that are interconnected via gap junctions. This network allows for electrical conduction, which is considerably faster than the chemical conduction of signals between synapses, though less spatially precise. Neural composition The VTA, like the substantia nigra, is populated with melanin-pigmented dopaminergic neurons. Recent studies have suggested that dopaminergic neurons comprise 50-60% of all neurons in the VTA, which is contrary to previous evidence that noted 77% of neurons within the VTA to be dopaminergic. In addition, there is a sizable population of GABAergic neurons in the rostromedial tegmental nucleus (RMTg), a functionally distinct brain structure. These GABAergic neurons regulate the firing of their dopaminergic counterparts that send projections throughout the brain to, but not limited to, the following regions: the prefrontal cortex, the nucleus accumbens, and the locus coeruleus. The VTA also contains a small percentage of excitatory glutamatergic neurons. Limbic loop The “limbic loop” is very similar to the direct pathway motor loop of the basal ganglia. In both systems, there are major excitatory inputs from the cortex to the striatum (accumbens nucleus), the midbrain projects neuromodulatory dopamine neurons to the striatum, the striatum makes internuclear connections to the pallidum, and the pallidum has outputs to the thalamus, which projects to the cortex, thus completing the loop. The limbic loop is distinguished from the motor loop by the source and nature of the cortical input, the division of the striatum and pallidum that process the input, the source of the dopaminergic neurons from the midbrain, and the thalamic target of the pallidal output. The limbic loop controls cognitive and affective functioning and the motor loop controls movement. CA3 loop Linking context to reward is important for reward seeking. In 2011, a group of researchers documented a CA3-VTA connection that uses the lateral septum as an intermediary. They used a pseudo-rabies virus (PRV) as a transsynaptic tracer, and injected it into the VTA. They found that unilateral injection into the VTA resulted in bilateral PRV labeling in CA3 beginning 48 hours after injection. Lesions of the caudodorsal lateral septum (cd-LS) before VTA PRV injection resulted in significantly less PRV labeled neurons in CA3. Theta wave stimulation of CA3 resulted in increased firing rates for dopamine cells in the VTA, and decreased firing rates for GABA neurons in the VTA. The identity of VTA neurons was confirmed by neurobiotin™ labeling of the recording neuron, and then histological staining for tyrosine hydroxylase