The influence of advanced age on novelty detection

Abstract

Aged rats are impaired at object recognition because they identify novel objects as familiar. The extent to which this impairment can be explained in terms of object discrimination deficits, or a decreased ability to detect novelty has not been described. Previous studies have suggested that a functionally intact noradrenergic system is necessary to facilitate novelty detection. The main source of noradrenaline in the brain, the locus coeruleus (LC), experiences morphological changes with age. The current experiment tests the hypothesis that these structural changes may partially account for the inability of aged rats to correctly identify novel objects. Young (9 months) and old (24 months) rats were placed in a hole board apparatus for a habituation and object phase separated by a 3‐hour period. The 9 holes of the hole board were left empty for the habituation phase while 4 of the holes were filled with 4 identical objects in the object phase. Novelty detection was quantified by comparing the number and duration of nose pokes in holes with objects relative to the holes without objects. There was no significant difference in the performance of young and old animals, implying that age‐related changes in LC neurons do not functionally impact novelty detection. This research was supported by the Howard Hughes Medical Institute ‘06 Grant (#52005889) and the McKnight Brain Research Foundation at the University of Arizona.