The scope of research focused on studying social memory and identity recognition in mice. The behavioral task we developed allowed us to understand how mice can recognize different individuals and associate them with different emotional valences. This protocol will be helpful for understanding social memory and study social impairments in some psychiatric disorders.
Most rodent study relies on social novelty task, but these fail to assess recognition between familiar individuals. Our valence-based tasks demonstrate that mice can recognize different conspecific with different emotional association. This paradigm provides valuable tools for studying social impairments in disorders like autism spectrum disorders and schizophrenia.
Our findings raise questions about brain mechanisms underlying identity recognition. These task enables studying identity recognition in healthy mice and mouse models of autism and schizophrenia. Additionally, they reveal how social valence, whether it's positive or negative, influences this process.
They use aversive and appetitive stimuli to examine how social interaction shapes identity recognition. To begin place an empty plexiglass enclosure with a non-conductive floor at the center to prepare the shock box. Then position the subject mouse in the corner of the shock box and allow it to freely explore for five minutes for shock box habitation.
To create a neutral context environment, place a white paper unique to each subject mouse on the floor of the rectangular transparent box. After one hour of shock box habitation, place the mouse on the paper for the habitation in the neutral context. Next, set the current to 0.3 milliamperes to prepare the shock box for negative valence training.
Place the negatively valenced social target in the plexiglass enclosure with a non-conductive bottom at the center of the shock box. Start video recording and place the subject mouse in the corner of the shock box. Then start the timer, and at 4 and 4.5 minutes deliver a one second long electric shock.
Next place the neutral social target in the plexiglass enclosure with a non-conductive bottom at the center of the neutral context. Start video recording and place the subject mouse in a corner of the neutral context. Start the timer and allow the subject mouse to freely explore.
After five minutes, remove the subject mouse and stop the recording and timer. For positive social valence, after sucrose food pellet habituation, place an empty plexiglass enclosure in the corner of the context to prepare the positive valence context. Place the subject mouse in a corner of the positive valence context and allow it to freely explore for 10 minutes.
After one hour, repeat the context habituation procedure in the neutral context in a rectangular transparent box. For positive valence training, place the positively valenced social target in the enclosure at the center of the positive valence context. Start video recording and place the subject mouse in a corner of the positive valence context.
Upon each interaction bout with the social target lasting longer than two seconds, deliver one sucrose food pellet using the food port. Define interaction as periods where the subject mouse's nose is less than two centimeters away from the periphery of the plexiglass enclosure with the head angle directed towards the enclosure. After 10 minutes, remove the mouse and stop the recording and timer.
For neutral training, place the neutral social target in the enclosure at a corner of the neutral context. Start video recording and place the subject mouse in a corner of the neutral context. Remove the subject mouse at 10 minutes and stop the recording and timer.
To test social discrimination, in session one place two empty wire cups in the opposite corners of the left and right chambers of the three-chamber social discrimination box. Start video recording. Place the subject mouse in the center of the middle chamber and start the timer.
After eight minutes, return to the testing room and, without touching the subject mouse, use the chamber doors to enclose the subject in the middle chamber. Replace the empty wire cups with an identical but different set of cups containing the social targets. Remove the chamber doors and start the timer as the subject mouse explores in session two.
After eight minutes, stop the recording and return the subject mouse and social targets to their respective home cages. For behavioral studies, analyze the interaction time with each social target and score the number of interaction bouts. Measure the amount of time the subject mouse investigates each cup during the uninterrupted eight minute test starting once the experimenter leaves the room.
Most mice consumed all sucrose food pellets by the last day of habitation compared to the initial day. Trained mice showed a preference for interacting with the positive valence-associated mouse over the neutral mouse during the social discrimination task. The intercession ratio of session two versus session one interaction time revealed a preference for the positive valence-associated mouse.
Subject mice reduced interaction time with the negative valence-associated mouse compared to the neutral mouse during the social discrimination test. The intercession ratio of session two versus session one interaction time revealed a preference for the neutral mouse over the negative valence-associated mouse.
