The role of the amygdala in the development of sexual arousal.

Author:Salu, Y.
Position:Author abstract
 
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Introduction

At the end of their childhood, youngsters experience a new sensation--sexual arousal. Some become sexually aroused by men, some by women, and some by both. Different people are aroused by different features of their arousers, but the bodily response and the overall experience of all the aroused are similar. During childhood, as the development of the sex organs is being genetically orchestrated, the mental aspects of sexual-arousal are developing unconsciously based on non-sexual experiences. While explicit and implied instructions by others may have some effects on it, it appears that the broad nature of sexual-arousal depends on the innate make-up of the individual.

A model that describes how the mental component of sexual-arousal evolves during childhood has been proposed recently (Salu, 2011). This model treats the entire process as a learning activity in which a brain program is built by biological mechanisms, based on individual experiences. The brain program has two groups of inputs: features of people based on which their sex can be determined, and features that induce the emotional part of sexual-arousal. The model assumes that there are root cues, common to all people, which the brain is innately hard-wired to detect. Based on the root cues, the individual's brain learns additional cues that depend on the societal environment in which the individual grows up. The learned cues may vary from one person to another. The root cues have to be robust and universal, to guarantee that everyone could be sexually-aroused at puberty, no matter where and when they happen to live.

The main learning mechanism of the individual cues is conditioning; a group of widespread innate mechanisms that enable animals to adapt to various environments. In conditioning, an animal learns new behaviors based on cues to behaviors that it already possesses.

Classical conditioning is an innate learning mechanism, first described by Pavlov in 1927. Since then, more variants of it were described. It involves, on one hand, a stimulus and its triggered response (the unconditioned stimulus (US, food) and the unconditioned response (UR, salivation)), and, on the other hand, a conditioned stimulus (CS, bell's ring). When the CS appears in conjunction with the US and its triggered UR, the CS too becomes a trigger of the UR (the bell's sound triggers salivation). In other conditioning paradigms, activities too can be learned. For example, if an owner whistles as the dog is approaching, and then rewards the dog, the dog will learn to come to the owner's whistle. In this case, a stimulus-reward pair elicited the linkage of a stimulus and an activity. If a whistle happens to be associated with a flash of light, and the animal is trained to respond to the whistle, it will respond also to the flash of light, with little or no training. The learning pace in conditioning depends on the emotional strength of the learned events. Events with higher emotional strength (positive or negative), are inseminated faster than events with lower emotional strengths. This is, in essence, how innate conditioning mechanisms build individualized complex behavior patterns. Conditioning is crucial for survival, because it enables animals to learn new behaviors that fit the environments in which they happen to be.

The underlying physiology that supports conditioning consists of a root neural network, whose input is the root US and the output is the root UR. Due to the conditioning, synaptic weights are modified between associated stimuli and/ or associated responses and the elements of the root network. As a result, an expanded neural network is created, that supports the original and the learned behaviors. It was demonstrated that humans and other animals can learn new sexual behaviors by conditioning (Klucken et al., 2009).

Innate Brain Wiring and Root Cues

The pitch of human voice

The innate network based on which sexual arousal develops has a root cue for identifying the gender of the arouser and a root cue for generating the emotions of sexual-arousal. According to the model (Salu, 2011) the root cue for identifying the gender of the arouser is the pitch of human voice. The human auditory and vocal systems have some dimorphic properties. The voice of women is different from the voice of men, and men's brains do some sound processing differently than women's. There are also some differences that are correlated with sexual orientation (McFadden, 2011). Since the root US's have to be robust and universal, and since the auditory and vocal systems are designed at the gene level, a model was constructed, suggesting that the pitch of the human voice is the US that the brain uses for learning to distinguish between the sexes (Salu, 2011). According to this model, the sex-activation centers (the UR's) of most boys are innately tuned to high pitch (women's) voice (the US's). The sex-activation centers of most girls (the UR's) are innately tuned to low pitch (men's) voice (the US's). As a result, at puberty, most boys are sexually attracted to women, based on learned cues (CS's) that have been associated with the women's high pitch voice. Similarly, most girls at puberty are attracted to men...

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