - pink). c: Three-axis view of the response to the nipple self-stimulation in the case of the center image of Figure 3(b) (downward pointing blue arrow).

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