St. Xavier's College (Autonomous),
Mumbai, Maharashtra, India
What is Sexuality?
Sexuality can be defined as the way one experiences and expresses themselves sexually. These human sexual behaviors that are exhibited may be physical, biological, emotional, spiritual, or social. The term lacks a precise definition because it has been mentioned in varied contexts throughout history. Sexuality in the modern era is primarily considered in terms of reproductive functions and it’s underlying biological and physical aspects. The physiological responses to a sexual stimulus are explained by the human sexual response cycle.
The four phases of this cycle are Excitement, Plateau, Orgasm, and the Resolution phase. Neural structures ranging from the Cerebral cortex to the peripheral nerves are involved in each of these phases. That means sex is quite literally in our heads! An elaborate interaction between the somatic and autonomic nervous system regulates sexual desire, arousal, and orgasm. In males and females, the biochemical mechanisms are similar for desire, arousal, and orgasm. However, the responses that are exhibited differ amongst genders.
What triggers sexuality?
Simply put, the smallest trigger that could elicit sexual arousal can trigger sexuality. Based on the sense involved, these stimuli are classified into somatosensory, visual, and olfactory. Historically, sexual desire had been regarded as an internal instinct that functioned much like hunger and thirst. To date, a well-accepted model to explain the neural correlates of sexual drives is the neurophenomenological model which consists of four components:
The Cognitive component - Incorporates a process of assessment through which each stimulus is perceived, classified as a sexual incentive, and as such, quantitatively evaluated. The parts of the brain involved in response to visual stimuli are the Orbito Frontal Cortex and the Superior Parietal Lobules. Once the sexual relevance of the stimulus is analyzed, the gates to motivational, emotional, and bodily responses are opened up.
The Motivational component - A motivational value gets related to the stimuli after it has been perceived as sexual, which makes the stimuli what we call ‘highly attractive’ or ‘wanted’.The corresponding areas of the brain associated are the caudal parts of the ACC (Anterior Cingulate Cortex).
The Emotional component - The ‘pleasure element’ that is associated with rising arousal, perception of bodily changes is incorporated. The neuronal associates of this component are the Somatosensory Cortex, Amygdala, and Posterior Insula.
Autonomic and Endocrine component - Includes all the bodily changes that arise as a result of sexual stimulation, including cardiovascular and respiratory responses. The activation of the Hypothalamus, Putamens, ACC, and Anterior Insulae participate in the mediation of the autonomic and neuroendocrine responses of sexual arousal.
Which regions of the brain are involved?
Fig1. Major areas of the brain involved in human sexual behavior.
Frued’s Theory of Psychoanalytic Sexual Drive
According to Sigmund Freud, a series of childhood stages are responsible for the development of one’s personality. In these stages, pleasure-seeking energies from the id become focused on certain areas sensitive to sexual stimulation. He came up with 5 psychosexual stages which each represent the fixation of Libido (roughly translates to sexual drive) to explain this developmental process. He also believed that life is built around pleasure and tension and that all pleasure is received by releasing tension. The 5 stages as described by him are the Oral stage, the Anal stage, the Phallic stage, the Latent, and the Genital stage. Gratification to all these stages of libido fixation is achieved through various stimulations and if failure of ‘libido fixation’ occurs, it may show up as disorders in adulthood.
Kisspeptin Signalling (KISS1R)
Kisspeptins are a group of peptide fragments which in humans, are encoded by the KISS1 gene. They are essential for reproductive function. Puberty is regulated by the maturation of
kisspeptin neurons and by an interplay between leptin and kisspeptins. They are also known to play a role in the regulation of the Gonadotropin-releasing hormone (GnRH) and sexual dimorphism of the human brain. Research also indicates that there may be a link between reproductive systems and energy homeostasis.
This article serves as an introduction to sexuality and its underlying mechanisms through two different perspectives; one from Neurology and the other from Psychology. The Neurophenomenological Model talks about the neural correlates of a sexual drive while Freud’s theory gives an insight into how one’s sexual personality develops.
So the next time someone tells you sex is all in your head, show them this article and tell them yes - it is all in your head!