Long-term memory formation of object in context task requires dorsal hippocampus and medial prefrontal cortex activity and it is interfered by another object in context experience.

VILLAR, MARÍA EUGENIA; MARTÍNEZ, MARÍA CECILIA; BALLARINI, FABRICIO; VIOLA, HAYDÉE

Congreso; 9th FENS Forum of Neuroscience; 2014

With the aim of analyzing if recognition long-term memory (LTM) formation is susceptible to retrograde interference (RI), we trained rats to learn two different trail associations between objects and their respective arena boxes. Separate groups of subjects were tested in these contexts in order to evaluate the LTM for each associate pair (object-context). Furthermore, given the involvement of hippocampus (Hp) and medial prefrontal cortex (mPFC) in several recognition memories, we also analyzed the participation of these structures in the LTM formation of the object-in-context task by the local infusion of muscimol. Our results show that object in context LTM formation is sensitive to interference by a different and subsequent object-context pair association experienced 1h later. This interference occurs in a restricted temporal window and works on the LTM consolidation phase, leaving intact STM expression. Such RI depends on the presentation of another object in context experience, regardless of whether they are familiar or novel. Moreover, this interpolated trail disrupted specifically the consolidation of the object-in-context memory and did not affect the object recognition memory formation. In addition, we show that the inactivation of the CA1 dorsal hippocampal or mPFC regions, previous to the second trail session, impaired the LTM formation for this trail pair association while restoring the first pair LTM expression. In conclusion these results suggest that object-in-context LTM formation is susceptible to RI by another object-in-context experience and it requires dorsal Hp and mPFC activity.