Prefrontal cortical-hippocampal-amygdala functional loop in memory formation

The involvement of the prefrontal cortex, the hippocampus and the amygdala in learning and memory processes has been studied over the past ۳۰ years. However, the neurotransmitter mechanisms underlying functional interactions among these brain sites in memory formation are not fully understood. Our studies using animal models suggest that the direct and indirect pathways among the prefrontal cortex, the hippocampus and the amygdala, which form a functionally important loop, may be critically involved in cognitive functions. It seems that the loop activation occurs when the hippocampus encrypts new information to store as long-term memory. The hippocampal projections to the PFC and the amygdala can change their activities to generate synaptic longterm potentiation or depression which is necessary for memory formation. The hippocampus is functionally divided into the dorsal part which is necessary for memory formation and the ventral part which is associated with both memory and emotional behaviors. The prefrontal cortex (PFC) as an important component in the central nervous system plays a key role in long-term and short-term memory. The amygdala connects with the PFC and the hippocampus through the efferent and afferent projections to create long-term emotional memory. The dysregulation of the PFC/hippocampal/amygdala neurotransmission may be a major reason for the memory loss. We found that there is an association between memory formation or impairment with the changes of BDNF/cFOS/CAMKII/CREB signaling pathways in the PFC, the hippocampus and the amygdala. Moreover, the different neurotransmitter systems including glutamatergic, GABAergic, dopaminergic and endocannabinoid systems in these brain areas have critically been involved in the reward-related memory.Taken to gather, these findings support the existence of a functional loop among the PFC, the hippocampus and the amygdala during processing learning and memory.

کلیدواژه ها:

Learning and memory ، Neurotransmission ، Signaling pathways ، Animal models