Mental disorders with adolescent onset, such as schizophrenia, are theorized to be a consequence of the abnormal maturation of brain circuits implicated in learning and memory. To understand how developing brain circuits become pathological, it is important to investigate how these neural circuits mature to support behaviour. This study investigated the behavioural expression of object recognition (OR) and temporal order recognition (TOR) memory in C57BLK/6J x 129S1/SvImJ mice and identified the age at which they expressed TOR memory. We found that: 1) C57BLK/6J x 129S1/SvImJ mice had an innate preference toward select objects; 2) they only expressed OR memory during the first 20 seconds of object exploration and required a long-term, 24-hour consolidation period; and 3) C57BLK/6J x 129S1/SvImJ mice are able to express TOR at postnatal day (PD) 32 but not at PD14, PD16 or PD23. These data suggest that TOR memory, which is known to depend on the medial prefrontal cortex (mPFC), features a late onset consistent with the delay in the maturation of the mPFC. Additionally, this indicates that behaviours such as TOR have a later onset than more survival-critical behaviours such as fear learning.
Written By Arely Cruz-Sanchez & Maithe Arruda-Carvalho
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