Gray distinguishes 3 Emotional subsystems: Conditioned appetive stimuli (Dopaminergic pathways), Unconditioned aversive stimuli (Central Gray), conditioned aversive stimuli (Septo-Hippocampal system) (Gray 1982, Gray 1991).
The subiculum acts as a comparator between the state of the world (through its connection with the Entorhinal Cortex) and Expectations (through its connections with the prefrontal cortex and Papez circuit).
Gray's circuit: The subiculum is a comparator between predictions (Papez) and real senses (EC). Dashed line: The hippocampal formation. Adapted from (Gray 1984).