**3.6 Novel object recognition test**

The current studies investigated attention/memory for novel object recognition, according to Ennaceur and Delacour [1988] and Bartolini and coll. [1996]. Rats, placed in a white arena (70 X 60 X 30 cm) were trained to discriminate objects of different shapes (cubes, pyramids and cylinders). The day before testing, animals were placed in the arena and allowed to explore for 2min. The day after, rats were tested on a task involving two exploratory trials for 5 min with a 60-min delay between each sessions. In the first trial (T1) two identical objects were presented in two opposite corners of the arena and rats were left there until criterion was reached. Exploration was defined as directing the nose at a distance < 2cm to the object and/or touching it with the nose. Following, the second exploratory trial (T2) was conducted where the rat was presented with one object from the first exploratory trial and one novel object (Fig. 4). The time spent exploring the familiar (F) and the novel object (N) was recorded separately and the difference between the two exploration times was taken as the discrimination index (DI, a measure of novelty preference).

Fig. 4. Novel Object Recognition Test. A. Trial 1; B. Trial 2 (see text for details).

Intact rats, as well as sham-operated, were able to discriminate between the familial and novel object (DI = 0.33 and 0.29 respectively). In NBM-lesioned animals, values of DI were significantly lower than those in intact rats (DI = 0.07; p<0.001 vs intact and sham). Administration of our compounds, as well as cholinergic drugs, established discrimination in lesioned animals again, and they displayed a larger DI when compared with NBMlesioned and saline-treated group. EEG activity in neocortex and hippocampus correlated directly with DI. Ability in novel object discrimination was evaluated as large DI, decreased theta power in neocortex and increased theta oscillation in hippocampus.

Results from the exploratory trials showed a significant impairment in exploration and discrimination in novel object in NBM-lesioned animals when compared with sham and intact group (Fig. 5). The test demonstrated that NBM-lesioned rats spent significantly less time exploring the novel object compared to familial object, indicating that lesioned rats showed disturbed attention and memory. However, NBM-lesioned rats showed no preference for novel object and spent a relatively equal amount of time exploring novel and familial objects. The results suggest that changes in attention and recent memory declines were a result of NBM-related neuronal loss and disruption in cholinergic central neurotransmission in the rodent brain. The findings also may reflect differences in 12 Advances in Object Recognition Systems

The current studies investigated attention/memory for novel object recognition, according to Ennaceur and Delacour [1988] and Bartolini and coll. [1996]. Rats, placed in a white arena (70 X 60 X 30 cm) were trained to discriminate objects of different shapes (cubes, pyramids and cylinders). The day before testing, animals were placed in the arena and allowed to explore for 2min. The day after, rats were tested on a task involving two exploratory trials for 5 min with a 60-min delay between each sessions. In the first trial (T1) two identical objects were presented in two opposite corners of the arena and rats were left there until criterion was reached. Exploration was defined as directing the nose at a distance < 2cm to the object and/or touching it with the nose. Following, the second exploratory trial (T2) was conducted where the rat was presented with one object from the first exploratory trial and one novel object (Fig. 4). The time spent exploring the familiar (F) and the novel object (N) was recorded separately and the difference between the two exploration times was taken as

**3.6 Novel object recognition test** 

the discrimination index (DI, a measure of novelty preference).

Fig. 4. Novel Object Recognition Test. A. Trial 1; B. Trial 2 (see text for details).

theta power in neocortex and increased theta oscillation in hippocampus.

Intact rats, as well as sham-operated, were able to discriminate between the familial and novel object (DI = 0.33 and 0.29 respectively). In NBM-lesioned animals, values of DI were significantly lower than those in intact rats (DI = 0.07; p<0.001 vs intact and sham). Administration of our compounds, as well as cholinergic drugs, established discrimination in lesioned animals again, and they displayed a larger DI when compared with NBMlesioned and saline-treated group. EEG activity in neocortex and hippocampus correlated directly with DI. Ability in novel object discrimination was evaluated as large DI, decreased

Results from the exploratory trials showed a significant impairment in exploration and discrimination in novel object in NBM-lesioned animals when compared with sham and intact group (Fig. 5). The test demonstrated that NBM-lesioned rats spent significantly less time exploring the novel object compared to familial object, indicating that lesioned rats showed disturbed attention and memory. However, NBM-lesioned rats showed no preference for novel object and spent a relatively equal amount of time exploring novel and familial objects. The results suggest that changes in attention and recent memory declines were a result of NBM-related neuronal loss and disruption in cholinergic central neurotransmission in the rodent brain. The findings also may reflect differences in attraction to objects in NBM-lesioned animals. These differences were not due to decreased exploration, motivation, or locomotion, but they likely were due to decresed cholinergic transmission arising from the NBM.

Fig. 5. Typical example of video tracking showing performance of rat with NBM lesion in novel object recognition (Noldus Ethovision® XT 8.0).

Performance in **A.** control animal (intact and sham-operated); **B.** NBM lesioned rat and **C**. NBM lesioned animal treated with AC1. Note the increased traces in T2 around the novel object in control (A) and NBM lesioned and AC1 treated animal (C).
