Memory reorganization in the ACC and thalamus

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Memory has been the focus of a lot of research in the last century, but much is still not understood. Scientists have found that memories are stabilized over time through a process called consolidation. Two types of consolidation have been proposed to exist. The first type, cellular consolidation, occurs over minutes to hours and is thought to involve rewiring the connections between nerve cells. The second type, systems consolidation, involves additional changes at the global level of brain structures over a much longer time frame. As such, memories that are initially dependent on a brain structure called the hippocampus become dependent on other structures over time. For over a century, scientists believed that consolidated memories were permanently stabilized, implying that memories were consolidated at both levels only once. However, recent findings have shown that a consolidated memory can return to an unstable state when it when it is remembered. In this state, the memory can be altered, erased or restabilized through a process called reconsolidation. This phenomenon can also take place at the systems level (systems reconsolidation), when a memory no longer depends on the hippocampus. These findings of cellular and systems reconsolidation have thus challenged the standard view of consolidation. Recently, a number of studies have shown that specific regions in what is called the medial prefrontal cortex (mPFC), such as the anterior cingulate cortex (ACC), mediate retrieval of remote memories. Furthermore, the intralaminar thalamic nuclei (ILN), a group of nuclei in another brain structure called the thalamus, have also recently been shown to be involved in systems consolidation. However, the roles of the ACC and the ILN in cellular and systems reconsolidation have not yet been investigated. This proposal will therefore combine behavioral and molecular studies to test whether the ACC and ILN undergo cellular and systems reconsolidation. This would provide a better understanding of these processes, as well as knowledge on how these brain structures function together on a regular basis.