The odors of a receptive female will evoke sexual motivation in the male common marmoset characterized by stereotyped """"""""tongue flicking"""""""" and anticipatory penile erection. This odor-induced, psychogenic behavior provides a unique opportunity to study the neuroanatomy of sexual motivation in a nonhuman primate. With the advent of functional magnetic resonance imaging (fMRI) it is now possible to use a noninvasive approach for observing brain activity without injury or sacrifice of the animal. Recently, a small animal holding device was developed for performing fMRI on a fully awake male marmoset. During MR imaging, a male marmoset shows intense tongue-flicking in response to the odors of a novel receptive female without any other visual, auditory or somatosensory stimulation. These studies will use fMRI to examine the neuroanatomy and neuropharmacology involved in the regulation of sexual motivation in the marmoset. It is hypothesized that smelling odors of a novel receptive female will increase neural activity in brain areas involved in sexual motivation. To test this hypothesis, changes in brain activity in male marmosets will be visualized with fMRI during exposure to odors of receptive females. During brain imaging, animals will be treated with dopamine receptor agonists and antagonists to examine the central effects of drug intervention on sexual motivation. Using fMRI on conscious marmosets, it will be possible to study the Neurobiology of affiliation, fear, and aggression triggered by relevant sensory cues and how experience can alter brain activity. Indeed, the long-term goal of this research is to understand the central mechanisms that regulate both sexual aggressive motivation. Throughout the animal kingdom there are many examples of heightened male sexual motivation rapidly reverting to intense aggressive behavior during competition for a receptive female. These studies on sexual motivation may help to identify neuroanatomical substrates and neurochemical signal that contribute at a common neural network regulating both sexuality and aggression.
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