In studies that observe the brain in action, the right hemisphere seems to be the sexy hemisphere. It lights up during orgasm—so much so that, in one study, much of the cortex went dark, leaving the right prefrontal cortex as a bright island. New research suggests the right hemisphere is also hyperactive amongst the “hypersexual,” a symptom of brain injury loosely defined as groping, propositioning or masturbating in public without shame.
What is surprising about this is that pleasure is classically thought of as the province of the left hemisphere, not the right. The left is most active when recalling happy memories, meditating on love for another, and during the expansiveness of grandiosity or mania.
The left hemisphere is even preferentially more active among people free of depression and less active among the unhappy. If the brain were a simpler and more cooperative organ, the left hemisphere would be lit up like the Fourth of July during an orgasm. Instead, it is surprisingly silent. Why might this be so?