Age-associated impairments in a test of attention: evidence for involvement of cholinergic systems.
We trained three groups of rats, young (Y; 3 months at the start of study), middle aged (MA; 15 months), and aged (AG; 22 months), in the serial five-choice serial reaction time task, a test of attention. There were clear age-related differences in task acquisition: Y acquired the task quicker than MA rats, which learned faster than AG rats. A subgroup of AG rats [AG(I)] could not reach criterion (> 80% correct, < 20% omissions under standard conditions of 0.5 sec stimulus duration, 5 sec limited hold). Accordingly, they were tested under conditions of 1 sec stimulus duration. Having acquired the task, under standard conditions both MA and AG groups were slower to make a correct response but not to collect the food reward. Furthermore, parameter changes, particularly reductions in stimulus duration and intensity, revealed further age-related changes in accuracy. Following completion of these studies, animals were trained in a simpler one-choice task. Importantly, reducing stimulus duration/intensity in this task revealed no differences between Y and MA/AG groups, although AG(I) rats were impaired. This dissociation between MA/AG impairments in the one- and five-choice task suggests that these animals may show attentional deficits compared with Y rats, which are independent of changes in sensory (visual), motor function, or motivation. Finally, the MA deficit in attention was partially reversed by tacrine pretreatment (3 mg/kg). Also scopolamine (0.01-0.075 mg/kg) and mecamylamine (0.3-5 mg/kg) pretreatment impaired choice accuracy of MA but not Y rats. Taken together, the drug studies imply that the attentional deficits may at least be partially due to changes in cholinergic function.
D000375:Aging / Q000502:physiology*; D000818:Animals; D001288:Attention / Q000502:physiology*; D001522:Behavior, Animal; D018678:Cholinergic Agents / Q000494:pharmacology; D005106:Exploratory Behavior / Q000502:physiology; D008297:Male; D008464:Mecamylamine / Q000494:pharmacology; D009043:Motor Activity / Q000502:physiology; D010275:Parasympathetic Nervous System / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D011930:Reaction Time / Q000187:drug effects; D012601:Scopolamine / Q000494:pharmacology; D013619:Tacrine / Q000494:pharmacology
D018678:Cholinergic Agents; D013619:Tacrine; D008464:Mecamylamine; D012601:Scopolamine