Table 1.
Sequences of object presentation used for three different types of object recognition memory study and an object recency study.
| Standard running recognition protocol | |||||||||||||
| Trial | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
| – | A | B | C | D | E | F | G | H | I | J | K | L | |
| A | B | C | D | E | F | G | H | I | J | K | L | M | |
| Object recognition protocol with short variable delay | |||||||||||||
| Trial | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
| – | A | B | C | D | E | F | E | E | D | C | B | A | |
| A | B | C | D | E | F | G | H | I | J | K | L | M | |
| Object recognition protocol with long variable delay | |||||||||||||
| Trial | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | ||
| – | A | B | C | D | E | Variable | A | B | C | D | E | ||
| A | B | C | D | E | F | Delay | G | H | I | J | K | ||
| Recency protocol | |||||||||||||
| Trial | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | ||
| – | A | B | C | Delay | – | E | F | G | Delay | E | F | G | |
| A | B | C | D | E | F | G | H | A | B | C | |||
Every trial consists of one novel object and one familiar object, each depicted by a letter, with the exception of Trial 0, which allows the initial object to become familiar. Novel objects are indicated in bold type. The length of time between initial exposure to an object and its subsequent use as a “familiar” object varied with the conditions. For the standard running recognition, each trial is 1 min. The delay to discrimination can be increased to several minutes using the short variable delay protocol or a long delay can be interposed between trials by removing the animal from the apparatus (long variable delay protocol). The recency protocol consists of two blocks of sample stimuli; the animal is removed from the apparatus after these blocks followed by a test phase in which an object from the first block is always paired with an object from the second block. Normal rats prefer to explore the item from further back in time.
Adapted from [69].