There are three perspectives on love: a first-person subjective experience, sometimes powerful and exhilarating in the case of romantic love; observable second-person relations and pair bonding; and a “third-person” objective perspective: the biophysical aspects of the phenomenon. The plurality of love, its varieties of meaning in globalized human culture, makes it difficult to study in neuroscience, as we search for this subjective construct using objective measures of observation. The possible subjective categories of love I can identify are: equal love (roughly Platonic, as in Jesus of Nazareth’s parable of the “Good Samaritan”), puritan love (non-sexual yet romantic, common among teenagers perhaps), lust, and romantic companionship. These experiences are undoubtedly part of human nature, and thus neuroscientists can expect to find common neural components responsible for their functions, some of which will be homologous across species. That said, behavioral displays of love are not consistent across species, and caution is necessary before generalizing from such research.
Animal studies can be used to map regions of the brain likely to be involved in certain aspects of love. Sexually experienced rats with damage to the preoptic area (POA) will still seek access to receptive females, but will not copulate. This suggests a separation between regions involved in social approach and sexual activity. Furthermore, activation of the POA occurs in male primates while they approach desired females, and during copulation, but not while they approach other objects of desire, say, bananas. Stimulating the septal area with ACh neurotransmitters evokes feelings of imminent orgasm in humans. Surely it is the integration of such neural functions that construct the ranging experiences that bring about love. Hormones, particularly gonadal ones such as testosterone, also play a part in the experience of love; pair bonding between couples is assisted by oxytocin in females, and vasopressin in males, evoking feelings of affection and attachment, often peaking during and shortly after sexual encounters.
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