Memory Reconsolidation and Extinction Have Distinct Temporal and Biochemical Signatures

Mappe: Boundaties/2004 a

Akinobu Suzuki, 1 Sheena A. Josselyn, 3,4Paul W. Frankland,3,4 Shoichi Masushige,1,2 Alcino J. Silva, 4 and Satoshi Kid


Reonsolidation and extinction, two opposing processes triggered by memory retrieval, have distinct biochemical signatures: cannabinoid receptor 1 or L-type voltage-gated calcium channels blocks extinction but not reconsolidation. These studies demonstrate the dynamic nature of memory processing after retrieval and represent a first step toward a molecular dissection of underlying

Experimental extinction does not reflect forgetting of the original memory trace but rather reflects new learning.

Memory retrieval may initiate two potentially dissociable but opposite processes: reconsolidation and extinction. Re-consolidation acts to stabilize, whereas extinction tends to weaken, the expression of the original memory. The duration of a reminder event may be an important determinant of subsequent memory processing: brief reminders lead to reconsolidation, whereas longer reminders result in memory extinction (Debiec et al., 2002; Eisenberg et al., 2003; Pedreira and Maldonado, 2003).

There has been renewed interest in memory processing after retrieval: brief exposure to the CS seems to trigger a second wave of memory consolidation (reconsolidation), whereas prolonged exposure to the CS leads to the formation of a new memory that competes with the original memory (extinction)

We provided a systematic demonstration of how reexposure duration, the age of the memory, and the strength of the memory interact to influence behavior in tasks that model declarative memory.

The results presented here reveal three distinct timedependent phases of memory processing after memory retrieval. 

During the first phase, the retrieved memory is in a state that precedes both the reconsolidation and extinction processes. Further extending reexposure, however, initiates the protein synthesis-dependent reconsolidation processes required for the stability of the memory trace. Hence, blocking protein synthesis during this second phase compromises the long-term stability of the trace. Finally, prolonged reexposures to the CS in the absence of the US trigger the formation of a new memory trace that encodes the dissociation between the CS and the US (CS–no US; extinction memory), therefore competing with the original memory (CS–US). Inhibition of protein synthesis at this stage blocks the formation of this new extinction memory, leaving expression of the original memory unchanged. It is important to note that our results also indicate that there is an interaction between the extinction and reconsolidation processes: although blocking protein synthesis during short reexposures (reconsolidation) disrupts the original memory, blocking protein synthesis during prolonged reexposure, conditions in which both reconsolidation and extinction would be expected to be initiated, leaves the original memory unaffected.

Extinction during reconsolidation of threat memory diminishes prefrontal cortex involvement

Mappe: Authors/D.Schiller/ 2013 a

Daniela Schiller a,1 , Jonathan W. Kanen b , Joseph E. LeDoux c,d,1 , Marie-H. Monfils e , and Elizabeth A. Phelps

Controlling learned defensive responses through extinction does not alter the threat memory itself, but rather regulates its expression via inhibitory influence of the prefrontal cortex (PFC) over amygdala. Individual differences in amygdala–PFC circuitry function have been linked to trait anxiety and posttraumatic stress disorder. This finding suggests that exposure-based techniques may actually be least effective in those who suffer from anxiety disorders. A theoretical advantage of techniques influencing reconsolidation of threat memories is that the threat representation is altered, potentially diminishing reliance on this PFC circuitry, resulting in a more persistent reduction of defensive reactions. We hypothesized that timing extinction to coincide with threat memory reconsolidation would prevent the return of defensive reactions and diminish PFC involvement. Two conditioned stimuli (CS) were paired with shock and the third was not. A day later, one stimulus (reminded CS+) but not the other (nonreminded CS+) was presented 10 min before extinction to reactivate the threat memory, followed by extinction training for all CSs. The recovery of the threat memory was tested 24 h later. Extinction of the non-reminded CS+ (i.e., standard extinction) engaged the PFC, as previously shown, but extinction of the reminded CS+ (i.e., extinction during reconsolidation) did not. Moreover, only the nonreminded CS+ memory recovered on day 3. These results suggest that extinction during reconsolidation prevents the return of defensive reactions and diminishes PFC involvement. Reducing the necessity of the PFC–amygdala circuitry to control defensive reactions may help overcome a primary obstacle in the long-term efficacy of current treatments for anxiety disorders.