Effects of smoking/nicotine on performance and event-related potentials during a short-term memory scanning task.
BACKGROUND
Nicotine absorbed from cigarette smoke shortens reaction time (RT) in a wide variety of cognitive tasks. However, relatively few studies have tried to isolate the specific stage(s) of information processing affected by smoking/nicotine.


OBJECTIVE
The present study was designed to investigate the effect of smoking/nicotine on the short-term memory (STM) scanning stage of information processing in minimally abstaining smokers. Both RT and event-related potentials (ERPs) were measured.


METHODS
A Sternberg-type STM-scanning task was performed before and after smoking each of two cigarettes. 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
Smoking the nicotine-yielding cigarette but not the denicotinized cigarette shortened RT. However, memory-scanning speed, as estimated from the increase in RT as a function of increasing set size, was not differentially affected by the two types of cigarettes. For the ERPs, smoking the nicotine-yielding but not the denicotinized cigarette (a) reduced N200 latency to both the memory-set stimuli and negative probes, (b) increased N200 amplitude to negative probes and P300 amplitude to both types of probes, and (c) produced a sustained negative shift in memory-set ERP amplitude beginning around 600 ms post-stimulus.


CONCLUSIONS
While smoking/nicotine shortened probe RT, it did not affect the speed of STM scanning. Moreover, the ERP-latency effects obtained for the probes were small relative to the effects of smoking/nicotine on RT, suggesting that smoking/nicotine shortens RT primarily by affecting response-related processes.
Houlihan
M E
ME
Department of Psychology, Dalhousie University, Halifax, NS, Canada B3H 4J1. houlihan@is.dal.ca
Pritchard
W S
WS
Robinson
J H
JH
D000328:Adult; D000704:Analysis of Variance; D002248:Carbon Monoxide / Q000378:metabolism; D018913:Event-Related Potentials, P300 / Q000187:drug effects* / Q000502:physiology; D005260:Female; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D008297:Male; D008570:Memory, Short-Term / Q000187:drug effects* / Q000502:physiology; D009538:Nicotine / Q000494:pharmacology*; D018722:Nicotinic Agonists / Q000494:pharmacology*; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D012907:Smoking / Q000503:physiopathology* / Q000523:psychology*; D013990:Tidal Volume / Q000187:drug effects / Q000502:physiology
D018722:Nicotinic Agonists; D009538:Nicotine; D002248:Carbon Monoxide