Neuroanatomical Neuroanatomical Theorized Behavioural Correlate
Cortical Piriform Nucleus Modulation of drive, initiation and
Frontal Lobes and sexual activation
Subcortical Hippocampus Modulation of sexual behaviours
Amygdala and genital responses
Brainstem Reticular Activating Maintenance of arousal and alertness
System and conduit for information
Peripheral Nervous Autonomic Genital sexual function
This pretty well indicates that sex is in your head and that it is a nervous condition. It also suggests that alone it's a very complex task even for the brain so theoretically it shouldn't be surprising that it's complexity increases with involvement with others. Once that happens there's politics and worse government. And as we all might guess government is about promises and then every attempt under the sun to collect the pay without actually doing the work. So sex is heady stuff and one shouldn't be mindless about it though given the mental baggage most people carry around with them it would be good if they could lighten up. Especially with age, given what gravity does to all the external sensory working apparatus. Candlelight helps in old age especially after massage by grape feeding nubile young people in wealthy vacation resorts after weeks of just lying around on the beach and getting prepared for the sexual event. It really doesn't matter much what the sex is then as it serves to break the monotony of relaxation. Familiarity breeds contempt. It's best to treat one's partner as a stranger and clearly dementia may prove beneficial for sexual arousal. If one is mentally saying, oh God, here they go again, with that maneuver, and now they're going to do that thing next, it really isn't conducive to frollicking. The utter boredom expressions and grimacing, are somewhat counterproductive to the sexual act. Feigning amusement is far better. It helps with masturbation as well as consensual sex.
That said it is to be remembered that the praying mantis female consumes her mates head at orgasm suggesting that their might be benefits to a headless partner. To date no opinion poll has been completed by a male praying mantis so we can only conjecture regarding his 'feelings' about the situation. Couples commonly close their eyes to have private fantasies while alcohol and drugs for one or the other simulates the praying mantis experience.
Shakespeare called it the "two backed beast". Today, thanks to advances in neurosciences, we might well call it the two headed human.