Reinforcing behavioral variability: an analysis of dopamine-receptor subtypes and intermittent reinforcement.
Variability is a functional and modifiable component of behavior that is necessary for learning or behavior change to occur. An appreciation of drug effects on reinforced variability could contribute to a fuller understanding of potential drug effects on behavior change. Dopamine agonists were examined under conditions that produced low and high levels of variability. In Experiment 1, D-amphetamine and dopamine-receptor-specific agonists (quinpirole and SKF 38393) were examined with rats that lever-pressed under a Multiple VARY 8:4 Fixed Ratio 4 (FR 4) schedule. In the VARY 8:4 condition, reinforcement followed every four-response sequence that differed from the previous eight sequences. Any four-response sequence was reinforced in the FR 4 component. Experiment 2 was an attempt to hold overall reinforcement rate constant by reinforcing criterion sequences under a Variable Interval 60" schedule of reinforcement. In Experiment 1, D-amphetamine and quinpirole (D₂ agonist) increased variability in the FR 4 component while having no effect on variability in the VARY 8:4 component. SKF 38393 (D₁ agonist) had little effect on variability, even at doses that lowered total responding. In Experiment 2, intermittent reinforcement elevated variability in the FR 4 component and attenuated differential effects of D-amphetamine. Thus, D-amphetamine and quinpirole increased variability when it was low under the FR 4 component in Experiment 1. The high variability under the VARY 8:4 schedule was unaffected by D-amphetamine, except for modest effects at high doses. These observations suggest that dopamine and specifically D₂-type receptors are involved in the production of behavioral variability, and that the drug effects depend upon the baseline level of variability.
Experimental Psychology, Thach Hall, Auburn University, AL 36849, USA.
Erin F
EF
Pesek-Cotton
Joshua E
JE
Johnson
M Christopher
MC
Newland
D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine / Q000494:pharmacology; D000661:Amphetamine / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal; D015259:Dopamine Agents / Q000494:pharmacology; D006801:Humans; D008297:Male; D019257:Quinpirole / Q000494:pharmacology; D051381:Rats; D020318:Rats, Long-Evans; D011954:Receptors, Dopamine / Q000502:physiology*
D015259:Dopamine Agents; D011954:Receptors, Dopamine; D019257:Quinpirole; D015647:2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine; D000661:Amphetamine