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. 2020 Jul 20;9(7):175. doi: 10.3390/biology9070175

Figure 4.

Figure 4

Hippocampal-dependent memory tasks. (A) On top, open field habituation test. Mice underwent a training session by being exposed to an open field. 24 h later, and 1 h after icv. administration, animals were re-exposed to the open field (habituation session). On each session, mice freely explored the environment for 15 min. Movements in the X, Y, and Z axis were detected with an infrared system. Below, total activity (movements in the XYZ axis), horizontal activity (XY axis), and vertical activity (Z axis) during training and habituation sessions (mean ± SEM) are represented. *** p < 0.001. Asterisks indicate differences between training and habituation sessions within each experimental group. ‡‡ p < 0.01, ‡‡‡ p < 0.001. Crosses reflect differences between Aβ and vehicle (control animals) in habituation. Note that exploratory activity decreases in the vehicle group during the habituation session compared to the training session, but also compared to the Aβ group during the habituation session. (B) On top, novel object recognition task. Three 5-min habituation trials were performed on Day 1. On Day 2, a 10 min training session with two identical objects occurred. A test session (NOR1) was performed 3 h later for evaluation of short-term memory, substituting one familiar object for a novel one. On days 3 and 4, NOR2 and NOR3 trials were performed to evaluate long-term memory. Icv. injections took place one hour before NOR2 trial. Below, discrimination index (defined as the difference in exploration time between the two objects divided by the total time spent exploring both objects) for each experimental group during trials. After icv. injections, only vehicle-injected mice showed positive discrimination toward the novel object. * p < 0.05, *** p < 0.001. Tr., training; Hab., habituation. (C) On top, Rotarod performance test. 1 h after icv. injections, animals performed a single session consisting of six trials. Mean latency to fall off the rod was calculated for each trial (bottom left graph) and the whole session (bottom bar plot). (D) Locomotion test. 1 h after icv. administration, mice freely explored an empty chamber for 15 min. Mean travelled distance was recorded by a LABORAS® system. Right, representative movement tracking of animals from both experimental groups. No differences were found between treatments in C or D.