Cognition

 Mice are usually placed fairly high on the scale of animal intelligence due to their problem-solving abilities. They are complex social creatures with highly-developed learning skills that make them stand out among others as inquisitive and easily-trained beings. For example, primates are tested on their ability to use tools, unlike mice, whose physiognomy prevents them from using that very same principal. Testing mouse intelligence will usually include factors such as the time it takes for them to respond to classical and operant conditioning, and how they respond to increasingly complex test patterns.

Due to human Interference, mice may become even smarter than they are naturally.  For instance; ncs-1 mutant mice can complete the spacial object recognition test much faster than control animals, accompanied with increased curiosity (Saab et al. 2009).

 

Morris Water Maze

 

Procedure

On the first day, each mouse is given four visible platform trials (V) in the Morris water maze. Mice are then subjected to 5 days (max) of four training trials per day with the platform being submerged in the same position (hidden phase).

Following the last day of training, the platform can be moved to a different position, and the mice subjected to 4 more days of four training trials per day (reversal phase).

A probe trial is administered 20 minutes after the last trial on the fifth day of the hidden phase and/or the fourth day of the reversal phase. Each subject is placed into the water diagonally opposite from the target quadrant (T) and allowed 60 seconds to search the water, from which the platform had been removed. Behavioural variables are quantified with the aid of HVS Water 2020 software.

 

Equipment

Figure 1.Morris Water Maze

 

Object Recognition

 

Procedure

This test consists of 4 different sessions, with inter-trial intervals of 2-3 minutes, during which mice are returned to their home cage.

During the first (open field) session, each mouse is placed into the center of an empty, brightly lit open field for 5 minutes and the baseline levels of locomotion and other behavioural parameters are recorded (latency to escape the center; time of freezing (remaining in one place with only slight movement of the head); time of self-grooming; number of risk assessments (behaviour involving the mouse stretching its body from the corners/wall towards the center).

During the habituation session, four identical objects are presented in the open field. Explorations of these four objects in the open field are measured for 15 minutes (later analyzed as three separate 5 minute time bins).

For the spatial object recognition session, all four objects initially placed in a square arrangement, are reconfigured into a polygon-shaped pattern that is achieved by moving two objects into a new location (displaced objects; DOs). The remaining two objects are left in the same location (non-displaced objects; NDO). The time spent exploring both DOs and NDOs is recorded during a 5 minute session and later expressed as a percentage of the total time of objects investigated.

For the novel object recognition session, one of two familiar NDOs, is replaced with a new object (NO) and left at the same location. The time spent examining this NO and familiar objects (FO) is recorded for 5 minutes and is then expressed as a percentage of the total time of objects investigated.

 

Equipment

 

  Y Maze

 

Procedure

Starting arms are alternated among mice from the same group. Once a mouse is lowered into one of three available arms (A,B, or C), video tracking is initiated. Following a 5 minute period, the mouse is returned back to its home cage. Latency to leave the starting arm, sequence or arms visitations, and number of arm entries are analyzed by Ethovision software (Noldus).

This is a simple procedure used to evaluate spatial working memory.

 

Equipment

T Maze

 

Procedure

1. Forced-alternation training. Following an adaptation period, mice are exposed to the T-maze for three days of ten forced-alternation runs, during which one goal arm is closed off and the mouse has up to 2 minutes to run and eat the bait in the open arm. After consuming some bait, the mouse is removed from the maze and, after a 10 second delay, placed back into the T-maze with access only to the arm that it had not visited previously.

2. Discrete paired-trial delayed alternation training. Each discrete trial consists of a forced run ("example") and free choice run ("test") pair. For the "example", the mouse is restricted to entering a randomly chosen arm. After consuming some bait, and a 10 second delay interval, the mouse is placed back into the T-maze with access to both arms, but only the arm not visited in the previous forced run is baited. After a 40 second inter-trial interval, the mouse is placed back into the maze for another "example"-"test" pair. A randomly chosen pattern of forced runs is used every day with an equal number of left and right open arms. Mice are trained with a 10 second intra-trial interval until they met the criterion of at least 70% correct choices on three consecutive days.

3. Testing. When a mouse meets the correct choice criterion, testing with 5, 15 and 30 second delay intervals begins the following day. Mice are given four trials of each delay on three days of testing for a total of twelve trials for each delay. Data are analyzed by one-way ANOVA with genotype as a between-subject factor and delay interval (or performance on each day) as a repeated measure factor).

 

 

  
  
    
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