pedunculopontine tegmental nucleus (PPTg) and the laterodorsal tegmental nucleus demonstrate that these circuits reinforce the discharge properties of VTA neurons, suggesting a modulatory influence on reward circuits. Outputs The two primary efferent fiber projections of the VTA are the mesocortical and the mesolimbic pathways, which correspond to the prefrontal cortex and nucleus accumbens respectively. In addition, experiments in rodents have identified a mesohabenular pathway consisting of VTA neurons that do not release dopamine, but glutamate and GABA. Other VTA projections, which utilize dopamine as their primary neurotransmitter, are listed below. Ventral tegmental area (VTA) projections VTA → Amygdala VTA → Entorhinal cortex VTA → Cingulate gyrus VTA → Hippocampus VTA → Nucleus accumbens VTA → Olfactory bulb VTA → Prefrontal cortex Development Because they develop from common embryonic tissue and partly overlap in their projection fields, Dopaminergic cell groups lack clear anatomical boundaries. During the development of the mammalian brain, both substantia nigra (SN) and VTA neurons initially project to the dorsolateral and ventromedial striatum. However, at birth the SN dopaminergic neurons project exclusively into the dorsolateral striatum, and the VTA dopaminergic neurons project solely into the ventromedial striatum. This pruning of connections occurs through the elimination of the unnecessary collaterals. Function As stated above, the VTA, in particular the VTA dopamine neurons, serve several functions in the reward system, motivation, cognition, and drug addiction, and may be the focus of several psychiatric disorders. The VTA has also been shown to process various types of emotion output from the amygdala, where it may also play a role in avoidance and fear-conditioning. Electrophysiological recordings have demonstrated that VTA neurons respond to novel stimuli, unexpected rewards, and reward-predictive sensory cues. The firing pattern of these cells is consistent with the encoding of a reward expectancy error. In 2006, MRI studies by Helen Fisher and her research team found and documented various emotional states relating to intense love correlated with activity in the VTA, which may help explain obsessive behaviors of rejected partners, since this is shared by the reward system. Nest sharing behavior is associated with increased V1aR expression in the VTA of newly paired zebra finches. However, V1aR expression was not related to female directed song rates, which may indicate a selective role of vasotocin in the VTA on pair maintenance versus courtship behavior. Presence of gap junctions The VTA has been shown to have a large network of GABAergic neurons