Time Units for Learning and their Implementation Through Neuronal Assemblies

In learning, repeated experiences might be integrated individually as they occur, or they might be combined within dedicated time windows, possibly promoting quality control. I will discuss recent findings from our laboratory providing evidence that in Pavlovian, incremental, and incidental learning, related information acquired within time windows of 5 hours (time units for learning) is combined to determine whether and what mice learn. Trials required for learning have to occur within 5 hours, when learning-related shared partial cues can produce association and interference with learning. Upon acquisition, cFos expression is elevated during 5 hours throughout specific system-wide neuronal assemblies. Time unit function depends on network activity and local cFos activity, which is required for distant assembly recruitment through network activity and distant BDNF. Activation of learning-related cFos assemblies is sufficient and necessary for time unit function. Therefore, learning processes consist of dedicated 5-hour time units, involving maintenance of specific system-wide neuronal assemblies through network activity and cFos expression.