Fixed ratio responding

Goldberg SR, KeUeher RT, Goldberg DM (1981a) Fixed-ratio responding under second-order schedules of food presentation or cocaine injection. J Pharmacol Exp Ther 218 271-281... 

Alterations in fixed ratio responding have been reported by Zenick et al. 

Fig. 1 Active choice of intravenous nicotine in experimentally naive squirrel monkeys, a Monkeys sat in chambers equipped with two levers and distinctly colored light stimuli above the levers. Completion of the response requirement (the ratio) on the active lever produced a brief 2-s presentation of a light stimulus and an intravenous injection of nicotine followed by a timeout (TO) period of 5-60 s. Completion of the ratio requirement on the inactive lever resulted in presentation of a brief 2-s light stimulus of a different color but no injection. The fixed-ratio (FR) response requirement was gradually increased over successive sessions from one to ten (FR 1-FR 10). b Mean percentage choice for responding on the active lever by monkeys when they were experimentally naive (first week under a FR 1 schedule) and when they had learned to self-administer nicotine under the FR 10, TO 60s schedule (first week under the FR 10 schedule). P < 0.01, compared to the first week of training. From Le FoU et al. (2007b)...

Rimonabant decreased intravenous self-administration of nicotine under a fixed-ratio schedule decreased responding maintained by nicotine-associated stimuh and blocked nicotine-induced conditioned place preference in rats. 

In order to distinguish specific effects on reinforcement from nonspecific effects on performance various studies on the effect of DA receptor blockers and 6-OHDA lesions on opiate self-administration have looked for an increase in responding in fixed-ratio... 

Griffiths RR, Bradford LD, Brady JV (1979) Progressive ratio and fixed ratio schedules of cocaine-maintained responding in baboons. Psychopharmacol 65 125-136. 

Figure 5 illustrates the criteria employed in the four simplest reinforcement schedules and the way in which these criteria influence responding. There are four basic criteria. When a "ratio" criterion is employed the animal is required to perform a specified number of responses (e.g., lever presses) before the food-consequence is produced. In the fixed-ratio (FR) cell the... 

Figure 5. Criteria for making food available following a response on fixed- and variable ratio and interval schedules. Each cell of the table shows the criterion for that schedule and the typical pattern of responding in the interval between successive food presentations. The criterion is shown by the straight lines which intersect the response axis on the time axis. Responding is shown by the dotted line curve in each cell The axes in each cell should be read as labeled in the fixed ratio ceU.

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