Effects of smoking/nicotine on performance and event-related potentials during a short-term memory scanning task

Rationale: Nicotine absorbed from cigarette smoke shortens reaction time (R T) in a wide variety of cognitive tasks. However, relatively few studies ha ve tried to isolate the specific stage(s) of information processing affecte d by smoking/nicotine. Objective: The present study was designed to investi gate the effect of smoking/nicotine on the short-term memory (STM) scanning stage of information processing in minimally abstaining smokers. Both RT a nd event-related potentials (ERPs) were measured. Methods: A Sternberg-type STM-scanning task was performed before and after smoking each of two cigar ettes. One cigarette had a 0.05-mg nicotine yield ("denicotinized") and the other had a 1.1-mg yield ("nicotine-yielding"). On each trial, either 2, 3 , or 4 consonants were displayed as a memory set. After a brief interval, a single probe consonant was displayed. If the probe was in the memory set ( positive probe) a right button press was required, and if the probe was not in the memory set (negative probe) the left button was pressed. Results: S moking the nicotine-yielding cigarette but not the denicotinized cigarette shortened RT. However, memory-scanning speed, as estimated from the increas e in RT as a function of increasing set size, was not differentially affect ed by the two types of cigarettes. For the ERPs, smoking the nicotine-yield ing but not the denicotinized cigarette (a) reduced N200 latency to both th e memory-set stimuli and negative probes, (b) increased N200 amplitude to n egative probes and P300 amplitude to both types of probes, and (c) produced a sustained negative shift in memory-set ERP amplitude beginning around 60 0 rns post-stimulus. Conclusion: While smoking/nicotine shortened probe RT, it did not affect the speed of STM scanning. Moreover, the ERP-latency eff ects obtained for the probes were small relative to the effects of smoking/ nicotine on RT, suggesting that smoking/nicotine shortens RT primarily by a ffecting response-related processes.