Effects of the Tranquillizer Diazepam and the Stimulant Methylphenidate on Alertness and Memory

Abstract

Effects of alertness and memory of a single dose of diazepam (10 mg) and the central stimulant methylphenidate (20 mg) were studied in healthy volunteers. It was questioned whether opposite effects of diazepam and methylphenidate are not only observed with respect to alertness but also with respect to memory. It was also questioned whether the two drugs equally affect the first (primacy) and last (recency) items in both the immediate and delayed recall of newly learned words. The experiment was performed in a double-blind, placebo-controlled way. 12 subjects were exposed to a subjective alertness scale and a verbal memory test: a 15-word test. Subjective alertness was found to be decreased after diazepam and increased after methylphenidate. Anterograde amnesia was found after diazepam in the memory test. More specifically, the primacy but not the recency effect was reduced during the immediate recall and both were reduced in the delayed recall. Methylphenidate had no effect on memory, however a ceiling effect might have obscured a putative drug effect. The results of a second experiment excluded this possibility. In all, the data demonstrate opposite effects of the two drugs on subjective alertness, suggesting opposite effects on vigilance. Opposite effects on memory were not established. This demonstrates that changes in alertness do not run in parallel with changes in memory. A scatter diagram, however, suggests a small effect of alertness on immediate recall. The effects of diazepam were also discussed in terms of the Atkinson and Shiffrin memory theory and it seems that diminished rehearsal processes are one of the key factors in explaining diazepam-induced amnesia.

Effects of a benzodiazepine on free recall of semantically related words

“…In the few studies that did evaluate BDZ effects considering serial position input, the recency effect was shown to be unaffected (Curran et al, 1987;Ghoneim and Mewaldt, 1975;Ghoneim et al, 1981;Unrug et al, 1997), in consonance with the lack of effects of BDZs on STM functioning as evaluated by digit span forward test (Curran et al, 1987;Gentil et al, 1989;Lister and File, 1984). In contrast, there are reports of reduction of the primacy effect induced by BDZs (Ghoneim et al, 1984;Unrug et al, 1997). These findings are based on comparative analysis between BDZ-and placebo-or methylphenidate-treated groups (Unrug et al, 1997).…”

“…In previous studies on BDZ effects on serial position curves, it was claimed that this class of drug reduces primacy effect due to impairment of active rehearsal (Unrug et al, 1997). However, this does not appear to completely explain BDZ effects on this phenomenon (Curran, 2000;File and Lister, 1982).…”

“…In contrast, there are reports of reduction of the primacy effect induced by BDZs (Ghoneim et al, 1984;Unrug et al, 1997). These findings are based on comparative analysis between BDZ-and placebo-or methylphenidate-treated groups (Unrug et al, 1997). However, as mentioned, primacy is in fact defined as the enhanced recall of initial items in comparison to the following ones in the same experimental group (Gershberg and Shimamura, 1994;Glenberg et al, 1980).…”

“…Brown et al, 1994;Ghoneim et al, 1984;Unrug et al, 1997), permitting the assessment of processing of isolated items or between items and context. However, mnemonic processes involved in the facilitating effects of semantically associated words in free recall after BDZ ingestion were little investigated and their mechanisms are unknown.…”

A 69-Year-Old Man With Chronic Dizziness

“…Because these drugs are sedative, I add 5 mg of methylphenidate hydrochloride in the morning and at noon. I find this combination to be effective in many patients with vertigo and generally well tolerated, 44 although efficacy in patients with vestibular disorders has not been studied systematically. For acute attacks of vertigo, I have used atropine, 0.4 mg, given sublingually for rapid absorption.…”