Effects of dopamine receptor blockade on alimentary behaviors: Home cage food consumption, magazine training, operant acquisition, and performance

Administration of the dopamine receptor blocker pimozide (1.0 mg/kg) disrupted the initiation, but not the maintenance, of home cage food consumption. Likewise, the number of pellets consumed during magazine training was decreased among pimozide-treated rats during the first, but not the second day of training. The acquisition of a bar-press response for food reinforcement (using a retractable bar) was severely retarded by pimozide. However, such an impairment was not evident if animals initially received 2 training days in the absence of the drug. Further, among rats trained to bar press to asymptote using a nonretractable bar, pimozide reduced the within and between days bar-press rate such that performance was indistinguishable from that of animals placed on extinction in the absence of the drug treatment. When transferred from the pimozide treatment to extinction in the absence of drug, the response rate increased to the level observed during the first session of either extinction or pimozide in the continuous reinforcement condition. The results are discussed in terms of sensory-motor and reinforcement consequences of dopamine receptor blockade

Extinction and dopamine receptor blockade after intermittent reinforcement training: Failure to observe functional equivalence

Response decrements in an operant task produced by either extinction or by the dopamine receptor blocker pimozide were examined in three experiments which employed intermittent reinforcement schedules. In contrast to the congruency between these treatments previously observed following continuous reinforcement training, treatment with pimozide was markedly more effective than extinction in decreasing performance after training with variable interval, fixed interval, and fixed ratio reinforcement. The two treatments also produced substantially different patterns of responding. A shift from extinction to pimozide did not alter the progressive decline in response rate over days, but a shift from pimozide to extinction caused a pronounced increase of performance. These results indicate that the pimozide and extinction treatment did not produce functionally equivalent effects, and that the role of dopamine on reward processes should not be inferred from comparisons between pimozide and extinction

The Computerized test of information processing (CTIP) Offers an alternative to the PASAT for assessing cognitive processing speed in individuals with multiple sclerosis

Objective: To compare the ability of the Computerized Test of Information Processing (CTIP) to detect impaired cognitive processing speed in patients with multiple sclerosis (MS) with a traditional 3.0 second Paced Auditory Serial Addition Test (PASAT) and the Adjusting-PASAT which allows for calculation of a speed score. Background: A primary cognitive deficit in MS is an impaired ability to process information quickly. Unfortunately, relatively few clinical tests effectively measure information processing speed. Of these, the PASAT is generally acknowledged to be the most sensitive, but use of this test is constrained by several factors. Methods: All tests were administered to 30 adults with relapsing-remitting MS and 30 control participants. Results: A series of analysis of variances revealed MS participants performed significantly worse than controls on the CTIP and the 3.0 second PASAT, whereas no significant difference was observed for the Adjusting-PASAT. Conclusions: The results suggest the CTIP can detect deficits in the speed at which people with MS process information. Thus, the CTIP offers an alternative means to the 3.0 second PASAT included in the Multiple Sclerosis Functional Composite for assessing such impairment. Copyrigh

Reaction time: An alternative method for assessing the effects of multiple sclerosis on information processing speed

The ability of a newly developed measure of information processing to detect deficits in cognitive functioning associated with multiple sclerosis (MS) was investigated. The Computerized Tests of Information Processing (CTIP; Tombaugh, T., & Rees, L. (1999). Computerized Tests of Information Processing (CTIP). Unpublished test. Ottawa, Ontario, Canada: Carleton University) was administered to 60 clinically definite MS patients and 60 healthy controls. MS patients responded significantly slower than controls on the reaction time tests composing the CTIP. Moreover, as the CTIP tests became more difficult (i.e. as processing demands increased), the difference between the performances of the two groups progressively increased. These results suggest the CTIP is sensitive to the cognitive deficits observed in MS and that this measure has the potential to serve as a viable alternative to traditional measures of information processing speed currently in use with MS patients