A new psychometric test of attention-related behavior in rats; its validity in the aging process

The ability to distinguish relevance from irrelevance has been attributed to an attention-related mechanism and may be supposed to be disturbed in aging. The reaction to low electrical stimuli which causes neither pain nor escape behavior was investigated by means of a newly developed test in adult and aged rats. The animals' reaction was classified into two different responses depending on the intensity of the electrical stimuli. The first reaction related to sensitivity, the second reaction contained two components, an orienting response and a cognition-controlled type of discriminative behavior. There was no significant difference between the amperage values of the two reactions in adult rats. With respect to aged rats, the amperage values of both reactions are significantly increased as compared with the adult rats. The sensitivity reaction and the attention-related behaviors diverged considerably. These findings show very precisely that certain behavioral reactions may decline differently or even independently with age indicating different age-related changes in the underlying neuroanatomical systems of attention. The results demonstrate the sensitivity of the test used as a model for studying some types of attention-related mechanisms in the aging process. The use of a relatively simple test of animals' reactivity to sensory stimuli may reveal changes that are critical to understanding not only of the aging brain, but of different types of brain lesions and disorders, as well as of drug treatments.