tokens: The present study sought to characterize the cognitive - enhancing effects of the 5 - HT ( 6 ) antagonist Ro4368554 ( 3 - benzenesulfonyl - 7 - ( 4 - methyl - piperazin - 1 - yl ) 1H - indole ) in a rat object recognition task employing a cholinergic ( scopolamine pretreatment ) and a serotonergic - ( tryptophan ( TRP ) depletion ) deficient model , and compared its pattern of action with that of the acetylcholinesterase inhibitor metrifonate .