Can the pattern of neuropsychological improvement obtained with cholinergic drugs be used to infer a cholinergic mechanism in other nootropic drugs?

Examined whether the pattern of neuropsychological improvement usually observed in Alzheimer's disease (AD) patients treated with cholinergic agents (mainly consisting of enhancement of episodic memory and reduction of intrusion errors) can be used to confirm a cholinergic mechanism in drugs that are not primarily cholinergic agents. Since the nootropic drugs piracetam and oxiracetam are deemed to act through a cholinergic mechanism, it was checked whether 45 AD patients treated with these drugs would show the same pattern of neuropsychological improvement. Results were negative, since (1) episodic memory showed a similar degree of improvement both in Ss treated with these drugs and in Ss treated with placebo; (2) the number of intrusions tended to increase, rather than to decrease, after the treatment period.