How do MRI studies of coitus correlate specific penetration depths with sites of vaginal sensation and reported orgasm in partners?

1. MRIs map where a penis physically contacts the vagina, not where nerves fire

Dynamic sagittal and coronal MRI sequences repeatedly show that during missionary‑type intercourse the erect penis bends into a “boomerang” shape and often reaches the anterior fornix or anterior vaginal wall, displacing bladder and raising the uterus; in rear‑entry trials the penis appears to preferentially contact the posterior fornix ^{[5] [1] [2]}. Those are anatomical, structural observations about penetration depth and direction, not direct measures of sensation or orgasmic response, since MRI visualizes soft‑tissue geometry and organ displacement rather than neural activation or subjective pleasure ^[1].

2. Correlates: anterior wall sensitivity and the so‑called “G‑spot” hypothesis

Separate experiments and electrical sensitivity testing cited by the MRI authors found a relatively sensitive area on the anterior vaginal wall (“12‑o’clock” position), lending anatomical plausibility to claims that anterior fornix contact can stimulate structures linked to female sexual sensation ^{[3] [6]}. The MRI team and later commentators therefore argued that penetration reaching the anterior vaginal wall could mechanically stretch or press the clitoral root/urethrovaginal complex, potentially explaining why contact at certain depths or angles may be experienced as especially pleasurable by some women ^{[6] [7]}.

3. Limits of MRI: clitoris, urethra, and subjective orgasm remain obscured

The original MRI researchers explicitly acknowledged that their images could not reliably distinguish the vaginal wall from the urethra and clitoris, and that MRI does not capture clitoral dynamics or neural firing patterns during coitus ^{[4] [7]}. Therefore, while images show that penetration can stretch tissue near the clitoral root and anterior wall, they cannot prove that a particular penetration depth causes orgasm; orgasm is a subjective psychophysiological event not directly measurable by the structural MRI sequences used ^{[4] [1]}.

4. Reported orgasm does not map simply to deeper penetration

The research and follow‑ups emphasize that coital penetration alone is an inefficient, inconsistent inducer of female orgasm: MRI anatomy shows which tissues are contacted, but sensitivity testing and questionnaire data reveal heterogeneity—some women report increased vasocongestion or pleasure with coitus, others less so, and women with dyspareunia can show decreased vasocongestion during coitus ^{[8] [3]}. In short, depth and location of contact are one piece of a multifactorial puzzle that includes clitoral activation, individual anatomy, arousal state, and psychosocial factors ^{[3] [8]}.

5. Balanced takeaways and future directions

MRI work established that penetration geometry varies by position and that the anterior vaginal wall is anatomically and electrophysiologically important, supporting models that view clitoris and vagina as an integrated unit, yet the technique cannot by itself link specific millimeters of penetration to orgasmic outcomes ^{[1] [6]}. Ultrasound and targeted sensory mapping provide complementary data—visualizing clitoral movement or measuring local sensitivity—but resolving causal links between precise penetration depth and reported orgasm will require multimodal studies combining imaging, neural/physiological measures, and careful subjective reporting ^{[7] [3]}.