Figure 1.
The ventral hippocampus (vHipp) regulates VTA dopamine neuron activity via a polysynaptic pathway. Glutamatergic inputs from the vHipp synapse onto GABAergic medium spiny neurons (msn) in the nucleus accumbens (NAc). The msn’s, in turn, provide an inhibitory input to the ventral pallidum (VP). Under resting conditions, the VP is tonically active and results in the hyperpolarization of a subset of dopamine neurons in the VTA. Thus, increases in vHipp activity result in the disinhibition of dopamine neuron activity, expressed as an increase in the proportion of DA neurons firing spontaneously and therefore capable of being phasically activated by appropriate stimuli.