Differential patterns of performance impairment result from changed reinforcer efficacy or distracting stimulation in...

Measures of the discriminabililty of stimuli in signal detection tasks can be influenced by alterations of motivational state. In the present study, rats performed an operant signal detection procedure that required the completion of a fixed number of responses before a stimulus was presented at one of two front cue lamps to separately measure the motivation to respond from the ability to respond accurately. One manipulation, presession water access, affected the speed and frequency that trials were initiated, but did not affect response accuracy. In contrast, a flashing houselight during the session, and i.p. ((5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d,] cyclohepten-5,10-imine (dizocilpine or MK-801), a glutamate N-methyl-D-aspartate receptor antagonist, impaired response accuracy in a stimulus duration-dependent manner. These results suggest that it is possible to procedurally isolate the motivation to respond to stimuli from accuracy of detection, and thereby protect attending from side effects of drugs that influence the motivation to respond.