Temporal Order Recognition

The temporal order recognition (TOR) test assesses recency discrimination, the ability to distinguish which of two previously encountered objects was experienced more recently. Subjects undergo two sample phases separated by a delay, each presenting a distinct pair of identical objects. During the test phase, one object from each sample phase is presented, and intact animals preferentially explore the object from the earlier sample phase. This form of temporal order memory critically depends on medial prefrontal cortex (mPFC) projections to the perirhinal cortex, distinguishing it from standard NOR which is mPFC-independent.

The recency discrimination ratio is calculated as (time exploring the object from Sample 1 minus time exploring the object from Sample 2) divided by total exploration time. A positive ratio indicates the subject recognizes the Sample 1 object as less recently encountered and thus more novel in terms of temporal context. The paradigm dissociates temporal from spatial and object identity memory components. Equal total exploration across groups is verified to ensure that differences in recency ratio are not confounded by motivational or motor deficits.

ConductMaze manages the multi-phase trial structure with automated inter-phase timing and object zone definitions for each session. The software tracks nose-point proximity to each object independently across all three phases, generating sample-phase exploration profiles that confirm adequate encoding. Recency discrimination ratios, exploration time courses, and zone transition matrices are computed automatically. The platform supports counterbalanced object assignment to eliminate object-specific biases.