Figure 8. High light conditions during acquisition are required for the formation of long-term memory.

Schematics depict experimental procedure; dark grey arenas denote low light (3 lux) conditions and white arenas denote high light (21 lux) conditions. Bar graphs show exploration time (as a percent of the total) for each object (mean ± SEM; n = 14 (A) or n = 17 (B); * p < 0.05). Total exploration time for each trial is indicated below the graphs. Scatter dot plots show individual discrimination ratios (open circles) and the group mean (horizontal line); positive values (>0) reflect a preference for the left-side object (familiarization trial) or the novel object (test trial). (A) Long-term memory was assessed using a 24-hour delay between the familiarization trial, conducted in low light, and the test trial, conducted in high light (A₁). There was no preference for object location (left or right side) during the familiarization trial (A₂). Further, mice failed to exhibit a significant preference for the novel object during the test trial 24 hours later (A₃), indicating an impairment of long-term memory for the familiar object. (B) Long-term memory was also assessed in a second group of mice with a 24-hour delay, except that the familiarization trial was conducted in high light while the test trial was conducted in low light (B₁). Again, there was no preference for object location (left or right side) during the familiarization trial (B₂). However, during the test trial 24 hours later, mice exhibited a preference for the novel object (B₃), indicative of the formation of long-term memory for the familiar object.