Age-related impairment in instrumental conditioning is restricted to initial acquisition

Abstract

Performance on a variety of cognitive tasks has been reported to decline across the life span. The present research evaluated appetitive instrumental learning in young and mature rats. In Experiment 1, subjects were trained to criterion, placed on extinction training to criterion, and subsequently retrained for a total of three cycles. Results indicated that mature animals were impaired in the initial acquisition of the bar-press response but reacquired the response as quickly as young animals. Resistance to extinction was not significantly impaired in the mature group, both groups increased resistance by the third extinction period, despite the brevity of reinforcement. In Experiment 2, young and mature subjects underwent appetitive instrumental training that continued beyond the acquisition criterion for the first experiment. After the response had been established (to criterion), performance levels were equivalent for young and mature subjects. The number of responses were not significantly different between young and mature groups on the day criterion was met; comparison of number of responses for 4 days after criterion also indicated no significant differences over days of training or between age groups. Examination of the number of responses occurring early in training indicated no significant group difference; hence, the earlier acquisition by young animals in Experiment 1 does not appear to reflect greater activity level in younger animals resulting in earlier and greater exposure to reinforced responses. Results may reflect the contribution of use-induced plasticity, such as long-term potentiation, within brain systems involved in learning and memory. These findings are consistent with evidence of the effects of use and disuse on neurobiological and cognitive function.

Lack of direct involvement of a diazepam long-term treatment in the occurrence of irreversible cognitive impairment: a pre-clinical approach

“…On the other hand, the outcomes of the Touchscreen test were fairly complex to interpret in the older mice population, since about half of these animals (in both the control and diazepam groups) did not achieve the set criterion allowing them to be tested in the dPAL task. While a lack of motivation for the sweet reward was ruled out by the sucrose preference test performed just before the beginning of the touchscreen paradigm (data not shown), this result underlined an age-related deficit in instrumental conditioning abilities consistent with previous clinical and preclinical reports [ 55 ] that did not appear to be influenced by diazepam exposure. Although it is more than likely that this finding prevented the detection of the effect of age × drug interaction on visuospatial learning abilities, the comparison of mice performances did not indicate a deleterious effect of high-dose diazepam exposure on this memory type.…”

Age-related deficits on the radial maze and in fear conditioning: Hippocampal processing and consolidation

“…The literature on extinction during aging has produced mixed results. Some studies show faster extinction rates in old rats (Solyom and Miller, 1965;Stephens et al, 1985), others find no difference (Birren, 1962;Kay and Sime, 1962;Sarter and Markowitsch, 1983;Port et al, 1996), and still others find that aged animals take longer to extinguish (Botwinick et al, 1962;Goodrick, 1968;Bartus et al, 1979;Sarter and Markowitsch, 1983). On tasks similar to the present fear conditioning paradigm, no differences have been found in extinction (Schneider-Rivas et al, 1995).…”

Age-related impairments of new memories reflect failures of learning, not retention

“…Of those studies that report retention deficits, in most of those studies the initial learning upon which the long-term memory was based was impaired relative to young animals (e.g., Barnes and McNaughton 1985;Kinney et al 2001a,b;Gould and Feiro 2005). Interestingly, in those few studies in which initial learning was equated across young and old animals, including studies of spatial water maze performance and appetitive instrumental responding, no retention deficits were observed, even after retention intervals as long as 21 d (Soffie and Lejeune 1991;Martinez-Serrano et al 1996;Port et al 1996).…”