The basolateral amygdala, rostral anterior cingulate cortex and hippocampus: Interactions and differential involvement in memory consolidation for distinct components of a task

The basolateral amygdala (BLA) is involved in memory consolidation for many emotionally arousing tasks, such as inhibitory avoidance (IA), contextual fear conditioning and spatial water maze. Extensive evidence indicates that the BLA modulates memory consolidation via interactions with other brain regions, including the hippocampus and cortical regions. The anterior cingulate cortex (ACC) is similarly involved in memory for aversive tasks and is directly connected with the BLA. Recent evidence suggests that the ACC is composed of two functionally distinct regions, of which the rostral ACC (rACC) may be selectively involved in memory for training that involves nociceptive stimulation. Conversely, the hippocampus appears to be specifically involved in learning about contextual cues. The experiments in the current dissertation investigated the involvement of two regions of ACC in IA memory consolidation as well as the interaction between the BLA and rACC. In addition, the present dissertation examined the relative contributions of the hippocampus, rACC and BLA in memory consolidation of the context and footshock components of IA training. Chapter 1 provides a brief background for the dissertation, and describes the role of BLA, rACC and hippocampus in memory. Chapter 2 presents the findings regarding the dissociation of the rACC and cACC, as well as the interaction between the rACC and BLA during IA memory consolidation. OXO infusions into the rACC, but not cACC, enhanced retention for IA training. Furthermore, lesions of either the BLA or rACC blocked the memory enhancing effect of drug infusions into the other region, indicating that the BLA and rACC interact during IA memory consolidation. Chapter 3 presents the findings regarding the differential involvement of the hippocampus, rACC and BLA in memory consolidation for the context and the footshock training of IA. OXO infusions into the hippocampus enhanced retention when given after context, but not footshock, training and OXO infusions into the rACC enhanced retention when given after footshock, but not context, training of IA. Moreover, infusions of OXO into the BLA enhanced retention when given after either context or footshock training of IA. Chapter 4 discusses the findings and addresses unanswered questions.