Spatial discrimination learning induces LTP-like changes in the lateral septum of mice.

The efficacy of synaptic transmission from the fimbria to the lateral septum (LS) of freely moving mice was monitored electrophysiologically over 9 days of training in a spatial discrimination task (radial maze). Electrical stimulation of the fimbria evoked two negative waves (N2 and N3) in the ipsilateral LS. Compared to a control group exposed to muscular effort (treadmill), trained animals displayed a significant and progressive increase in the amplitude of N3 with no changes in N2. Moreover, this increase was of greater magnitude in fast learners than in slow learners and persisted for at least 24 h following the last (9th) training session. These changes might play a role in spatial learning through the regulation of septohippocampal cholinergic activity.