Collectively, these experiments have led us to conclude that the NMDA receptor is critical for learning/consolidation, but not essential for pattern completion during associative memory recall.
Thus, our genetic analyses suggest that the NMDA receptor is not required for pattern completion during associative memory recall.
Therefore, our results reveal that a delicate control of the brain's dopamine level is critical for pattern completion during associative memory recall.
In conclusion, our study suggests that a delicate balance in dopamine levels is crucial for pattern completion during associative spatial memory recall.
To determine whether the delicate balance of dopamine is essential for pattern completion under partial cue conditions, we conducted the second probe test (P2) the next day by removing three of the four distal cues (day 12).
To determine whether the forebrain NMDA receptor is necessary for pattern completion under the partial cue condition, the next day we conducted the second probe test (P2) in which three of the four distal cues were removed.
In other words, due to distinct circuitry properties in memory processes, CA1 NMDA receptor is mostly involved in learning and consolidation, whereas, CA3 may be preferential for pattern completion during recall.
Although it can be argued that 90% of NR1 knockout in CA3 cells of the forebrain knockout mice may still leave residual amount of cells for pattern completion during recall, the systemic blockade of NMDA receptor function by CPP also did not affect partial cue-initiated pattern completion.
Since the NMDA receptor channel has a longer opening-duration, it has been speculated by computational biologists that the NMDA receptor might be a candidate molecule for initiating pattern completion within the auto-associative memory network during memory retrieval.
In conclusion, our present experiments from both inducible knockout mice and pharmacological experiments demonstrate that the NMDA receptor in the cortex and hippocampus is not necessary for the pattern completion during associative memory recall in the spatial water maze task.
